State of the Technology
Present Obstacles & Future Potential
A Report for:
United States Department of Energy
Conservation and Renewable Energy
Office of Energy Related Inventions
Prepared by
Larry Dobson
Northern Light Research & Development
in Fulfillment of the Terms of
Energy Related Inventions Grant
Project Number DE-FG01-89CE15425
Project Officer: Glenn Ellis
June 23, 1993
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CONTENTS AT A GLANCE
SECTION 1- OVERVIEW 1
History of the Project 1
Northern Light Technology 3
References 4
Energy Equivalents 4
Biomass Energy 4
Solar Batteries 4
Limitations of Fossil Fuels 5
Reserves Running Out 5
Prices Rising for
Fossil Fuels, Falling for Biomass 5
Delivered Fuel Costs - Chart 6
Fossil
Fuels Cause Global Warming 6
Renewable Energy 6
Biomass Can Replace Fossil Fuels
6
CO2 Emissions - Chart 7
Biomass Fuels Prevent Global Warming
8
Landfill Debris 8
Recycling 8
Logging and Agricultural Residue
9
Biomass Farming 9
Biomass Energy
Saves Dollars, Creates Local Jobs 10
Political Climate Improving 10
Environmental Regulations
Demand Better Technology
11
Permits Need to be Streamlined 11
Biomass Energy - The Problems 12
Negative Perception 12
Regulations 12
Fuel Nature & Availability 13
Fuel Handling 13
Defects of Available Technology
14
Defining the Market 14
Best Size System 16
Cogeneration 17
Biomass Energy Potential - 18
Municipal Solid Waste 19
Wood Burns Cleaner Than Oil. 21
Heat Transfer & Furnace Design - Graph 23
Emissions from "Helen" Prototype - Chart 24
Woodstove Emissions - Graph 25
Carbon Monoxide Emissions & Standards - Chart 26
PSAPCA Emission Standards - Chart 26
Industrial Boilers Emission Levels - Chart 27
Excess Air Requirements - Chart 27
Fuel Cost Comparisons - Chart 28
SECTION 2- MORE DETAILS 29
Grendle Family Lineage 29
Fossil Fuels 29
Biomass Fuels 30
Global Patterns Of Fuel Use 30
Economics of Logging Cleanup 32
Urban Wood Waste 33
Agricultural & Food Processing Residues 33
Pelletized Fuel 33
U.S. Statistics 34
Regional Statistics 35
Pacific Northwest & Alaska Region 35
Agricultural Field Residues 37
Typical Installations In Washington 37
Western Region 38
Southeastern Region 39
Nonforestry Related Biomass Fuel 39
Northeastern Region 39
Great Lakes Region 41
Emissions Control 43
Effect Of Wood Combustion
On Climate Change 43
Cause of Emissions In Biomass
Combustion 44
Air Pollution Control (APC) 45
Emissions Statistics 48
RELATIVE EMISSIONS COMPARISONS 48
Wood Ash: 48
Potential Problems: 49
Ash Disposal & Utilization: 49
Condensate: 50
Governmental Regulations 51
U.S. Federal 51
EPA's Woodstove Regulations 52
New Source Performance Standards (NSPS) 52
Prevention of Significant Deterioration Requirements
(PSD) 53
Emissions from MSW Combustion Facilities - Chart 53
The 1990 Clean Air Act Amendments 53
Financial Assistance 54
Regional 55
Northeast Region 55
Southeast Region 55
MSW Combustion in SERBEP 56
Municipal Solid Waste (MSW) 56
Nature of the Fuel 57
Landfills 57
Projected Growth Of MSW Combustion 57
EPA Study 57
Market Studies 59
SERBEP Study 59
Great Lakes Study 62
Washington Study 63
South Carolina Study 63
Public Opinion 64
Fuel Feed, Storage, Transport 64
Fuel Transport 64
Weather Considerations 64
Fuel Storage 64
Fuel Handling Equipment 66
Front-end loaders 67
Pneumatic conveyors 67
Screw conveyors 67
Belt conveyors 67
Drag or flight chain conveyors 67
Bucket elevators 67
Oscillating conveyors 67
Screens 68
Canadian Fuel Feed Research 68
Current Combustion Systems 69
Pile Burning Equipment- Dutch Oven 69
Conifer Furnace 69
Horizontal Return Tubular (HRT) Industrial Boiler 70
Modified Firebox Industrial Boiler 70
Watertube Industrial Boiler 70
Suspension Burning Equipment 70
Injection Suspension Burning 71
External Direct-Fired Suspension Burning 71
Fluidized Bed Combustion Equipment 71
Hot Air Furnace 72
Wood Gasifier 72
Future Potential of Gasifiers 72
Efficiency 73
Turn-Down Ratio 74
System Features 74
Furnace 74
Boilers 77
Draft 80
Stacks and Fans 80
Boiler and Combustion Controls 81
Small-Scale Cogeneration 82
Costs Of Complete Systems 83
Case Studies 85
- Typical Problems - Case Studies 88
The Agni Boiler System 90
Agni Fuel Handling 91
Agni Fabrication Costs 92
Total Package Cost 92
APPENDIX 94
UNITS AND CONVERSION 94
BIBLIOGRAPHY 97
SUPPLEMENTAL BIBLIOGRAPHY
SECTION 1
- OVERVIEW
The prevailing image of wood and waste burning as dirty and
environmentally harmful is no longer valid. The use of biomass
combustion for energy can solve many of our nation's problems: waste
cleanup, cheap energy as heat and electricity, conservation of fossil
fuel
reserves, reduction of our foreign debt, increased local employment,
retention of energy dollars in the local economy, improved air quality,
land reclamation, and retarding of global warming. Numerous factors
combine to produce unprecedented opportunities in the field of biomass
energy:
· Wood and other biomass residues that are now causing expensive
disposal problems can be burned as cleanly and efficiently as natural
gas, and at a fraction of the cost.
· New breakthroughs in integrated waste-to-energy systems, from
fuel
handling, combustion technology and control systems to heat transfer
and power generation, have dramatically improved system costs,
efficiencies, cleanliness of emissions, maintenance-free operation,
and
end-use applications.
· Increasing costs for fossil fuels and for waste disposal, strict
environmental regulations and changing political priorities have changed
the economics and rules of the energy game.
This report will describe the new rules, new playing field and key
players, in the hopes that those who make our nation's energy policy
and
those who play in the energy field will take biomass seriously and
promote its use.
The subject and content of this report has been dictated not by the
originally projected scope of the project but by the realities of the
economic and political climate of this country. This DOE
Energy-Related Inventions Grant was applied for six years ago, and
much has happened since then. The original task was to build a
pre-production prototype 1.5 Million Btu/hr wood-fueled boiler (named
Agni) based on the clean combustion and efficient heat-transfer
technology developed through ten previous prototypes.
During the initial two years before the grant was awarded to Northern
Light R&D, we developed a 150,000 Btu/hr hot air furnace (named
"Vaagner") for Vaagen Timber Products Company, the new
manufacturing wing of Vaagen Brothers Lumber Company. This
residential size system complimented the large industrial wood-waste
burner (the Johnson burner) they were manufacturing.
Vaagner evolved from the revolutionary design of "Helen", a
sawdust-burning cookstove that officially proved for the U.S. DOE that
green wood can be burned as clean as gas. Design, fabrication, and
controls were further refined, but the company was loosing its shirt
on
the Johnson burner and soon dropped out of manufacturing entirely.
Vaagner was never commercialized by them, but it proved the
soundness of many new design features, indicated new improvements,
and allowed extensive development of the microprocessor controls.
Vaagner was put through lengthy and rigorous testing, and plans for
the
larger Agni system were further refined.
Meanwhile, the 40,000 sq. ft. greenhouse which was to be heated by the
Agni boiler decided to go out of business, so it became necessary to
seek
a new site to install the prototype. (This proved to be an elusive
2½ year
challenge.) A number of sites expressed interest in heating their facilities
with wood waste, but the great expense of installing an automated fuel
feed system (which the original greenhouse already had), along with
the
depressed economic times and concern about future dependability,
serviceability and spare parts for an untested prototype, combined
to
eliminate many of the potential users. Concern about obtaining permits
in a political climate hostile to wood burning, and uncertainty about
future regulations and dependable fuel supplies in the rapidly changing
logging/waste biomass industries also made the sales job tough. We
were
slowly learning the many obstacles and pitfalls to commercialization.
Pyro industries, the major pellet stove manufacturer in the industry,
became enthusiastic about the project and decided to seriously explore
the manufacturing and sales potential of the Agni size commercial boiler.
They revised the plans for their new 100,000 square foot manufacturing
facilities in Burlington, WA to include a hot water heating system
and
gas-fired boiler, with provisions for the Agni boiler and feed system
to be
installed within a year. The burner/boiler plans were redrawn to
incorporate their manufacturing expertise, and the ceramic heat
exchanger castings were redesigned to reflect test data from Vaagner
and the new boiler configuration.
Existing fuel feed systems can be 2/3 the cost of an installed
burner/boiler/ feed system for the commercial/small industrial
market. Because they are too complex and over built for our use,
Northern Light designed an automated feed system that can be
fabricated and installed for 1/3 to 1/4 the cost of the ones presently
available.
The design allows a delivery truck to dump its load straight into a
storage
area, where it is slowly fed to the fuel hopper by a low-powered "pile
feeder" and low-cost conveyor belts. It is designed to handle a large
variety of fuel types, including stringy bark and branches, major
problems for conventional feed systems.
Still, the board of directors was not convinced that they should launch
so
quickly into this major new product line, so they commissioned an
exhaustive six month marketing/feasibility study. They also requested
thorough testing of the Vaagner prototype at the Pyro R&D facilities.
We tested a wide variety of fuels, including refuse-derived-fuel
(RDF) pellets and agricultural waste pellets. This yielded more
exciting evidence that our technology could handle the least
desirable biomass fuels without the problems usually associated with
their combustion and with unequaled efficiencies. We also
discovered that we could burn wetter fuels than ever thought
possible in the industry.
After two years of deliberation and several unforeseen challenges to
their corporate health, Pyro decided not to make the required
multimillion dollar investment at this time and not to build the Agni
prototype. We were greatly disappointed, but all the more convinced
by
the findings of the marketing study that we had a winner.
Since time was running out on the grant, we decided to pursue the
prospect of installing the prototype at a remote penal institute on
the
Olympic Peninsula. The Clearwater Correction Center was enthusiastic
about utilizing locally-available logging waste to save them $30,000
in
annual fuel bills, but the state procurement officials were in no hurry
to
rush the slow steps of bureaucracy. They are still studying the case.
Next, Clean Fuels, Inc., a waste-stream-technology marketing firm in
Washington state, became enthusiastic about Northern Light's
technology and wanted to fund the production prototype, but their
expected financing fell through and they are struggling to maintain
their
present commitments. Two other very promising options were pursued
to no avail within the time constraints of the DOE grant.
Eventually, Northern Light R&D developed a business plan to seek
private funding for a limited production run of Agni size commercial
combustors and boilers. The figures are very encouraging and we are
eager to get on with the project.
We will first build the production-prototype low-pressure
hot-water/steam boiler fueled with waste biomass. It will incorporate
all
of the advanced features described below. We will test emissions from
notorious "problem" fuels, such as wet, stringy hogged fuel, sawdust
that
has been stored out in the rain for years, agricultural wastes, hospital
waste, chicken manure, and municipal solid waste (MSW).
Emissions are expected to be well below the most stringent
regulations in the nation without expensive stack cleanup
equipment. Efficiencies are expected to be above 90% within a very
broad power range. Our market study showed this commercial-size
to meet the needs of the largest potential market and its production
costs to be highly competitive.
Meanwhile, Sunpower, Inc., a major R&D firm specializing in the
development of free-piston Stirling engines with linear alternators,
approached Northern Light concerning a joint development effort to
produce a biomass-fueled residential cogeneration system incorporating
their grid-coupling linear alternator and duplex cooler technologies.
These engines and coolers use hermetically-sealed helium to transfer
externally-produced heat, in this case from biomass combustion, to
apply power to the piston.
We are currently assessing the technical merits of Sunpower providing
the Stirling alternator, to generate household energy, and their cooler
technology, for CFC-free refrigeration and air-conditioning. Northern
Light R&D would develop a biomass-fueled combustion/heat-transfer
system to power the engines and transfer the remaining heat to the
dwelling and its hot water. We are excited about its potential impact
on
the alternative energy market throughout the world.
Ultimately, a central energy system is envisioned, providing the
power, cooking, baking, clothes drying, refrigeration, air
conditioning and waste disposal needs of a household. The
integrated components of the system would be fully automated to
provide efficiencies several times that of separate stand-alone units.
Because of superior combustion and heat-exchanger design, a
Northern Light Energy System can also burn fuel pellets, oil,
natural gas, propane or alcohol more efficiently and cleaner than in
commercially available heating systems. The auxiliary fuel can be
used for startup and as an automatically switched-on backup fuel.
Cheap biomass fuel is not being utilized primarily because no
combustion system is available on the market that is clean-burning
enough to pass strict new emission regulations and is also affordable,
fully automated, reliable and able to feed and burn the great variety
of
biomass fuels available, in diverse sizes, composition and moisture
content. Northern Light R&D has been working on these problems
for
twenty years now, and we think we have most of the answers. This
unique technology evolved through 10 prototypes which were designed,
built, extensively tested, modified and redesigned in a long lineage
beginning 20 years ago. Three of the prototypes are still in operation,
in
service for as long as 10 years.
Throughout this development we have tried to solve the problems of
existing technology in the context of real world needs and constraints
to
optimize efficiency, compactness, cost-effectiveness, durability, and
maintenance-free operation. These factors are quite complex, which
is
why the tremendous opportunity for biomass energy has not been
capitalized on sooner, and why this report summarizes all these factors
in
such detail.
The information used to compile this report comes from over 150
different document sources, as well as a large variety of other sources,
including first-hand interviews and Dialog database searches. Much
valuable research work has been done in recent years by universities,
state energy offices, and most commendably, the U.S. Department of
Energy Bioregional Offices. If you find some of the figures quoted
conflict, don't be surprised. Considering the fact that we have been
in
the habit of discarding what we don't use and forgetting about it,
it is
laudable that so many people are beginning to catalog our wasted
resources.
Bibliographical reference numbers are cited at the end of a particular
source in brackets.[43] I have sometimes quoted verbatim from the
original document. I have taken the liberty to set off in bold type
what I
consider to be some of the more important points. I have also injected
comments freely after quotes {in bold italic brackets.}
The Bibliography was originally compiled alphabetically with 98
references. New sources were continually added, inserted in alphabetical
order, with addresses like 45A, 45B, etc.
I apologize for the occasional reference number omitted in shuffling
information around. Give me a call if you can't ascertain the source
from
the bibliography, if you find any erroneous or outdated fact, if you
are
aware of new and exciting breakthroughs happening in the industry,
or
you just want to help out the cause, give me a ring at (360)-579-1763
Throughout this report many figures will be given on volumes, weights
and energy equivalents of biomass fuels. To give some feel for the
size
of these numbers, I will sometimes give an "AGNI" equivalent. This
means roughly the amount of biomass fuel that the AGNI boiler would
consume over a year operating at 50% capacity day & night, or the
amount of fuel that will heat a typical 100,000 sq. ft. uninsulated
industrial facility or a 200,000 sq. ft. insulated building using an
AGNI
Boiler in the Pacific Northwest.
One "AGNI" is roughly equivalent to 7.3 Billion Btu high heat
content, 777 tons of green wood/year, 420 Bone Dry Tons (BDT) of
most biomass (forest and agricultural), or 2,400 cu. yd. wood
chips/yr.
1 Million Btu (1 MBtu) = 293 kW
= 29.9 Boiler Hp = 1,000 lb Steam
= 120 lb dry wood = 7 gal. Diesel Oil
= 1000 cu.ft. (10 Therms) Natural Gas
It is obvious that the sun keeps our earth warm with its radiant energy.
It
is perhaps not so obvious that all living and once living matter on
this
planet is a form of solar battery, storing the suns energy in chemical
bonds of air, earth and water, to be later released in a profusion
of life
processes...or as fire.
When we burn a plant we release the stored water, carbon dioxide and
ash along with heat. If we do it right, that's all we get - no pollution.
This
has been our obsession for twenty years, discovering how to do it right.
Biomass fuel consists of any organic matter available on a renewable
basis including forest residues, agricultural crops and wastes, wood
and
wood wastes, animal wastes, livestock operation residue, aquatic plants,
and municipal wastes. Such fuels can provide cheap, clean, efficient
and
environmentally friendly contributions to the world's energy and waste
problems.
A complex interplay of forces have prevented the realization of this
potential, and more importantly, continue to retard its development.
The
U.S. is facing an unprecedented energy/environmental crisis which
demands long-range solutions based on detailed knowledge of what is
happening in many diverse areas of commerce, government, agriculture,
forestry, waste disposal, combustion technology, pollution prevention,
and ecology. This report is the culmination of six years of effort
pursuing
the original mandate of the DOE Energy-Related-Inventions Grant, to
commercialize this technology and help meet the nation's energy needs.
I will attempt to show the big picture: the potentials and problems
of
biomass energy, the solutions that Northern Light and others have
developed to solve the problems, and the governmental, attitudinal
and
marketing constraints to its successful commercialization.
SECTION 1 - an overview. If you want more detail in any area, go to
SECTION 2 - lots of facts , case studies and comments. If you want still
more facts, read the appropriate bibliographical references.
Natural gas is the preferred fossil fuel of the "clean" 90's, but prices
are
predicted to steadily rise. Imports from Canada & Mexico will also
increase, along with greenhouse gas emissions from burning this fossil
fuel. In the U.S., gas is found in only 9 out of 100 natural gas wells
drilled, and only 2 of these are of commercial value. The surplus of
natural gas that has existed in North America in recent years has driven
wellhead prices down to less than the long-term replacement cost in
many cases. In the last 2 years, only 65% of U.S. gas production was
replaced. As a result, we are close to a balance of supply & demand
for
the first time in 9 years, and prices should increase.
Extraction costs of oil & coal have also increased, along with the
costs
of complying with environmental regulations. Major oil companies are
finding it much more profitable to invest their resources abroad. The
ratio of energy in coal to the energy required to mine the coal has
dropped to 59% of what it was 24 years ago. The price of commercial
coal in Washington State has increased 238% in 10 years. In contrast,
wood chippers use less than 1% of the energy produced, compared to
the high extraction and refining costs of coal and oil, often well
over
30% of the energy in the final product. Where steam is used to extract
heavy offshore crude oils, well over half of the extracted oil is burned
to
produce the steam. Such wasteful behavior will impoverish our
grandchildren. Our valuable fossil reserves are better invested in
recyclable plastic and other refinements for future abundance.
Prices Rising for Fossil Fuels, Falling for Biomass
All fossil fuel prices are predicted to escalate at an increasing rate,
while
costs for biomass fuels such as logging and wood-processing waste,
tree
trimmings, sawdust, bark, demolition and land-clearing debris, chicken
and stockyard manure, orchard prunings, corn cobs and other
agricultural field and processing wastes are dropping, as disposal
costs
rise.
Energy costs for wood residues burned in an efficient Northern Light
system are presently only one-eighth of the cost of energy from natural
gas in most areas of the U.S., and energy savings are greater yet for
biomass residues that would otherwise be disposed of in costly landfills.
Twenty-five billion dollars worth of imported oil could be replaced
yearly with the biomass in our nation's municipal waste. The
potential exists to supply fifty times this amount of energy from
other biomass fuels .
Fossil Fuels Cause Global Warming
Scientists now broadly agree that the greenhouse effect
is
bringing about the greatest and most rapid climatic change in the history
of civilization, with enormous consequences for all life on earth.
Its
primarily cause is the burning of fossil fuels (oil, coal and gas),
which
dump some 24 billion metric tons of CO2, the primary greenhouse gas,
into our atmosphere annually. 750 million metric tons more are added
each year.
Each American sends 15,000 pounds of carbon into the air every year,
adding up to 22% of the total world-wide carbon release from a country
containing less than 5% of the world's population. [World Watch, 6/93]
When biomass decays in a landfill, it generates methane gas, a more
potent greenhouse gas than carbon dioxide; it is better all around
to
burn it rather than bury it. Scientists predict that until we stop
burning
fossil fuels and begin reversing this trend by increasing the vegetation
upon the earth many dire consequences will follow, including inundation
of land by a rising sea level, water shortages and crop failures
worldwide. Biomass fuels have the potential to reverse this trend
when planting levels exceed harvesting. [5B]
Biomass Can Replace Fossil Fuels
According to the International Energy Agency, even though biomass
conversion provides 15 percent of the world's energy, only one percent
of the available biomass is used. Yet biomass meets the direct fuel
requirements of a majority of the world's population. Despite the fact
that we are now destroying our natural ecosystems faster than we are
replanting, there exists a vast untapped global energy resource in
annually renewable biomass.
About 3.7%, or 2.7 quads, of all energy consumed in the U.S. today
comes from woody biomass, comparable to our use of hydropower and
nuclear power.[83A] Various authorities predict that biomass energy
from our forest, agricultural, industrial and municipal waste streams
can
replace from 10% to 90% of our current energy needs. Even in urban
areas the biomass produced from land clearing, tree trimming and
demolition alone can provide much of the residential heating
requirements of the area, rather than disposing of it in ever more
costly
dumps. According to a 1989 U.S. Department of Energy study, solar
and biofuels account for 87.8% of the economically accessible fuels
of the future.
Biomass Fuels Prevent Global Warming
Fast-growing biomass takes up more carbon than any other process and
yields oxygen. In taking into account the total fuel cycle, several
studies
show that biomass energy is the only option that has a net gain over
the
carbon/oxygen cycle. Planting trees can reverse the CO2 buildup faster
than any other means, and young forests fix more carbon than mature
forests. Woody plants capture more sun and are more efficient than
annual crops in temperate climates.
Woody crops actually fix over three times more carbon per field per
year than a single crop of corn.
Annual crops require annual tilling, which harms the soil by killing
not
only macroorganisms, but by impoverishing the soil microbiota. During
peak sun annual crops have at best only half their photosynthetic surface
deployed. Woody plants with rapid early leaf deployment, multiple leaf
layers and longer growing season can capture significantly more solar
energy than traditional annual crops. Deep roots allow them to continue
this even during moderate dry spells. This means more -- potentially
much more -- CO2 fixed. The significance for global climate change
is
profound.
In our throwaway society, biomass waste is generally becoming an
increasingly costly disposal problem. Landfills are filling faster
and
faster, and EPA's strict new regulations are expected to cost
taxpayers $1 Million per acre to open new ones and force the closing
of half of the nation's 5,499 dumps by 1996. From 1/3 to 3/4 of our
MSW is biomass suitable for fuel which could replace nationwide 824
Million barrels of imported oil a year.
Urban wood waste processing and delivery services are springing up
across the country, charging a tipping fee less than the local landfill
for
yard waste, tree trimmings, land clearing and demolition debris and
reselling chips and compost for a tidy profit. Secondary wood product
industries, tree services and agricultural processing industries are
looking
for alternatives to costly dumping of their residues.
"Recycle" is the buzzword of the '90s because it is generally cheaper
and
more environmentally sound to do so. Premium grade wood residue can
be sold as fiber chips, paper recycled, and yard waste composted. But
there is always a large part of our biomass waste stream that is too
poor
quality to recycle into products. Household garbage and low grade
mixed waste paper are better recycled into energy, as long as there
is no
mercury present to contaminate the exhaust. In the Puget Sound region,
270,000 tons of mixed waste-paper are generated daily from recycling,
and much of it landfilled because no one wants it. This would heat
75,000 homes for one fifth the cost of natural gas, and just as cleanly.
Even premium grade fiber chips are a quarter to a third the price of
gas. Tree trimmings and other woody residues compost slowly and
would be much more economically used as fuel.
"Since 1986, 40 states have enacted legislation requiring communities
to
recycle parts of their waste. The effect has been dramatic. In 1980
the
nation recycled only 14 million tons of its MSW and burned virtually
none to produce energy. In 1988, 24 million tons were recycled, and
26
million more were incinerated to produce electricity." [62A, 1/92]
Recycling of certain materials continues to increase steadily. The
country now recycles 55% of all aluminum cans. While Americans
recycle one quarter of the 67 million tons of paper consumed
annually, the recycling industry probably couldn't handle the
remaining three quarters even if people brought it in. Because
demand for recycled paper now roughly equals supply, few recycling
mills are being built. [62A]
"The paper recycling process has been refined so that it's inexpensive
and efficient. But recycling plastic is expensive, requires a lot of
energy,
and generates pollution. The furor over juice boxes epitomizes the
plastic-recycling predicament: Americans purchase more than four
billion of the convenient little boxes each year and recycle almost
none.
Made of laminated layers of paper, foil, and plastic, these so-called
aseptic packages produce pulp of such a low grade that no one wants
to
buy it." [62A] This material would make excellent fuel in a Northern
Light burner.
Communities throughout the U.S. are now accumulating mountains of
recycled glass and low grade waste paper with little or no demand for
these raw materials. The waste paper, along with other combustibles
from municipal waste, is an excellent fuel in our Northern Light
combustors to melt waste glass and turn it into useful commercial
products.
Northern Light is also developing new technology to recycle glass
into durable, lightweight, strong and insulating foamed building
products. Currently foamed glass insulation is the monopoly of
Pittsburgh Corning, does not utilize recycled glass, and is about
three times the price of foamed plastic. Studies show very promising
economic viability for such products.
Logging and Agricultural Residue
The amount of unused biomass residue produced in this country is
monumental. Most of it doesn't end up in municipal landfills.
MSW is less than 2% of the total available biomass fuel from logging,
agricultural harvesting and processing, industrial and municipal waste
streams.
In the Pacific Northwest alone, about one quad (1,000 trillion BTUs)
of biomass residues are physically generated each year. This is
equivalent to 160 million barrels of oil, or $10 billion per year in
residential fuel oil. It represents the heat equivalent of 1½
times the
annual electric power consumption of the Pacific Northwest. This
scenario is repeated across the nation and around the world.
While fossil fuel costs are steadily increasing, the cost of wood fuels
is generally declining, with increasing disposal costs for land clearing,
logging cleanup, yard trimmings, and mill waste. A BPA study, Regional
Logging Residue Supply Curve Project, states,
"Current indications are that recovery and transportation costs for
any
given piece size will decline...In no case can it be shown that there
will be a significant rise in wood fuel prices for the remainder of
this
century."
"American demand for wood continues to rise, yet the nation's forests
are growing faster than they're being harvested. In 1990, logging
companies planted some 41.9 billion seedlings, according to the
American Forest Council (AFC)." [22]
Dr. Harold E. Young calculated Maine's wood resources, based on
utilizing the whole tree, and compared them with the U.S. Forest
Service's figures, which are based only on the merchantable bole
(excluding tops, needles & leaves, branches & roots). The annual
production of the complete forest is 8.75 times as great as the
merchantable bole harvest! This impressive number gives some
indication of the increased potential for energy from logging waste.[22]
Energy crops are seriously being considered as an alternative to fossil
fuels, sparked by environmental concerns about conventional forestry
practices, the Clean Air Act, global climate change, soil conservation
and energy needs. While only 15,000 to 20,000 acres of short-rotation
woody crops are planted in the U.S. today, the feedstock potential
could easily lead to more than 20 gigawatts of new capacity by 2010.
Jerry R. Allsup, director of DOE's Office of Alternative Fuels,
Transportation Technologies, Conservation & Renewable Energy, says
the agency "believe(s) that (wood's) role in energy is likely to grow
in
the future because of an increased research effort to produce faster
growing trees, better utilization of the existing stands of energy
and a
renewed effort to utilize wood waste for energy as a part of better
integrated resource planning." [Alternative Energy Retailer]
In Minnesota, short rotation intensive culture (SRIC) of trees can
produce 3 to 6 dry tons/acre/year, as compared to yields of 1 dry
ton/acre/year in native forest stands.[Pamphlet published by University
of Minnesota, Office of Biomass Research, 10/91]
Hemp cultivation can produce 8 to 24 BDT/acre/year. Sugar cane and
some tropical crops yield 40 or 50 tons per acre. [45]
Crop set-aside programs, conservation programs, emission taxes &
air
quality non-attainment areas have helped energy crops to become
marginally competitive in some areas. Delivered energy crop production
costs are now estimated at about $39 to $63/dry ton.
Energy crops could be planted on the 200 million acres of underutilized
and marginal agricultural land in the United States. [62B] Much of
this
land could be improved with the proper balance of biomass plantations,
while at the same time generating a large renewable fuel supply. BACH
(Business Alliance for Commerce in Hemp) claims that if only 5% of
the
nation's land were devoted to hemp, it would supply all the energy,
and
that land doesn't even have to be arable."
Sweden demonstrates the economic viability of biomass energy. The
country plans to double its present reliance on wood energy in the
next decade, providing 28% of its energy needs largely from
fuelwood plantations surrounding decentralized power plants
located in each community.
Biomass Energy Saves Dollars, Creates Local Jobs
The most expensive biomass fuel, premium grade fiber chips for paper
making and chipboard, costs only one third as much as Texas
intermediate crude oil at the pump and one fourth the price of
commercial natural gas for the same energy content. Typical fuel-grade
biomass is often one eighth the cost of fossil fuels, delivered.
Additionally, Northern Light biomass energy systems extract more heat
from the fuel than most fossil fuel fired systems.
By substituting Municipal Solid Waste (MSW) for imported oil, we
could save an estimated $25 billion a year in foreign exchange, while
at the same time creating thousands of new jobs locally and saving
$10 Billion on landfill costs.
The economic benefits in other areas of biomass energy are much
greater. Energy investments stay in local communities; workers of
varied skill levels can be employed. Industrial wood energy utilization
in
the Southeastern Region of the U.S. is projected to generate
approximately 97,000 jobs and $1.4 billion annually by the year 2000.
State and regional governments are waking up to the manifold
possibilities of a local waste-to-energy infrastructure to provide
jobs,
keep energy investments from leaving the state, solve waste disposal
problems and eliminate air pollution from slash and field burning.
Programs to inform businesses of the advantages of biomass energy and
to fund demonstration and research projects are being developed
nationally and locally. The vast potential for biomass farming is
receiving more and more serious consideration and funding. The net
gain
in the greenhouse cycle has the capacity to preserve our planet, and
a
growing wave of environmental concern may push biomass energy into
the forefront of future energy options.
"I'm hearing from the marketplace, " says Stan Sorrell president and
C.E.O. of the Calvert Group of mutual funds, "and what I am hearing
is
that environment is and will be the main issue of the nineties." [The
Nation, 3/26/93]
Environmental Regulations Demand Better Technology
Recently, tough environmental laws passed by the EPA, notably the
Clean Air Act, Clean Water Act, new landfill regulations, and
Woodstove Performance Standards, have dramatically changed the
playing field in the biomass energy game. State and local regulations
have compounded the effect in many areas.
"Changing landfill regulations have a decided impact on the
availability of mill residues. More stringent disposal standards increase
the cost of disposal forcing mill operators to explore additional options
including potential fuel applications. Currently, some sawmills are
finding disposal costs so expensive that they may be forced to close
down. This situation is partially responsible for the low current (1990)
price of mill residues. In fact, some mills are paying a fee to energy
users to dispose of their residues. They do so because the landfill
disposal costs are even higher. This is another case where
environmental policy can make more material available for energy
uses."[6]
The new Clean Water Act will indirectly provide significantly more
biomass feedstock and need for incineration of wastes that are now
polluting ground water in landfills and storage dumps. Candidates
include poultry and chicken litter, manure from dairies and feedlots,
onion culls, chicken carcasses, etc.[77] Because Northern Light's
burners can handle such diverse wet fuels, they should serve this market
well.
Title XIX of the Energy Policy Act of 1992 included tax provisions to
encourage investment in renewable energy sources, including biomass.
The Energy Act also provides a 1.5 cent tax credit for every
kilowatt-hour of electricity produced from "closed-loop biomass" (crops
grown exclusively to produce electricity).
The U.S. Department of Energy, Office of Utility Technologies, is
enthusiastic about biomass energy. [62B]
"The future for biomass power looks particularly attractive given the
potential for substantially expanding biomass supplies by growing new
energy crops on millions of acres of underutilized land; the potential
for significantly improving the performance of biomass power
technologies through R&D; important environmental benefits offered
by biomass power such as recycling of atmospheric carbon and its low
sulfur content; as well as the potential for biomass power to provide
substantial rural economic development benefits.
The growing demand for electricity, in conjunction with a new
regulatorycompetitive environment and environmental pressures such
as those created by the clean air act, has created a substantial target
of
opportunity for biomass power over the next decade. The 1980's
provided a decade of technological progress to build upon."
"The plan of the DOE Biomass Power Program is to make the
1990's a decade of commercialization. The strategy is to develop
advanced high-efficiency biomass power systems with competitive
feed stocks and to capitalize on Clean Air Act requirements and
state environmental actions."
Much more governmental support needs to be directed toward these
ends than is now in the budget. Sweden has taken biomass energy
seriously, and is now spending as much on R&D in this area as is
the
entire United States. "At the heart of Sweden's program is public
support. Enlightened, environmentally-conscious citizens and an elected
body free from the domination of nuclear and fossil fuel lobbyists
have
been essential for the progress to date." [83A]
Permits Need to be Streamlined
Regional regulatory officials tend to be suspicious of poorly performing
old-technology wood-fueled systems. This makes permitting difficult
and
time-consuming. In contrast, numerous officials in the Department of
Energy, the Environmental Protection Agency, and State Energy Offices
are anxious to see such clean, efficient technology as Northern Light
has
developed commercially available. Government funding is available for
extensive emissions testing, and with the support of the EPA and DOE,
local permitting should become easier than at present.
Biomass Energy - The Problems
Surprisingly, this increasingly favorable renewable energy
alternative is not being capitalized on and few people are even aware
of it. In fact, general public and governmental attitudes are often
decidedly negative. Influential environmental groups, such as The Sierra
Club and Friends of the Earth, equate wood burning with noxious
emissions and environmental degradation. They maintain that garbage
and processing waste should either not be generated in the first place
or
should be recycled. Energy conversion is not considered recycling,
yet
the facts show it to be a better option than burning of 40 million
year-old
fossilized biomass, at least for the next few decades until energy
becomes cheaply available without using fuel. Even then, there will
always be byproducts of human endeavors that can best be disposed of
by burning, and where heat is needed, combustion is the most direct
approach to getting it, outside of direct solar radiation.
The New York State Energy R&D Authority gave up on trying to get
any large wood-fueled installations permitted. Public sentiment is
against
"incineration" of any kind, and burning wood waste is seen in the same
light as municipal waste.
The Northwest Power Planning Council has dismissed biomass as a
potential future source of energy. In fact, in their 40 page draft
plan
(vol.I), only two sentences are devoted to biomass, and its projected
contribution to the regional power pool is only 0.6% of the total!
Cost
and public sentiment seem to be keys to that decision.
Heat from waste wood in the area can directly replace electric heat
- at
one ninth the cost. This is not currently being factored into the Regional
Power Plan, despite the fact that already one fifth of all Washington
State households heat their homes with both wood and electricity,
displacing up to 1,000 MWa of electric power in the region. [41A, 6]
In
other parts of the country, the cost advantage of wood heat over electric
heat is more like 30 to 1 and rising.
Instead, 76% of the new power sources under development in the region
are generators that run on natural gas, a fuel imported primarily from
Colorado and Alberta. Yet the quantities of biomass residues produced
each year in the region are equivalent to 7,600 MW of electric
generating capacity, almost twice NPPC's projected new generator
capacity requirements to the year 2010!
The standardization and coordination of regional and national
regulations for biomass-fueled boilers is complicated by several
factors:[80]
* Each state may require different levels of emission control to satisfy
their State Implementation Plan.
* Each state has a different level of industrialization.
* Each state may pursue promotion of energy resources most abundant
in their area.
* The impact of emissions varies with terrain and climatic factors.
"While the potential for conversion to wood-energy is high, fossil
fuel sources will remain prominent in some areas as long as the
current state regulatory scenario is perceived to be
detrimental."[80]
There has been major reduction in the number of new wood-waste
combustion systems installed in the Puget Sound region in the last
7
years. Much of this is due to (1) state regulations to discourage
residential woodstoves and (2) Puget Sound Air Pollution Control
Authority's (PSAPCA) strict 1990 emissions regulations on new
wood-fueled boiler installations. The latter regulations allow new
systems to emit only a tenth of the particulates that the older systems
are permitted. This has prohibited small to medium sized
installations of any waste-wood-fueled system now on the market
because of the extremely costly cleanup equipment required to
achieve compliance (cyclone separators, baghouse filters, electrostatic
precipitators, etc.). Even the new state-of-the art 46 megawatt biomass
power generating facilities in Kettle Falls, WA, just barely meets
this
standard.
Despite great improvements in residential woodstove design over the
past 7 years, Most people assume that wood can never be burned
cleanly. Wood smoke has become synonymous with pollution in official
circles as well. A joint report by the State of Washington and the
U.S.
Environmental Protection Agency, "Toward 2010: An Environmental
Action Agenda", recommends that Washington State "Phase out
residential wood-burning stoves and inserts." The logic is that, "A
decade or so ago, heating a home with wood was considered a clean
alternative and an answer to the energy crisis. Today, residential
wood
burning is widely recognized as one of the most significant sources
of air
pollution--especially of small particulates--in our state."
There seems to be little interest in the results of a study commissioned
by the local Bonneville Power Administration, Environmental Impacts
of Advanced Combustion Systems, which proved that a residential
cookstove designed by Northern Light R&D burned wood 65 times
cleaner than the average woodstove and cleaner than most oil and gas
fueled residential furnaces, without contributing to the greenhouse
effect. The disturbing destruction of our remaining virgin forests
has
totally overshadowed the fact that forests can be a renewable crop
and
that large quantities of biomass waste of all kinds are continuously
being
produced and need to be disposed of.
Biomass fuels are produced wherever plant material is harvested,
processed or used, generally in millions of decentralized locations
throughout the country. They exists in such varied location and form
as
logging slash, agricultural crop residue, stockyard manure, food
processing remains, demolition debris and cabinet maker scraps. No
national distribution system is possible. Biomass fuels are locally
generated and must be locally utilized to be cost-effective. While
this
has economic advantages, it does not lend itself to centralized
coordination, and therefore is not so attractive to large corporations
and
governmental bodies.
Local processing and hauling operations are springing up wherever
waste has become an expensive disposal problem, but a well-established
and dependable fuel delivery service does not exist in many areas,
simply because there has not been the customer base of biomass fuel
users.
Without an existing fuel delivery infrastructure, potential customers
are reluctant to invest in a biomass energy system. This situation
also dissuades potential investors, manufacturers and marketing
firms from getting involved in the biomass energy game. The
prevailing attitude is, "Let the industry get further developed...Then
I will get involved." Now is the time for government and industry to
make major investments in the future of a decentralized biomass
energy industry to get it established and over the initial hurdles.
Fully automated fuel feed systems are expensive. Currently available
fuel feed systems are individually designed and fabricated for the
logging
industry. They are too complicated, over built, and expensive for such
small-scale systems as we have determined to be the best market. This
has been a major factor in preventing greater utilization of bioenergy
on
the commercial scale. A fully automated fuel storage/feed system of
present design could make up two thirds of the total cost of an installed
commercial wood-fueled boiler system of Agni size. Such an investment
is not cost-effective in today's short-term investment market. Northern
Light R&D has done considerable research in this area and has
developed a simple system which should drop the cost by 50 to 75%.
Additional funding will be needed to perfect the most economical fuel
feed system and open up the market to the widest customer base.
Defects of Available Technology
All indications point to a very promising future for bioenergy, but
the
industry is not yet prepared with answers to the many perplexing
problems confronting the would-be customer. Equipment is complex,
costly and too often plagued with aggravating problems and limitations.
Variations in fuel type, size and moisture content are not easily
accommodated in any one combustion/fuel-handling system. Much of
the potential fuel is too wet, too stringy, not uniform enough in size
and
moisture content or too high in ash and dirt content for existing systems
to handle at all. Most biomass combustion systems available at present
have a very narrow range of clean combustion, with a turn-down ratio
of
only 2 or 3 to 1. This makes them inappropriate for many applications
that have seasonal variations in heat demand.
All wood-burning boilers on the market today have difficulty meeting
increasingly strict emissions regulations without costly stack clean-up
air
pollution controls. Typical flue gas scrubbing and conditioning
equipment costs average from 25 to 40% of the total capital costs of
coal-fired plants and consume large amounts of power
(approximately 3% of the total unit output). [Biologue, Dec'88/Jan'89]
Fuels with moisture content higher than 40% have unacceptable
emissions problems, and nothing currently available can even burn fuel
above 66% moisture content. Yet there are huge outdoor stockpiles of
wood-waste throughout the country that are wetter than that. Because
all of the moisture in the fuel is vaporized and sent up the stack,
net
system efficiencies drop to unacceptable levels with high moisture
fuels.
Controls are generally very basic and incapable of analyzing changes
in
multiple variables to self-correct imbalanced conditions and optimize
combustion conditions. None except the very largest industrial
installations even monitor fuel/air ratios.
A boiler with fully-automated feed system is so expensive that it has
not
been cost-effective in sizes below 10 million Btu/hr, but this size
represents the largest customer base. For a heating system the size
of
Agni (1.5 MBtu/hr) a fully-automated feed system could amount to 75%
of the total installation cost.
If, in addition to a hassle-free fully automated feed system one requires
a
sophisticated microprocessor control system for feed, combustion, boiler
monitoring and control, with multiple alarms; automated ash-removal;
the capacity to automatically handle various low-grade fuels; a high
turn-down ratio; very low emissions to meet strict governmental
standards; and high efficiencies even with wet fuels; they will find
nothing on the market at any price.
But most of these problems have been solved and extensively tested
in the 10 prototypes Northern Light R & D has developed over the
past 20 years. The remaining challenges have been addressed in the
most recent improvements to the Agni design, and in new approaches
to
inexpensive fuel handling described at the beginning of this paper.
The experts seem to agree that, at the present time, the best way to
recycle wood waste is to convert it to energy by combustion. There
is
not a sufficient demand for alternative uses such as composting or
animal bedding to absorb the large amounts of wood waste produced in
the U.S. The primary forest products industry is already doing a good
job
of generating its heat and process steam requirements through the
combustion of its wood waste. The secondary forest products industry
could generate a good deal more of its heat and process energy needs
by
wood combustion. Beyond that, the potential market is determined by
numerous factors that have been well researched for the economics and
capacities of presently available systems.
Four market studies have been carried out in different areas of the
country to define the existing and potential users of commercial and
industrial wood fueled boilers.[5], [48], [48A], & [77]
The SERBEP 1986 study [5], "Analyzing Market Constraints in Woody
Biomass Energy Production", determined that there were about 5843
reported industrial wood energy users in the continental U.S.. A 1977
study [80] reported about 10,500 wood-fired boilers installed nationally.
The discrepancy can be attributed mostly to the fact that close to
half of
these were smaller than industrial size. In 1977, wood-fired boilers
represented only one-third of one percent of the total national boiler
installations. Approximately 76% of fossil fuel boilers installed in
the United states are rated at below 1.5 million Btu/hr.
The largest market for wood-fired boilers is below 1.5 MBtu/hr, but
this
is generally below the cutoff considered cost effective for presently
available systems and below the size of concern to half of the studies.
Yet this is the most appropriate market for decentralized collection
and distribution of biomass wastes and application of the Stirling
engine linear alternator technology for cogeneration.
The SERBEP study [5] identifies five important constraints preventing
wood energy use in the Southeast:
1. a general lack of knowledge concerning industrial
wood energy
and a poor perception regarding its application
2. high capital costs of conversion to a wood energy system
3. problems associated with wood fuel handling
4. concern over dependable long-term supply
5. lack of knowledge about the proper operation
of a wood energy
system
A major constraint identified by this study is a lack of knowledge
about industrial wood energy and a poor perception towards its
implementation.
The lack of confidence in the availability of outside sources of wood,
of funding for conversion to wood, and of incentive to convert to
wood (as well as industries requiring outside wood sources) are
speculative reasons for the slow growth of the wood-fired boiler
population. Costs of conversion to a wood energy system is perceived
as the most significant barrier.[5]
Today, conversion to a wood energy system may be two to seven times
the capital cost for an oil or natural gas energy system, and twice
the
capital investment of a coal energy system. Fuel handling costs are
a
significant part of this high initial investment. However, Northern
Light
R&D has developed a much simpler low-cost option for automatic
feed.
A study in South Carolina [77] concluded that if the cost per million
Btus from wood residue is at least $3.65 less than the cost from fossil
fuels, conversion for a minimum or larger industry becomes a real
possibility. However, these figures were based on very costly feed
system and boiler installation costs and on 65% boiler efficiencies,
rather
than the 90%+ efficiencies of a Northern Light system.
This means that the wood residue prices can be 38% more for the
same energy yield. Taking representative commercial fuel prices from
the Pacific Northwest as an example, natural gas is around $4.44/MBtu,
which would give an appropriate cost for wood waste at $1.09/MBtu.
The most expensive wood chips are delivered in the area for
$0.94/MBtu. Therefore, even for presently available wood-fueled
boilers and costly feed systems, wood energy is a profitable
investment in the region.
Looking at the potential for residential cogeneration, we have a different
set of economics. If a home or apartment energy system produces
electricity and replaces a central heating system, hot water heater,
cookstove, and perhaps also supplies refrigerator cooling and
air-conditioning, hot air for the drier, and waste disposal, a more
expensive system could be cost-effective. Adding up all the costs of
the
individual appliances that are replaced and their combined energy costs
show a major investment indeed. This potential deserves serious R&D
work.
Because biomass fuel is available in decentralized locations, and
transportation costs are a big factor in both disposal costs and potential
fuel delivery economics, small commercial systems afford significant
advantages.
There are over 1480 landfills in the 13-state Southeast Region. 55%
of
these are small (<30,000 cu.yd./yr.). In MS, WV, KY, and GA there
are
537 small landfills and only 3 large (600,000 cu.yd./yr.). If one third
of
the waste going to these landfills can be cleanly burned for energy,
the
average size of incinerator needed by most Southeastern counties
would be less than 10 MBtu/hr. If a more decentralized cogeneration
siting approach were taken, even smaller units would be appropriate.[72]
One Agni-sized boiler (1.5MBtu/hr) could serve a community of
1,500 people. (@ 5,000 Btu/lb with recycled beverage containers
removed, and about 33% moisture.)
Small biomass combustion systems can have permitting advantages. In
some areas, permitting for larger systems (over 12 tons/day) is much
more difficult, due to classification as a potential industrial pollution
source.
"Small, hospital-sized incinerators such as the Therm Tech in
Fairbanks (Hospital) could provide opportunities for using solid
waste to heat community buildings or schools in rural Alaska. Small
communities in Alaska are experiencing difficulties in properly disposing
of MSW, particularly where high water tables and lack of suitable cover
cause landfill problems. Most waste-to-energy facilities use incinerators
that are large, continuously fed systems that are too big for small
communities. An incinerator the size of the Fairbanks unit could process
2.5 tons of solid waste per day on two shifts, providing adequate disposal
for a community of 1,000 people." [3]
BioBurn Corp. of Utica, NY, is a sales representative and distributor
for
over ten different manufacturers of solid fuel combustion equipment
ranging from 50,000 Btu/hr to 1000 boiler horsepower. They are
constantly seeking and testing new equipment to find a good range of
systems that can meet the needs of different users. They contend that
there is no wood chip combustion equipment under 100 hp (3.3
MBtu/hr) that is both economical and technically reliable. [93]
This observation is echoed by numerous authorities in the field. The
report, "Stack Emission Standards for Industrial Wood-Fired Boilers"
[80], concludes,
"After review of the current situation, it is apparent that efforts
to
promote wood energy use is best directed to small boilers. In
addition to representing over 90% of the total number of boilers, the
0-1.5 million Btu per hour capacity boiler, and small (less than 10
million Btu per hour) regulated boiler, offers the following
advantages for conversion to wood-firing:"[80]
* "The greatest number of wood-fired boilers are fueled using residue
generated by production at the facility. This residue does not have
to be
hauled off-site, thus reducing the deleterious effects of other
contributors of pollution e.g. fugitive dust. There are few large facilities
which generate sufficient wood residue to be energy self-sufficient."[80]
* "Wood-fired boilers fired with residue from the production facility
are
immune from wood shortages and fuel transportation problems."[80]
* "Small wood-fired boilers are easily switched to fossil fuel firing
in an
emergency situation compared to larger boilers of the same design and
operation."[80]
* "Small boilers will have minimal impact on the local ambient air
quality singularly or cumulatively (assuming normal distribution of
small
boilers). This conclusion is supported by modeling results."[80]
* "Small boilers will not impact local wood fuel supplies (assuming
normal distribution of small boilers)."[80]
* "Small boilers are best suited for retrofit and are the most flexible
compared to large boilers of similar design and operation."[80]
"Other findings of this study include:
* "A correlation between the wood-fired boiler population in a state
and the state's particulate emissions standard is not readily
apparent."
* "Potential users of biomass are not aware of the availability of
wood, the operation of wood-fired systems, the applicable air
pollution regulations, or the permitting process."
* "Efficient operation of the boiler and associated equipment will
also result in the lowest emission rates."
* "Innovative methods of operation can eliminate the requirement
for air pollution control equipment or at least reduce the cost of
control equipment."
Each statement is supported by detailed discussion in the report.[80]
Greatest fuel savings and payback within 2 years can be realized in
commercial installations such as greenhouses, hospitals, schools,
county seats and other public buildings, laundries, factories, wood-
and agricultural-processing facilities, shopping centers, hotels,
resorts, and nursing homes, wherever there is nearby biomass waste
and space to store the fuel.
Small, efficient, cost-effective cogeneration systems fueled with biomass
promise the greatest near-term potential for solving the world's energy
needs of any available renewable energy option. The energy and
environmental crisis we are facing on all fronts has forced us Americans
to reevaluate our "mega" approach to problem solving. Utilities are
suddenly looking to conservation and efficiency as an alternative to
building more power plants. Decentralized electric power cogeneration
is
preferred to wasteful large central power plants. We must use less,
use
it more efficiently, reuse it again and again. The operating principles
are Conserve, Reuse, Recycle.
Applying these principles to energy and waste recycling, we must
conclude that small decentralized settings are the best cogeneration
sites. A community could recycle local biomass, household waste and
low grade paper into energy for a recycling operation, providing heat,
mechanical power, and electricity for transforming recycled glass into
foamed building insulation and roofing tiles, for an aluminum foundry,
pottery and glass blowing studios, etc.. The waste heat, too, could
be
recycled first back into the combustion air, then into process steam
or
used in a Laundromat, car wash, sauna, heated swimming pool or
greenhouses.
By recycling waste biomass into energy, recycling waste energy
back into the combustion process, and using the waste heat again
and again, increases in efficiency are possible that are many times
what is presently achievable.
According to the Union of Concerned Scientists, "Buildings use more
than one-third of the energy
consumed in the United States. Heating and cooling systems account
for 60% of this energy." Of that
amount about 20% is reasonably recoverable with the use of appropriate
heat engines. This amounts to
about 15% of the electricity requirement of the country.[37A] There
are 54 million single-family dwellings
in the U.S. which could take advantage of cogeneration to generate
much of its power from the nation's
waste .
Electric utility customers at the end of the power grid are losers for
the power company. Electricity that
makes it to the end may be 15% less than the power sent out of the
power plant, which in turn is only
about a third of the energy stored in the fuel. It would be far more
efficient to generate electricity right at
the remote site, with no transformer or line losses, using most of
the remaining valuable heat energy for
space heating, hot water, etc., by burning locally generated and continually
renewable biofuels.
Economical, reliable residential cogeneration systems are the key,
and this is what Northern Light &
Sunpower are currently investigating.
MSW has become a major disposal problem worldwide, and burying it is
no longer a viable solution. Incineration has just as bad a reputation,
despite the costly gas cleanup technology employed. Part of the
pollution problem is poor combustion (Dioxins, Furans, PAHs, PCBs,
etc.), and part of the problem is heavy metal and other contaminants.
With proper source separation, heavy metals can be eliminated from
most waste streams. Poor combustion requires in most cases an entirely
new combustion approach. Pyrolytic gasifiers are much better
technologies in this regard, but they are too costly and complex for
small
municipalities.
MSW incinerator plants presently tend to be very large (200 - 3000
tons/day) because of the complexity and cost of the equipment, but
there are significant advantages to small, decentralized installations:
1. Waste is mainly produced in local, decentralized homes and
businesses. Shorter hauling distances mean reduced disposal costs.
2. MSW is a valuable fuel which can best be burned in numerous smaller
decentralized locations where heat and processing steam can be utilized,
along with cogeneration.
3. Large garbage-collection sites have traffic congestion, odors, large
volumes of emissions, and strong public opposition.
4. Many municipalities do not generate enough waste to support a large,
expensive disposal installation.
There needs to be more thought and support given to the clean
conversion of municipal waste to energy in small, decentralized
community settings. Existing systems are prohibitively expensive
and unreliable. Because Northern Light's technology is so clean and
simple and capable of handling such a diversity of fuels, it should
be
ideally suited for such application.
The Biomass Energy Research Association (BERA) recently testified
before the House Committee on Science, Space, & Technology,
Subcommittee on Environment,
"In combustion research, a need still exists for improved solid waste
incinerators that meet environmental requirements and cost goals.
Research should be focused on systems that can be used for
economic disposal of MSWs in small communities. Research is also
needed to reduce the emissions of solid waste disposal processes..."
Northern Light R&D has done this research and has come up with a
number of major improvements. Gasification and combustion processes
are separated by preheating to very high temperatures the fuel and
the
air for pyrolysis and combustion and by controlling primary and
secondary air through a microprocessor linked to various sensors and
dampers. This allows extremely wet material of diverse physical
properties to be burned completely without carrying ash and other
particulate out the stack. In tests burning RDF (Refuse-Derived-Fuel)
pellets, excess air was brought down to ½%, while maintaining
low
carbon monoxide emissions (0.02%). This is unprecedented in biomass
combustion. Only large state-of-the-art gas furnaces approach such
efficiencies.
Further advantages to this staged combustion approach are reduced NOx
emissions and elimination of ash-slagging problems associated with
low
melting temperature ash from MSW and agricultural fuels. This latter
problem has plagued the industry and is aggravated by the larger system
approach.
The smokeless, odor-free exhaust is further scrubbed of fly-ash in the
condensing boiler, where moisture from the fuel is precipitated out
as
clear water. There is no need for the costly stack clean-up equipment
currently used in the industry. Because the whole system is so
elegantly simple, it should be able to meet the disposal and heating
needs of small municipalities at one quarter the cost of systems now
on the market and easily pass the most stringent emissions
regulations.
A prototype residential cook stove developed by Northern Light R.&D.
(named "Helen") was officially tested by OMNI Environmental
Laboratories for the U.S. Department of Energy/Bonneville Power in
1986, burning green sawdust of 44% moisture content, with no
catalytic afterburner or stack cleanup of any kind. [40]
Its particulate emissions were 65 times cleaner than the average
state-of-the-art woodstove, several times cleaner than the best pellet
burner, and considerably cleaner than the average oil furnace.
Carbon Monoxide emissions in the stack gases were 1/7500th of the
Federal Auto Emissions standard, 1/100th of the gas industry's
standard for "CO-free combustion", and 1/2 of the EPA's standard
for acceptable 24 hour indoor air quality.
These emissions are less than half of the most stringent PSAPCA
standards for new wood and refuse burners. Since this prototype, two
improved versions have been built.
The most recent 150,000 BTU/hr hot air furnace (Vaagner) is capable
of
burning the wettest wood (logs, chips, sawdust, etc.) extremely cleanly
and efficiently. Primary and secondary air is precisely controlled
by a
state-of-the-art microprocessor continually monitoring input from
various temperature and position monitors and an oxygen sensor in the
exhaust stream.
Flue gases are usually so cool that clear water is condensed out in
the
heat exchanger. This reclaims the heat of vaporization and allows wet
fuels with over 70% water to be burned as efficiently as dry ones.
No
other combustion system yet tested comes close to this capacity. (The
condensate poses no disposal problems in sewers or septic tanks. It
contains no sulfur and is less acid {pH 4.5} than rainfall near many
fossil-fueled industrial areas of the world {pH 3.5}) The unit can
be
fitted with a large hopper to hold several day's fuel at one loading.
It will
also burn pellets cleaner and more efficiently than commercial
pellet burners, and can be operated without electricity if necessary.
Most commercial systems presently available in any size produce
unacceptably smoky emissions and drastically reduced efficiencies when
operated at half or third of rated output. In contrast, Northern Light
furnaces burn as clean, and with higher net efficiencies (over 95%
with
wet fuels!) when turned down as low as 7% of full power output (14
to 1
turndown ratio). No other system can even approach this versatility.
This feature alone opens up a much greater market than ever before
for biomass energy applications.
State-of-the-art Silicon Carbide heat exchanger transmits heat to the
incoming combustion air 6 to 10 times as fast as firebrick. Extremely
strong, durable, fatigue- and shock-resistant refractory ceramics are
used
in the combustion areas, High-temperature ceramic fiber insulation
is
used along with concentric heat-exchanger shells to move the heat
where it is needed to optimize pyrolysis and combustion and to eliminate
excessive heat which produces slag buildup and ceramic fatigue.
Counterflow gravity-stratified condensing heat-exchangers, specifically
designed for high-ash biomass fuels, scrub the exhaust & reclaim
the
heat of vaporization of the moisture in the fuel. Thereby wet fuels
can be
burned as efficiently as dry. The thermodynamic properties of these
heat-exchangers increase natural draft and eliminate the need for
exhaust fans (and their tendency to send unburned embers, soot and
ash
to clog up the heat-exchanger and increase particulate emissions).
All
soot is burned in the combustion zone. The remaining fly-ash is removed
from the exhaust stream through a combination of centrifugal/gravity
precipitation and steam-condensation entrainment, which continuously
scrubs the lower heat-exchanger surfaces. We have built hot air and
hot
water systems and have designed a low pressure steam boiler.
A gravity feed hopper operates when the power is out and takes any
size, shape and configuration of fuel without hang-ups. Counterweighted
hopper flaps prevent uncontrolled combustion and heat loss in the upper
hopper. They also indicate status of fuel reserves, turn on fuel feed
in
automatic feed systems, facilitate smoke-free loading of the hopper.
The
lower hopper is vertical sided with no constrictions to hang up stringy
hogged fuel or logs.
We have developed a powerful but inexpensive central microprocessor
control system with built-in analysis and correction routines and an
alarm system. In both the commercial Agni system and the residential
cogeneration system it will control the fully automated feed system,
automatic ash removal system, and dual-fuel switching functions.
With the new fuel feed system, the economics of the installed package
is
very favorable compared to natural gas, and no contest when replacing
oil or electricity. We expect to offer a complete Agni 1.5 MBtu/hr
system, with condensing boiler, fully automated computer control, ash
removal and fuel handling systems for under $90,000 installed.
Eventually, with the development of an even more economical feed
system and optimizing of all the components in the system, the total
package installed cost could be substantially less.
*****POPULATIONS:*****
*Large Cities > 100,000
**Medium Cities 5,000 - 100,000
***Small Cities 800 - 5,000
Additional wood waste is generated by private tree services, land
clearing and construction projects and by individual homeowners.
"For city forestry work, wood waste will also increase as Iowa's city
trees, which are old and large, are gradually removed and replaced.
Wood waste can be a particular problem after major storms--as the
recent ice storm in Des Moines proved by yielding 18,000 dump
truck loads of wood waste. Up to 40% of an Iowa community's land
surface is covered by street, park and yard trees."[97]
This is the situation in many cities throughout the US. Tree trimmings
and land-clearing debris could be diverted from landfills to produce
significant energy.
Presently, only 25 firms in Iowa have installed wood energy systems.
Iowa Department of Natural Resources predicts that wood waste in Iowa
has the potential to produce about 10% of the state's energy needs.
This
could replace about $300 million in fossil fuel energy expenditures
now
flowing out of the state every year.
"The U.S. Forest Service estimates national forest wastes at one billion
dry tons {2,400,000 "AGNI"}. In Minnesota alone, 7.2 million tons of
wood residue is available every year for fuel...Hennepin County in
Minnesota (part of the seven-county metropolitan Twin Cities area)
produces almost 5,000 tons per day of burnable paper garbage. This
waste could be effectively converted to briquette fuel that would
provide 80 billion Btus of heat energy daily...This 80 billion Btus
of daily
untapped heat energy is equivalent to that produced by 500,000 gallons
of fuel oil, which, at $.90 per gallon, would cost $450,000 per day,
or
$2.5 million per week!" [From a brochure by BMSI, Briquetting
Marketing & Services, Inc., Lee Machines, 7126 Newton Ave. S,
Richfield, Minn. 55423]
Minnesota has a vast biomass resource of six million acres of peat,
equivalent to 12 billion barrels of oil. [10] This is another untapped
resource which should burn well in an Agni boiler.
Jim Fisher of Energy Resource Systems, MN, (they install wood-fueled
boilers in the region) says, "There are 'islands of opportunity' for
wood
users. 'A lot of people think they have to be located in the woods
to
burn wood and that's just not true.' Fisher estimated that in the Great
Lakes region, more than one half of all the states contain wood supplies
that could be utilized within a 100-mile radius at prices competitive
with
conventional fuels. 'The main thing is that a user has to know the
fuel: its
moisture content range, the correct particle size for the burner chosen,
and so on.' Fisher added that it's worth paying $2 more per ton for
clean
fuel. 'We've had an entire 1958 Buick emerge from old sawdust piles'
If
the bumper gets through the system--or even a bolt--Fisher said the
system will have to be shut down, costing far more than the savings
the
company attempted to achieve by purchasing a cheaper, dirtier
fuel."[92] {That is a big advantage to Northern Light's belt-feed,
gravity-feed hopper and non-auger ash-removal system combination.
Bolts, rocks and dirt in moderation are no problem.}
Aitkin Iron Works in northern Minnesota has developed a district
heating plant fueled with wood. Dave Haaskamp, the plant manager, is
enthusiastic about the concept: "'It's the logical next step in state
economic development. Why send all the revenues associated with fuel
oil out of state?' Haaskamp points out that timber is already a vital
industry in Minnesota. It accounts for one half of the state's economic
base, employs approximately 55,000 people and generates $2 billion
in
revenues from wood products sold each year. Haaskamp believes 'the
state could increase the number of employed to 100,000 just in the
fuels,
forest management sector alone,' by utilizing wood in small heating
plants. He concludes that any community that has a business that is
burning 75,000 gallons of oil 'ought to be looking into wood.' Each
community could develop its own energy farm or hybrid aspen lot to
produce an assured supply of fuel." [92] {75,000 gallons of oil would
be
just about the heat output of a 1.5MBtu/hr Agni at average 50% load.}
Corn cobs in the midwest are an extremely attractive fuel source, selling
for $5 -$10 a ton ($0.36 - $0.71/MBtu) in Ohio. [10, 1987]
In 1990 Wisconsin's Wood Waste Energy Incentive Program awarded
grants for 26 wood energy projects, 19 involving installation of new
wood energy systems. [96, 10/90] 40,000 tons of wood waste are
consumed annually by these projects, retaining over $1 million a year
in
local energy expenditures. Through surveys conducted by the Energy
Bureau, it was determined that 250 to 300 businesses in the state are
generating a significant amount of excess wood waste which could be
used as fuel. Many of the respondents indicated that they were
beginning to experience difficulties in eliminating their waste
economically. Major concerns were rising landfill costs and/or
reduced landfill availability. [96]
An entire school district in northern Wisconsin heats with wood, paying
$21/ton for wood chips in 1985. Superintendent Tomasich is enthusiastic
about wood heat and its future potential: "The farther north one goes
in
Wisconsin, the lower the fuel costs, as there are more sawmill operators.
A lot of wood is just stockpiled in the field or hauled to the swamp
as
unwanted waste." Tomasich said he's disappointed that more industries
and institutions haven't investigated wood burning. "It's true, there's
a
relatively high first cost, but the benefits -- cheaper costs over
conventional fuels in the long-term and recycling of waste wood --
outweigh this."
Effect Of Wood Combustion On Climate Change
"Just as there is controversy in the need for mitigation of climate
change,
there is controversy over the benefits of using wood fuel for mitigating
climate change. There are those who look at wood combustion as part
of
the problem rather than part of the solution. The most efficient way
to
obtain energy from wood by direct combustion is to recover heat, steam
or electricity. Combustion of wood does return carbon to the
atmosphere. however, if the wood burned is continually replaced
through reforestation, this carbon is continually recycled and there
is no
new carbon added to the atmosphere or carbon sinks. To the extent that
wood is used to replace fossil fuels, there is a direct reduction of
new
carbon in the atmosphere from fossil fuel combustion. Thus wood that
does not have other uses should be used for energy to replace fossil
fuels."
"However according to Rogers and Fiering (Rogers, 1989), man's
involvement in contributing excess carbon to the atmosphere is minimal
and of the contributions from civilization, contributions from biomass
are a significant portion. Their reasoning is based on net primary
productivity of terrestrial ecosystems of 60 billion tons of carbon
per
year. This anthropogenic "excess" is composed of fossil fuel combustion
(58%), biomass fuel combustion (12%), crop residue burning (1%),
grassland burning (20%), shifting agriculture (4.2%), cement production
(1.4%) and solid waste production (1.1%). Total excess is estimated
at
6.5 +/- 1.5 billion tons of carbon. these annual fluxes are viewed
against
an estimated stock of 560 +/- 100 billion tons in the living biomass
systems. Viewed in this perspective, man's contribution from burning
biomass are in the same category as burning fossil fuels, and man's
contribution to atmospheric carbon is small in comparison to nature's."
"Viewed from another context, such as that expressed by Houghton
(Houghton, 1989), the atmospheric carbon dioxide balance hinges on
the
annual anthropogenic emissions of this gas, which are about 70% from
fossil fuels and 30% from forest abandonment from shifting agriculture.
Burning biomass from forest lands that are managed on a sustained yield
basis is part of the solution, since the carbon dioxide released from
burning and otherwise consuming wood is constantly recycled over a
short time frame. I believe this scenario is more realistic."
"Regardless of the source, carbon has been accumulating in the
atmosphere at the rate of about three billion tons annually (Houghton,
1989). If we can reduce the carbon dioxide flux into the atmosphere
by
three billion tons annually, the carbon dioxide level would stabilize
around the present level. The major sources of which man has some
control is reducing the level of combustion of fossil fuels which releases
5.6 billion tons of carbon into the atmosphere annually, halting
deforestation which releases 2.5 billion tons of carbon, and
implementing a reforestation plan which might store 2.5 billion tons
of
carbon (Houghton, 1989)." [77]
"Despite squabbles over the cost, the 1970 clean air act and subsequent
amendments went a long way toward cleaning up industrial emissions.
But they failed to neutralize the rain. From 1970 to 1988 man-made
emissions of sulfur dioxide in the United States decreased between
28%
and 30%, according to the U.S. National Acid Precipitation Assessment
Program (NAPAP). The 1990 amendments to the act mandate that by
the year 2000 such emissions be reduced to 50% of 1980 levels. It
seems scrubbers installed to remove fly ash from smokestacks also
removed the alkaline calcium that used to help neutralize acid rain.
[62A, 1992] {A condensing boiler largely eliminates this problem.
Burning sulfur-& chlorine-free biomass solves the rest.}
Germany will reduce its CO2 emissions by 25% by 2005, it was
announced at the Second World Climate Conference. [The FAO review,
Ceres (via Delle Terme de Caracalla, 1-00100 Rome Italy).] Japan &
the
European Community agreed to stabilize CO2 emissions in the same
period, but not the U.S.A. Denmark is aiming for a 20% reduction by
2005 and 50% thereafter. [World Watch, 7/93]
Fossil fuels supply 85% of the energy in the European Community.
[source: EC Energy Monthly, June'91]
Seri (the Solar Energy Research Institute) just completed a 14-nation
survey for the IEA (International Energy Agency) on the status of
bioenergy and greenhouse-gas reduction programs. "Most of the
countries responding to the survey lack a formal policy on the
greenhouse effect. But seven of them specifically noted that reducing
or
stabilizing carbon dioxide emissions is a national environmental goal.
Five countries mentioned a plan or policy to levy emission fees or
pollution taxes as an incentive to limit greenhouse-gas buildup. Only
three, including the United States, mentioned setting emission
standards." Member countries are Austria, Belgium, Canada, Denmark,
Finland, Italy, Japan, the Netherlands, New Zealand, Norway, Sweden,
Switzerland, the United Kingdom, and the United States. [75] {Why not
England, France, Australia?}
Eleven cities from three continents are negotiating proposals for actions
to reduce the risk of global warming. Portland, San Jose, Miami, Denver,
Minneapolis-St.Paul, Ankara, Turkey; Copenhagen, Hannover &
Saarbrucken, Helsinki, Toronto & Ontario. [Source: Calgary Herald,
quoted in Clearing Up, June, 1991]
The push is on in California, Europe & elsewhere to substantially
reduce
CO2 emissions. This should favor biomass, especially in conjunction
with landfill methane (a worse greenhouse gas) problems. [10,
May/June,'91]
Cause of Emissions In Biomass Combustion
"The amount of particulate matter leaving the stack depends primarily
on fuel type and boiler operation. The type and amount of fuel and
ash
content, as well as size and consistency, affect boiler operation and
emissions. Oversize pieces burn slowly and are difficult to distribute
in
the furnace. These factors contribute to higher particulate loading."[11]
{A wide variety of fuels are burned very cleanly in the Northern Light
systems, with combustion parameters optimized by the microprocessor
controls, high ash automatically removed, and suspended particulates
precipitated throughout the system.}
"The worst possible example of inappropriate fuel feeding is to slug
load
or batch feed a furnace. {like a woodstove or hand stoked boiler} The
best situation is to carefully meter and control feed rates for each
fuel
that is fired on a continuous basis and further, to ensure that the
air/fuel
ratio for each fuel fired is in an appropriate range to assure complete
combustion. These goals are often very difficult to achieve, particularly
when solid fuels are co-fired. A major limitation in feeding of solid
fuels is that there is currently no accurate technology available to
measure the feed rate of solid fuels on a continuous basis."[77]
{Northern Light's continuous gravity-feed hopper is perfect metering
without measuring. It feeds exactly what it burns. The burn rate is
controlled by the primary combustion air, not the fuel feed. The
air-fuel ratio is precisely controlled in the secondary combustion
zone
by the microprocessor in conjunction with the oxygen sensor.}
"Boiler design specifications - firing methods and fuel distribution
in the
furnace, air distribution and furnace configuration, furnace heat release,
residence time, and upward velocity - are set to increase the efficiency
of combustion and limit emissions. For example, lower gas velocities
in
the boiler reduce emissions by increasing the fuel residence time in
the
combustion zone and decreasing entrainment of fine particles by high
speed air. One way to decrease gas velocity is to decrease air flow
by
designing a larger grate area. These kinds of boiler design parameters
should be investigated when selecting for low emissions." [11] {These
are fundamental design-principles of the Northern Light systems.}
"Time and temperature are interdependent parameters for controlling
PICs (Products of Incomplete Combustion). It appears from the
literature that 1 second residence time at 1500 - 1600°F is adequate
to
control PICs (Lee, 1988). However, where co-fired fuels include any
hazardous wastes (i.e., waste oils), BACT may well require 2 seconds
of
residence time at 1500 - 1600°F"[77] {NL systems exceed these specs.}
"Finally, operator maintenance availability and level of expertise must
also be considered. Because boiler operating and firing methods have
a
direct affect on emissions, maintenance personnel available on site
must
be factored into the boiler selection decisions."[11] {The fact that
the
Agni system is fully computer controlled, with automatic fuel feed,
ash
removal and alarm system, and that it is a low pressure hot water or
steam system means that operator involvement is minimal.}
"Pollution controls should be considered as an integral part of the
design of a wood energy system because emission rates are influenced
by the type of fuel and the design of the wood combustion equipment.
Five major types of pollution control equipment are available--cyclone
collectors, wet scrubbers, dry scrubbers, baghouses, and electrostatic
precipitators."[11] {With the universal fuel capacity and condensing
boiler design of Agni, emissions clean-up equipment becomes
unnecessary.}
"Cyclone collectors are the most widely used emissions control device
for wood-burning systems...cyclone collectors are more suitable for
the
removal of large particulates--collection efficiency decreases in direct
proportion with particulate size. The smallest particles efficiently
removed with cyclone collectors are approximately five microns in
diameter...a more efficient secondary collector is often used behind
a
cyclone collector to improve the overall collection sufficiently to
ensure
compliance with air quality regulations."[11] "Several cyclones may
be
placed parallel to one another to form a multicyclone. These devices
are
often used with systems for which boilers are rated up to 50,000 pph
(48
MBtu/hr). Multicyclones have relatively low initial and operating costs.
A multicyclone and collector for 42,000 pph (40 MBtu/hr) costs
approximately $42,000. [92, '86]
"Baghouses are the most widely used type of secondary collector for
wood energy systems. They are not normally required nor
economically feasible on small-sized systems. {Yet some state and
regional (PSAPCA) regulations are so strict that a baghouse must be
used with existing systems to ensure compliance.} A baghouse contains
rows of cylindrical bags that filter the particulates from the flue
gas
stream. The trapped particulates are removed by temporarily reversing
the gas flow or by shaking the bags. Baghouses have a very high
collection efficiency - removing more than 99% of the particulate from
the flue gas stream." "The high temperature of the particulates
associated with wood energy systems can lead to fires and explosions
of
the filters. Baghouses are expensive to maintain: while baghouse
suppliers often claim the bags will last four to five years, most users
find it necessary to replace them every year or two."[92]
"Wet scrubbers and dry scrubbers are seldom used on wood energy
systems because of their higher capital cost and higher operation and
maintenance (O&M) cost. They may be needed, however, in areas not
meeting air compliance in particulates. When scrubbers are used, the
by-products of combustion are passed through a device that contains
a
chemical, such as limestone. The sulfur oxides react with the chemical
and are trapped before emission into the atmosphere. Electrostatic
precipitators are ineffective on wood-fired energy systems."[11] {They
are now used extensively, however, on large wood-fired power plants.}
Recent improvements in wet scrubber technology offer strong
competition to baghouses, as argued by Garry P. Isaacs of Procom
Environmental Inc. [77, '91], "Recent clean air legislation has provided
a
necessity for serious flue gas cleanup. As a general rule, the baghouse
has been recognized by the enforcement authorities to be the best
available control technology (BACT) for a biomass combustion process.
Since baghouses commonly burn down or explode, they have been
largely undesirable for biomass flue gas cleanup. For this reason,
in
the BACT top down analysis, a wet system is usually opted as best
technology for wood waste combustion. {The most effective scrubber
is a mist scrubber, which emulates the way a cloud precipitates out
raindrops, formed on nuclei of particulate - a costly and less effective
copy of Agni's condensing heat-exchanger.}
"While it is theorized that lower temperature will have a positive impact
on condensation and collection of PICs (products of incomplete
combustion), the literature contains no references to plant sites which
do
this purposefully. An offsetting consideration is that temperatures
above
the acid dew point must be maintained for fabric filters and for some
ESPs (Makansi, 1987)."[77] {This feature is purposefully built into
the
Agni system)
The level of particulate emission (lb/MBtu) attainable with the various
APC techniques are listed below:[80]
APC Technique: Lb/MBtu
Cyclone (MC) 0.6
Multicyclone (DM) 0.4
Wet Scrubber (VS) 0.05 - 0.3
Electrostatic Precipitator (ESP) 0.02 - 0.05
Baghouse (FF) 0.01 - 0.02
Helen (green fir; no cleanup) 0.017
Helen (organic particulate only) 0.007
"In order to meet state particulate emission standards cofiring with
a
fossil fuel is a reasonable alternative to APC equipment in some
cases."[80] Note that even cofiring with 95% natural gas and 5%
hogged fuel does not approach the strict 1990 PSAPCA standard.
"Typical flue gas scrubbing and conditioning equipment costs average
from 25 to 40% of the total capital costs of coal-fired plants and
consume large amounts of power (approximately 3% of the total unit
output)."[10]
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