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BIOMASS ENERGY 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
SECTION 2
Fossil Fuels Coal usually contains trace quantities of the metals Arsenic, Beryllium Cadmium Chromium, Manganese, Mercury, Nickel, and the radio nuclides thorium and uranium. Virtually all of the mercury leaves in the exhaust as vapor and is "extremely difficult to capture" with present APC equipment. While traces of metals including arsenic, cadmium, chromium, manganese, mercury and nickel have been detected in exhaust from wood combustion, the quantities are considered insignificant. [77] This means that as the EPA's more stringent emissions limits for these pollutants phase in tighter, wood fuel will be a more and more attractive alternative. Landfill gas is 50 to 70% Methane by volume, with the balance being carbon dioxide, with only trace amounts of other gases. Collection of this gas is costly, and done for regulatory compliance, not profit. The process equipment necessary for the conversion of the landfill gas to a pipeline quality product is costly and expensive to operate, and only feasible for extremely large sites.[77] No matter how we look at it, we humans are burning up the earth's fossil fuel reserves far faster than we should. Just focusing on the 45 billion tons of carbon we Americans release into the atmosphere annually by burning fossil fuels, it is hard to see how the greenhouse effect can be reversed without drastically curtailing our energy consumption. Biomass plantations are capable of fixing the most carbon in the shortest time of any natural mechanism. Such tree farming can capture 4 or 5 tons of carbon per acre per year. [83A] If half of the 200 million acres of marginal and unproductive land in the U.S. were dedicated to tree farming, one billion tons of carbon per year could be removed from the atmosphere. This is still only 4% of the fossil fuel carbon we must recapture to keep atmospheric carbon in balance. "Tests on oil wells in the South found that the oil and water mixture pumped to the surface has radiation levels 5 to 30 times higher than the level allowed at nuclear power plants. Oil drilling over the decades has brought radium to the earth's surface, causing contamination in oil-producing regions in the U.S. and worldwide. This discovery has led the federal government and industry to investigate the seriousness of the situation, which could prove costly for oil industries." [The Energy Report, A comprehensive, weekly review of energy policy, 12/17/90] _________________________________________________________________________ Biomass Fuels Global Patterns Of Fuel Use Except for nuclear power, all our energy comes ultimately from the sun. Our little earth gets only 1/5-millionth of the sun's radiation, which reaches us in 8 minutes and then mostly reflects off into space again. Of the solar energy that does penetrating the earth's atmosphere, only about one quarter of 1% is converted to biomass each year and yet this small fraction is about seven times the total flow of nonbiomass energy sources used by humanity.[9B] This biomass flow is equivalent to about 75 TW (1 terawatt = 1012 watts) or 75 billion tons of coal equivalent in energy per year. About 10% of this total is directly tapped by humanity in the form of food, fiber, feed, fertilizer, fuel, or feedstock. The remainder, however, provides critical services for global ecosystems by moderating climate, recycling water and essential nutrients, and performing myriad other ecosystem functions. These functions are no less vital to the economy and to human well-being than those provided by the more obvious societal uses of biomass. In addition, humanity has directly or indirectly co-opted as much as 40% of the pre-human biomass productivity of the world by disrupting natural ecosystems (Vitousek et al., 1986)."[9B] "The total energy directly supplied to humanity by biofuel is small compared to that supplied by fossil fuels although exceeding the energy supplied together by nuclear power and hydropower. These biofuels are largely used in developing countries and, within these countries, predominantly in rural areas. They are the traditional fuels-fuelwood, crop residues, dried animal dung, and scrub plants-that have supplied human energy needs for tens of thousands of years (Smil, 1983)."[9B] "Although such fuels today supply a relatively small fraction (somewhat over 10%) of global energy requirements in terms of total energy content, they meet the direct fuel requirements of a majority of the world's population. Most of the people in the world depend on these traditional fuels for most of their energy supply. Even more biomass combustion energy is used in indirect applications, as in clearing land by fire (Rambo, 1986). In consequence, it is fair to say that most of the energy used by most of the people throughout history has been in the form of biofuels, a situation as true today as since the discovery of fire.'[9B] "Most of this fuel today is used for the same tasks for which it has traditionally been needed-cooking and space heating-although as much as one-fifth may be used in industry (Ramsay, 1985). It is estimated, for example, that about half the world's households cook daily with biofuels (see figure 1.4). Approximate 30% of urban households and 90% of rural households in developing countries rely on such fuels for cooking (Hughart, 1979). Also true today is the observation that it is mostly women who participate in the biofuel cycle-usually sharing or having primary responsibility for fuel gathering, particularly when collecting is done for household use and not for sale. In nearly all cultures, of course, women do most of the cooking (Cecelski, 1985). In those many developing countries with relatively small urban industrial centers, biofuels not only supply the most people, they constitute the largest source of energy - exceeding in energy content the fossil fuels. Even a country with as large an industrial sector as India still relies on biofuels for nearly half of its total energy supply and more than 80% of its residential energy consumption. Poor countries such as Nepal, Bangladesh, and Botswana rely on biofuel for close to 90% of their total energy needs (Wood and Baldwin, 1985)."[9B] Each year over 60 million acres of tropical forests, an area the size of Florida, are degraded and destroyed and an area the size of New England changes from forest to desert. [statistics from Trees For The Future, Inc.] Every year we continue to lose forest lands the size of New York State and New Jersey combined. (New Forests Project Newsletter) The Winrock International Institute For Agricultural Development estimates that biomass energy could provide 10-20% of the new (electric) capacity needed by developing countries, and could do so relatively quickly. [10, 12/91] "In Britain alone 250 million tonnes of collectable organic wastes are generated each year from homes factories farms and forests with a total energy content equivalent to at least 25 million tonnes of coal or 8% of (British) energy needs." [45a] At the Weltkongress Alternativen Und Umwelt, Vienna, it was proposed that 1/5 of earth's unproductive land (i.e., desert & tundra) can be made to yield a renewable biomass harvest sufficient to supply most of the world's energy needs. [98A] "Bioenergy currently supplies 2% to 15% of the total energy demand in the 11 countries responding to a recent survey. Finland reported the highest contribution, 15%. The United States ranked tenth with a 4% contribution. Most surveyed countries projected significant growth in the development and use of biofuels; for example, the United States forecasts a 14% contribution by 2030." [75] In 1995, Sweden will begin phasing out the country's 12 nuclear power reactors. To replace this energy, Sweden is turning to trees. "Already, cull trees removed while improving forest stands, pruned branches, sawmill waste and bark account for 60 terawatt hours, or about 13% of Sweden's total energy supply. But with reduced crop subsidies to farmers and new taxes on industries that foul the air with SO2, CO2 and NOx, the nation is also finding that planting and using fast-growing trees can add as much as 35 more terawatt hours to the electricity grid with far less pollution than most other fuels. "Energy forests' may soon replace approximately one fifth of the country's grain production as farmers find trees to be a more economical use of their land." [National Arbor Day Journal, Jan/Feb, 1992] Economics of Logging Cleanup Research shows that one forth to one half of the total above-ground biomass of cut trees is not removed during conventional logging operations. This is too much biomass to leave on most sites. At the same time, environmental concerns for clean air dictate no broadcast nor pile burning in many locations. Here, then, is a huge supply of energy wood, provided it can be economically accessed. Using new prototype logging equipment designed for this integrated harvesting and multiple-product marketing approach, a test near Port Angeles, WA, showed that whole-tree harvesting can be profitable at a site that could not have been economically harvested previously. "In some parts of the country broadcast burning is avoided through cleanup credits for harvesting excess wood for energy...Dense brush in forests at urban-forest interface areas is being successfully harvested for energy, thereby providing a significantly decreased fire hazard to houses at the forest perimeter."[77] A 1988 study made in eastern Oregon found that logging residue recovery was quite profitable if done right. The study suggests that second-growth thinnings could supply five times the present consumption, given more efficient harvest methods. And it forecasts that the decline of old-growth logging in national forests will accelerate change, as equipment is perfected for harvesting second-growth small trees. In all, the residue supply was judged to be adequate for doubled or tripled wood-fired energy generation for the next few decades. "Timber sales contracts require the sale purchaser to remove logging residue to the land manager's specifications. Contracts will call for Yarding or Piling of all unmerchantable Material (YUM or PUM) exceeding a contract-specified size...YUM and PUM requirements significantly reduce the costs of logging residue to a fuel user. The common perception that logging residues are too expensive to use for fuel fails to take YUM and PUM contract requirements into consideration." [77] The volume of wood fiber available after harvest of a old growth timber sale in western Washington and Oregon is very large. From a typical 25-acre sale in the Willamette National Forest in Oregon, 30% of the total wood tonnage logged was chip culls and wood fiber logs. From this one timber sale, the weight of chip cull logs and larger wood fiber logs totaled almost 97 green tons per acre. Public agencies see advantages in encouraging energy markets for wood fiber, and are frequently willing to work out desirable contract terms as long as residue recovery does not delay reforestation. Some of their perceived benefits are the following: Energy markets provide a new source of revenue. · The risk of soil damage and the fire danger posed by slash burning are minimized because debris volumes are reduced. · Air quality regulations and public opinion frequently restrain slash burning. Removing wood residue may reduce the need to burn. · Collecting forest residues provides a stable, new source of employment in the otherwise cyclical wood products industry. · Energy markets may permit earlier thinning and stand conversion sales. About one-fifth of all hardwood trees are cull trees in the SERBEP area, and these cull trees comprise the single most important unused source of woody biomass which could be harvested for use as an energy material. According to a recent study conducted under the auspices of SERBEP, hardwood cull trees comprise 47% and logging residues constitute 29% of the annual wood energy available in the region. [44] Urban Wood Waste Several counties in Washington have been forced by new landfill regulations to truck their solid waste hundreds of miles to Oregon, and other counties will soon follow, paying $53.00/ton for the privilege and forcing tipping fees above $100/ton. This new situation is creating new opportunities for source separation of waste materials suitable for fuel. Urban wood waste recycling businesses are springing up throughout the region that take in tree trimmings and stumps from landscapers, excavation contractors, tree surgeons, etc. for a tipping fee considerably less than the local landfill. Some of these processors are amassing large piles of biomass with no place put them. Yard waste represents about 15-25% of the total municipal waste stream, and urban landscape services produce significant amounts of chipped tree prunings throughout the U.S.. There are over 200 tree service companies in the Seattle-Bellevue area, collecting an average of 10 cu. yd./day of chipped branches and trees. Most of this "waste" is currently delivered free to anyone who will take it. There are several large gullies and swamps that are being filled, but that practice is becoming illegal, dramatically changing the economics of disposal. This is ideal fuel for a Northern Light furnace, and represents the equivalent of 210 "AGNI". Wood recovered from urban landscaping, construction and building demolition has become an important fuel in California, where more than 800 MW of biomass capacity has been added at 57 plants since 1980 for an accumulated demand of 7.5 million dry tons per year. Independent power producers are adapting to urban wood fuels in increasing quantities. [Biologue, Sept,'91] Urban wood waste is available everywhere. Until recently. its separation and use as a fuel was limited to a few wood working industries. However, as landfill space for solid waste has diminished, incentives, uses and markets have been found for wood wastes in composition board, compost and fuel. Fuel markets in California have created an urban wood waste industry almost over night. Agricultural & Food Processing Residues Agricultural residues, including hulls, pits, straw and stalks, are not used in biomass power facilities because they are difficult to burn and cause problems with deposits in furnaces. [Biologue, 9/91] {Northern Light combustion systems are specifically designed to burn this vast fuel resource without the slagging problems.} The most likely wastes from the food processing industries for fuel use are: [72] * Peanut & sunflower hulls; rice and other grain husks; walnut, almond, pecan and other nut shells; and other dry shells. Moisture content is generally 4-10%(wet). * Pit waste from fruits which contain hard pits, such as apricots, cherries, peach, olives, etc. Moisture content is typically about 50% (wet). * Bagasse (pressed sugar cane fiber). Generally, quantities of this waste and process heat needs are much larger than the commercial size systems we are interested in, although there should be a sizable third-world market.
Pelletized Fuel Pelletized biomass fuels have advantages in dryness, uniformity, increased density, ease of handling and feed, and controllability of combustion. Since the pelletizing operation involves extensive fuel preparation & drying, and expensive equipment and labor in handling, considerable cost is added to the raw fuel. Pellets have the disadvantage of costing 5 to 10 times as much as lower grade unprocessed biomass fuels. Because the damp low grade fuels can be burned as efficiently as pellets in a Northern Light system, there is no reason to pay the additional expense for fuel. "A detailed account of the failure of a well-financed fuel-pellet venture in Livingston, Montana, was described (at the 1986 Washington Wood Utilization Conference held in Bellevue) by Hal Holtquist, managing partner of Mountain Energy Co. He said the firm made major marketing mistakes; mainly, 'tunnel vision' in not recognizing that dry hog fuel is an attractive alternative to pellets and should have been offered as a product. 'The institutional market will grow,' he said, 'and not by pelletizing dried fuel, by selling it in bulk.' Then he will be able to compete with any fossil fuel." U.S. Statistics During the last decade of the eighteen hundreds in the U.S.A., wood from our abundant forests was the primary fuel used in our factories, railroads and homes, totaling approximately 60 million tons per year. [11] "Recent studies (1980) by the U.S. Forest Service have shown that on an annual basis in the U.S. there are 600 million dry tons of unused wood available for energy use, enough to replace 1,675 million barrels of oil {143,000 "AGNI"}. The bulk of this wood exists in the form of logging residues (160 million tons) and excess tree growing stock (215 million tons). Timber harvesting systems that utilize this excess wood represent an ideal opportunity to improve the wood energy situation in the U.S." [33A] {U.S. Forest Service estimates tend to be far lower than other estimates.} The Federal Office of Technology Assessment forecasted in 1984 that this contribution could be increased sevenfold by the year 2000. Dr. James Duke of the U.S. Department of Agriculture's Beltsville Research Facility claims that the U.S. could replace fossil fuels and be entirely self-sufficient in renewable energy from the biomass grown on the 62.5 million acres of deteriorated marginal land in this country. Other studies show that dedicating just 6% of our agricultural land to sustained yield biomass crops, from hybrid poplar to hemp, could replace all our present reliance on fossil fuels and nuclear power. In 1980, less than 200 MW of electricity were produced from biomass. In 1990, the figure was 7500 MW produced from biomass, primarily wood. This figure represents about five percent of all energy used in the U.S. and is comparable to our use of hydropower and nuclear power. Solar, wind and geothermal now account for 5,800 megawatts equivalent of energy. [Biologue, 12/91] Wood energy is the single largest use of wood in the U.S. About 2.7 quads of our energy comes from 160 million dry tons of wood consumed annually. [22, '91] {381,000 "AGNI"} This could be increased to about 10 quads or about 13.5% of our current usage."[77] "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...Not only does biomass represent a massive resource base, but this resource base can be accessed now, not like many of our other alternative energy options that may have impacts 20 years or more in the future." "The United States has the potential to easily meet half of our liquid fuel needs and half of our electricity needs from this diverse resource that can be derived from direct combustion, gasification and liquification." "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. This net gain has the capacity to preserve our planet." [Biologue editorial by Scott Sklar, Sept, 91] Although detailed analysis of all sustainable biomass energy sources is just beginning to be accumulated, especially from the agricultural sector, the U.S. Department of energy (DOE) estimates that the sustainable energy potential of biomass in the U.S. is 42 quads, equivalent to 55% of total U.S. Energy consumption. [10] {5.7 million "AGNI"} Slash burning in Washington State alone wastes 34 trillion BTUs annually (equivalent to 5.4 Million Barrels of oil... $194,000,000 F.O.B. Kuwait, or 2.7 Billion Dollars of residential heating oil!* 10/90). This wasteful practice contributes far more acrid smoke to the atmosphere than woodstoves do. Increasing restrictions on slash-burning, mounting costs of logging clean-up, and greater efficiencies of residue handling/chipping/delivery systems are making slash chipping a necessity and wood waste a significant energy option. The future availability of wood-chip fuel will increase within areas 50 miles from logging and land-clearing operations. Wood waste and tree trimmings, along with other yard waste, have typically made up a third of landfill. Wood waste dumps leach concentrates into the soil that can contaminate the ground water supply for decades. Increasingly restrictive environmental regulations and disposal costs are causing tree trimmers, wood-products manufacturers, etc. to seek other outlets for their waste. This represents a vast decentralized source of cheap biomass fuel for energy. Wood fuel use by the forest products sector has increased markedly over the last 20 years, and it is generally assumed that the pulp & paper industry, large sawmills, plywood mills, and other large wood processing facilities will continue to use their waste for process energy, and that these fuels will not be available outside these industries.[5] "Public pressure is forcing environmental regulators to further restrict open burning as a residue disposal option. If environmental regulations become more restrictive, land managers will be forced to seek alternative residue disposal methods including increased utilization. If part of the removal cost for residues is paid by the user of the commercial timber, then the cost of logging residues for electric generation should decrease."[6] The most prevalent type of fuel used by respondents to the National Wood Energy Survey was: hogged fuel - 24%, chipped mill waste - 22%, sawdust - 22% slabs from mill waste - 9%, whole tree chips - 7%, logging residue - 5%, wood pellets - 4%, uncut logs - 2%, other - 5%. [5] Green sawdust comprises about 13% of the wood waste of a mill. [13] Regional Statistics Pacific Northwest & Alaska Region "The five western States representing the pacific Northwest and Alaska Regional Biomass program of the U.S. Department of Energy, cover about 256 million acres of land and contain approximately one-third of the Nation's timber resource (U.S. Department of Agriculture 1981). This vast resource is concentrated on approximately 30% of the total area (80 million acres), referred to as timberland; land supporting timber that is generally considered to be available for continuing production of woody fiber. This resource supports a large forest products industry, accounting for a significant share of the wood products consumed in the United States. This resource also represents a source of supply for a potentially significant wood using industry - energy. Energy production based on woody biomass grew considerably following the fuel shortages of the mid-seventies. This growth occurred primarily within the forest products industry and residential sectors of the economy. New legislation, advancing technology, and the renewable nature of wood provide the basis for greater reliance on biomass as a contributor to the region's energy needs in the future." Nearly 19 quads of potentially available woody biomass residues have been identified in the bioregion. This is equivalent to 25 percent of current U.S. energy consumption. Annual logging residue alone accounts for 0.3 quad, and is now the main source of biomass fuel. Washington State's forests store far more energy from the sun annually than all the energy needs of the state, and this biomass energy is perpetually renewing itself. Depending on conditions, forests in the Pacific Northwest produce on the average 5 dry tons of above ground woody biomass per acre per year, and at least that much below ground, 175 Billion BTU of stored solar energy per acre. In some locations four times that growth has been recorded, and some species suitable for biomass farming yield 8 times this average. The 5 northwest states of WA, OR, ID, MT, & AK consumed energy from all sources (petroleum, coal, gas, electricity, etc.) totaling 3,896 Trillion Btus in 1988, equivalent to the biomass energy stored annually in 23,000 square miles of Pacific Northwest forest land, or 2.5% of the land area of these 5 states. The following information in from Biomass Estimates for Five Western States [16]: In addition to woody biomass currently being converted to energy, primarily in the forest industries and for residential heating, the forests of the Pacific Northwest and Alaska represent a significant opportunity to help meet future energy needs. The extent to which these forests contribute is a function of a complex set of criteria, and varies considerably from one geographic area to another. Expanding the use of woody biomass for energy holds promise not only for meeting growing demands, but may provide an economic incentive for intensifying management of the region's forests. Obviously only a small portion of the nearly 19 quads of energy from the sources in this report will be physically available in any given year. Even less may find its way to markets because of critical economic factors. But, the amount that does reach conversion facilities can make a significant and lasting contribution to the region's energy requirements. Unlike other sources of energy, woody biomass is a renewable resource. There are other sources of forest biomass not addressed by this report. The largest such source is biomass occurring on what are frequently referred to as non-commercial forests. Juniper stands in eastern Oregon and Washington are examples of this type of forest. There are just over 25 million acres of "other forest land" in the 5-State area. Much of this land is covered with trees that are not generally considered to be of commercial value - Eastern Oregon alone has over 3.6 million acres of other forest land, most of which is occupied by non-commercial species (Farrenkopf 1982). The very definition of these stands indicates that few products are removed from trees growing on these sites. In some cases products such as posts, poles, and firewood are taken from these forests. Large scale removal of biomass from these forests may not be reasonable for a number of reasons. They do, however, represent a potentially large source of biomass, particularly for products that do not require high quality wood--such as energy. The logging residue produced annually in the Pacific Northwest bioregion, about 0.3 quad, is almost 10 times the energy output of the Trojan nuclear plant operating at 80% of capacity. [16] The annual logging residue production in Washington is 315 trillion tons [90] The Washington State Biomass Data Book [90A] estimates a realistic availability of 143 trillion Btu annually, at competitive energy prices. Washington's industrial sector uses 200 trillion Btu of fuel per year. The Biomass Energy Project Development Guidebook [13, 1989] compares the logging residues generated to the amount that can be chipped & delivered to a site 50 miles away for less than $3.30/MBtu, for possible electric power plants in WA, OR, MT, & ID, from the present to 2010. The amounts generated are 4 to 9 times greater than the amount economically available close to a potential power generating facility. This leaves a current logging residue, uneconomically located for power generation in the 4 state region, of 184 trillion Btu/year, declining to 117 trillion Btu {16,027 "AGNI"} by the year 2010. To get an idea of the market potential of this fuel source, using the average of these two figures and assuming that all potential power plants have been built and are using the surrounding wood waste for fuel, and only 10% of the remaining residue is potentially available to decentralized commercial boiler installations, 15 trillion Btus of logging residue would still be available, enough to fuel 2,055 AGNI sized boilers. Agricultural Field Residues
According to the Biomass Energy Project Development Guidebook [13, 1989], the average amount of energy from agricultural field residues available for fuel in the Pacific Northwest Bioregion is 132 trillion Btu per year. This is a tremendous energy potential {18,000 "AGNI"}, equivalent to the energy available from logging residue in the 4-state region. However, it is not as desirable for fuel because of its higher delivery cost, lower bulk density, and generally higher ash content (with lower ash-slagging temperature). Some residues also have value as green manure fertilizer. Costs of collection and delivery within 50 miles averaged $33/ton, or $2.20/MBtu. This is still half the price of natural gas. To put this in perspective, compare the total annual average quantity of residues generated in Washington (315 trillion Btu) {43,000 "AGNI"} with Washington's total industrial fuel use for 1986 (284 trillion Btu)" [6] One study of potential power plant siting in Washington found 8,000 acres of fruit orchards in one area, which could supply 17,500 tons of tree prunings within a 50 mile radius of the proposed plant site. "Residues from orchards have two particularly desirable characteristics. They are most available during the winter months when logging residues are scarce, and recovery costs are generally very low." [13] Typical Installations In Washington Greenhouse heat is an ideal application for the Agni-size system, and I have found considerable interest from that sector. Many of the existing facilities use hot water heat circulating through tubes in the benches, so conversion is simple. Those in outlying areas use oil or propane rather than natural gas, so the conversion economies are very good, and heat is a large part of their expenses. Their greatest concerns are dependability and up-front system costs, since many seem to be operating on a tight budget. Mountain View Greenhouses in Woodenville is a typical conversion candidate, replacing a 1.5MBtu/hr natural gas hot water boiler. The owner has heard too many horror stories of unreliable wood-fueled boiler installations to trust a prototype installation, but he is eager to know when it will be manufactured. Briggs nursery in Olympia is very interested in heating with hog fuel, as they have a large and expanding operation and a ready supply of fuel. Their major concern is meeting the strict Olympia air emissions standards, and are particularly interested in getting emissions data on cofiring polyethylene plastic and lunchroom waste with the hog-fuel. Tim Newcomb, of Seattle City Light Energy Management Services Division has been very supportive in my earlier endeavors to find a site for the Agni prototype. City light produces about 6 "AGNI" of chips annually from their transmission line right-of-way tree trimming operations. They would be interested in some cooperative deal to deliver their chips to several centrally located facilities. M.J. Macdonald, Deputy Superintendent, Engineering and Utility Systems of Seattle City Light, stated in a letter to me (6/90) that, although City Light has determined that large-scale wood-fueled power plants are not practical due to decentralized fuel sources, "Wood might prove to be an attractive alternative source of heat for other applications requiring smaller supplies if emissions are minimized by your concept. To the extent that such applications might replace electrical energy and nonrenewable resources, City Light would be interested and might pursue a demonstration project at some time in the future." Of the 143 Washington State facilities listed by the State Energy Office in 1987, one third of them (47) have heating systems of 5 MBtu/hr or less, most of these are low pressure hot water or steam systems, fueled with #2 diesel oil @ $4.88 - $6.48/MBtu (5 yr. old figures). Many of these facilities are rural and would be good potential customers. The State Energy Office has just recently cataloged hundreds of potential wood-energy users, from the wood products industries and other likely industries. Secondary wood processing facilities in the state offer a large potential customer base. There are 37 public schools in rural Skagit County alone, 16 of them with an existing low pressure hot water heating system. There are 34 hospitals in the state with heat needs from 1 to 6 MBtu/hr. These are predominantly small rural hospitals that would be most likely to have the space for fuel storage and a cheap local source. The State Energy Office is interested in promoting the use of bioenergy in hospitals and schools, and there may be state funds to assist the conversion. The great potential for bioenergy applications lies in the diversity of likely customers, from a fish-processing plant in Anacortes to the Glue Extender Company in Marysville. Seattle Disposal has tons of low-grade paper fines that are costly to landfill, and several large warehouses and other facilities to heat. The Whidbey Island Naval Air Station has begun an extensive recycling program that is including the city of Oak Harbor. Since their landfill will be closing in July, all refuse must then be trucked to Oregon, so they are serious about optimizing recycling and including waste-to-energy as an efficient way to heat their various buildings as well. They will soon be collecting 400 to 500 tons/month and purchasing a chipper to process their woody yard-waste. They also collect a lot of low-grade waste paper that they want to burn. Western Region Crop residues examined in the report, "Resource Assessment of Waste Feedstocks for energy Use in the Western Regional Biomass Energy Area" include: wheat, barley, oats, rye, rice & flaxseed straw; corn stover, huskage & cobs; sorghum & sunflower stalks & leaves; whole cotton plants after seed collection; and orchard prunings. "There are nearly 35 million dry tons of waste biomass in the WRBEP region that can be economically collected and delivered to energy plant sites in volumes of 50,000 dry tons per year or more. The total waste paper and agricultural residue resource for the WRBEP region is 175 million dry tons per year (including 14.8 million tons of waste paper and 1.7 million tons of orchard trimmings). {417,000 "AGNI"} The potential deliverable resource approaches 36.5 million tons per year or 21% of the total resource. This figure is based on deliverability to large energy facilities. Decentralized utilization patterns could make use of a much larger percentage of the available resources. According to the Western Region biomass energy report, Biologue, Mr/Ap'91: Biomass contributes about 1% of California's energy supply, increasing from 100MW in 1979 to slightly less than 500 MW in 1988, to exceed 500 MW by 1994. Although California has seen unprecedented demand for biomass fuel, with power producing facilities paying as high as $50/BDT to get premium chips from Canada, prices are expected to fall in the future, as the market stabilizes and more biomass becomes available. "In general, biomass fuel is projected to be less available from the wood products industry and more available from non-traditional sources of fuel. One exception is that more fuel is expected to be derived from forest stand improvement thinnings and logging residue recovery. In the future, some fuel will likely be obtained from Eucalyptus, Salix or other energy plantation species."[77] A study of coastal California (I.C.R.W.E.) concludes, "Improved biomass utilization would have significant benefits from the viewpoint of fire and resource management (reforestation, wildlife habitat management, recreation area management, range management) and jobs." In Nebraska there is much interest in ethanol and concern with sizing mass-burn waste-to energy facilities to the needs of rural communities. The present efforts are on separation of recyclables & producing RDF for remote boilers. Nebraska's Arbor Day Foundation plans to build wood-chip processing facility & wood-fired boiler room for educational use Two state colleges plan wood-fired boilers for steam heat. Kansas agribusiness generates $9 billion in goods and services annually, making it the largest revenue-producing industry in the state. It also produces large volumes of waste that may have value as feedstocks for biomass energy. A database characterizing this waste is presently being prepared. More than 600 agribusinesses associated with the meat packing, grain milling, and food processing industries have been identified in the state. A recent study (1991) estimates the amount of agricultural crop residue that can be removed for energy purposes in Kansas without adversely affecting soil productivity. The crops considered in this study were corn, grain sorghum and wheat. Available biomass from the three crops considered varies from 0% to roughly 72% of the above-ground crop residue produced. Estimates of removable residues for sorghum and wheat totaled 4.7 million tons. (Corn was not estimated.) [77] {6,700 "AGNI"} Southeastern Region "Eight of the top 10 industrial wood using states are located in the Southeast United States with Georgia the number one state."[77] Georgia's goal is to supply 20% of its energy needs with biomass. [First National Fuelwood Conference, 11/91, Lincoln, NB] In the TVA region, approximately 3.4 million tons of wastes were produced by the wood products industries in 1979, with a heat content of about 51,163 trillion Btus, or 7.1 million barrels of oil. About 50% of these wastes are now (1986) being burned to produce energy. Each year approximately 33 million green tons of wood and bark are potentially available for use as fuel in the region {42,500 "AGNI"}, 10 times the amount of mill wastes. [11] Nonforestry Related Biomass Fuel
"The Southeastern Region of the United States can produce approximately the annual equivalent of 897 trillion Btu of energy from nonforestry wastes such as agricultural crop residues, animal excreta from confined feedlots, crops that could be grown on agricultural set-aside land, MSW, and sewage sludge. Of the total resources, 53.5% are in the form of crop residues, 25.3% in MSW, 18.7% available from grasses that could be grown on agricultural setaside lands, 1.8% from sewage sludge and 0.7% from animal excreta."[72] "In conclusion, available biomass waste and residues in the SERBEP region can annually provide about 897 trillion Btu {123,000 "Agni"}."[72] "Mississippi could reasonably expect to obtain from 20 to 30% of its energy needs from biomass resources. [10, May/June,'91] About 60% of raw cotton ends up as cotton gin trash , consisting of stems, leaves, hulls, and immature bolls. Comprised primarily of cellulose, gin trash has a 6,000-7,000 Btu/lb energy content, which can be used for drying the cotton and sold for fuel. Northeastern Region A 1984 report titled, "Wood Chips: an Exploration of Problems and Opportunities," prepared for the Northeast Regional Biomass Program, offers the following insights: [93]In 1983, more than 30 million tons of wood, the equivalent of 30 million barrels of oil, were used in the region. Despite the increase, wood currently comprises less than 4% of the total energy consumed by residences, businesses, institutions, and industries in the northeast. Current usage is estimated at less than 10% of the potential contribution of wood. ...the market for whole tree chips is evolving more slowly than the production side of the operation. If the economics of burning chips were thus improved, and that information disseminated, it is likely that the market for whole tree chips would escalate. Once demand increases, operators will have incentive to solve the problems of production and delivery, creating the necessary infrastructure for a successful wood chip industry. Before the end of this century, whole tree chips may be the primary wood product used for energy. Surveys conducted in 1979 and 1985 indicate that approximately 30% of the residences in Connecticut use wood for energy. With 1.8 million acres of forested land, Connecticut has a significant supply of wood. Research completed by professional foresters in the state indicates that substantial volumes of fuel wood could be harvested. Many foresters believe the use of wood for fuel can create markets for low-quality wood that is otherwise unmarketable. The use of integrated forest management techniques produces the opportunity to harvest low-quality wood while simultaneously improving the quality of the forest. After a recent period of only modest increases in the amount of wood fuel used by industries, it now appears that wood use by Connecticut firms may grow substantially during the next few years. This is primarily due to two factors: independent power producers have received favorable power sales agreements with electric utilities serving the state; and skyrocketing landfill costs are encouraging the recycling of wood wastes. There are currently three wood-fired power plants proposed in Connecticut totaling 69MW. All three facilities plan to burn a mixture of recycled wood waste and harvested wood chips.[10, 6/91] Main is the most heavily forested state in the union, 86% of it being covered with trees. In 1989, thirty-one biomass operations in the State of Maine were non-utility power producers. Of these, one burned peat, four burned municipal waste, and the remaining twenty-six plants burned wood - either mill residues or whole tree chips. Of these 31 operating biomass plants, 22 were classified as cogeneration and 9 as small power producers. Presently, 640 MW or 23% of Main's electric capacity, is fueled by wood, and six new ones are being built. In the early 1980's over half of the households heated with wood, wholly or partially. By 1986-87, with lower oil prices, annual surveys indicted a leveling off at about 42%"[10, 1991] "There are substantial excess quantities of wood in Maryland that could be used as an industrial energy resource, but only a small fraction of the potential is currently being used." [10, 1987] Approx. 64% of the state of Massachusetts is forested. = 3.2 million acres. The noticeable increase in wood burning in late 70's & 80's was stopped by cheap fossil fuels. in 1988 industrial/ commercial wood fuel use totaled 65,000 tons/yr., residential wood fuel use 95,000 tons/yr. A substantial source of biomass energy comes from the incineration of MSW; totaling 7,000 tons/day in Mr,'89.[10,1991] New Hampshire has built 6 new wood-fired small power plants with a combined capacity of 90 MW in the past 3 years. Six older ones bring the total to 130 MW, or 8% of peak demand in the state (2.4 million tons fuel annually). Another 60 smaller commercial & industrial systems (mostly sawmill & other wood product manufacturers burning their waste) burn 200-300,000 tons/yr. Residential heating use has dropped from high of 640,000 cords in '84-'85 to 400,000 cords in '87-'88.[10, 1991] The New York State Energy Research and Development Authority has evaluated and published an assessment of wood energy sources in the state. "...NY state could produce 400 to 800 MW of electric power on a continuous basis over the next 20 years using relatively low-cost waste-wood materials at a price competitive with conventional power generation technologies. In addition, traditional forest materials combined with processed clean wood waste could generate an additional 2800 MW of electricity at higher prices. NY state's forest resource has been expanding, according to a 1980 U.S. Forest Service Survey, with 18.5 million acres of land area forested. An additional 4.5 million tons of construction and demolition debris are generated annually, 40% of which is waste wood that could generate energy {equivalent to 8,600 "AGNI"}. Vermont (the "Green Mountain State") is 80% forested. Residential heating with wood has dropped from a high of 50%. Over 75 state-owned and commercial buildings utilize biomass energy for process steam or space heating. [10, 1991] Great Lakes Region In the Great Lakes Bioregion, some companies refused to reveal their use of cheap wood energy by taking part in a case study. "The food processing and canning industry, because of its highly competitive character, is understandably reluctant to reveal those secrets that contribute to its competitive edge. Wood burning has enabled several companies to stay abreast--or ahead--of the competition." [92] "Whole tree chips are probably the largest available source of wood fuel due to the extensive amount of waste wood present in the forests of the Great Lakes region. Green mill residues at $5 to $10 per ton are the cheapest source of wood fuel available on a bon-by-ton basis, though their lack of uniformity and the possibility that dirt and stones will be mixed in with the residue are important considerations for purchasers."[92] This price means natural gas is 8 to 12 times as costly as wood-waste fuel. "Currently Iowa imports 98% of the energy it uses, including the coal & natural gas burned to generate electricity. Under a recent ruling by the Iowa Utilities Board, utility companies will pay alternative energy producers for the electricity the generate at a uniform statewide rate."[10A] Although Iowa is not a heavily forested state, it does produce considerable wood waste that could contribute to its energy needs. "For years there have been problems in marketing or disposing of this wood waste. With additional environmental regulations, wood waste disposal may be even more difficult to handle economically in the future." [97] WOOD WASTE IN IOWA [97]
*****POPULATIONS:*****
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. IowaDepartment 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."
Emissions Control 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
"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] Analyzing figures for typical APC equipment costs (1984) for larger systems in Stack Emission Standards For Industrial Wood-Fired Boilers, if we extrapolate the figures down to an Agni size 1.5 MBtu/hr system, we arrive at the following costs in 1980 dollars: APC EQUIPMENT COSTS Mechanical Collector Fabric Filter $130,000 Venturi Scrubber $210,000 Electrostatic Precipitator $460,000
These figures are higher than those from [11]. These are additional costs over and above the boiler and feed handling systems, and the figures are low because there are economies of scale not factored in! This is the main reason why there have been no small wood-fueled boiler installations in any heavily populated areas (with strict emissions regulations) in recent years. "Based on the available literature, it is apparent that for industrial sized wood boilers (less than 100 MBtu/hr) SO2, CO, NOx, and VOC emission control equipment is not required but particulate control equipment will be required in a majority of cases for new installations to meet allowable state emission rates."[80] Emissions Statistics The following chart compares emissions from Helen (burning green fir sawdust, 44% moisture) to emissions from large uncontrolled industrial boilers burning wood, coal, oil and natural gas (per identical energy input). Figures given are calculated from "Stack Emission Standards for industrial Wood-Fired Boilers". RELATIVE EMISSIONS COMPARISONS
"More than 10% of Washington's air pollution comes from outdoor burning: land clearing debris, logging slash, leaf burning, agricultural. field burning: According to the Department of Ecology, outdoor burning is a major source of citizen complaints, including 3,000 - 5,000 agricultural fires annually, burning more than 300,000 acres. All in all, outdoor burning contributes 256,000 tons of CO, 21,000 tons of VOC, 32,000 tons particulate, 10,000 tons toxic air pollutants. Wood Ash: "Ash content and chemical composition are variable among tree species and also depend on soil type and climate. Temperate climate woods yield 0.1-1.0% ash, while tropical and subtropical woods yield up to 5%. Hardwoods, in general, contain more ash than softwoods. Ash content is highly variable within the tree, being highest in Ash is composed of major and minor elements needed by the tree for growth. The major elements are calcium (7-33%), potassium (3-4%), magnesium (1-2%), phosphorus (0.3-1.4%, manganese (0.3-1.3%), and sodium (0.2-0.5%). Essential trace elements for plant growth include zinc, boron, copper, molybdenum, and others at mg/kg (ppm) levels. Heavy metal concentrations are typically low...Wood ash is substantially different from coal ash which has a lower alkalinity but higher silicon, aluminum, iron and heavy metal content. The combustion temperature directly affects the total yield and chemical composition of ash. Some elements, particularly potassium, are volatized at high combustion temperatures thereby lowering their content in the ash. The alkali metal and alkaline earth elements in the wood ash are present mainly in the form of oxides, hydroxides, and carbonates such as potassium oxide, calcium oxide, potassium carbonate, and calcium carbonate. The oxides react exothermically over time with moisture and carbon dioxide to form hydroxides and carbonates. These components produce a highly alkaline ash with a typical pH range of 11-13. The soluble potassium hydroxide and potassium carbonate react rapidly with acids, while the less soluble calcium hydroxide and calcium carbonate react more slowly. [77] Potential Problems: Science News reported (Aug. 10, 1991) that Stewart Farber, an environmental lab manager for a nuclear energy plant in Massachusetts, found that wood ash contains high levels of radiation, apparently the result of nuclear weapons tests in the 1950s and '60s. Tests of ashes from his fireplace showed concentrations of radioactivity that "was easily 100 times greater than anything (our lab) had ever seen in an environmental sample." "He has since obtained radioactivity assays from 16 other scientists representing 14 states, and the data suggest that fallout in wood ash is a major source of radioactivity released into the environment.' With the exception of some very low readings in California, Farber says all measures of ash with fallout exceed - some by 100 times or more - the fallout that may be released by nuclear plants." The trace element Cadmium can be a limiting factor on the amount of wood ash that can be used in agricultural applications.[from talk at the National Fuelwood Conference, 11/91, Lincoln, NB, by Nels Christopherson, Research Mechanical Engineer, USDA Forest Service] Ash Disposal & Utilization: "Until recently, ash was a valuable raw material, but today ash wastes have a negative value due to their disposal costs. For the most part, ash is either landfilled (90%) or land applied. In the Northeast, approximately 15% of wood ash is landfilled, 80% is land applied, and 5% is disposed of in some other way, mainly as a sewage sludge composting agent. Most other areas of the country landfill wood ash. In Europe, ash is used as a feedstock for cement production, a soil amendment on forest lands, and a roadbase material." One study suggests that wood/coal ash could be valuable in neutralizing acid landfill leachate." "Ash has been used effectively in four Northeastern towns as a bulking and odor control agent in composting of municipal sewage sludge in aerated static piles. In addition, ash has been granulated to yield a fertilizer and liming agent. Land application appears to be one of the best methods for ash disposal, as the nutrients that were taken from the land during harvest are recycled back to the land. Ash has a low fertilizer equivalent (NPK ratio of 0:1:2), but it can be used as an excellent substitute for lime and limestone to neutralize acidic soils and to add Ca, K, and Mg. Liming with wood ash may also reduce the toxic effect of aluminum and manganese in acidic soils. Ash will probably be sold in the future as a liming agent/soil amendment." "Wood ash has shown positive benefits in forest and agricultural land application in a variety of tests: Yields increased (superior to limestone), even at high application rates because the elements in ash are released more slowly than those in fertilizer, showing a higher release in the second growing season. In one study, the wood ash increased all microbial activities that were examined: nitrogen availability, mineralization, cellulose decomposition, nitrogen fixation, and denitrification." "In Maine, wood ash is classified as a specified waste which requires regulatory approval prior to land spreading...The approval process takes approximately 6 months. The State of Oregon DEQ does not require permits for each individual property but does require quarterly and annual reports identifying which properties are being utilized. County governments regulate ash utilization to the extent that they are responsible for land use issues and solid waste disposal. Some counties require that every adjacent property owner be notified by mail that the ash is to be utilized on a given site. The state of Washington classifies wood ash as a dangerous waste when its pH exceeds 12.5. This classification necessitates special handling and disposal procedures which have caused major problems for several ash generating facilities. for example, a pulp and paper mill in Washington attempted to neutralize its ash for three months with sulfuric acid, but the cost was prohibitive." {If this proved to be a problem, the mildly acidic condensate from the Agni boiler could be run through the basic ash to neutralize it on site.} Wood ash is a good liming agent. This makes ash land spreading feasible where the agricultural soils tend to be acidic, as they are in the Northeast. Four northeastern states, Maine, New Hampshire, Vermont, and New York have developed land spreading regulations for wood ash. In the other northeastern states as well as in most of the rest of the country, wood ash is still landfilled. This practice will undoubtedly change as landfill tipping fees increase. [22] In the SERBEP region, ash disposal in landfills does not require a solid waste permit. [65] Some states in the SERBEP region issue general permits to cover minor discharges that are not likely to cause serious water quality problems, such as boiler blowdown water. [65] The boiler condensate should be covered in this category, and "when a general permit has been granted for a source category, any additional source conducting the same activity is permitted...", which means that after the first installation in a state, future permitting in this area would be automatic. In a paper titled, "Comparative Analysis Of Gasification/Pyrolysis Condensates" [68], Douglas C. Elliott of Pacific Northwest Laboratory, Richland, analyzed the aqueous phase of the condensate from three different gasifiers, which were "highly contaminated with organics". "The more contaminated aqueous streams have a lower (more acidic) pH (as low as 2.1!) which indicates the presence of water-soluble organic acids. Although the more contaminated streams show increases in viscosity and density as well as being highly colored they can easily be handled in systems designed for water if proper consideration is given for the streams with corrosive potential." "For a modern efficient coal-fired plant, exhaust gas temperatures. are typically maintained near 300°F at full load because of the acid nature of the flue gas. At lower temperatures acids form that damage gas path components. Due to the low levels of SO2 & NOx products associated with the whole tree burner, the flue gas condensate can actually |