Evaluation of Replacing Natural Gas Heat Plant with a Biomass Heat Plant - A Technical Review of Greenhouse Gas Emission Trade-Offs

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Evaluation of Replacing Natural Gas Heat
Plant with a Biomass Heat Plant – A Technical
Review of Greenhouse Gas Emission Trade-Offs
James G. Droppo and Xiao-Ying Yu
Pacific Northwest National Laboratory
USA
1. Introduction
Proposed fuel conversions can involve more than a simple reduction of emission rates. For
example, a Renewable Fuel Heating Plant (RFHP) was proposed for the U.S. Department of
Energy (DOE) National Renewable Energy Laboratory (NREL) to replace a natural gas
plant. The proposed RFHP replacement plant was to use a biomass fuel, wood chips. A
review was conducted to address questions related to how increases in the plant’s carbon
dioxide (CO2) emission rates could represent a desirable outcome. This review and its
results are published here in the hope that it may be useful to others considering similar
conversions. This chapter addresses 1) why despite an increase in emission rate the
conversion is considered an effective reduction in greenhouse gas emissions, and 2) how the
proposed wood chip combustion process emissions compare with other means of disposing
of or using wood chips.
The 2001 and 2007 Assessment Reports of the Intergovernmental Panel on Climate Change
(IPCC) considers the evidence for global climate change and the potential consequences of
such changes [IPCC, 2001; 2007]. Based on the result of worldwide research efforts, this
paper concludes that the earth's climate has changed over the last century. It also notes that
there is recent strong evidence that human activities have caused most of the warming
observed in the last 50 years. The current computer models are predicting that this
temperature rise should continue over this century.
In terms of the net CO2 in the atmosphere, the argument is made based on current scientific
understanding on climate change processes, that burning of wood chips is much more
desirable than a fuel that contains carbon that has been sequestered underground. The CO2
from wood chip combustion has a “net zero” emission rate based on factors in the
Environmental Protection Agency’s AP-42. The “net zero” emission rate is based on an
assumption that CO2 from burning wood from forests represents no increase in the net
amount of CO2. A cycling of carbon between the atmosphere and forests results in no net
gain or loss of airborne CO2. On the other hand CO2 from burning natural gas represents an
increase in the net amount of CO2 from the introduction of “new” carbon that has been
previously sequestered underground. Thus argument for the proposed conversion is to stop
the introduction of the new carbon into the current atmospheric carbon cycle.

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From the viewpoint of minimizing impacts on global climate change, the burning of wood
chips also tends to be more desirable than the common alterative use of wood chips in
composting activities. Although there is great variability and uncertainty in the published
emission rates, the gaseous emission from both open burning and composting tend to have
much larger emissions of greenhouse gases, and specifically larger fractions of gases such as
methane (CH4) and ammonia (NH3) than the proposed process for burning the wood chips.
The published source terms for open burning show the incineration option to be preferable
from the viewpoint of having lower emissions. Of particular importance are mixtures of
combustion products from these activities. For example because methane is currently thought
to be many times more effective for inducing climate changes than CO2, the potentially higher
methane levels from open burning and composting make these activities less desirable from
the viewpoint of minimizing the potential impact of greenhouse gas emissions.
The paradox in the proposed conversion is that from an absolute quantity perspective the
RFHP would emit more CO2 than what is being currently emitted with natural gas firing.
Although the main thrust in reducing atmospheric levels of greenhouse gases has been to
reduce introduction of “new” carbon by the combustion of fossil fuels, some efforts have
considered the possibility of combustion control strategies for agricultural and forestry
products.
A review was conducted of recent literature relevant to these issues. The predominance of
current literature points to a need to reduce greenhouse emissions, and it is assumed for the
purpose of this review to be a reasonable basis for proceeding with actions that will reduce
those emissions. The results of this review are reported below. A form of these results were
posted as a DOE report, we would like to make it avaiable in the public domain for people
who are interested in this topic.
2. Background
The Third and Fourth Assessment Reports of the IPCC [2001, 2007] considers the evidence for
global climate change and the potential consequences of such changes1. Based on the result of
worldwide research efforts, the report concludes that the earth's climate has changed over the
last century. These reports also notes that there is mounting evidence that human activities
have caused most of the warming observed in the past 50 years. The current computer models
predict that this temperature rise should continue over this century.
The IPCC reports note that changes in climate are the result of both internal variability
within the climate system and external factors (both natural and anthropogenic). Human
emissions are significantly modifying the concentrations of some gases in the atmosphere.
Some of these gases are expected to affect the climate by changing the earth's radiative
balance, measured in terms of radiative forcing.
The 2007 IPCC reports provide an overview of the global effects of greenhouse gases and
conclude that they tend to warm the earth surface by absorbing some of the infrared
radiation it emits.
1 The reader is referred to the websites http://www.ipcc.ch/ and “http://www.greenfacts.org” for
additional information. The latter site provides summaries as well as quotes from the IPCC (2007) report.

Evaluation of Replacing Natural Gas Heat Plant
with a Biomass Heat Plant – A Technical Review of Greenhouse Gas Emission Trade-Offs 233
“The principal anthropogenic greenhouse gas is carbon dioxide (CO2), whose
concentration has increased by 31% since 1750 to a level which is likely to have not been
exceeded for 20 million years. This increase is predominantly due to fossil fuel burning,
but also to land-use change, especially deforestation. The other significant
anthropogenic greenhouse gases are CH4 (151% increase since 1750, 1/3 of CO2's
radiative forcing), halocarbons such as CFCs and their substitutes (100% anthropogenic,
1/4 of CO2's radiative forcing) and nitrous oxide (N2O) (17% increase since 1750, 1/10
of CO2's radiative forcing).”
The IPCC [2007] attributes that about three-quarters of the anthropogenic emissions of CO2
to the atmosphere during the past 20 years is due to fossil fuel burning. The rest is attributed
to predominantly land-use change, especially deforestation.
“Currently the ocean and the land together are seen as taking up about half of the
anthropogenic CO2 emissions. On land, the uptake of anthropogenic CO2 is thought to
very likely exceed the release of CO2 by deforestation during the 1990s. The rate of
increase of atmospheric CO2 concentration has been about 1.5 ppm (0.4%) per year over
the past two decades. During the 1990s the year to year increase varied from 0.9 ppm
(0.2%) to 2.8 ppm (0.8%). A large part of this variability is due to the effect of climate
variability (e.g., El Niño events) on CO2 uptake and release by land and oceans."
Studies of the signatures of emissions from biomass and fossil fuel burning conducted by
Reiner et al. [2001] over the tropical Indian Ocean provides some insight into the relative
source importance. In the air from the continent they found that most of the CO is from
biomass/biofuels burning and the majority of the aerosols are from fossil fuel burning.
These results underscore the apparent importance of incomplete combustion products in the
current emissions from combustion of biomass/biofuels.
The literature indicates that there is a world-wide effort to define means and methods of
using bio-energy while minimizing greenhouse gas emissions. Faaij [2006] states that bio-
energy is one of the key options to mitigate greenhouse gas emissions and substitute fossil
fuels. The efforts are reflected in the wide range of activities and programs for developing
and stimulating bio-energy.
3. Emission rates
This review focuses on greenhouse gas emissions from a proposed wood fired boiler and
their existing natural gas boiler and from other alternative uses of the wood chips. The
current and proposed emissions rates as well as the assumed annual tonnage of wood
consumed are provided by DOE/NREL. A literature search was conducted with the
objective of quantifying annual air emissions that would result from the likely alternative
uses of the wood proposed to be used by PRFHP. The three alternatives considered were
composting, land filling and open burning. Because each of these alternatives represents a
wide range of processes, it is expected that there will be correspondingly a wide range of
potential emissions from each of these alternatives.
As a result of a worldwide concern over the potential effect of greenhouse gases, the current
literature contains considerable information on the potential emissions. These papers
include process-specific studies of the emissions from biomass burning and other biofuel
combustion processes (i.e. Borgwardt, 1997; Turn et al., 1997; Dennis et al., 2002; Hays

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234
et al.2, 2002; Kasische and Penner, 2004; Hayes et al., 2005; Pronobis, 2006; Hashaikeh et al.,
2007; Tilman et al., 2007] as well as quantification of global emissions from conventional and
biogenic processes (i.e. Oros and Simonett, 2001; Ito and Penner, 2004; Liebig, 2005;
Wiedinmyer et al., 20063; Schmid et al., 20064; Khalil et al.,20075). The attached list of
citations for papers considered in this review contains additional references concerning both
process and global emission rates.
The emphasis of this review is to compare the emissions from natural gas and the wood
fired boiler with comparable emission numbers for the same annual volume of wood
disposed of by the alternative means. Specifically the comparison is based on the wood is
either 1) processed into compost; 2) dumped in a landfill; or 3) subjected to open burning à
la the forest service’s preferred method for slash pile disposal.
Winiwarter [2001] detailed evaluation shows that “much of the overall uncertainty derives
from a lack of understanding of the processes associated with N2O emissions from soils.
Other important contributors to greenhouse gas emission uncertainties are CH4 from
landfills and forests as CO2 sinks. The uncertainty of the trend has been determined at near
5% points, with solid waste production (landfills) having the strongest contribution.”
3.1 Proposed heat plant emissions
Table 1 shows a comparison of the emissions from the current natural gas and proposed
biomass heat plants. Annual emissions from the proposed heat plant are based on a
permitted 3,800 tons of biomass, at approximately 6,500 Btu/lb heating value. This
maximum annual fuel consumption is based on the assumption that biomass has thirty to
forty percent moisture. Uncontrolled emissions are based on emission factors referenced
in the United States Environmental Protection Agency’s (U.S. EPA’s) AP-42 Compilation
of Air Pollutant Emission Factors (5th edition), Chapter 1.6 Wood Residue Combustion in
Boilers.
Combustion Scenario Current Heat Plant Woodchip Heat Plant
Air Pollutant Existing Emissions using
Natural Gas Boilders Wood Combustion
Units tons/yr tons/yr
Carbon Monoxide (CO) 1.69 3.58
Sulfur Dioxide (SO2) 0.012 0.5
Nitrogen Oxide (NOx) 3.3 4.3
PM Total 0.1 3.2
VOC (non methane) 0.1 0.1
Carbon Dioxide (CO2) 2340 Net zero
Table 1. Emissions Comparison of Current Natural Gas and Proposed Biomass Heat Plants
2 Considers emissions from burning of several types of wood.
3 Estimation of emissions from fires in North America.
4 Considers carbon budget for forests.
5 Recent summary of importance of atmospheric methane as a greenhouse gas.

Evaluation of Replacing Natural Gas Heat Plant
with a Biomass Heat Plant – A Technical Review of Greenhouse Gas Emission Trade-Offs 235
3.1.1 Composting
For all compositing activities, the products produced depend heavily on conditions. High
(i.e. greater than 50%) moisture content is a prerequisite for having high levels of microbial
activities [Lang et al., 2006]. Dispite the wide range of possible emissions; it is possible to
describe general trends from composting.
The aerobic composting of chips from clear-cut trees is considered by Suzuk et al. [2004]. They
found that certain combinations of materials could be composed within 10 months time
period. Although they did not specifically consider the emissions, it is likely that emissions of
CO2 and CH4 are much lower than what would have occurred with anaerobic composting.
IPCC (2007) states that:
“Composting refers to the aerobic digestion of organic waste. The decomposed residue,
if free from contaminants, can be used as a soil conditioner. As noted above under
landfilling, greenhouse gas emissions from composting are comparable to landfilling
for yard waste, and lower than landfilling for food waste. These estimates do not
include the benefits of the reduced need for synthetic fertilizer, which is associated with
large CO2 emissions during manufacture and transport, and N2O releases during use.
USDA research indicates that compost usage can reduce fertilizer requirements by at
least 20% [Ligon, 1999], thereby significantly reducing net greenhouse gas emissions.
Composting of yard waste has become widespread in many developed countries, and
some communities compost food waste as well. Small, low-technology facilities
handling only yard waste are inexpensive and generally problem-free. Some European
and North American cities have encountered difficulties implementing large-scale,
mixed domestic, commercial and industrial bio-waste collection and composting
schemes. The problems range from odor complaints to heavy metal contamination of
the decomposed residue. Also, large-scale composting requires mechanical aeration
which can be energy intensive (40-70 kW/t of waste) [Faaij et al., 1998]. However,
facilities that combine anaerobic and aerobic digestion are able to provide this energy
from self-supplied methane. If 25% or more of the waste is digested anaerobically the
system can be self-sufficient [Edelmann and Schleiss, 1999].
For developing countries, the low cost and simplicity of composting, and the high
organic content of the waste stream make small-scale composting a promising solution.
Increased composting of municipal waste can reduce waste management costs and
emissions, while creating employment and other public health benefits.
Anaerobic digestion to produce methane for fuel has been successful on a variety of scales
in developed and developing countries. The rural biogas programmes based upon
manure and agricultural waste in India and China are very extensive. In industrial
countries, digestion at large facilities utilizes raw materials including organic waste from
agriculture, sewage sludge, kitchens, slaughterhouses, and food processing industries. “
3.1.2 Landfill
Disposal of wood chips in a landfill can result in a wide range of greenhouse gas emissions.
Although conditions in a land fill are typically anaerobic, it is also possible to have aerobic

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conditions. The majority of current research articles report studies based on controlling
mixtures and conditions to minimize greenhouse emissions.
Pier and Kelly [1997] indicate that as a result of it high degradable organic carbon content of
wood wastes combined with a tendency for anaerobic onsite storage conditions, wood
wastes are a potent potential source of methane production. They also indicate that the
emissions from such wastes would be much higher if such stored wastes were put in soil-
capped landfills. CO2 and methane emission rates were measured in terms of mass emitted
per surface area of a sawdust pile. They found methane flux rates that were within, but at
the low end of the range of landfill methane emission values, as reported in the literature.
Traditional landfills tend to be significant sources of greenhouse gases. If one assumes
similar processes will occur for the wood as for the other organic materials in the landfill,
then the disposal of wood chips in a landfill will result in significant releases of potent
greenhouse gases – and thus from the viewpoint of the potential to generate greenhouse gas,
burial in a traditional landfill will be a less desirable fate for the wood chips than the
proposed incineration process.
Typical landfill gas composition includes 63.8% CH4, 33.6% CO2, 0.16% O2, 2.4% nitrogen
(N2), 0.05 % hydrogen (H2), 0.001% carbon monoxide (CO), 0.005% ethane (C2H6), 0.018%
ethane (C2H4), 0.005% acetaldehyde (C2H5O), 0.002% propane (C3H8), 0.003% butanes
(C3H8), 0.00005% helium (He), < 0.05% higher alkanes, 0.009% unsaturated hydrocarbons,
0.00002% halogenated compounds, 0.00002% hydrogen sulphide (H2S), 0.00001%
organosulphur compounds, 0.00001% alcohols, and 0.00005% other compounds [Al-Dabbas,
1998]. Although recent work by Launghi et al. and references therein suggested different
percentages of the landfill gas composition in Europe, CH4 content is highest among landfill
gas emission [Lunghi et al., 2004]. Based on the Italian report, CH4 accounts for 58.01%, CO2,
41.38%, O2, 0.13%, N2 0.48%, and H2O 0.41%.
Methane can be formed by various paths including biogenic (bacterial) methane formation,
thermogenic formation, and incomplete combustion of biomass or fossil fuels. After
formation of CH4, it can be modified by secondary processes. One of the most important
processes is aerobic CH4 oxidation by methanotrophic bacteria, which occurs in many
natural and anthropogenic environments producing CH4 under anaerobic conditions.
Substantial aerobic methane oxidation has been found in various environments such as
natural wetlands, rice paddies and landfill sites [Bergamaschi et al., 1998].
Emission of CH4 from landfills is causing increasing concerns in global climate change,
because its warming potential is 20 times higher than that of CO2 in a time trajectory of 100
years [Kumar et al., 2004a; Kumer et al., 2004b]. Formation of organic compounds including
degradable materials with high molecular weights is closely linked with emission of CH4 in
landfills [Pan and Voulvoulis, 2007].
IPCC (2007) states that:
“Worldwide, the dominant methods of waste disposal are landfills and open dumps.
Although these disposal methods often have lower first costs, they may contribute to
serious local air and water pollution, and release high GWP landfill gas (LFG). LFG is
generated when organic material decomposes anaerobically. It comprises
approximately 50%-60% methane, 40%-45% CO2 and the traces of non-methane volatile

Evaluation of Replacing Natural Gas Heat Plant
with a Biomass Heat Plant – A Technical Review of Greenhouse Gas Emission Trade-Offs 237
organics and halogenated organics. In 1995, US, landfill methane emissions of 64 MtCeq
slightly exceed its agricultural sector methane from livestock and manure.
Methane emission from landfills varies considerably depending on the waste
characteristics (composition, density, particle size), moisture content, nutrients,
microbes, temperature, and pH [El-Fadel, 1998]. Data from field studies conducted
worldwide indicate that landfill methane production may range over six orders of
magnitude (between 0.003-3000g/m2/day) [Bogner et al., 1985]. Not all landfill methane
is emitted into the air; some is stored in the landfill and part is oxidized to CO2. The
IPCC theoretical approach for methane estimation has been complemented with more
recent, site-specific models that take into account local conditions such as soil type,
climate, and methane oxidation rates to calculate overall methane emissions [Bogner et
al., 1998].
Laboratory experiments suggest that a fraction of the carbon in landfilled organic waste
may be sequestered indefinitely in landfills depending upon local conditions. However,
there are no plausible scenarios in which landfilling minimizes greenhouse gas emissions from
waste management (italics added). For yard waste, greenhouse gas emissions are roughly
comparable from landfilling and composting; for food waste, composting yields
significantly lower emissions than landfilling. For paper waste, landfilling causes
higher greenhouse gas emissions than either recycling or incineration with energy
recovery [US EPA, 2000].”
The potential for the gases produced in landfills to be collected as a biomass source is being
considered [McKendry, 2002 a;b;c] as a process that potentially could put the landfill
greenhouse emissions on a par with the proposed heat plant.
3.1.3 Open burning
The disposal of the wood chips by open burning is considered. Fires produce gases and
aerosols to the atmosphere such as CO2, CO, nitrogen oxides (NOx), volatile and
semivolatile organic compounds (VOC and SVOC), particulate matter (PM), NH3, sulfur
dioxide (SO2), and CH4 [Clinton et al., 2006].
The literature on biomass combustion encompasses biofuels (wood, crop waste, and dug-
cake) and forest fires (accidental, shifting, cultivation, and controlled burning). In a study
based in India, forest fires were reported as only being a 7% portion of the 93% of total
combustion sources from biomass consumption [Reddy and Venkataraman, 2002].
Greenhouse gas emission from biofuel burning is much less in comparison to emission from
open vegetation fires [Ito and Penner, 2005].
Open burning produces a much more complex mix of gas emissions. Hays et al. examined
fine particulate matter (PM2.5) and gas phase emissions from open burning of six fine foliar
fuels commonly found in fire-prone ecosystems in the U.S. [Hays et al., 2002]. They
identified more than 100 individual organic compounds in the fine carbonaceous particulate
matter using gas chromatography/mass spectrometry. The emission ranges by organic
compound class are the following, n-alkane 0.1-2%, ploycyclic aromatic hydrocarbon (PAH)
0.02-0.2%, n-alkanoic acid 1-3%) n-alkanedioic acid 0.06-0.3%, n-alkenoic acid 0.3–3%, resin
acid 0.5–6%, triterpenoid 0.2-0.5%, methoxyphenol 0.5-3%, and phytoseterol 0.2–0.6%.

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Table 2 compares the relative emissions from the proposed heat plant and the alternative of
open burning of the wood chips based on emission factors listed in US EPA guidance [US
EPA, 2008].
Combustion Scenario Current Heat Plant Proposed
Heat Plant
Equivalent Mass
of Wood
Air Pollutant
Existing
Emissions Using
Natural Gas Boilers
Wood
Combustion Open Burning
Units tons/yr tons/yr tons/yr
Carbon Monoxide (CO) 1.69 3.58 270. (b)
170-370 (c)
Sulfur Dioxide (SO2) 0.012 0.5 Not
listed
Nitrogen Oxide (NOx) 3.3 4.3 7.7 (b)
PM Total 0.1 3.2 32. (b)
7.6 – 32.(c)
VOC (non methane) 0.1 0.1 45.8 (b)
7.6-36. (c)
Carbon Dioxide (CO2) 2340 Net zero Net Zero
(Not Listed)
Methane (CH4) (a) (a) 6.2-10.8 (c)
(a) no value listed, expected to be negligible
(b) estimated based on Rocky Mountain wildfire forest burning emission factors (AP-42, Table 13.1-3)
(c) estimated based on forest wastes burning emission factors (AP-42, Table 2.5-5)
(d) can be a significant source depending on conditions in the landfill.
(e) can be a significant source depending on the composting conditions.
Table 2. Comparison of Emissions: Current Plant, Proposed Plant, and Open Burning
Mouillot et al. [2006] concluded that “The total amount of carbon emitted to the atmosphere
from biomass burning is uncertain.” Neither combustion efficiencies nor the extent of
burned areas are known with precision [Ito and Penner, 2005; Kasischke and Penner, 2004].
The argument for increased use of biofuels instead of fossil fuels is based on considering
CO2 from biomass burning as recyclable. An obvious question is whether the use of biofuels
should be reduced as a strategy for reducing the total emissions of greenhouse gases. In fact,
researchers predict that the effect of controls on biomass burning on climate change will be
mildly effective in reducing CO2 emissions – leading to a prediction of a short-term
warming followed by a longer-term global cooling [Jacobson, 2004]. Although the Kyoto
Protocol did not consider biomass-burning controls as a means of reducing global warming,
there is an argument that at least in the time-frame of the next decade this strategy has the
potential of reducing global warming.
3.2 Waste to energy facilities
The emission rates from waste to energy combustion in the proposed biomass heat plant are
likely to be similar to those from incineration as opposed to those discussed above for open
burning, landfilling, and composting.

Evaluation of Replacing Natural Gas Heat Plant
with a Biomass Heat Plant – A Technical Review of Greenhouse Gas Emission Trade-Offs 239
ITCC [2007] states:
“Incineration is common in the industrialized regions of Europe, Japan and the
northeastern USA where space limitations, high land costs, and political opposition to
locating landfills in communities limit land disposal. In developing countries, low land
and labor costs, the lack of high heat value materials such as paper and plastic in the
waste stream, and the high capital cost of incinerators have discouraged waste
combustion as an option.
Waste-to-energy (WTE) plants create heat and electricity from burning mixed solid waste.
Because of high corrosion in the boilers, the steam temperature in WTE plants is less than
400 degrees Celsius. As a result, total system efficiency of WTE plants is only between
12%–24% [Faaj et al., 1998; US EPA, 1998; Swithenbank and Nasserzadeh, 1997].
Net greenhouse gas emissions from WTE facilities are usually low and comparable to
those from biomass energy systems, because electricity and heat are generated largely
from photosynthetically produced paper, yard waste, and organic garbage rather than
from fossil fuels. Only the combustion of fossil fuel based waste such as plastics and
synthetic fabrics contribute to net greenhouse gas releases, but recycling of these
materials generally produces even lower emissions.”
Based on a broader life-cycle perspective, Borjesson and Berglund [Borjesson and Berglund,
2006; Berglund and Borjesson, 2006] address the overall environmental impact when biogas
systems are introduced to replace various conventional systems for energy generation,
waste management and agricultural production. Their conclusion is that biogas systems
normally also lead to indirect environmental improvements, which in some cases are
considerable. They note that these indirect benefits (e.g. reduced nitrogen leaching,
emissions of ammonia and methane) often exceed the direct environmental benefits
achieved in situation when fossil fuels are to be replaced by biogas.
4. Conclusions
Conversion of the NREL heat plant will replace combustion of fossil fuels with a biomass fuel.
The literature was found to support this action in terms of emissions of greenhouse gases.
Although the reduction of any of the major emission sources can be an effective strategy for
slowing the increase in atmospheric greenhouse gases, the literature also strongly supports
the replacement of fossil fuels with biomass fuels based on the concept of stopping the
release of “new” carbon currently sequestered in fossil fuels.
When compared to open burning, the proposed conversion is desirable in terms of the
emission of pollutants. The comparison in Table 2 based on EPA’s AP-42 indicates the same
mass wood chips by open burning would significantly increase the emissions of carbon
monoxide, total particulate matter, and VOCs. The literature indicates only a factor of 2
increase in nitrogen oxide emissions.
When compared to disposal in a landfill, the evidence is also in favor of the proposed
conversion. Disposal landfills have the advantage over the biomass heat plant in that the
landfill will generally not be a significant source of particulate matter. On the other hand,
wood chips in a landfill with actively decomposing materials would produce a more potent

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mixture of greenhouse gasses (i.e. increased levels of methane and ammonia). The potential for
the gases produced in landfills to be collected as a biomass source is considered as a process
that potentially in the future could put the landfill greenhouse emissions on a par with the
proposed heat plant [McKendry, 2002a]. IPCC [2007] indicates that there are no plausible
scenarios in which landfilling minimizes greenhouse gas emissions from waste management.
When compared to composting, the proposed conversion is desirable in terms of the
emission of pollutants. Although the literature is full of studies to make the emissions from
composting more “greenhouse gas friendly,” the current status is that a composting
technology for organic material such as wood chips only minimizes the emissions of
greenhouse gases. The high temperature combustion process used in the proposed biomass
heat plant mainly produces CO2 while nearly eliminating the emissions of the other more
potent greenhouse gases.
Thus the concept of reducing the potential global warming impacts from burning of biomass
is consistent with the proposed conversion of the heat plant. As seen in this review, in
addition to using a recycled source of carbon, the high temperature combustion of the wood
chips results in a net decrease in the climate-change potency of the greenhouse gas
emissions compared to current use/destruction of wood chips in composting and open
burning.
5. References
Al-Dabbas, M. A. F. (1998), Reduction of methane emissions and utilization of municipal
waste for energy in Amman, Renewable Energy, 14(1-4), 427-434.
Bergamaschi, P., C. Lubina, R. Konigstedt, et al. (1998), Stable isotopic signatures (delta C-
13, delta D) of methane from European landfill sites, Journal of Geophysical Research-
Atmospheres, 103(D7), 8251-8265.
Berglund, M., and P. Borjesson (2006), Assessment of energy performance in the life-cycle of
biogas production, Biomass & Bioenergy, 30(3), 254-266.
Bogner, J., K. Spokas, E. Burton, et al. (1995), LANDFILLS AS ATMOSPHERIC METHANE
SOURCES AND SINKS, Chemosphere, 31(9), 4119-4130.
Bogner, J. E., K. A. Spokas, and E. A. Burton (1999), Temporal variations in greenhouse gas
emissions at a midlatitude landfill, Journal of Environmental Quality, 28(1), 278-288.
Borgwardt, R. H. (1997), Biomass and natural gas as co-feedstocks for production of fuel for
fuel-cell vehicles, Biomass & Bioenergy, 12(5), 333-345.
Borjesson, P., and M. Berglund (2006), Environmental systems analysis of biogas systems -
Part 1: Fuel-cycle emissions, Biomass & Bioenergy, 30(5), 469-485.
Clinton, N. E., P. Gong, and K. Scott (2006), Quantification of pollutants emitted from very large
wildland fires in Southern California, USA, Atmospheric Environment, 40(20), 3686-3695.
Dennis, A., M. Fraser, S. Anderson, et al. (2002), Air pollutant emissions associated with
forest, grassland, and agricultural burning in Texas, Atmospheric Environment,
36(23), 3779-3792.
Faij, A. P. C. (2006). "Bio-energy in Europe: changing technology choices." Energy Policy,
34(3): 322-342.
Hays, M. D., C. D. Geron, K. J. Linna, et al. (2002), Speciation of gas-phase and fine particle
emissions from burning of foliar fuels, Environmental Science & Technology, 36(11), 2281-
2295.

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with a Biomass Heat Plant – A Technical Review of Greenhouse Gas Emission Trade-Offs 241
Hays, M. D., P. M. Fine, C. D. Geron, et al. (2005), Open burning of agricultural biomass:
Physical and chemical properties of particle-phase emissions, Atmospheric
Environment, 39(36), 6747-6764.
IPCC, 2007. Climate Change 2007: The Physical Science Basis: Summary for Policymakers.
Contribution of Working Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change. Available at http://www.ipcc.ch, last
accessed May 4, 2007.
IPCC, 2001. Climate Change 2001: Mitigation. Contribution of Working Group III to the
Third Assessment Report of the Intergovernmental Panel on Climate Change.
Available at http://www.ipcc.ch, last accessed May 4, 2007.
Ito, A, and J. E. Penner (2005), Historical emissions of carbonaceous aerosols from biomass
and fossil fuel burning for the period 1870-2000, Global Biogeochemical Cycles, 19(2).
Ito, A., and J. E. Penner (2004), Global estimates of biomass burning emissions based on satellite
imagery for the year 2000, Journal of Geophysical Research-Atmospheres, 109(D14).
Jacobson, M. Z. (2004), The short-term cooling but long-term global warming due to biomass
burning, J. Clim., 17(15): 2909-2926.
Kasischke, E. S., and J. E. Penner (2004), Improving global estimates of atmospheric emissions
from biomass burning, Journal of Geophysical Research-Atmospheres, 109(D14).
Khalil, M. A. K., and R. A. Rasmussen (2003), Tracers of wood smoke, Atmospheric
Environment, 37(9-10), 1211-1222.
Kumar, S., S. A. Gaikwad, A. V. Shekdar, et al. (2004a), Estimation method for national methane
emission from solid waste landfills, Atmospheric Environment, 38(21), 3481-3487.
Kumar, S., A. N. Mondal, S. A. Gaikwad, et al. (2004b), Qualitative assessment of methane
emission inventory from municipal solid waste disposal sites: a case study,
Atmospheric Environment, 38(29), 4921-4929.
Lang, D. J., C. R. Binder, R. W. Scholz, et al. (2006), Impact factors and regulatory
mechanisms for material flow management: Integrating stakeholder and scientific
perspectives - The case of bio-waste delivery, Resources Conservation and Recycling,
47(2), 101-132.
Liebig, M. A., J. A. Morgan, J. D. Reeder, et al. (2005), Greenhouse gas contributions and
mitigation potential of agricultural practices in northwestern USA and western
Canada, Soil & Tillage Research, 83(1), 25-52.
Ligon, J. M., D. S. Hill, P. Hammer, et al. (1999), Natural products with antimicrobial activity
from Pseudomonas biocontrol bacteria, in Pesticide Chemistry and Bioscience: The
Food-Environment Challenge, edited by G. T. Brooks and T. R. Roberts, pp. 179-189.
Lunghi, P., R. Bove, and U. Desideri (2004), Life-cycle-assessment of fuel-cells-based landfill-
gas energy conversion technologies, Journal of Power Sources, 131(1-2), 120-126.
McKendry, P. (2002a), Energy production from biomass (part 1): overview of biomass,
Bioresource Technology, 83(1): 37-46.
McKendry, P. (2002b), Energy production from biomass (part 2): conversion technologies,
Bioresource Technology, 83(1): 47-54.
McKendry, P. (2002c.) Energy production from biomass (part 3): gasification technologies,
Bioresource Technology, 83(1): 55-63.
Mouillot, F., A. Narasimha, Y. Balkanski, J.F. Lamarque, and C.B. Field (2006), Global carbon
emissions from biomass burning in the 20th century, Geophysical Research Letters, 33(1).
Oros, D. R., and B. R. T. Simoneit (2001), Identification and emission factors of molecular
tracers in organic aerosols from biomass burning Part 1. Temperate climate
conifers, Applied Geochemistry, 16(13), 1513-1544.

Municipal and Industrial Waste Disposal
242
Pan, J. L., and N. Voulvoulis (2007), The role of mechanical and biological treatment in
reducing methane emissions from landfill disposal of municipal solid waste in the
United Kingdom, Journal of the Air & Waste Management Association, 57(2), 155-163.
Pier, P. A., and J. M. Kelly (1997), Measured and estimated methane and carbon dioxide
emissions from sawdust waste in the Tennessee Valley under alternative
management strategies, Bioresource Technology, 61(3), 213-220.
Pronobis, M. (2006), The influence of biomass co-combustion on boiler fouling and
efficiency, Fuel, 85(4), 474-480.
Reddy, MS, and C Venkataraman (2002), Inventory of aerosol and sulphur dioxide
emissions from India. Part II - biomass combustion, Atmos. Environ., 36(4): 699-712.
Reiner, T., D. Sprung, C. Jost, et al. (2001), Chemical characterization of pollution layers over
the tropical Indian Ocean: Signatures of emissions from biomass and fossil fuel
burning, Journal of Geophysical Research-Atmospheres, 106(D22), 28497-28510.
Schmid, O., P. Artaxo, W. P. Arnott, et al. (2006), Spectral light absorption by ambient
aerosols influenced by biomass burning in the Amazon Basin. I: Comparison and
field calibration of absorption measurement techniques, Atmospheric Chemistry and
Physics, 6, 3443-3462.
Swithenbank, J., V. Nasserzadeh, R. Taib, et al. (1997), Incineration of wastes in novel high-
efficiency tumbling and rotating, fluidized bed incinerator, Journal of Environmental
Engineering-Asce, 123(10), 1047-1052.
Suzuki, T, Y Ikumi, S Okamoto, I Watanabe, N Fujitake, and H Otsuka. (2004), Aerobic
composting of chips from clear-cut trees with various co-materials, Bioresource
Technology, 95(2): 121-128.
Tilman, D., J. Hill, and C. Lehman (2006), Carbon-negative biofuels from low-input high-
diversity grassland biomass, Science, 314(5805), 1598-1600.
Turn, S. Q., B. M. Jenkins, J. C. Chow, et al. (1997), Elemental characterization of particulate
matter emitted from biomass burning: Wind tunnel derived source profiles for
herbaceous and wood fuels, Journal of Geophysical Research-Atmospheres, 102(D3),
3683-3699.
Wiedinmyer, C., B. Quayle, C. Geron, et al. (2006a), Estimating emissions from fires in North
America for air quality modeling, Atmospheric Environment, 40(19), 3419-3432.
Wiedinmyer, C., X. X. Tie, A. Guenther, et al. (2006b), Future changes in biogenic isoprene
emissions: How might they affect regional and global atmospheric chemistry?,
Earth Interactions, 10.
Winiwarter, W., and K. Rypdal (2001), Assessing the uncertainty associated, with national
greenhouse gas emission inventories: a case study for Austria, Atmospheric
Environment, 35(32), 5425-5440.
US EPA (1998), Compilation of Air Pollutant Emission Factors, AP-42, 5th Edition, Volume
1: Stationary Point and Area Sources Chapter 2: Solid Waste Disposal, Section 2.4, U.S.
EPA Supplement E, November 1998. p. 2.4 - 4.
US EPA (2000), Municipal solid waste in the United States: 2000 Facts and Figures. 2000
Update, EPA530-R-02-001.
USEPA (2007), Technology transfer network clearinghouse for inventories & emissions
factors, edited.
USEPA (2008), Climate leaders: Greenhouse gas inventory protocol core module guidance -
Direct emissions from stationary combustions sources, EPA430-K-08-003,
www.epa.gov/climateleaders, May 2008.