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Manager of IEA Bioenergy Task 38
The publications below are listed alphabetically by name of the (first) author.
Apps M.J. and D.T. Price (1996):
NATO Meeting “Forest Ecosystems, Forest Management and the Global Carbon Cycle” – Introduction
Eriksson H. and G. Hallsby (1992):
Biomass Fuels – Effects on the Carbon Dioxide Budget
Graham R.L., L.L. Wright, and A.F. Turhollow (1992):
The Potential for Short-Rotation Woody Crops to Reduce U.S. CO2 Emissions
Gustavsson L., P. Börjesson, B. Johansson, and P. Svenningsson (1995):
Reducing CO2-Emissions by Substituting Biomass for Fossil Fuels
Lazarus M., C. Heaps, and D. Hill (1995):
The SEI/UNEP Fuel Chain Project: Methods, Issues and Case Studies in Developing Countries
Makundi W.R., J. Sathaye, and A. Ketoff (1995):
COPATH – A Spreadsheet Model for the Estimation of Carbon Flows Associated with the Use of Forest Resources
Marland G. and B. Schlamadinger (1995):
Biomass Fuels and Forest-Management Strategies: How Do We Calculate the Greenhouse Gas Emission Benefits?
Marland G. and A.F. Turhollow (1991):
CO2 Emissions from the Production and Combustion of Fuel Ethanol from Corn
Marland G. and S. Marland (1992):
Should We Store Carbon in Trees?
Ranney J.W., L.L. Wright, and C.P. Mitchell (1991):
Carbon Storage and Recycling in Short-Rotation Energy Crops
Savolainen I., K. Hillebrand, I. Nousiainen, and J. Sinisalo (1994):
Comparison of Radiative Forcing Impacts of the Use of Wood, Peat, and Fossil Fuels
Schlamadinger B., J. Spitzer, G.H. Kohlmaier, and M. Lüdeke (1995):
Carbon Balance of Bioenergy from Logging Residues
Schlamadinger B. and G. Marland (1996):
Carbon Implications of Forest Management Strategies
Schlamadinger B. and G. Marland (1996):
Full Fuel Cycle Carbon Balances of Bioenergy and Forestry Options
Schlamadinger B. and G. Marland (1996):
The Role of Forest and Bioenergy Strategies in the Global Carbon Cycle
Shapouri H., J.A. Duffield, and M.S. Graboski (1995):
Estimating the Net Energy Balance of Corn Ethanol
Turhollow A.F. and R.D. Perlack (1991):
Emissions of CO2 from Energy Crop Production
Tyson K.S., C. J. Riley, and K.K. Humphreys (1993):
Fuel Cycle Evaluations of Biomass-Ethanol and Reformulated Gasoline, Volume I
Wright L.L. and E.E. Hughes (1993):
U.S. Carbon Offset Potential Using Biomass Energy Systems
In: “Forest Ecosystems, Forest Management and the Global Carbon Cycle“, edited by M.J. Apps and D.T. Price, NATO ASI Series Vol. 40, 1-15, Springer-Verlag Berlin Heidelberg 1996
KEYWORDS: GLOBAL, FORESTS, CARBON CYCLING, ECOSYSTEM DYNAMICS, SUSTAINABILITY
ABSTRACT. Current scientific assessment of the role of forests in the global C cycle is reviewed, including possible contributions to the ‘missing’ C sink, and possible effects of global change. Assessments are needed by policymakers, if global problems such as greenhouse gas emissions, deforestation, land degradation, and non-sustainable ecosystem management are to be solved.Socio- economic aspects of C management interact with other uses of global forests. The ‘scaling problem’, a major issue in ecosystem science, extends into the global policy arena: can we develop global management policies with incomplete scientific knowledge? The book addresses effects of human- induced changes on structure and function of global forests and feedbacks to these changes in terms of the carbon cycle. The view that natural forest ecosystems are always at steady state with respect to C uptake/loss is challenged. Energy substitution (direct and indirect) of products for fossil fuel use, including recycling, has potential to provide cumulative carbon benefits. Monitoring of forest C cycling and comprehensive C budget assessments are needed; C budget estimates can be an important performance indicator of forest sustainability.
United States Department of Energy Report, ANL/ESD/TM-22, 1991
KEYWORDS: GREENHOUSE GASES, CO2, METHANE, NITROUS OXIDE, TRANSPORTATION FUELS, ELECTRICITY, BIOMASS, FULL FUEL-CYCLE, CARBON MONOXIDE, NITROGEN OXIDES, NMOC, MANUFACTURE, LAND USE CHANGES, GASOLINE, DIESEL, METHANOL, WOOD, ETHANOL FROM CORN
ABSTRACT. This report presents estimates of full fuel-cycle emissions of greenhouse gases from using transportation fuels and electricity. The data cover emissions of carbon dioxide (CO2), methane, carbon monoxide, nitrous oxide, nitrogen oxides, and nonmethane organic compounds resulting from the end use of fuels, compression or liquefaction of gaseous transportation fuels, fuel distribution, fuel production, feedstock transport, feedstock recovery, manufacture of motor vehicles, maintenance of transportation systems, manufacture of materials used in major energy facilities, and changes in land use that result from using biomass-derived fuels. The results for electricity use are in grams of CO2-equivalent emissions per kilowatt-hour of electricity delivered to end users and cover generating plants powered by coal, oil, natural gas, methanol, biomass, and nuclear energy. The transportation analysis compares CO2-equivalent emissions, in grams per mile, from base-case gasoline and diesel fuel cycles with emissions from these alternative-fuel cycles: methanol from coal, natural gas, or wood; compressed or liquefied natural gas; synthetic natural gas from wood; ethanol from corn or wood; liquefied petroleum gas from oil or natural gas; hydrogen from nuclear or solar power; electricity from coal, uranium, oil, natural gas, biomass, or solar energy, used in battery-powered electric vehicles; and hydrogen and methanol used in fuel-cell vehicles.
United States Department of Energy Report, ANL/ESD/TM-22, 1993
Appendix K: Biofuels (Ethanol from Corn; Ethanol, Methanol, and Synthetic Natural Gas from Wood).
KEYWORDS: BIOFUELS, ETHANOL FROM CORN, CO2, BIOMASS, GREENHOUSE EFFECT, LAND USE, METHANOL, BYPRODUCTS, SYNTHETIC NATURAL GAS, GASOLINE FROM WOOD
ABSTRACT. Biological matter (biomass) can be a feedstock for the production of a range of liquid and gaseous fuels.
Chapter K.2, Energy Used to Process Biomass and Biofuels: Ethanol from Corn: also by-products are taken into account (chapter K.2.14,Handling of Multiple Products: The By-Product-Credit Problem).
Chapter K.3, Energy Used to Make Methanol, Ethanol, Synthetic Natural Gas, and Gasoline from Wood: Wood can be gasified and cleaned up to produce a substitute, medium-Btu NG; gasified and then converted to methanol, via normal methanol synthesis; or hydrolyzed by enzymes and converted to methanol. Energy-use data are available for all three routes, and all are analyzed in this report.
Also relevant to “Bioenergy and Greenhouse Gases” is chapter K.5, Land Use and the Estimation of the Greenhouse Effect of Biofuels: It is usually assumed that because the CO2 released from the burning of a biofuel is equal to the CO2 removed from the atmosphere by the biofuel-feedstock, a biofuel program will be in carbon balance, with no net emissions of greenhouse gases (emissions from the use of process energy and fertilizers aside). In this section, the author shows that generally this will not be true.
Närings- och teknikutvecklingsverket, R 1992:10 NUTEK-Report No. R 1992:10, 30 pages, 1992
KEYWORDS: CARBON, CARBON DIOXIDE, C EMISSIONS, BIOMASS, SOIL ORGANIC MATTER, FUELS, BIOENERGY, FORESTRY, SOIL
ABSTRACT. Fossil-fuel combustion is the main reason why the CO2 concentrations in the atmosphere are increasing. Since such an increase could affect the global climate, it is highly desirable that the possible effects on the carbon dioxide balance of alternative energy sources are being evaluated. Two important alternatives being intensively studied in Sweden are the extraction of logging residues otherwise left in the forest and willow production on farmland. In connection with an increase in the use of forest biomass it is essential that the site productivity of the forest soils will be maintained. Nutrient budgets indicate that at many sites there is a definite risk that nutrients and acid-neutralizing compounds will be removed through forest biomass harvest and leaching faster than they are added through deposition and weathering/fixation. Thus compensatory measures will probably be necessary to maintain site productivity if large-scale whole-tree harvesting is to be conducted. It seems likely that such considerations will be made in accordance with the best available knowledge. Considered in isolation, a conversion from stem-wood harvest to whole-tree harvest do have a negative effect on the carbon dioxide balance, because the amount of soil organic matter decreases. With the assumption that it takes 20 years for the logging residues to decompose with a constant amount per year, if they would have been left at site, the net decrease in emissions that would result from the replacement of fossil fuels by logging residues appear moderate after 20 years with a continuous annual combustion. However, it will grow significant as time passes. After 100 years with an annual combustion of logging residues the emissions are calculated to be about 12% of those associated with the production of an equivalent amount of energy through oil combustion. Corresponding values for 300 and 500 years are 4% and 2,5% respectively. In less than 100 years there should be a considerable reduction in the Swedish CO2-C emissions even if only every second new logging residue-produced TWh replaces an fossil-fuel-produced TWh. All conversion from annual to perennial crop production on redundant farmland should have a positive effect on the carbon dioxide balance, owing to an increase in carbon storage. Planting spruce would result in an increase in the carbon storage per unit area about three times larger than the increase caused by planting willow, counted as averages for the rotation periods. However, the degree to which the net emission of carbon dioxide from Sweden will decrease, depends more on to the extent to which fossil-fuel energy will be replaced by biomass energy from this land area. From a long-term perspective (many centuries), both the positive and negative effects on carbon reservoirs in Sweden, caused by conversions to whole-tree harvesting in forestry and to willow production on redundant farmland, can be considered negligible in terms of their influence on the carbon dioxide budget of Sweden. The relation between orders of magnitude of influencing fluxes is exemplified in the following: The annual production of 50 TWh, whereof 40 TWh from logging residues, 8 TWh from willow and 2 TWh from annual crops is estimated to cause a total net decrease of the carbon reservoirs within Sweden corresponding to 32 Tg CO2-C, whereas the annual production of 50 TWh from oil combustion should emit 1200 Tg CO2-C in 300 years, 2000 Tg CO2-C in 500 years and so on.
Climate Change, Vol. 22, 223-238, 1992.
KEYWORDS: SHORT ROTATION WOODY CROPS (SRWC), CARBON, CO2, MITIGATION, FOSSIL FUEL DISPLACING, WOOD CONVERSION EFFICIENCIES, ELECTRICITY, LIQUID FUELS, FOSSIL FUELS, CARBON MITIGATION POTENTIAL
ABSTRACT. Short-rotation woody crops (SRWC) could potentially displace fossil fuels and thus mitigate CO2 buildup in the atmosphere. To determine how much fossil fuel SRWC might displace in the United States and what the associated fossil carbon savings might be, a series of assumptions must be made. These assumptions concern the net SRWC biomass yields per hectare (after losses); the amount of suitable land dedicated to SRWC production; wood conversion efficiencies to electricity or liquid fuels; the energy substitution properties of various fuels; and the amount of fossil fuel used in growing, harvesting, transporting, and converting SRWC biomass. Assuming the current climate, present production and conversion technologies and considering a conservative estimate of the U.S. land base available for SRWC (14 x 106 ha), we calculate that SRWC energy could displace 33.2 to 73.1 x 106 Mg of fossil carbon releases, 3-6% of the current annual U.S. emissions. The carbon mitigation potential per unit of land is larger with the substitution of SRWC-derived ethanol for gasoline. Assuming current climate, predicted conversion technology advancements, an optimistic estimate of the U.S. land base available for SRWC (28 x 106 ha), and an optimistic average estimate of net SRWC yields (22.4 dry Mg/ha), we calculate that SRWC energy could displace 148 to 242 x 106 Mg of annual fossil fuel carbon releases. Under this scenario, the carbon mitigation potential of SRWC-based electricity production would be equivalent to about 4.4% of current global fossil fuel emissions and 20% of current U.S. fossil fuel emissions.
Energy – the International Journal, Vol. 20, No. 11, 1097-1113, 1995
KEYWORDS: GREENHOUSE GASES, BIOMASS, FOSSIL FUELS, ELECTRICITY, HEAT, TRANSPORTATION FUELS, FUEL CYCLE, CO2, ENERGY INPUTS
ABSTRACT. Replacing fossil fuels with sustainably-produced biomass will reduce the net flow of CO2 to the atmosphere. We express the efficiency of this substitution in reduced emissions per unit of used land or biomass, and in costs of the substitution per ton of C. The substitution costs are calculated as the cost difference between continued use of fossil fuels at current prices and the use of biomass, assuming that the biomass technologies are implemented when reinvestments in existing technologies are required. Energy inputs into biomass production and conversion are biomass-based, resulting in a CO2-neutral fuel cycle, while CO2 emissions from fossil fuels are estimated for the complete fuel cycles. Substituting biomass for fossil fuels in electricity and heat production is, in general, less costly and provides larger CO2 reductions per unit of biomass than substituting biomass for gasoline or diesel used in vehicles. For transportation, methanol or ethanol produced from short-rotation forests or logging residues provide larger CO2-emission reductions than rape methyl ester from rape seed, biogas from lucerne (alfalfa), or ethanol from wheat. Of these, methanol has the lowest emission-reduction costs. Increasing biomass use by 125 TWh/yr, the estimated potential for increased utilization of logging residues, straw and energy crops, would eliminate more than half of the Swedish CO2 emissions from fossil fuels of 15 Mtons C in 1992.
SEI Stockholm Environment Institute – Boston, Report May 1995
KEYWORDS: FUEL CHAIN ANALYSIS, BIOMASS, WOODFUEL, BIOMASS SYSTEMS
TABLE OF CONTENTS
(not complete, mainly biomass related items are mentioned here)
|PART 1 – Main Report
|1. Project Overview|
|1.2 Incorporating environmental considerations in energy decisions
1.6 Directions for the Future
|2. An Approach to Fuel Chain Analysis|
|2.1 Why fuel chain analysis?
2.2 Some key methodological considerations
2.3 A new tool for fuel chain analysis
|3. An Approach to Biomass Analysis|
3.2 Issues in woodfuel planning
3.3 Modeling biomass systems
3.4 A new tool for biomass analysis
|PART 2 – Case Studies|
|PART 3 – Enhancements to LEAP and EDB|
|6. The LEAP Fuel Chain Program|
|6.1 Using the fuel chain program
6.2 The main menu
6.3 Sharing data with energy scenario programs
6.4 General options
6.5 Enter data
6.6 View results
6.7 Calculation methodology
|7. The LEAP Biomass Program|
7.2 Enter data
7.3 Scenario data entry
7.4 View results
7.5 View data echo
7.6 Biomass calculations
|8. Other Revisions to LEAP and EDP|
|PART 4 – Fuel Chain Fact Sheets|
|9. Biomass Fuel Chain Fact Sheets|
|9.1 Biomass production
9.2 Biomass transport
9.3 Electricity generation
|10. Coal Fuel Chain Fact Sheets
11. Natural Gas Fuel Chain Fact Sheets
12. The Petroleum Products Fuel Chain
13. Materials Production Fact Sheets
|A Listing of Core Environmental Database (EDB) Coefficients|
Biomass and Bioenergy, Vol. 8, No. 5, special issue “Forestry and Climate Change“, edited by J. Coombs, D.O. Hall, R.P. Overend, and W.H. Smith, 369-380, 1995
KEYWORDS: FORESTRY, MODEL, LAND USE CHANGE, CARBON FLUX
ABSTRACT. The forest sector plays a key role in the global climate change process. A significant amount of net greenhouse gas emissions emanate from land use changes, and the sector offers a unique opportunity to sequester carbon in vegetation, detritus, soil and forest products. However, the estimates of carbon flows associated with the use of forest resources have been quite imprecise. This paper describes a methodological framework – COPATH – which is a spreadsheet model for estimating carbon emissions and sequestration from deforestation and harvesting of forests. The model has two parts, the first estimates carbon stock, emissions and uptake in the base year, while the second part forecasts future emissions and the uptake under various scenarios. The forecast module is structured after the main modes of forest conversion, i.e. agriculture, pasture, forest harvesting and other land uses. The model can be used by countries which may not possess an abundance of pertinent data, and allows for the use of forest inventory data to estimate carbon stocks. The choice of the most likely scenario procides the country with a carbon flux profile necessary to formulate GHG mitigation strategies.
Energy – the International Journal, Vol. 20, No. 11, 1131-1140, 1995
KEYWORDS: CARBON, CO2, GREENHOUSE GASES, BIOMASS ENERGY, ENERGY INPUT, BYPRODUCTS, FULL FUEL-CYCLE ANALYSIS, OPPORTUNITY COST, WOOD PRODUCTS, ACCOUNTING
ABSTRACT. We show in this study that a full fuel-cycle analysis of the greenhouse gas (CO2) implications of biomass energy systems has not only to take into account the inputs and outputs of energy (and associated carbon content) but must recognize that many biomass systems have by- products that are produced along with the biofuel. The analysis must also account for the temporal variability of carbon stocks and fluxes associated with the standing biomass and its harvest. Where land resources are limited, we need to consider the opportunity cost of managing the land to produce biomass fuels. Establishing a system of parties, each accountable for its own greenhouse-gas emissions, would require detailed deliberations on how to treat carbon flows in biofuels and wood products exchanged between the parties. An accounting for credits and debits has to be found that encourages each party to act in a way that is optimal for the carbon budget of the whole system.
Energy – the International Journal, Vol. 16, No. 11/12, 1307-1316, 1991
KEYWORDS: CO2, BIOMASS FUEL, ETHANOL, CORN, BIOENERGY, GREENHOUSE GASES, BYPRODUCTS, ENERGY INPUTS, LIQUID FUEL
ABSTRACT. Concern over the increasing concentration of CO2 in the Earth’s atmosphere is causing us to re-evaluate how we use energy. In particular, we need to inquire if there are alternative energy systems which discharge less net CO2 per unit of energy service. This paper deals with the CO2 fluxes associated with the use of one biomass fuel, ethanol derived from corn. In a sustainable agricultural system, there is no net CO2 flux to the atmosphere from the corn itself but there is a net CO2 flux due to the fossil-fuel supplements currently used to produce and process corn. A comparison between ethanol from corn and gasoline from crude oil becomes very complex because of the variability of corn yield, the lack of available data on corn processing, and the complexity of treating the multiple products from corn processing. When the comparison is made on an energy content basis only, with no consideration of how the products are to be used, and at the margin of the current U.S. energy system, it appears that there is a net CO2 saving associated with ethanol from corn. This net saving in CO2 emissions may be as large as 40% or as small as 20%, depending on how one chooses to evaluate the by-product credits. This analysis also demonstrates that the frequently posed question, whether the energy inputs to ethanol exceed the energy outputs, would not be an over-riding consideration even if it were true, because most of the inputs are as coal and natural gas, whereas the output is as high-quality liquid fuel.
Water, Air, and Soil Pollution, Vol. 64, No. 1-2, 181-195, 1992, Special Issue “Natural sinks of CO2“, edited by J. Wisniewski and A.E. Lugo
KEYWORDS: CARBON, CO2, EMISSIONS, BIOMASS, FOREST, BIOFUELS, HARVESTING, REFORESTATION, C SEQUESTRATION, MODEL, FOSSIL FUEL SUBSTITUTION, EFFICIENCY, TIME PERSPECTIVE
ABSTRACT. In order to explore for the most effective strategy for using forests to mitigate global climate change, we have constructed a simple model of C uptake during forest growth and the fate of this C when forests are harvested and used as fuel to replace fossil fuels. We suggest that trees are equally effective in preventing the accumulation of CO2 in the atmosphere if they remove a unit of C from the atmosphere or if they supply a sustainable source of energy that substitutes for a unit of C discharged by burning fossil fuels. The model shows that the most effective strategy for using forest land to minimize increases in expected, the efficiency with which the forest harvest is used to substitute for fossil fuels, and the time perspective of the analysis. For forests with large standing biomass and low productivity the most effective strategy is to protect the existing forest. For land with little standing biomass and low productivity, the most effective strategy is to reforest or otherwise manage the land for forest growth and C storage. Where high productivity can be expected, the most effective strategy is to manage the forest for a harvestable crop and to use the harvest with maximum efficiency either for long-lived products or to substitute for fossil fuels. The longer the time perspective, the more likely that harvesting and replanting will result in net C benefits.
In: Bioenergy and the Greenhouse Effect, Proceedings of a Seminar organized by IEA Bioenergy Agreement and National Energy Administration, NUTEK, B 1991:1, 39-59
Närings- och teknikutvecklingsverket, Liljeholmsvägen 32, 117 86 Stockholm, SWEDEN
KEYWORDS: ENERGY CROPS, SHORT-ROTATION, PLANTATIONS, CARBON, BIOMASS, SOIL CARBON, LITTER LAYER, ROOT BIOMASS, C SEQUESTRATION, CROPLAND
ABSTRACT. Short-rotation energy crops can play a significant role in storing carbon compared to the agricultural land uses they would displace. However, the benefits from these plantations in avoiding further use of fossil fuel and in taking pressure off native forests for energy uses provides longer term carbon benefits than the plantation carbon sequestration itself. The fast growth and harvest frequency of plantations tends to limit the amount of above- and below-ground carbon storage in them.
The primary components of plantation carbon sequestering compared to sustained agricultural practices involve above ground wood, possible increased soil carbon, litter layer formation, and increased root biomass. On the average, short-rotation plantations in total may increase carbon inventories by about 10 to 40 tons per hectare over about a 20 to 50 year period when displacing cropland. This is about doubling in storage over cropland and about one-half the storage in human- impacted forests. The sequestration benefit of wood energy crops over cropland would be negated in about 75 to 100 years by the use of fossil fuels to tend the plantations and handle biomass.
Plantation interactions with other land uses and total landscape carbon inventory is important in assessing the relative role plantations play in terrestrial and atmospheric carbon dynamics. It is speculated that plantations, when viewed in this context, could generate a global Leveling of net carbon emissions for approximately 10 to 20 years.
World Resource Review, Vol. 6, No. 2, 248-262, 1994
KEYWORDS: PEAT, WOOD, ENERGY PRODUCTION, GREENHOUSE EFFECT, ENERGY PRODUCTION CHAIN, RADIATIVE FORCING, CO2, CH4, N2O
ABSTRACT. The present study investigates the greenhouse impacts and the relevant time factors of the use of peat and wood for energy production and compares with those of fossil fuels. Emissions and sinks of the whole energy production chain and subsequent use of the wood or peat production site are taken into account. The radiative forcing caused by energy production is used as a measure for the greenhouse impact. Economical considerations are not included.
Radiative forcing is calculated for carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions. The real emissions of energy production are calculated by subtracting the emissions of non-use from the emissions of energy production. All the emissions are given as a function of time, i.e. their evolution over time is taken into account. At this point the estimates for some emission developments are quite crude and should be considered exemplary.
The studied energy production chains can be divided roughly into three groups, if the greenhouse impact caused by continuous energy production of hundred years is considered. In this case forest residues, planted stands and unused merchantable wood cause the least radiative forcing per unit of primary energy generated. Natural gas and peat from cultivated peatland form the middle group. According to our calculations coal and conventional peat cause the greatest greenhouse impact.
Biomass and Bioenergy, Vol. 8, No. 4, 221-234, 1995
KEYWORDS: LOGGING RESIDUES, FORESTRY, SOIL, CARBON BALANCE, CARBON CYCLE, CARBON DIOXIDE, BIOMASS, ENERGY, BIOENERGY
ABSTRACT. Bioenergy as a substitute for fossil energy is regarded a possibility to reduce the energy related carbon dioxide emissions to the atmosphere, because “the carbon, which is set free from biomass combustion, is taken up again by regrowing plants and thus the carbon cycle of bioenergy is closed”, as it is often argued. In a more detailed analysis of bioenergy strategies, two main effects have to be investigated: on the one hand, carbon in fossil fuels is substituted and thus not emitted to the atmosphere, while on the other hand, the use of biofuels might result in a reduction of carbon stored in the biosphere (plants, litter and soil). One of the possibilities to use biomass for energy is to burn logging residues from conventional forestry for heat and/or power production. For this type of bioenergy strategy, a model has been developed which allows one to calculate the change in carbon storage in three soil carbon pools and the carbon fluxes to and from these pools. The model results indicate that the carbon stored in the forest soil is reduced when logging residues are removed for bioenergy to displace fossil fuels. However, this effect is limited, as eventually a new equilibrium of carbon storage in the forest soil is reached, while fossil fuel substitution is continued further on. The time-dependent characteristic value “carbon neutrality” (CN), which is the ratio of net emission reduction (fossil fuel substitution minus carbon losses of the soil) to the ‘saved’ carbon emissions from the substituted reference energy system, reflects this effect. CN equal to one means that bioenergy is completely “CO2-neutral”. For bioenergy from logging residues, CN is very low at the beginning when bioenergy is introduced, increases continuously and approaches one at infinity. According to the results of parameter studies, CN of bioenergy from logging residues lies between 0.49 and 0.82 after 20 years and between 0.75 and 0.88 after 100 years.
In: “Forest Ecosystems, Forest Management and the Global Carbon Cycle“, edited by M.J. Apps and D.T. Price, NATO ASI Series Vol. 40, 217-232, Springer-Verlag Berlin Heidelberg 1996
KEYWORDS: CARBON BALANCE, CARBON DIOXIDE, BIOMASS, BIOENERGY, WOOD PRODUCTS, FOREST MANAGEMENT
ABSTRACT. Forest management may offer opportunities for mitigating the increasing concentration of carbon dioxide in the earth’s atmosphere. This study uses a simple mathematical model to examine the flows of carbon that accompany several forest management strategies. Forest management strategies can affect the net flux of C to the atmosphere in 4 ways: changing the amount of C stored in the biosphere, changing the amount of C stored in forest products, producing biofuels to displace use of fossil fuels, and producing wood products to displace products from other materials which often require more fossil fuel for their production. Over long time intervals, the dominant component of the net reduction in C emissions for many scenarios based on highly productive forests is fossil-fuel displacement. Model results emphasize that the effectiveness of forest management as a vehicle for reducing net C emissions to the atmosphere depends very importantly on the productivity of the site and the efficiency with which the forest harvest is used.
Energy Conversion and Management, in press, 1996
Paper presented at the “Greenhouse Gases: Mitigation Options” Conference of the IEA Greenhouse Gas R&D Programme, 22-25 August 1995, London, UK
KEYWORDS: CARBON BALANCE, SHORT ROTATION FORESTRY, WOOD PRODUCTS, BIOENERGY, SENSITIVITY ANALYSIS, EFFICIENCY
ABSTRACT. Forestry projects can – at least temporarily – mitigate the net flux of anthropogenic CO2 to the atmosphere by removing C from the atmosphere and sequestering it in growing trees. The net flux of C to the atmosphere can also be reduced if trees are burned to displace the burning of fossil fuels and are then replanted to recycle the C back into the biosphere, or if wood is used for products that store carbon and are otherwise made from other, more energy-intensive materials. A computer model is employed to calculate carbon balances of two land management and biomass utilization scenarios – conventional forest management and short-rotation forestry. Sensitivity analyses reveal that the most important site and system dependent parameters for the net reduction of carbon emissions are the site occupancy prior to the project, growth rate, efficiency of biomass conversion into energy and non-energy products, and carbon emission rates and efficiencies of displaced fossil fuel cycles. The results demonstrate that time is another important consideration and that projects can look considerably different, in terms of C balance, when the endpoint of the analysis is 20, 50, or 100 years.
Biomass and Bioenergy, Vol. 10, No. 5/6, 275-300, 1996
KEYWORDS: CARBON CYCLE, CARBON BALANCE, CARBON DIOXIDE, BIOMASS, BIOENERGY, BIOFUELS, FOREST MANAGEMENT, WOOD PRODUCTS, MATERIALS SUBSTITUTION, ENERGY SUBSTITUTION
ABSTRACT. Forest and bioenergy strategies offer the prospect of reduced CO2 emissions to the atmosphere. Such strategies can affect the net flux of carbon to the atmosphere through 4 mechanisms: storage of C in the biosphere; storage of C in forest products; use of biofuels to displace fossil-fuel use; use of wood products which often displaces other products that require more fossil fuel for their production. We use the mathematical model GORCAM (Graz/Oak Ridge Carbon Accounting Model) to examine these mechanisms for 16 land-use scenarios. Over long time intervals the amount of C stored in the biosphere and in forest products reaches a steady state and continuing mitigation of C emissions depends on the extent to which fossil fuel use is displaced by the use of bioenergy and wood products. The relative effectiveness of alternative forest and bioenergy strategies and their impact on net C emissions strongly depend, for example, on the productivity of the site, its current usage, and the efficiency with which the harvest is used. When growth rates are high and harvest is used efficiently, the dominant opportunity for net reduction in C emissions is seen to be fossil-fuel displacement. At the growth rates and efficiencies of harvest utilization adopted in many of our base scenarios, the net C balance at the end of 100 years is very similar whether trees are harvested and used for energy and traditional forest products, or reforestation and forest protection strategies are implemented. The C balance on a plantation system that provides a constant output of biomass products can look different than the balance of a single parcel of land.
U.S. Department of Agriculture, Agricultural Economic Report No. 721 (AER-721), 1995
copies: U.S. Department of Agriculture ERS-NASS, 341 Victory Drive, Herndon, VA 22070 USA
KEYWORDS: ETHANOL, NET ENERGY BALANCE, CORN PRODUCTION, ENERGY SECURITY
KEYWORDS (n.o.): BYPRODUCTS
ABSTRACT. Studies conducted since the late 1970’s have estimated the net energy value of corn ethanol. However, variations in data and assumptions used among the studies have resulted in a wide range of estimates. This study identifies the factors causing this wide variation and develops a more consistent estimate. We conclude that the net energy value of corn ethanol has become positive in recent years due to technological advances in ethanol conversion and increased efficiency in farm production. We show that corn ethanol is energy efficient as indicated by an energy ratio of 1.24.
Biomass and Bioenergy, Vol. 1, No. 3, 129-135, 1991
KEYWORDS: CELLULOSIC ENERGY CROPS, CARBON DIOXIDE EMISSIONS
KEYWORDS (n.o.): CARBON BALANCE, ENERGY CROPS
ABSTRACT. Estimates of CO2 emissions in kg C dry Mg-1 of biomass produced under present and likely future production technology (with biomass yields in dry Mg ha-1 in parentheses) are: hybrid poplar, 25.8 (11.3) and 21.8 (18.5); sorghum, 32.0 (13.3) and 21.8 (30.2); and switchgrass, 32.9 (9.0) and 29.2 (14.4). The lower yield for each energy crop can be achieved today, while the potential exists to reach the higher yield, and under some circumstances the higher yield can be reached today. On a kg C GJ-1 basis, CO2 emissions from production of energy crops range from a high of 1.9 for switchgrass to a low of 1.1 at the higher yield for hybrid poplar. These carbon releases are considerably lower than emissions from fossil fuels, which on a kg C GJ-1 basis are 13.78, 22.29, and 24.65 for natural gas, petroleum, and coal, respectively.
National Renewable Energy Laboratory (NREL), Oak Ridge National Laboratory, Pacific Northwest Laboratory. Report No. NREL/TP-463-4950, DE 94000227, 1993, 129 pages
copies: National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161 USA
KEYWORDS: FUEL CYCLE, BIOMASS, ETHANOL, TRANSPORTATION FUELS, ENERGY CROPS, LIGNOCELLULOSIC MATERIAL, CO2
ABSTRACT. This study is limited to creating an inventory of inputs and outputs for three transportation fuels: (1) reformulated gasoline (RFG) that meets the standards of the Clean Air Act Amendments of 1990 (CAAA) using methyl tertiary butyl ether (MTBE); (2) gasohol (E10), a mixture of 10% ethanol made from municipal solid waste (MSW) and 90% gasoline; and (3) E95, a mixture of 5% gasoline and 95% ethanol made from energy crops such as grasses and trees.
The ethanol referred to in this study is produced from lignocellulosic material – trees, grass, and organic wastes – called biomass. Corn-ethanol is nor discussed in this report.
The industrial activities for each fuel cycle are divided into five stages: feedstock production, feedstock transportation, fuel production, fuel distribution, and end use.
The E10 fuel cycle produces less carbon monoxide (CO), carbon dioxide (CO2), and sulfur dioxide (SO2), and creates substantial reductions in MSW sent to landfills compared to RFG 2000. E95 fuel cycles produce 90% fewer CO2, 67% less SO2, and 14% less volatile organic carbon (VOC) emissions compared to the RFG fuel cycle
From this study, we can conclude that replacing a portion of the transportation fuel market with ethanol fuels can reduce global CO2 emissions. Fossil fuel combustion accounts for all of the CO2 produced in the E95 fuel cycles. E95 fuel cycles produce only 9% of the net CO2 produced by the RFG fuel cycle.
Water, Air, and Soil Pollution, Vol. 70, No. 1-4, 483-497, 1993, Special Issue “Terrestrial Biospheric Carbon Fluxes“, edited by J. Wisniewski and R. Neil Sampson
KEYWORDS: CARBON, FOSSIL FUEL DISPLACEMENT, C EMISSIONS, BIOENERGY, SHORT ROTATION WOODY CROPS (SRWC), EFFICIENCY
ABSTRACT. A previous analysis had assumed that about 20% of 1990 U.S. C emissions could be avoided by the substitution of biomass energy technologies for fossil energy technologies at some point in the future. Short-rotation woody crop (SRWC) plantations were found to be the dedicated feedstock supply system (DFSS) offering the greatest C emission reduction potential. High efficiency biomass to electricity systems were found to be the conversion technology offering the greatest C emission reduction potential. This paper evaluates what would be required in terms of rate of technology implementation and time period to reach the 20% reduction goal. On the feedstock supply side, new plantings would have to be installed at an average a rate of 1 x 106 ha yr-1 while average yields would have to increase by 1.5% annually over the 35-year period. Such yield increases have been observed for high value agricultural crops with large government research support. On the generation side, it requires immediate adoption of available technologies with a net efficiency of 33% or higher (such as the Whole Tree EnergyTM technology), installation of approximately 5000 MWe of new capacity each year, and rapid development and deployment of much higher efficiency technologies to result in an average of 42% efficiency by 2030. If these technology changes could be achieved at a linear rate, U.S. C emission reduction could progress at a rate of about 0.6 % yr-1 over the next 35 years.