Global Biomass Energy Potential

The intensive use of renewable energy is one of the options to stabilize CO₂atmospheric concentration at levels of 350 to 550ppm. A recent evaluation of the global potential of primary renewable energy carried out by Intergovernmental Panel on Climate Change (IPCC) sets a value of at least 2800EJ/yr, which is more than the most energy-intensive SRES scenario forecast for the world energy requirement up to the year 2100. Nevertheless, what is really important to quantify is the amount of final energy since the use of renewable sources may involve conversion efficiencies, from primary to final energy, different from the ones of conventional energy sources. In reality, IPCC does not provide a complete account of the final energy from renewables, but the text claims that using several available options to mitigate climate change, and renewables is only one of them, it is possible to stabilize atmospheric carbon dioxide (CO₂) concentration at a low level. In this paper, we evaluate in detail biomass primary and final energy using sugarcane crop as a proxy, since it is one of the highest energy density forms of biomass, and through afforestation/reforestation using a model presented in IPCC Second Assessment Report (SAR). The conclusion is that the primary-energy potential for biomass has been under-evaluated by many authors and by IPCC, and this under-evaluation is even larger for final energy since sugarcane allows co-production of electricity and liquid fuel. Regarding forests we reproduce IPCC results for primary energy and calculate final energy. Sugarcane is a tropical crop and cannot be grown in all the land area forecasted for biomass energy plantation in the IPCC/TAR evaluation (i.e. 1280Mha). Nevertheless, there are large expanses of unexploited land, mainly in Latin America and Africa that are subject to warm weather and convenient rainfall. With the use of 143Mha of these lands it is possible to produce 164EJ/yr (1147GJ/hayr or 3.6W/m²on average) of primary energy and 90EJ/yr of final energy in the form of liquid fuel (alcohol) and electricity, using agricultural productivities near the best ones already achievable and biomass gasification technology. More remarkable is that these results can be obtained with the operation of 4,000 production units with unitary capacity similar to the largest currently in operation. These units should be spread over the tropical land area yielding a plantation density similar to the one presently observed in the state of São Paulo, Brazil, where alcohol and electricity have been commercialized in a cost-effective way for several years. Such an amount of final energy would be sufficiently large to fulfill all the expected global increase in oil demand, as well as in electricity consumption by 2030, assuming the energy demand of such sources continues to grow at the same pace observed over the last two decades. When sugarcane crops are combined with afforestation/reforestation it is possible to show that carbon emissions decline for some IPCC SRES scenarios by 2030, 2040 and 2050. Such energy alternatives significantly reduce CO₂emissions by displacing fossil fuels and promote sustainable development through the creation of millions of direct and indirect jobs. Also, it opens an opportunity for negative CO₂emissions when coupled with carbon dioxide capture and storage.     

Global and regional potential for bioenergy from agricultural and forestry residue biomass

As co-products, agricultural and forestry residues represent a potential low cost, low carbon, source for bioenergy. A method is developed for estimating the maximum sustainable amount of energy potentially available from agricultural and forestry residues by converting crop production statistics into associated residue, while allocating some of this resource to remain on the field to mitigate erosion and maintain soil nutrients. Currently, we estimate that the world produces residue biomass that could be sustainably harvested and converted into nearly 50 EJ yr⁻¹ of energy. The top three countries where this resource is estimated to be most abundant are currently net energy importers: China, the United States (US), and India. The global potential from residue biomass is estimated to increase to approximately 50–100 EJ yr⁻¹ by mid- to late- century, depending on physical assumptions such as of future crop yields and the amount of residue sustainably harvestable. The future market for biomass residues was simulated using the Object-Oriented Energy, Climate, and Technology Systems Mini Climate Assessment Model (O^bjECTS MiniCAM). Utilization of residue biomass as an energy source is projected for the next century under different climate policy scenarios. Total global use of residue biomass is estimated to be 20–100 EJ yr⁻¹ by mid- to late- century, depending on the presence of a climate policy and the economics of harvesting, aggregating, and transporting residue. Much of this potential is in developing regions of the world, including China, Latin America, Southeast Asia, and India.     

Impact of bioenergy crops in a carbon dioxide constrained world: an application of the MiniCAM energy-agriculture and land use model

In the coming century, modern bioenergy crops have the potential to play a crucial role in the global energy mix, especially under policies to reduce carbon dioxide emissions as proposed by many in the international community. Previous studies have not fully addressed many of the dynamic interactions and effects of a policy-induced expansion of bioenergy crop production, particularly on crop yields and human food demand. This study combines an updated agriculture and land use (AgLU) model with a well-developed energy-economic model to provide an analysis of the effects of bioenergy crops on energy, agricultural and land use systems. The results indicate that carbon dioxide mitigation policies can stimulate a large production of bioenergy crops, dependent on the level of the policy. This production of bioenergy crops can lead to several impacts on the agriculture and land use system: decreases in forestland and unmanaged land, decreases in the average yield of food crops, increases in the prices of food crops, and decreases in the level of human demand of calories.

Greenhouse gas mitigation with scarce land: The potential contribution of increased nitrogen input

Agricultural lands have been identified to mitigate greenhouse gas (GHG) emissions primarily by production of energy crops and substituting fossil energy resources and through carbon sequestration in soils. Increased fertilizer input resulting in increased yields may reduce the area needed for crop production. The surplus area could be used for energy production without affecting the land use necessary for food and feed production. We built a model to investigate the effect of changing nitrogen (N) fertilizer rates on cropping area required for a given amount of crops. We found that an increase in nitrogen fertilizer supply is only justified if GHG mitigation with additional land is higher than 9–15 t carbon dioxide equivalents per hectare (CO₂-eq._./ha). The mitigation potential of bioenergy production from energy crops is most often not in this range. Hence, from a GHG abatement point of view land should rather be used to produce crops at moderate fertilizer rate than to produce energy crops. This may change if farmers are forced to reduce their N input due to taxes or governmental regulations as it is the case in Denmark. However, with a fertilizer rate 10 % below the economical optimum a reduction of N input is still more effective than the production of bioenergy unless mitigation effect of the bioenergy production exceeds 7 t carbon dioxide (CO₂)-eq._./ha. An intensification of land use in terms of N supply to provide more land for bioenergy production can only in exceptional cases be justified to mitigate GHG emissions with bioenergy under current frame conditions in Germany and Denmark.     

The potential of world cropland soils to sequester C and mitigate the greenhouse effect

Soil emission of CO₂ is closely linked to soil degradation, decrease in soil organic carbon (SOC) content and decline in soil quality. Enhancing soil quality through adoption of best management practices (BMPs) and soil restoration can increase SOC content and soil productivity, and partially mitigate the greenhouse effect. The C sequestration potential through judicious management of world cropland includes 0.08–0.12 Pg/yr by erosion control, 0.02–0.03 Pg/yr by restoration of severely degraded soils, 0.02–0.04 Pg/yr by reclamation of salt-affected soils, 0.15–0.175 Pg/yr by adoption of conservation tillage and crop residue management, 0.18–0.24 Pg/yr by adoption of improved cropping system and 0.30–0.40 Pg/yr as C offset through biofuel production. The total C sequestration potential of the world cropland is about 0.75–1.0 Pg/yr or about 50% of annual emission of 1.6–1.8 Pg by deforestation and other agricultural activities. This finite soil-C sink could be filled over a 20 to 50-year period, during which energy related emission reductions gradually take effect at global scale. Improving soil quality is a win–win strategy, while increasing productivity it also improves environment and partially mitigates the greenhouse effect. Intensification of farming and increasing biomass production can lead to increased sequestration of C in soils, and to partly meet commitments under the Kyoto Protocol at national and global scales. Global reduction in C emission may have to be substantial if the atmospheric concentration of CO₂ is to be stabilized at 550 ppmv. However, realization of this potential would require developing channels of communication between scientists and land managers and policy makers, and providing economic incentives.     

Carbon storage versus fossil fuel substitution: a climate change mitigation option for two different land use categories based on short and long rotation forestry in India

Short rotation bioenergy crops for energy production are considered an effective means to mitigate the greenhouse effect, mainly due to their ability to substitute fossil fuels. Alternatively, carbon can be sequestered and stored in the living biomass. This paper compares the two land use categories (forest land and non-forest land) for two management practices (short rotation vs. long rotation) to study mitigation potential of afforestation and fossil fuel substitution as compared to carbon storage. Significant carbon benefit can be obtained in the long run from using lands for growing short rotation energy crops and substituting fossil fuels by the biomass thus produced, as opposed to sequestering carbon in the biomass of the trees. When growth rates are high and harvest is used in a sustainable manner (i.e., replanting after every harvest), the opportunities for net carbon reductions appear to be fossil fuel substitution, rather than storage in ecosystem biomass. Our results suggest that at year 100 a total of 216 Mg C ha⁻¹ is sequestered for afforestation/reforestation using long rotation sal (Shorea robusta Gaertn.f) species, as opposed to offset of 412 Mg C ha⁻¹ for carbon storage and fossil fuel substitution for short rotation poplar (Populus Deltoides Marsh) plantations. The bioenergy option results in a continuous stream of about 3 Mg C ha⁻¹ yr⁻¹ of carbon benefits per year on forest land and 4 Mg C ha⁻¹ yr⁻¹ on non-forest land. Earlier studies have shown that in India waste land availability for establishing energy plantations is in the range of 9.6 to 36.5 Mha. Thus, using the 758 Tg biomass per year generated from 9.6 Mha waste land gives a mitigation potential in the range of 227 to 303 Tg C per year for carbon storage and fossil fuel substitution from poplar plantation for substituting coal based power generation. Depending upon the land availability for plantation, the potential for energy generation is in the range of 11,370 PJ, possibly amounting to a bioenergy supply of 43% of the total projected energy consumption in 2015. Further studies are needed to estimate the mitigation potential of other species with different productivities for overall estimation of the economic feasibility and social acceptability in a tropical country like India.     

Production potential for spring wheat in the Canadian prairie provinces — An estimate

A method for estimating long-term crop yield and production potentials for spring wheat in Canada is described. The assessment was made at a map scale of 1:5 000 000, and is based on map units from the Soils of Canada.Potential net biomass and dry matter yield values were computed using procedures adapted from those described by the FAO. Potential values were determined using a form of photosynthesis model which calculates crop photosynthesis response to temperature and radiation averaged over a growing season. Anticipated yields were derived from these values by employing yield-reducing factors related to moisture stress, autumn workday probability and soil constraints. The anticipated (corrected) yield for each map unit was compared to the maximum potential yield obtainable in the country.The results of the procedure are expressed as a quantitative land suitability assessment. Each map unit was classified into one of 6 suitability classes. Areas with anticipated yields of less than 20% of maximum potential were considered as not suitable for production. From this data base, total crop production potentials were computed for the prairie provinces for various land-use allocations.Analysis of the soil and climatic resources indicates that a production level of 50 million tonnes of wheat, or its equivalent in coarse grains and oilseeds, is possible without altering the present land allocation to pasture, forage or specialty crops. Results of the production model estimates, however, suggest that this figure represents the upper limit of the production capability of the available soil and climatic resources for this region.     

中国农产品贸易的虚拟土地资源量化研究

虚拟资源对于揭示农产品贸易隐含的资源流动及效应具有重要意义。随着我国农产品贸易量和贸易格局的变化,定量核算我国农产品贸易隐含的土地资源量变化,可以从资源利用的角度评价我国农产品贸易的合理性,为相关贸易政策的制定提供理论依据。研究重点探讨了农产品及加工制品的虚拟土地资源量的核算方法,分别从生产者角度和消费者角度对1986—2009年我国农作物产品及其加工制品贸易的虚拟土地资源量进行了核算。计算结果表明,我国农作物产品隐含的虚拟土地资源量由1986年的净出口442.6×10⁴ hm²,转变为2009年的净进口2 889.0×10⁴ hm²,假设进口农产品在本国生产的情况下,2009年我国所需的虚拟土地资源量为3 817.5×10⁴ hm²。从虚拟土地资源进口结构和空间分布来看,我国虚拟土地资源净进口主要作物类别由谷物转变为油料作物,主要进口来源国由美国、加拿大、澳大利亚转变为美国、巴西、阿根廷。     

A review of assessments conducted on bio-ethanol as a transportation fuel from a net energy,greenhouse gas,and environmental life cycle perspective

Interest in producing ethanol from biomass in an attempt to make transportation ecologically sustainable continues to grow. In recent years, a large number of assessments have been conducted to assess the environmental merit of biofuels. Two detailed reviews present contrasting results: one is generally unfavourable, whilst the other is more favourable towards fuel bio-ethanol. However, most work that has been done so far, to assess the conversion of specific feedstocks to biofuels, specifically bio-ethanol, has not gone beyond energy and carbon assessments. This study draws on 47 published assessments that compare bio-ethanol systems to conventional fuel on a life cycle basis, or using life cycle assessment (LCA). A majority of these assessments focused on net energy and greenhouse gases, and despite differing assumptions and system boundaries, the following general lessons emerge: (i) make ethanol from sugar crops, in tropical countries, but approach expansion of agricultural land usage with extreme caution; (ii) consider hydrolysing and fermenting lignocellulosic residues to ethanol; and (iii) the LCA results on grasses as feedstock are insufficient to draw conclusions. It appears that technology choices in process residue handling and in fuel combustion are key, whilst site-specific environmental management tools should best handle biodiversity issues. Seven of the reviewed studies evaluated a wider range of environmental impacts, including resource depletion, global warming, ozone depletion, acidification, eutrophication, human and ecological health, smog formation, etc., but came up with divergent conclusions, possibly due to different approaches in scoping. These LCAs typically report that bio-ethanol results in reductions in resource use and global warming; however, impacts on acidification, human toxicity and ecological toxicity, occurring mainly during the growing and processing of biomass, were more often unfavourable than favourable. It is in this area that further work is needed.     

The impact of climate change mitigation on water demand for energy and food: An integrated analysis based on the Shared Socioeconomic Pathways

Climate change mitigation, in the context of growing population and ever increasing economic activity, will require a transformation of energy and agricultural systems, posing significant challenges to global water resources. We use an integrated modelling framework of the water-energy-land-climate systems to assess how changes in electricity and land use, induced by climate change mitigation, impact on water demand under alternative socioeconomic (Shared Socioeconomic Pathways) and water policy assumptions (irrigation of bioenergy crops, cooling technologies for electricity generation). The impacts of climate change mitigation on cumulated global water demand across the century are highly uncertain, and depending on socioeconomic and water policy conditions, they range from a reduction of 15,000 km³ to an increase of more than 160,000 km³. The impact of irrigation of bioenergy crops is the most prominent factor, leading to significantly higher water requirements under climate change mitigation if bioenergy crops are irrigated. Differences in socioeconomic drivers and fossil fuel availability result in significant differences in electricity and bioenergy demands, in the associated electricity and primary energy mixes, and consequently in water demand. Economic affluence and abundance of fossil fuels aggravate pressures on water resources due to higher energy demand and greater deployment of water intensive technologies such as bioenergy and nuclear power. The evolution of future cooling systems is also identified as an important determinant of electricity water demand. Climate policy can result in a reduction of water demand if combined with policies on irrigation of bioenergy, and the deployment of non-water-intensive electricity sources and cooling types.     

Global warming potential factors and warming payback time as climate indicators of forest biomass use

A method is presented for estimating the global warming impact of forest biomass life cycles with respect to their functionally equivalent alternatives based on fossil fuels and non-renewable material sources. In the method, absolute global warming potentials (AGWP) of both the temporary carbon (C) debt of forest biomass stock and the C credit of the biomass use cycle displacing the fossil and non-renewable alternative are estimated as a function of the time frame of climate change mitigation. Dimensionless global warming potential (GWP) factors, GWP_bio and GWP_biouse, are derived. As numerical examples, 1) bioenergy from boreal forest harvest residues to displace fossil fuels and 2) the use of wood for material substitution are considered. The GWP-based indicator leads to longer payback times, i.e. the time frame needed for the biomass option to be superior to its fossil-based alternative, than when just the cumulative balance of biogenic and fossil C stocks is considered. The warming payback time increases substantially with the residue diameter and low displacement factor (DF) of fossil C emissions. For the 35-cm stumps, the payback time appears to be more than 100 years in the climate conditions of Southern Finland when DF is lower than 0.5 in instant use and lower than 0.6 in continuous stump use. Wood use for construction appears to be more beneficial because, in addition to displaced emissions due to by-product bioenergy and material substitution, a significant part of round wood is sequestered into wood products for a long period, and even a zero payback time would be attainable with reasonable DFs.     

Carbon Management in Agricultural Soils

World soils have been a major source of enrichment of atmospheric concentration of CO₂ ever since the dawn of settled agriculture, about 10,000 years ago. Historic emission of soil C is estimated at 78 ± 12 Pg out of the total terrestrial emission of 136 ± 55 Pg, and post-industrial fossil fuel emission of 270 ± 30 Pg. Most soils in agricultural ecosystems have lost 50 to 75% of their antecedent soil C pool, with the magnitude of loss ranging from 30 to 60 Mg C/ha. The depletion of soil organic carbon (SOC) pool is exacerbated by soil drainage, plowing, removal of crop residue, biomass burning, subsistence or low-input agriculture, and soil degradation by erosion and other processes. The magnitude of soil C depletion is high in coarse-textured soils (e.g., sandy texture, excessive internal drainage, low activity clays and poor aggregation), prone to soil erosion and other degradative processes. Thus, most agricultural soils contain soil C pool below their ecological potential. Adoption of recommend management practices (e.g., no-till farming with crop residue mulch, incorporation of forages in the rotation cycle, maintaining a positive nutrient balance, use of manure and other biosolids), conversion of agriculturally marginal soils to a perennial land use, and restoration of degraded soils and wetlands can enhance the SOC pool. Cultivation of peatlands and harvesting of peatland moss must be strongly discouraged, and restoration of degraded soils and ecosystems encouraged especially in developing countries. The rate of SOC sequestration is 300 to 500 Kg C/ha/yr under intensive agricultural practices, and 0.8 to 1.0 Mg/ha/yr through restoration of wetlands. In soils with severe depletion of SOC pool, the rate of SOC sequestration with adoption of restorative measures which add a considerable amount of biomass to the soil, and irrigated farming may be 1.0 to 1.5 Mg/ha/yr. Principal mechanisms of soil C sequestration include aggregation, high humification rate of biosolids applied to soil, deep transfer into the sub-soil horizons, formation of secondary carbonates and leaching of bicarbonates into the ground water. The rate of formation of secondary carbonates may be 10 to 15 Kg/ha/yr, and the rate of leaching of bicarbonates with good quality irrigation water may be 0.25 to 1.0 Mg C/ha/yr. The global potential of soil C sequestration is 0.6 to 1.2 Pg C/yr which can off-set about 15% of the fossil fuel emissions.     

An estimated 400–800 million tons of prey are annually killed by the global spider community

Spiders have been suspected to be one of the most important groups of natural enemies of insects worldwide. To document the impact of the global spider community as insect predators, we present estimates of the biomass of annually killed insect prey. Our estimates assessed with two different methods suggest that the annual prey kill of the global spider community is in the range of 400–800 million metric tons (fresh weight), with insects and collembolans composing >90% of the captured prey. This equals approximately 1‰ of the global terrestrial net primary production. Spiders associated with forests and grasslands account for >95% of the annual prey kill of the global spider community, whereas spiders in other habitats are rather insignificant contributors over a full year. The spider communities associated with annual crops contribute less than 2% to the global annual prey kill. This, however, can be partly explained by the fact that annual crop fields are “disturbed habitats” with a low buildup of spider biomass and that agrobiont spiders often only kill prey over short time periods in a year. Our estimates are supported by the published results of exclusion experiments, showing that the number of herbivorous/detritivorous insects and collembolans increased significantly after spider removal from experimental plots. The presented estimates of the global annual prey kill and the relative contribution of spider predation in different biomes improve the general understanding of spider ecology and provide a first assessment of the global impact of this very important predator group.     

Mass-cultivation of carbohydrate rich macroalgae, a possible solution for sustainable biofuel production

Global demand for bio-fuels continues unabated. Rising concerns over environmental pollution and global warming have encouraged the movement to alternate fuels, the world ethanol market is projected to reach 86 billion litres this year. Bioethanol is currently produced from land-based crops such as corn and sugar cane. A continued use of these crops drives the food versus fuel debate. An alternate feed-stock which is abundant and carbohydrate-rich is necessary. The production of such a crop should be sustainable, and, reduce competition with production of food, feed, and industrial crops, and not be dependent on agricultural inputs (pesticides, fertilizer, farmable land, water). Marine biomass could meet these challenges, being an abundant and carbon neutral renewable resource with potential to reduce green house gas (GHG) emissions and the man-made impact on climate change. Here we examine the current cultivation technologies for marine biomass and the environmental and economic aspects of using brown seaweeds for bio-ethanol production.     

Climate impact potential of utilizing forest residues for bioenergy in Norway

The utilization of forest residues for bioenergy in Norway is foreseen to increase due to the government call to double bioenergy output by 2020 to thirty Tera-Watt hours. This study focuses on the climate impacts of bioenergy utilization where four forest residue extraction scenarios at clear-cut are considered: i) 75 % above ground residues (branches, (25 %) foliage, tops); ii) 75 % above and below ground residues (branches, tops, (25 %) foliage, stumps, coarse and small roots); iii) extracting 100 % of all available forest residue; and iv) leaving all residues in the forest. The Yasso07 soil-carbon model was utilized to quantify the carbon flux to the atmosphere due to the forest residues that are left in the forest in each scenario. The climate impact potential for each scenario was then calculated for the carbon-flux neutral Norway Spruce (Picea abies) forest system in five regions of Norway. The biogenic carbon dioxide emissions associated to decomposition upon forest floor, procurement losses and bioenergy conversion are included in these calculations. Results suggest that if such bioenergy can directly replace a fossil source of energy, the utilization of this biomass was found to be climatically beneficial in most fossil energy replacement cases and time horizons when compared to leaving the residues in the forest. Integrated global temperature change displacement factors have been developed which have been used to estimate the magnitude of this climate change mitigation over a particular time horizon.     

我国燃料乙醇的生产潜力与发展对策研究

论文测算了我国能源作物和农林废弃物等原料的燃料乙醇转化潜力,发现2015-2030年我国燃料乙醇的理论生产能力将从6 364×10⁴ t 增长到1.18×10⁸ t,可行的产量水平将在1 387.9×10⁴ t 以上。如果能实现这一产量,将在很大程度上缓解我国的石油供求矛盾。今后提高燃料乙醇生产能力的可行策略主要有以下方面：加强边际土地资源评估和开发,促进能源作物的规模化利用,通过利益引导加强秸秆能源化利用,延长林木采伐加工产业链,在农村地区发展沼气等新型能源替代薪柴。     

Bioenergy to mitigate for climate change and meet the needs of society,the economy and the environment

Changes towards environmental improvementsare becoming more politically acceptableglobally, especially in developedcountries. Society is slowly moving towardsseeking more sustainable productionmethods, waste minimisation, reduced airpollution from vehicles, distributed energygeneration, conservation of native forests,and reduction of greenhouse gas (GHG)emissions. Modern biomass, when used tosupply useful bioenergy services, has arole to play in each one of theseenvironmental drivers at both the large andsmall scales.This paper describes recent developments inbiomass supply and the technologies for itsconversion to bioenergy including biofuelsfor transport. It examines the economic,environmental and social benefits andidentifies barriers to bioenergy projectimplementation. Future opportunities forbiomass as a carbon (C) sink, a C offsetand a potential source of renewablehydrogen are discussed.Whether or not a bioenergy project iseconomically viable, as well as being trulyrenewable, sustainable and environmentallysound, is determined mainly by the sourceof biomass. The social benefits from usingbiomass are also valuable, though they areoften not clearly presented when proposingnew bioenergy projects or conductinganalyses of existing plants. Employmentrates per MWh or per GJ exceed those whenusing fossil fuel supplies to provide thesame energy service. `Ownership' bystakeholders and local communities at anearly stage in the development process isthe key to successful project developmentin order to share the benefits. Bioenergyhas a significant global role to play inthe mitigation of atmospheric GHG concentrations.     

Effects of bioenergy policies and targets on European wetland restoration options

The EU is committed to combat climate change and to increase security of its energy supply. Bioenergy from forestry and agriculture plays a key role for both. Concurrently, the EU agreed to halt the loss of biodiversity within its member states. To fulfil the biodiversity target more nature conservation and restoration sites need to be designated. There are arising concerns that an increased cultivation of bioenergy crops will decrease the land available for nature reserves and for “traditional” agriculture and forestry. To assess the role of bioenergy in light of possible negative impacts on ecosystems, the European Forest and Agricultural Sector Optimization Model (EUFASOM) assesses simultaneously economic and environmental aspects of land use. This study contributes to the assessment by analyzing the effect of bioenergy production on European wetland allocations by incorporating the spatial wetland distribution model SWEDI into EUFASOM. Results show that bioenergy targets increase land competition and thus marginal costs of wetland preservation but also of food prices. The designation of national wetland conservation targets, on the other hand, stimulates land use intensification in countries without these targets and here only a transfer of environmental stresses takes place. The model is able to illustrate regional differences of results.     

Biogas in the United States: estimating future production and learning from international experiences

The substitution of biogas, an energy source derived from biological feedstock, for fossil natural gas (NG) can mitigate the build-up of greenhouse gases in the atmosphere, making it an attractive renewable energy source in a carbon-constrained future. Although upgraded, pipeline-quality biogas can augment the NG market supply in the United States of America (USA), researchers and energy industry experts have little studied its long-term potential. This report estimates (1) levelized costs of energy for biogas production facilities operating with landfill waste, animal manure, wastewater sludge, and biomass residue feedstocks, (2) feedstock and technology pathway-specific biogas supply functions, and (3) the aggregate national biogas supply potential for the USA by 2040. Under a range of specified assumptions, generation of biogas could be expanded to approximately 3–5 % of the total domestic NG market at projected prices of $5–6/MMBtu, with the largest potential source coming from thermal gasification of agriculture and forest residues and biomass. As market signals have not spurred widespread adoption of biogas in the USA, policy incentives, similar to those used in the European Union (E.U.), may be necessary to increase its production and use. Bioenergy policy in the E.U. and the resulting market penetration achieved there therefore provides important lessons for how biogas markets in the USA can overcome barriers to market expansion and, in doing so, provide substantial climate mitigation benefits.     

Sustainability criteria for bioenergy systems: results from an expert survey

Environmental impacts associated with the use of fossil fuels, rising prices, potential limitations in supply and concerns about regional and national security are driving the development and use of biomass for bioenergy, biofuels and bioproducts. However, the use of biomass does not automatically imply that its production, conversion and use are sustainable. In order to operationalize sustainability assessments of biomass systems, it is crucial to identify critical criteria, but keep their number and measurement at a manageable level. The selection of these criteria can vary depending on individual's expertise, geographical region where they work, and spatial scale they are focused on. No clear consensus has yet emerged on what experts consider as critical indicators of sustainability. Objectives of this paper were to analyze how key experts perceive the 35 sustainability criteria for bioenergy found in emerging sustainability assessment frameworks and to identify levels of agreement and uncertainty. Experts were asked to rate the criteria for attributes of relevance, practicality, reliability, and importance.Perceptions of the importance of the 35 criteria varied among the experts surveyed. Only two criteria, energy balance and greenhouse gas balance, were perceived as critical by more than half of the respondents. Social criteria and locally applied criteria were generally ranked low for all four attributes. Seven of the 12 criteria scored as most important focused on environmental issues, four were social and only one was economic. Of the 12 most important criteria, seven were ranked low in practicality and reliability indicating that mechanisms to assess a number of important criteria need to be developed. The spatial scale the experts worked at and their profession explained most of the differences in importance ranking between experts, while regional focus had minimal effect. Criteria that were ranked low for importance, were characterized by a lack of consensus, suggesting the need for further debate regarding their inclusion in sustainability assessments.Outcomes of the survey provide a foundation for further discussions and development of sustainability assessments for bioenergy systems and may also provide a basis for assessing individual bioenergy projects within their specific geographic, ecological, societal, and technological context and scale.