This is a list of papers on GHG emissions from bioenergy related land-use. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.
Damaged forests provide an opportunity to mitigate climate change – Lamers et al. (2014) “British Columbia (BC) forests are estimated to have become a net carbon source in recent years due to tree death and decay caused primarily by mountain pine beetle (MPB) and related post-harvest slash burning practices. BC forest biomass has also become a major source of wood pellets, exported primarily for bioenergy to Europe, although the sustainability and net carbon emissions of forest bioenergy in general are the subject of current debate. We simulated the temporal carbon balance of BC wood pellets against different reference scenarios for forests affected by MPB in the interior BC timber harvesting area using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). We evaluated the carbon dynamics for different insect-mortality levels, at the stand- and landscape level, taking into account carbon storage in the ecosystem, wood products and fossil fuel displacement. Our results indicate that current harvesting practices, in which slash is burnt and only sawdust used for pellet production, require between 20–25 years for beetle-impacted pine and 37–39 years for spruce-dominated systems to reach pre-harvest carbon levels (i.e. break-even) at the stand-level. Using pellets made from logging slash to replace coal creates immediate net carbon benefits to the atmosphere of 17–21 tonnes C ha−1, shortening these break-even times by 9–20 years and resulting in an instant carbon break-even level on stands most severely impacted by the beetle. Harvesting pine dominated sites for timber while using slash for bioenergy was also found to be more carbon beneficial than a protection reference scenario on both stand- and landscape level. However, harvesting stands exclusively for bioenergy resulted in a net carbon source unless the system contained a high proportion of dead trees (>85%). Systems with higher proportions of living trees provide a greater climate change mitigation if used for long lived wood products.” Lamers, P., Junginger, M., Dymond, C. C. and Faaij, A. (2014), Damaged forests provide an opportunity to mitigate climate change. GCB Bioenergy, 6: 44–60. doi: 10.1111/gcbb.12055. [Full text]
Sequester or substitute—Consequences of increased production of wood based energy on the carbon balance in Finland – Kallio et al. (2013) “Forests play an important role in mitigating climate change. Forests can sequester carbon from the atmosphere and provide biomass, which can be used to substitute for fossil fuels or energy-intensive materials. International climate policies favor the use of wood to substitute for fossil fuels rather than using forests as carbon sink. We examine the trade off between sequestering carbon in forests and substituting wood for fossil fuels in Finland. For Finland to meet its EU targets for the use of renewable energy by 2020, a considerable increase in the use of wood for energy is necessary. We compare scenarios in which the wood energy targets are fully or partially met to a reference case where policies favoring wood based energy production are removed. Three models are used to project fossil fuel substitution and changes in forest carbon sinks in the scenarios through 2035. Finnish forests are a growing carbon sink in all scenarios. However, net greenhouse gas (GHG) emissions will be higher in the medium term if Finland achieves its current wood energy targets than if the use of energy wood stagnates or decreases. The volume of GHG emissions avoided by replacing coal, peat and fossil diesel with wood is outweighed by the loss in carbon sequestered in forests due to increased biomass removals. Therefore, the current wood energy targets seem excessive and harmful to the climate. In particular, biodiesel production has a significant, negative impact on net emissions in the period considered. However, we did not consider risks such as forest fires, wind damage and diseases, which might weaken the sequestration policy. The potential albedo impacts of harvesting the forests were not considered either.” A.M.I. Kallio, O. Salminen, R. Sievänen, Journal of Forest Economics, Volume 19, Issue 4, December 2013, Pages 402–415, http://dx.doi.org/10.1016/j.jfe.2013.05.001.
Effects of stump extraction on the carbon sequestration in Norway spruce forest ecosystems under varying thinning regimes with implications for fossil fuel substitution – Alam et al. (2013) “The overall aim of this work was to assess the effects of stump and root extraction on the long-term carbon sequestration and average carbon storage in the integrated production of energy biomass and stemwood (pulpwood and sawlogs) under different thinning options (unthinned, current thinning and 30% increased thinning thresholds from current thresholds). The growth and development of Norway spruce (Picea abies L. Karst.) stands on a fertile site (Oxalis-myrtillus) in central Finland (Joensuu region: 62˚39΄N, 29˚37΄E) was simulated for two consecutive rotation periods (80 + 80 years/160 years). Stemwood and energy biomass production, carbon sequestration, and average storage and emission dynamics related to the entire production process of biomass were assessed. The assessment was done by employing a life cycle assessment tool, which combines simulation outputs from an ecosystem model and the related technosystem emissions. It was found that stump and root harvesting constituted 21–36% of the total biomass production (energy biomass and stemwood) depending on the thinning regimes and rotation period. No considerable effect was found in stemwood production when stump and root extraction was compared to the regime in which stumps and roots were left at the site. Stump and root extraction did not affect carbon sequestration on the following rotation and, in fact, an increase in forest growth was found for the unthinned and 30% increased thresholds compared to the first rotation. The results also showed that if current thinning threshold is increased, win-win situations are possible, especially when climate change mitigation is the main concern. The substitution of coal with energy biomass is possible without reducing carbon storage in the forest ecosystem. The utilization of energy biomass, including stumps and roots, instead of coal could reduce up to 33% of emissions over two rotation periods depending on the thinning regimes. Even if stumps and roots were excluded, a maximum of 19% carbon emissions could be reduced by using only logging residues.” Alam, A., Kellomäki, S., Kilpeläinen, A. and Strandman, H. (2013), Effects of stump extraction on the carbon sequestration in Norway spruce forest ecosystems under varying thinning regimes with implications for fossil fuel substitution. GCB Bioenergy, 5: 445–458. doi: 10.1111/gcbb.12010.
The ‘debt’ is in the detail: A synthesis of recent temporal forest carbon analyses on woody biomass for energy – Lamers & Junginger (2013) “The temporal imbalance between the release and sequestration of forest carbon has raised a fundamental concern about the climate mitigation potential of forest biomass for energy. The potential carbon debt caused by harvest and the resulting time spans needed to reach pre-harvest carbon levels (payback) or those of a reference case (parity) have become important parameters for climate and bioenergy policy developments. The present range of analyses however varies in assumptions, regional scopes, and conclusions. Comparing these modeling efforts, we reveal that they apply different principle modeling frameworks while results are largely affected by the same parameters. The size of the carbon debt is mostly determined by the type and amount of biomass harvested and whether land-use change emissions need to be accounted for. Payback times are mainly determined by plant growth rates, i.e. the forest biome, tree species, site productivity and management. Parity times are primarily influenced by the choice and construction of the reference scenario and fossil carbon displacement efficiencies. Using small residual biomass (harvesting/processing), deadwood from highly insect-infected sites, or new plantations on highly productive or marginal land offers (almost) immediate net carbon benefits. Their eventual climate mitigation potential however is determined by the effectiveness of the fossil fuel displacement. We deem it therefore unsuitable to define political guidance by feedstock alone. Current global wood pellet production is predominantly residue based. Production increases based on low-grade stemwood are expected in regions with a downturn in the local wood product sector, highlighting the importance of accounting for regional forest carbon trends.” Lamers, P. and Junginger, M. (2013), The ‘debt’ is in the detail: A synthesis of recent temporal forest carbon analyses on woody biomass for energy. Biofuels, Bioprod. Bioref., 7: 373–385. doi: 10.1002/bbb.1407.
Carbon dioxide emissions from wood fuels in Sweden 1980–2100 – Wibe (2012) “It is often assumed that wood fuels are carbon neutral. This is approximately true in the very long run since the emissions from burning wood fuels are compensated by the uptake from new trees. But it is not true in the short- and the medium term due to a number of factors. This problem is analyzed in detail in this paper, where the net carbon (dioxide) effect of using wood residues in Sweden 1980–2100 is calculated. Two important implications of the program for using wood fuels are considered: (i) the decrease of carbon stored in logging residues due to a faster transformation to carbon dioxide and (ii) delayed growth of new forest generations when logging residues are removed from the forest and used as fuel. The effects of both these factors are calculated (and projected) for the period 1980–2100. The main result is that wood fuels (in the form of wood residues) emits about 60% of the carbon dioxide that would have been emitted if the corresponding amount of energy would, have been produced by oil. One policy implication of this is that emissions from wood fuels should not, as is now the practice, be ignored and by definition equaled to zero, in national and international statistics of green house gas emissions.” Sören Wibe, Journal of Forest Economics, Volume 18, Issue 2, April 2012, Pages 123–130, http://dx.doi.org/10.1016/j.jfe.2011.11.003.
Net atmospheric impacts of forest bioenergy production and utilization in Finnish boreal conditions – Kilpeläinen et al. (2012) “The net CO2 exchange of forests was investigated to study net atmospheric impact of forest bioenergy production (BP) and utilization in Finnish boreal conditions. Net CO2 exchange was simulated with a life cycle assessment tool over a 90-year period and over the whole Finland based on National Forest Inventory data. The difference in the net exchanges between the traditional timber production (TP) and BP regime was considered the net atmospheric impact of forest bioenergy utilization. According to the results, forests became net sources of CO2 after about 20 years of simulation, and the net exchange was higher in the BP regime than in the TP regime until the middle of the simulation period. From 2040 onwards, the net exchange started to decrease in both regimes and became higher in the TP regime, excluding the last decade of the simulation. The shift of forests to becoming a CO2 source reflected the decrease in CO2 sequestration due to the increasing share of recently harvested and seedling stands that are acting as sources of CO2, and an increase of emissions from degradation of wood products. When expressed in terms of radiative forcing, the net atmospheric impact was on average 19% less for bioenergy compared with that for coal energy over the whole simulation period. The results show the importance of time dependence when considering dynamic forest ecosystems in BP and climate change mitigation. Furthermore, the results emphasize the dualistic role and possibilities of forest management in controlling the build and release of carbon into and from the stocks and in controlling the rate of the build speed, i.e. growth. This information is needed in identifying the capability and possibilities of ecosystems to produce biomass for energy, alongside other products and ecosystem services (e.g. pulp wood and timber), and simultaneously to mitigate climate change.” Kilpeläinen, A., Kellomäki, S. and Strandman, H. (2012), Net atmospheric impacts of forest bioenergy production and utilization in Finnish boreal conditions. GCB Bioenergy, 4: 811–817. doi: 10.1111/j.1757-1707.2012.01161.x.
Is woody bioenergy carbon neutral? A comparative assessment of emissions from consumption of woody bioenergy and fossil fuel – Zanchi et al. (2012) “Under the current accounting systems, emissions produced when biomass is burnt for energy are accounted as zero, resulting in what is referred to as the ‘carbon neutrality’ assumption. However, if current harvest levels are increased to produce more bioenergy, carbon that would have been stored in the biosphere might be instead released in the atmosphere. This study utilizes a comparative approach that considers emissions under alternative energy supply options. This approach shows that the emission benefits of bioenergy compared to use of fossil fuel are time-dependent. It emerges that the assumption that bioenergy always results in zero greenhouse gas (GHG) emissions compared to use of fossil fuels can be misleading, particularly in the context of short-to-medium term goals. While it is clear that all sources of woody bioenergy from sustainably managed forests will produce emission reductions in the long term, different woody biomass sources have various impacts in the short-medium term. The study shows that the use of forest residues that are easily decomposable can produce GHG benefits compared to use of fossil fuels from the beginning of their use and that biomass from dedicated plantations established on marginal land can be carbon neutral from the beginning of its use. However, the risk of short-to-medium term negative impacts is high when additional fellings are extracted to produce bioenergy and the proportion of felled biomass used for bioenergy is low, or when land with high C stocks is converted to low productivity bioenergy plantations. The method used in the study provides an instrument to identify the time-dependent pattern of emission reductions for alternative bioenergy sources. In this way, decision makers can evaluate which bioenergy options are most beneficial for meeting short-term GHG emission reduction goals and which ones are more appropriate for medium to longer term objectives.” Zanchi, G., Pena, N. and Bird, N. (2012), Is woody bioenergy carbon neutral? A comparative assessment of emissions from consumption of woody bioenergy and fossil fuel. GCB Bioenergy, 4: 761–772. doi: 10.1111/j.1757-1707.2011.01149.x.
Harvesting in boreal forests and the biofuel carbon debt – Holtsmark (2012) “Owing to the extensive critique of food-crop-based biofuels, attention has turned toward second-generation wood-based biofuels. A question is therefore whether timber taken from the vast boreal forests on an increasing scale should serve as a source of wood-based biofuels and whether this will be effective climate policy. In a typical boreal forest, it takes 70–120 years before a stand of trees is mature. When this time lag and the dynamics of boreal forests more generally are taken into account, it follows that a high level of harvest means that the carbon stock in the forest stabilizes at a lower level. Therefore, wood harvesting is not a carbon-neutral activity. Through model simulations, it is estimated that an increased harvest of a boreal forest will create a biofuel carbon debt that takes 190–340 years to repay. The length of the payback time is sensitive to the type of fossil fuels that wood energy replaces.” Bjart Holtsmark, Climatic Change, May 2012, Volume 112, Issue 2, pp 415-428, DOI: 10.1007/s10584-011-0222-6. [Full text]
Land-use change to bioenergy production in Europe: implications for the greenhouse gas balance and soil carbon – Don et al. (2012) “Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha−1 yr−1 for poplar and willow and 0.66 Mg soil C ha−1 yr−1 for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.” Don, A., Osborne, B., Hastings, A., Skiba, U., Carter, M. S., Drewer, J., Flessa, H., Freibauer, A., Hyvönen, N., Jones, M. B., Lanigan, G. J., Mander, Ü., Monti, A., Djomo, S. N., Valentine, J., Walter, K., Zegada-Lizarazu, W. and Zenone, T. (2012), Land-use change to bioenergy production in Europe: implications for the greenhouse gas balance and soil carbon. GCB Bioenergy, 4: 372–391. doi: 10.1111/j.1757-1707.2011.01116.x.
Global warming potential factors and warming payback time as climate indicators of forest biomass use – Pingoud et al. (2012) “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, GWPbio and GWPbiouse, 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.” Kim Pingoud, Tommi Ekholm, Ilkka Savolainen, Mitigation and Adaptation Strategies for Global Change, April 2012, Volume 17, Issue 4, pp 369-386, DOI: 10.1007/s11027-011-9331-9.
Forest Bioenergy or Forest Carbon? Assessing Trade-Offs in Greenhouse Gas Mitigation with Wood-Based Fuels – McKechnie et al. (2011) “The potential of forest-based bioenergy to reduce greenhouse gas (GHG) emissions when displacing fossil-based energy must be balanced with forest carbon implications related to biomass harvest. We integrate life cycle assessment (LCA) and forest carbon analysis to assess total GHG emissions of forest bioenergy over time. Application of the method to case studies of wood pellet and ethanol production from forest biomass reveals a substantial reduction in forest carbon due to bioenergy production. For all cases, harvest-related forest carbon reductions and associated GHG emissions initially exceed avoided fossil fuel-related emissions, temporarily increasing overall emissions. In the long term, electricity generation from pellets reduces overall emissions relative to coal, although forest carbon losses delay net GHG mitigation by 16−38 years, depending on biomass source (harvest residues/standing trees). Ethanol produced from standing trees increases overall emissions throughout 100 years of continuous production: ethanol from residues achieves reductions after a 74 year delay. Forest carbon more significantly affects bioenergy emissions when biomass is sourced from standing trees compared to residues and when less GHG-intensive fuels are displaced. In all cases, forest carbon dynamics are significant. Although study results are not generalizable to all forests, we suggest the integrated LCA/forest carbon approach be undertaken for bioenergy studies.” Jon McKechnie, Steve Colombo, Jiaxin Chen, Warren Mabee, and Heather L. MacLean, Environ. Sci. Technol., 2011, 45 (2), pp 789–795, DOI: 10.1021/es1024004. [Full text]
Paying for forest carbon or stimulating fuelwood demand? Insights from the French Forest Sector Model – Lecocq et al. (2011) “As European countries move towards steeper cuts in greenhouse gases emissions, questions are mounting, in the forest sector, about the best balance between policies that favor carbon sequestration in biomass, and policies that favor fossil-fuel substitution, with potentially conflicting implications for forest management. We provide insights on this debate by comparing the environmental and economic implications for the French forest sector of a “stock” policy (payment for sequestration in situ), a “substitution” policy (subsidy to fuelwood consumption), and a combination thereof – all calibrated on the same price of carbon. To do so, we use the French Forest Sector Model (FFSM), which combines a dynamic model of French timber resource and a dynamic partial-equilibrium model of the French forest sector. Simulations over the 2010–2020 period show that the stock policy is the only one that performs better than business-as-usual in terms of carbon. In the substitution policy, cumulative substitution benefits are not sufficient to offset carbon losses in standing forests over this biologically short, but politically relevant period of time. And the combination policy does not perform better. However, the stock policy has negative impacts on consumers welfare, its costs are increasing over time as carbon is accumulated, and it raises political economy questions about the negotiability of the reference against which excess carbon is measured.” Franck Lecocq, Sylvain Caurla, Philippe Delacote, Ahmed Barkaouia, Alexandre Sauquet, Journal of Forest Economics, Volume 17, Issue 2, April 2011, Pages 157–168, http://dx.doi.org/10.1016/j.jfe.2011.02.011.
Agricultural crop-based biofuels – resource efficiency and environmental performance including direct land use changes – Börjesson & Tufvesson (2011) “This paper analyses biofuels from agricultural crops in northern Europe regarding area and energy efficiency, greenhouse gases and eutrophication. The overall findings are that direct land use changes have a significant impact on GHG balances and eutrophication for all biofuels, the choice of calculation methods when by-products are included affecting the performance of food crop-based biofuels considerably, and the technical design of production systems may in specific cases be of major importance. The presented results are essential knowledge for the development of certification systems. Indirect land use changes are recognised but not included due to current scientific and methodological deficiencies.” Pål Börjesson, Linda M. Tufvesson, Journal of Cleaner Production, Volume 19, Issues 2–3, January–February 2011, Pages 108–120, http://dx.doi.org/10.1016/j.jclepro.2010.01.001.
Indirect carbon dioxide emissions from producing bioenergy from forest harvest residues – Repo et al. (2011) “Forest harvest residues are important raw materials for bioenergy in regions practicing forestry. Removing these residues from a harvest site reduces the carbon stock of the forest compared with conventional stem-only harvest because less litter in left on the site. The indirect carbon dioxide (CO2) emission from producing bioenergy occur when carbon in the logging residues is emitted into the atmosphere at once through combustion, instead of being released little by little as a result of decomposition at the harvest sites. In this study (1) we introduce an approach to calculate this indirect emission from using logging residues for bioenergy production, and (2) estimate this emission at a typical target of harvest residue removal, i.e. boreal Norway spruce forest in Finland. The removal of stumps caused a larger indirect emission per unit of energy produced than the removal of branches because of a lower decomposition rate of the stumps. The indirect emission per unit of energy produced decreased with time since starting to collect the harvest residues as a result of decomposition at older harvest sites. During the 100 years of conducting this practice, the indirect emission from average-sized branches (diameter 2 cm) decreased from 340 to 70 kg CO2 eq. MWh−1 and that from stumps (diameter 26 cm) from 340 to 160 kg CO2 eq. MWh−1. These emissions are an order of magnitude larger than the other emissions (collecting, transporting, etc.) from the bioenergy production chain. When the bioenergy production was started, the total emissions were comparable to fossil fuels. The practice had to be carried out for 22 (stumps) or four (branches) years until the total emissions dropped below the emissions of natural gas. Our results emphasize the importance of accounting for land-use-related indirect emissions to correctly estimate the efficiency of bioenergy in reducing CO2 emission into the atmosphere.” Repo, A., Tuomi, M. and Liski, J. (2011), Indirect carbon dioxide emissions from producing bioenergy from forest harvest residues. GCB Bioenergy, 3: 107–115. doi: 10.1111/j.1757-1707.2010.01065.x.
From the global efforts on certification of bioenergy towards an integrated approach based on sustainable land use planning – van Dam et al. (2010) “This paper presents an overview of 67 ongoing certification initiatives to safeguard the sustainability of bioenergy. Most recent initiatives are focused on the sustainability of liquid biofuels. Content-wise, most of these initiatives have mainly included environmental principles. Despite serious concerns in various parts of the world on the socio-economic impacts of bioenergy production, these are generally not included in existing bioenergy initiatives. At the same time, the overview shows a strong proliferation of standards. The overview shows that certification has the potential to influence direct, local impacts related to environmental and social effects of direct bioenergy production. Key recommendations to come to an efficient certification system include the need for further harmonization, availability of reliable data and linking indicators on a micro, meso and macro levels. Considering the multiple spatial scales, certification should be combined with additional measurements and tools on a regional, national and international level. The role of bioenergy production on indirect land use change (ILUC) is still very uncertain and current initiatives have rarely captured impacts from ILUC in their standards. Addressing unwanted LUC requires first of all sustainable land use production and good governance, regardless of the end-use of the product. It is therefore recommended to extend measures to mitigate impacts from LUC to other lands and feedstock.” J. van Dam, M. Junginger, A.P.C. Faaij, Renewable and Sustainable Energy Reviews, Volume 14, Issue 9, December 2010, Pages 2445–2472, http://dx.doi.org/10.1016/j.rser.2010.07.010.
Greenhouse Gas Emissions from Biofuels’ Indirect Land Use Change Are Uncertain but May Be Much Greater than Previously Estimated – Plevin et al. (2010) “The life cycle greenhouse gas (GHG) emissions induced by increased biofuel consumption are highly uncertain: individual estimates vary from each other and each has a wide intrinsic error band. Using a reduced-form model, we estimated that the bounding range for emissions from indirect land-use change (ILUC) from US corn ethanol expansion was 10 to 340 g CO2 MJ−1. Considering various probability distributions to model parameters, the broadest 95% central interval, i.e., between the 2.5 and 97.5%ile values, ranged from 21 to 142 g CO2e MJ−1. ILUC emissions from US corn ethanol expansion thus range from small, but not negligible, to several times greater than the life cycle emissions of gasoline. The ILUC emissions estimates of 30 g CO2 MJ−1 for the California Air Resources Board and 34 g CO2e MJ−1 by USEPA (for 2022) are at the low end of the plausible range. The lack of data and understanding (epistemic uncertainty) prevents convergence of judgment on a central value for ILUC emissions. The complexity of the global system being modeled suggests that this range is unlikely to narrow substantially in the near future. Fuel policies that require narrow bounds around point estimates of life cycle GHG emissions are thus incompatible with current and anticipated modeling capabilities. Alternative policies that address the risks associated with uncertainty are more likely to achieve GHG reductions.” Richard J. Plevin, Michael O’Hare, Andrew D. Jones, Margaret S. Torn, and Holly K. Gibbs, Environ. Sci. Technol., 2010, 44 (21), pp 8015–8021, DOI: 10.1021/es101946t. [Full text]
Effects of US Maize Ethanol on Global Land Use and Greenhouse Gas Emissions: Estimating Market-Mediated Responses – Hertel et al. (2010) “Releases of greenhouse gases (GHG) from indirect land-use change triggered by crop-based biofuels have taken center stage in the debate over the role of biofuels in climate policy and energy security. This article analyzes these releases for maize ethanol produced in the United States. Factoring market-mediated responses and by-product use into our analysis reduces cropland conversion by 72% from the land used for the ethanol feedstock. Consequently, the associated GHG release estimated in our framework is 800 grams of carbon dioxide per megajoule (MJ); 27 grams per MJ per year, over 30 years of ethanol production, or roughly a quarter of the only other published estimate of releases attributable to changes in indirect land use. Nonetheless, 800 grams are enough to cancel out the benefits that corn ethanol has on global warming, thereby limiting its potential contribution in the context of California’s Low Carbon Fuel Standard.” Thomas W. Hertel , Alla A. Golub , Andrew D. Jones , Michael O’Hare , Richard J. Plevin and Daniel M. Kammen, BioScience 60(3):223-231. 2010, doi: http://dx.doi.org/10.1525/bio.2010.60.3.8. [Full text]
Direct and indirect land-use competition issues for energy crops and their sustainable production – an overview – Fritsche et al. (2010) “Biofuel production from energy crops is land-use intensive. Land-use change (LUC) associated with bioenergy cropping impacts on the greenhouse gas (GHG) balance, both directly and indirectly. Land-use conversion can also impact on biodiversity. The current state of quantifying GHG emissions relating to direct and indirect land-use change (iLUC) from biomass produced for liquid biofuels or bioenergy is reviewed. Several options for reducing iLUC are discussed, and recommendations made for considering LUC in bioenergy and biofuel policies. Land used for energy cropping is subject to competing demands for conventional agriculture and forest production, as well as for nature protection and conservation. Biomass to be used for bioenergy and biofuels should therefore be produced primarily from excess farm and forest residues or from land not required for food and fiber production. The overall efficiency of biomass production, conversion, and use should be increased where possible in order to further reduce land competition and the related direct and iLUC risks. This review of several varying approaches to iLUC substantiates that, in principle, GHG emissions can be quantified and reductions implemented by appropriate policies. Such approaches can (and should) be refined and substantiated using better data on direct LUC trends from global monitoring, and be further improved by adding more accurate estimates of future trade patterns where appropriate. This brief discussion of current policies and options to reduce iLUC has identified a variety of approaches and options so that a quantified iLUC factor could be translated into practical regulations – both mandatory and voluntary – with few restrictions. Depending on the future development of energy cropping systems and yield improvements, sustainable bioenergy production could make a significant contribution to the future global energy demand.” Fritsche, U. R., Sims, R. E. H. and Monti, A. (2010), Direct and indirect land-use competition issues for energy crops and their sustainable production – an overview. Biofuels, Bioprod. Bioref., 4: 692–704. doi: 10.1002/bbb.258. [Full text]
Proper accounting for time increases crop-based biofuels’ greenhouse gas deficit versus petroleum – O’Hare et al. (2009) “The global warming intensities of crop-based biofuels and fossil fuels differ not only in amount but also in their discharge patterns over time. Early discharges, for example, from market-mediated land use change, will have created more global warming by any time in the future than later discharges, owing to the slow decay of atmospheric CO2. A spreadsheet model of this process, BTIME, captures this important time pattern effect using the Bern CO2 decay model to allow fuels to be compared for policy decisions on the basis of their real warming effects with a variety of user-supplied parameter values. The model also allows economic discounting of climate effects extended far into the future. Compared to approaches that simply sum greenhouse gas emissions over time, recognizing the physics of atmospheric CO2 decay significantly increases the deficit relative to fossil fuel of any biofuel causing land use change.” M O’Hare et al 2009 Environ. Res. Lett. 4 024001 doi:10.1088/1748-9326/4/2/024001. [Full text]
Set-asides can be better climate investment than corn ethanol – Piñeiro et al. (2009) “
Although various studies have shown that corn ethanol reduces greenhouse gas (GHG) emissions by displacing fossil fuel use, many of these studies fail to include how land-use history affects the net carbon balance through changes in soil carbon content. We evaluated the effectiveness and economic value of corn and cellulosic ethanol production for reducing net GHG emissions when produced on lands with different land-use histories, comparing these strategies with reductions achieved by set-aside programs such as the Conservation Reserve Program (CRP). Depending on prior land use, our analysis shows that C releases from the soil after planting corn for ethanol may in some cases completely offset C gains attributed to biofuel generation for at least 50 years. More surprisingly, based on our comprehensive analysis of 142 soil studies, soil C sequestered by setting aside former agricultural land was greater than the C credits generated by planting corn for ethanol on the same land for 40 years and had equal or greater economic net present value. Once commercially available, cellulosic ethanol produced in set-aside grasslands should provide the most efficient tool for GHG reduction of any scenario we examined. Our results suggest that conversion of CRP lands or other set-aside programs to corn ethanol production should not be encouraged through greenhouse gas policies.” Gervasio Piñeiro, Esteban G. Jobbágy, Justin Baker, Brian C. Murray, and Robert B. Jackson 2009. Set-asides can be better climate investment than corn ethanol. Ecological Applications 19:277–282. http://dx.doi.org/10.1890/08-0645.1. [Full text]
Biofuel Plantations on Forested Lands: Double Jeopardy for Biodiversity and Climate – Danielsen et al. (2009) “The growing demand for biofuels is promoting the expansion of a number of agricultural commodities, including oil palm (Elaeis guineensis). Oil-palm plantations cover over 13 million ha, primarily in Southeast Asia, where they have directly or indirectly replaced tropical rainforest. We explored the impact of the spread of oil-palm plantations on greenhouse gas emission and biodiversity. We assessed changes in carbon stocks with changing land use and compared this with the amount of fossil-fuel carbon emission avoided through its replacement by biofuel carbon. We estimated it would take between 75 and 93 years for the carbon emissions saved through use of biofuel to compensate for the carbon lost through forest conversion, depending on how the forest was cleared. If the original habitat was peatland, carbon balance would take more than 600 years. Conversely, planting oil palms on degraded grassland would lead to a net removal of carbon within 10 years. These estimates have associated uncertainty, but their magnitude and relative proportions seem credible. We carried out a meta-analysis of published faunal studies that compared forest with oil palm. We found that plantations supported species-poor communities containing few forest species. Because no published data on flora were available, we present results from our sampling of plants in oil palm and forest plots in Indonesia. Although the species richness of pteridophytes was higher in plantations, they held few forest species. Trees, lianas, epiphytic orchids, and indigenous palms were wholly absent from oil-palm plantations. The majority of individual plants and animals in oil-palm plantations belonged to a small number of generalist species of low conservation concern. As countries strive to meet obligations to reduce carbon emissions under one international agreement (Kyoto Protocol), they may not only fail to meet their obligations under another (Convention on Biological Diversity) but may actually hasten global climate change. Reducing deforestation is likely to represent a more effective climate-change mitigation strategy than converting forest for biofuel production, and it may help nations meet their international commitments to reduce biodiversity loss.” Danielsen, F., Beukema, H., Burgess, N. D., Parish, F., Brühl, C. A., Donald, P. F., Murdiyarso, D., Phalan, B., Reijnders, L., Struebig, M. and Fitzherbert, E. B. (2009), Biofuel Plantations on Forested Lands: Double Jeopardy for Biodiversity and Climate. Conservation Biology, 23: 348–358. doi: 10.1111/j.1523-1739.2008.01096.x. [Full text]
Carbon payback times for crop-based biofuel expansion in the tropics: the effects of changing yield and technology – Gibbs et al. (2008) “Biofuels from land-rich tropical countries may help displace foreign petroleum imports for many industrialized nations, providing a possible solution to the twin challenges of energy security and climate change. But concern is mounting that crop-based biofuels will increase net greenhouse gas emissions if feedstocks are produced by expanding agricultural lands. Here we quantify the ‘carbon payback time’ for a range of biofuel crop expansion pathways in the tropics. We use a new, geographically detailed database of crop locations and yields, along with updated vegetation and soil biomass estimates, to provide carbon payback estimates that are more regionally specific than those in previous studies. Using this cropland database, we also estimate carbon payback times under different scenarios of future crop yields, biofuel technologies, and petroleum sources. Under current conditions, the expansion of biofuels into productive tropical ecosystems will always lead to net carbon emissions for decades to centuries, while expanding into degraded or already cultivated land will provide almost immediate carbon savings. Future crop yield improvements and technology advances, coupled with unconventional petroleum supplies, will increase biofuel carbon offsets, but clearing carbon-rich land still requires several decades or more for carbon payback. No foreseeable changes in agricultural or energy technology will be able to achieve meaningful carbon benefits if crop-based biofuels are produced at the expense of tropical forests.” Holly K Gibbs et al 2008 Environ. Res. Lett. 3 034001 doi:10.1088/1748-9326/3/3/034001. [Full text]
Land Clearing and the Biofuel Carbon Debt – Fargione et al. (2008) “Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced. Converting rainforests, peatlands, savannas, or grasslands to produce food crop–based biofuels in Brazil, Southeast Asia, and the United States creates a “biofuel carbon debt” by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions that these biofuels would provide by displacing fossil fuels. In contrast, biofuels made from waste biomass or from biomass grown on degraded and abandoned agricultural lands planted with perennials incur little or no carbon debt and can offer immediate and sustained GHG advantages.” Joseph Fargione, Jason Hill, David Tilman, Stephen Polasky, Peter Hawthorne, Science 29 February 2008: Vol. 319 no. 5867 pp. 1235-1238, DOI: 10.1126/science.1152747. [Full text]
Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change – Searchinger et al. (2008) “Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.” Timothy Searchinger, Ralph Heimlich, R. A. Houghton, Fengxia Dong, Amani Elobeid, Jacinto Fabiosa, Simla Tokgoz, Dermot Hayes, Tun-Hsiang Yu, Science 29 February 2008: Vol. 319 no. 5867 pp. 1238-1240, DOI: 10.1126/science.1151861. [Full text]