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WIREs Energy Environ.
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Bioenergy and land use change—state of the art

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Abstract Bioenergy projects can lead to direct and indirect land use change (LUC), which can substantially affect greenhouse gas balances with both beneficial and adverse outcomes for bioenergy's contribution to climate change mitigation. The causes behind LUC are multiple, complex, interlinked, and change over time. This makes quantification uncertain and sensitive to many factors that can develop in different directions—including land use productivity, trade patterns, prices and elasticities, and use of by‐products associated with biofuels production. Quantifications reported so far vary substantially and do not support the ranking of bioenergy options with regard to LUC and associated emissions. There are however several options for mitigating these emissions, which can be implemented despite the uncertainties. Long‐rotation forest management is associated with carbon emissions and sequestration that are not in temporal balance with each other and this leads to mitigation trade‐offs between biomass extraction for energy use and the alternative to leave the biomass in the forest. Bioenergy's contribution to climate change mitigation needs to reflect a balance between near‐term targets and the long‐term objective to hold the increase in global temperature below 2°C (Copenhagen Accord). Although emissions from LUC can be significant in some circumstances, the reality of such emissions is not sufficient reason to exclude bioenergy from the list of worthwhile technologies for climate change mitigation. Policy measures to minimize the negative impacts of LUC should be based on a holistic perspective recognizing the multiple drivers and effects of LUC. This article is categorized under: Bioenergy > Economics and Policy Bioenergy > Climate and Environment
Illustration of direct and indirect land use changes arising as a consequence of a bioenergy project using crop A as feedstock. Note that in the case of iLUC, there need not be a one‐to‐one relationship between the land area claimed for bioenergy and the area converted to new pasture/cropland. This relationship depends on the relative productivity of the land claimed for bioenergy versus the new pasture/cropland. The iLUC taking place will also be determined by possible changes in meat/milk consumption and land use intensity (due to changes in food prices), and the displaced actors may turn to other activities than those connected to land use. The biofuel production in itself often generates protein rich by‐products that are suitable for animal feeding, displacing other animal feed production and thereby reducing the net LUC effect of the bioenergy project. An example of when meat/dairy production displaces crop production is when crop rotation patterns are adjusted to include one or several years under temporary grasslands for animal feed.
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Accumulated anthropogenic C emissions to the atmosphere since 1850 (left y‐axis). The red line (right y‐axis) shows the share of annual GHG emissions that comes from fossil fuel burning. Most of the remaining part of the annual GHG emissions is associated with LUC. A small part comes from cement manufacturing and gas flaring, which has contributed some 1–2% of the total accumulated emissions. Source: Ref 35. (Reprinted with permission from Ref 35. Copyright 2011, IEA Bioenergy.)
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Cumulative CO2 emissions and indicative remaining emission space in relation to 2°C target. (Reprinted with permission from Refs 35 and 138. Copyright 2011 and 2009, IEA Bioenergy.)
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Development of C stocks and GHG flows over a 240‐year period for typical fertilized and unfertilized stands in northern Sweden. The top diagram shows living tree biomass and the bottom diagram shows net substitution benefits of wood product use assuming coal reference fuel, with deductions made for N2O, CH4, and fossil CO2 emissions. The dynamics of C in soils and dead biomass (not shown) is highly influenced by the forest management but occurs at a smaller scale (fluctuations are within 250 ton CO2 ha−1). A and B denote two possible cases of forest bioenergy accounting (see text). (Reprinted with permission from Ref 128. Copyright 2010, IEA Bioenergy.)
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Tree biomass in a chronosequence of 100 identical simulations of Norway spruce stands, illustrating the difference between stand level and landscape level dynamics in a forest in southern Sweden. The assumed management resembles the dominant management regime during the previous decades, i.e., only stem wood has been removed at harvests, and thinning has been done at intervals prescribed by the Swedish Forest Agency. The stand is thinned three times (year 33, 48, and 65, with biomass harvest corresponding to about one‐fourth of the basal area) and final harvest takes place after 100 years where only stems are removed. It is assumed that 10% of the stem biomass is left as harvest residue (tops). Each stand is planted 1 year after the other starting from year 0. The average C content of the trees included each year is shown in the front most bar representing the landscape level. The losses and gains of C from individual forest stands in the landscape counterbalance and the average C content in the forest is stable over time. (Reprinted with permission from Ref 127. Copyright 2011, Peter Eliasson.)
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Effects on the C balance of increased removal of felling residues in a Norway spruce forest in south Sweden. In the ‘Stems Only’ scenario, harvest residues are left on the ground both after thinning and final felling. The ‘Stems 8 GROT’ scenario involves extraction of 80% of the logging residue after thinning and final felling (GROT is the Swedish acronym for branches and tops—GRenar Och Toppar in Swedish), and the ‘Stems, GROT 8 Stumps’ scenario includes in addition the removal of 50% of stumps‐coarse root systems at final felling. The increased residue removal continues over the whole 300‐year period. Upper panes show the amount of removal in comparison to the ‘Stems Only’ scenario and lower panes the corresponding variation in soil C. Single stands are plotted behind the landscape averages in the foreground. The sharp declines in stand level soil carbon shown at each harvest occasion are caused by the removal of residues, reducing litter addition to soil C. (Reprinted with permission from Ref 127. Copyright 2011, Peter Eliasson.)
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Historic overview of gross felling (1853–2003) and—placed behind the area showing gross felling—annual increment (1926–2003) in the Swedish forest. The method of estimating felling changed between 1945 and 1955, resulting in two overlapping curves (Ref 125). (Reprinted with permission from Ref 126. Copyright 2010, Peter Eliasson.)
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Accumulated net GHG savings in four biofuel scenarios. The green ‘Biofuel use’ bars show GHG savings (positive) from biofuel replacement of gasoline and diesel; the red ‘Land use change’ bars show GHG emissions (negative) caused by dLUC and iLUC; and the blue ‘Net GHG balance’ bars show the result of subtracting the LUC emissions from ‘Biofuel use’ savings. WEO has regional biofuel use up to 2030 as projected by the IEA World Energy Outlook 2008 reference scenario and 2nd generation biofuels are gradually deployed after 2015. TAR has roughly twice as high biofuel use as WEO and faster deployment of 2nd generation biofuels. The vP scenarios have higher agricultural productivity growth in developing countries leading to lower LUC. (Reprinted with permission from Refs 35 and 117. Copyright 2011 and 2009, IEA Bioenergy.)
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Ranges of model‐based quantifications of LUC (dLUC + iLUC) emissions associated with the expansion of selected biofuel/crop combinations. The studies are reported with LUC emissions amortized over 30 years of production for comparison. (Reprinted with permission from Ref 35. Copyright 2011, IEA Bioenergy.)
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Integrated production of biomass and milk/meat. Photo Credit: Laercio Cuoto. (Photo taken by Laercio Cuoto.)
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