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Can large-scale biofuels production be sustainable by 2020?
Agricultural Systems 101 (2009) 197–199
Contents lists available at ScienceDirect
Agricultural Systems journal homepage: www.elsevier.com/locate/agsy
Short Communication
Can large-scale biofuels production be sustainable by 2020? Prem S. Bindraban a,*, Erwin H. Bulte b, Sjaak G. Conijn a a b
Plant Research International, 6700 AP Wageningen, The Netherlands Chair Group Development Economics, Wageningen UR, The Netherlands
a r t i c l e
i n f o
Article history: Received 6 May 2009 Received in revised form 3 June 2009 Accepted 10 June 2009 Available online 7 July 2009 Keywords: Radiation use efficiency GHG emissions Land use change Development Food security
a b s t r a c t Worldwide, many nations impose blending of their transport fuels with biofuels, approximating 10% globally by 2020, to contribute to energy security while reducing emission of green house gasses (GHG). Food riots, scientific insights that question the GHG benefits and raised concern about the loss of biodiversity, have lead to the formulation by various governments of sustainability criteria for biofuels to comply with. In this paper, we assess this conditionality and argue that large-scale biofuels production will be unable to comply with these criteria in 2020, and can therefore not be qualified as sustainable. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
2. Reduction of GHG emissions
Worldwide, many nations have formulated policies to blend a certain proportion of their transport fuels with biofuels (FAO, 2008). The targets aimed for may approximate about 10% globally in 2020. Biofuels production is driven mainly by policy measures, including tax exemptions, investment subsidies and obligatory blending of biofuels with fossil fuels, as in the EU and USA (European Parliament, 2008; Energy Policy Act of 2005, 2005). From 2001 to 2007, world ethanol production almost tripled from 20 to 50 billion litres (Licht, 2007) and world biodiesel production increased from 0.8 to almost 4 billion litres. However, food riots and the unprecedented increase in the number of hungry people in 2007 and 2008 have alerted nations to scrutinize their ambitions with respect to biofuels, as these, together with some other factors, have caused the food problems (e.g. Banse et al., 2008; World Bank, 2008). Scientific insights that question the environmental benefits and high production costs further triggered the European Union to propose sustainability criteria for biofuels to comply with. These criteria impose threshold values for the reduction of greenhouse gas (GHG) emissions relative to fossil fuels and prevention of loss of biodiversity. Moreover, expanded production of biofuels should not compete with food or feed, and must stimulate the development of countries that produce feedstock and/or biofuels. Here we assess whether the production of biofuels to meet blending targets in 2020 can comply with the sustainability criteria.
The Achilles’ heel of biofuels production is the low utilization efficiency of sunlight by plants. The maximum attainable efficiency (Spedding, 1988) of around 3.5% with year-round cultivation in the tropics and about 1.5% in temperate regions, ultimately reduces to 0.2–1% for biofuels after correction for non-harvestable crop parts and energy needed during production, transport and processing of the biomass (Corré and Conijn, 2008). This applies to crops grown under optimal conditions – adequately supplied with water and nutrients, and well protected against pest and diseases. Efficiencies will be even lower under marginal growing conditions, when crop radiation use efficiency declines due to yield reducing factors (Sinclair and Horie, 1989). Improving conversion efficiencies along the various steps in the production chain will not overcome the inherently low utilization efficiency of solar energy by plants. While the transport sector will have to make an effort in cutting down greenhouse gas emissions and contribute to meet long-term climate stabilization targets, it is unlikely that major gains can be achieved via biofuels. Indeed, the contrary may be true. . . Net savings of GHG emissions up to 10 ton CO2 ha 1 y 1 in the production chain for biofuels from feedstocks like sugarcane and palm oil have been calculated (Righelato and Spracklen, 2007). Savings will be lower under poor management – when soil organic matter is lost during production, or when too much nitrogen fertilizer is used (Crutzen et al., 2007; Smeets et al., 2007). Worse, when cultivation of biomass leads to the direct or indirect clearing of natural lands (see Section 3), net CO2 savings may turn negative. Emissions 30–200 times the amount potentially saved in the chain may occur (Searchinger et al., 2008; Fargione et al., 2008). Regional options for
* Corresponding author. Address: Plant Research International, P.O. Box 616, 6700 AP Wageningen, The Netherlands. Tel.: +31 317 480881; fax: +31 317 423110. E-mail address: [email protected] (P.S. Bindraban). 0308-521X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.agsy.2009.06.005
198
P.S. Bindraban et al. / Agricultural Systems 101 (2009) 197–199
biofuels to mitigate GHG emissions (e.g. European Environment Agency, 2006) will have to be evaluated in a global perspective because GHG have no national or regional borders. To be more specific; the gross emissions reduction of a global 10% blending obligation in 2020 would be 450–600 million tons of CO2-equivalents (assuming good agronomic management with a 60–80% efficiency in GHG replacement of biofuels relative to fossil fuels). This equals on average 1.1% of total CO2-equivalent emission in 2005. However, these gross gains turn negative if more than 30% of the required land would be obtained through clearing of natural lands (Bindraban et al., 2009). We argue that this is the most likely scenario when ambitious mandatory biofuels mixing rules are in place (see below). Moreover, even for positive GHG emissions savings, the social costs are high—by far exceeding those of alternative approaches to mitigating climate change. Total costs for biofuels range from 960–1700 US$ per tons of CO2 saved, while alternative means of GHG savings exist with costs in the range of 7–22 US$ per ton (OECD, 2008).
favorable ratios of cost to GHG/energy savings. These uncertainties further increase investment risks. It is therefore almost inevitable that in the short and medium term biofuels will continue to be derived from food crops, or from crops that displace food crops. For the mid- and long-term, most studies estimate blending obligations to increase equilibrium food price levels by 10–30% (OECD, 2008; Banse et al., 2008; Von Braun, 2008). Moreover, while linking food and energy markets implies introducing a price ceiling for food crops (potentially contributing to price stability), it is also evident that food prices may become more volatile because of mandatory mixing (von Braun, 2007). Any volatility in energy prices will be transferred to food markets. Also, mandatory blending targets imply extra demand for food crops even if prices are high – contributing to higher price peaks. For example, the high volatility of food prices that was experienced in 2008, was caused by several factors, including biofuels (estimates of the contribution of biofuels vary from 30% and 80% – see Rosegrant, 2008 and World Bank, 2008). As a result of these effects, the food security of poor people is expected to structurally deteriorate (Von Braun, 2008).
3. Competition for resources and biodiversity loss 5. Opportunities for development? The critical question is whether agricultural productivity can be increased to such an extent that sufficient agricultural land can be freed up for the production of energy crops. Most studies indicate that this is unlikely to be the case, and argue that to meet future food demand the global acreage of both arable land and grassland will have to increase (OECD/FAO, 2008; IAASTD, 2008). Moreover, these studies may be too optimistic as they are partly based on extrapolating existing trends, whereas a deteriorating resource base (notably water availability and physical and chemical soil fertility) will limit future productivity increases in biomass production. While measures to mitigate resource degradation and scarcity have been identified, implementation is a complex and time-consuming undertaking, involving agro-technical, institutional and economic innovations. Arguably more rather than less land will be necessary for food production to meet food demand, certainly until 2020 (e.g. Bruinsma, 2003). This implies that the production of biofuels to meet the blending targets in 2020 will imply additional demand for land. It is unlikely that this additional demand for land can be met without a net clearing of natural lands – resulting in carbon emissions as well as a loss of biodiversity. Can we use non-food biomass produced on marginal lands as a sustainable option (e.g. Searchinger et al., 2008)? The use of marginal lands is unlikely to create significant volumes of biomass in the near term. They are beset with a range of difficulties, and overcoming such difficulties will compromise the natural character of the ecosystem (likely implying a loss of ecosystem services and biodiversity). To raise and stabilize yields, increased inputs are needed, and investments in institutions and infrastructure are required. Favorable estimates for biomass yields from low-input, high-diversity grassland for instance (Tilman et al., 2006) appear to be open for discussion (Russelle et al., 2007). 4. Competition with food Many advocates of biofuels have vested their hopes on so called 2nd generation technologies, i.e. the production of biofuels from non-edible plant parts (e.g. EEA, 2008). However, the implementation of such technologies, in terms of timing and volumes, remains highly uncertain until 2020. It has not yet been proven at a (large) industrial scale and its implementation requires investments that exceed food-based biofuels plants by a factor of 10 (Deurwaarder et al., 2007). Moreover, on the longer term strong competition may be expected from alternative technologies, including electrical and hydrogen-driven cars, and solar and wind energy with more
An expanding biofuels sector involves both opportunities and threats for development. Similarly, higher prices of food involve opportunities, for (potential) net producers as well as threats for net consumers. Structurally higher food prices may invite a badly-needed intensification strategy among farmers, contributing to rural economic development with possible positive spillover effects for the rest of the economy (WDR, 2008). However, the set of opportunities for smallholder farmers remains unclear, and will importantly depend on the types of supply chains that eventuate. Small scale initiatives for local use of biofuels may catalyze rural development and facilitate transport or operation of small equipment (irrigation pumps and pressing). However, these initiatives are not likely to contribute significantly to the international trade in biofuels. It is likely that production and processing of biofuels is subject to ‘‘economies of scale”. If so, large-scale commercial farming (plantations of jatropha, sugar cane, oil palm, etc.) may crowd out other activities, possibly displacing smallholder farming. The net development impact will depend on newly created job opportunities, price effects on local (food) markets, and so on. These effects are difficult to predict. 6. Concluding remarks It seems unlikely that large-scale biofuels production will be able to comply with a reasonable set of sustainability criteria before 2020. Imposing a worldwide 10% obligatory blending target of biofuels for transport, would, for instance, claim 85–176 million hectares of fertile land, depending on the fraction 1st or 2nd generation biofuels, the fraction of residues used in the 2nd generation feedstock, the crop mixture as feedstock for the biofuels and the assumed crop yield levels (Bindraban et al., 2009). These lands tied up for biofuels production could produce enough food to feed 320– 460 million people with a diet currently consumed in the EU. It is likely that the additional claim for land will contribute to the loss of biodiversity, result in extra GHG emissions and trigger competition with food and for scarce resources. In light of this knowledge, current biofuels promotion policies appear ill-advised. Acknowledgement We would like to thank Bas Eickhout of the Netherlands Environmental Assessment Agency for his valuable comments on the manuscript.
P.S. Bindraban et al. / Agricultural Systems 101 (2009) 197–199
References Banse, M.A.H., Nowicki, P.L., van Meijl, J.C.M., 2008. Why Are Current World Food Prices So High? A Memo. Wageningen: LEI Wageningen UR, The Netherlands, p. 27. Bindraban, P.S., Bulte, E.H., Conijn, J.G., Eickhout, B., Hoogwijk, M., Londo, M., 2009. Can biofuels be sustainable by 2020? An assessment for an obligatory blending target of 10% in The Netherlands. Report to the Scientific Assessment and Policy Analysis on Climate Change, The Netherlands. Report No. 500102024, p. 94.. European Environment Agency, 2006. How much bioenergy can Europe produce without harming the environment? Copenhagen. EEA Report No. 7/2006. European Environment Agency, 2008. Maximising the environmental benefits of Europe’s bioenergy potential. Copenhagen. EEA Report No. 10/2008. European Parliament, 2008. Report on the proposal for a directive of the European Parliament and of the Council on the promotion of the use of energy from renewable sources (COM(2008)0019 – C6 0046/2008 – 2008/0016(COD)). European Parliament, Committee on Industry, Research and Energy, Brussels, Belgium. FAO, 2008. Biofuels: Prospects, Risks and Opportunities. The State of Food and Agriculture. FAO, Rome, p. 129. . Fargione, J., Hill, J., Tilman, D., Polasky, S., Hawthorne, P., 2008. Land clearing and the bio-fuel carbon debt. Science 319, 1235–1238. IAASTD, 2008. Synthesis Report of the International Assessment of Agricultural Science and Technology for Development, Washington.
199
Licht, F.O., 2007. Licht Interactive Data.. OECD/FAO, 2008. OECD–FAO Agricultural Outlook 2008–2017. Organisation for Economic Co-operation and Development (OECD), Paris, France and Food and Agriculture Organisation of the United Nations (FAO), Rome, Italy, p. 72. . Righelato, R., Spracklen, D.V., 2007. Carbon mitigation by biofuels or by saving and restoring forests? Science 317, 902. doi:10.1126/science.1141361. Rosegrant, M.W., 2008. Biofuels and grain prices: impacts and policy responses. Testimony for the US Senate Committee on Homeland Security and Governmental Affairs, 7th May 2008. Russelle, M.P., Vance Morey, R., Baker, J.M., Porter, P.M., Jung, H.G., 2007. Comment on ‘‘carbon-negative biofuels from low-input high-diversity grassland biomass”. Science 316, 1567b. Searchinger, T., Heimlich, R., Houghton, R.A., Dong, F., Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D., Yu, T.H., 2008. Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land use change. Science 319, 1238– 1240. Sinclair, T.R., Horie, T., 1989. Leaf nitrogen, photosynthesis and crop radiation use efficiency: a review. Crop Sci. 29, 90–98. Smeets, E.M.W., Faaij, A.P.C., Lewandowski, I.M., Turkenburg, W.C., 2007. A bottom– up assessment and review of global bio-energy potentials to 2050. Progr. Energy Combust. Sci. 33, 56–106. Spedding, C.R.W., 1988. An Introduction to Agricultural Systems. Elsevier Applied Science, London, UK, p. 189. Tilman, D., Hill, J., Lehman, C., 2006. Carbon-negative biofuels from low-input highdiversity grassland biomass. Science 314, 1598–1600. Von Braun, J., 2007. The World Food Situation: New driving Forces and Required Actions. Food Policy Report 18, IFPRI, Washington DC. . Von Braun, J., 2008. The food crisis isn’t over. Nature 456, 701. WDR, 2008. Agriculture for Development. World Development Report, 2008. World Bank, Washington, DC. World Bank, 2008. A Note on Rising Prices. Policy Research Working Paper 4682. The World Bank, Development Prospects Group, Washington, DC.
Contents lists available at ScienceDirect
Agricultural Systems journal homepage: www.elsevier.com/locate/agsy
Short Communication
Can large-scale biofuels production be sustainable by 2020? Prem S. Bindraban a,*, Erwin H. Bulte b, Sjaak G. Conijn a a b
Plant Research International, 6700 AP Wageningen, The Netherlands Chair Group Development Economics, Wageningen UR, The Netherlands
a r t i c l e
i n f o
Article history: Received 6 May 2009 Received in revised form 3 June 2009 Accepted 10 June 2009 Available online 7 July 2009 Keywords: Radiation use efficiency GHG emissions Land use change Development Food security
a b s t r a c t Worldwide, many nations impose blending of their transport fuels with biofuels, approximating 10% globally by 2020, to contribute to energy security while reducing emission of green house gasses (GHG). Food riots, scientific insights that question the GHG benefits and raised concern about the loss of biodiversity, have lead to the formulation by various governments of sustainability criteria for biofuels to comply with. In this paper, we assess this conditionality and argue that large-scale biofuels production will be unable to comply with these criteria in 2020, and can therefore not be qualified as sustainable. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
2. Reduction of GHG emissions
Worldwide, many nations have formulated policies to blend a certain proportion of their transport fuels with biofuels (FAO, 2008). The targets aimed for may approximate about 10% globally in 2020. Biofuels production is driven mainly by policy measures, including tax exemptions, investment subsidies and obligatory blending of biofuels with fossil fuels, as in the EU and USA (European Parliament, 2008; Energy Policy Act of 2005, 2005). From 2001 to 2007, world ethanol production almost tripled from 20 to 50 billion litres (Licht, 2007) and world biodiesel production increased from 0.8 to almost 4 billion litres. However, food riots and the unprecedented increase in the number of hungry people in 2007 and 2008 have alerted nations to scrutinize their ambitions with respect to biofuels, as these, together with some other factors, have caused the food problems (e.g. Banse et al., 2008; World Bank, 2008). Scientific insights that question the environmental benefits and high production costs further triggered the European Union to propose sustainability criteria for biofuels to comply with. These criteria impose threshold values for the reduction of greenhouse gas (GHG) emissions relative to fossil fuels and prevention of loss of biodiversity. Moreover, expanded production of biofuels should not compete with food or feed, and must stimulate the development of countries that produce feedstock and/or biofuels. Here we assess whether the production of biofuels to meet blending targets in 2020 can comply with the sustainability criteria.
The Achilles’ heel of biofuels production is the low utilization efficiency of sunlight by plants. The maximum attainable efficiency (Spedding, 1988) of around 3.5% with year-round cultivation in the tropics and about 1.5% in temperate regions, ultimately reduces to 0.2–1% for biofuels after correction for non-harvestable crop parts and energy needed during production, transport and processing of the biomass (Corré and Conijn, 2008). This applies to crops grown under optimal conditions – adequately supplied with water and nutrients, and well protected against pest and diseases. Efficiencies will be even lower under marginal growing conditions, when crop radiation use efficiency declines due to yield reducing factors (Sinclair and Horie, 1989). Improving conversion efficiencies along the various steps in the production chain will not overcome the inherently low utilization efficiency of solar energy by plants. While the transport sector will have to make an effort in cutting down greenhouse gas emissions and contribute to meet long-term climate stabilization targets, it is unlikely that major gains can be achieved via biofuels. Indeed, the contrary may be true. . . Net savings of GHG emissions up to 10 ton CO2 ha 1 y 1 in the production chain for biofuels from feedstocks like sugarcane and palm oil have been calculated (Righelato and Spracklen, 2007). Savings will be lower under poor management – when soil organic matter is lost during production, or when too much nitrogen fertilizer is used (Crutzen et al., 2007; Smeets et al., 2007). Worse, when cultivation of biomass leads to the direct or indirect clearing of natural lands (see Section 3), net CO2 savings may turn negative. Emissions 30–200 times the amount potentially saved in the chain may occur (Searchinger et al., 2008; Fargione et al., 2008). Regional options for
* Corresponding author. Address: Plant Research International, P.O. Box 616, 6700 AP Wageningen, The Netherlands. Tel.: +31 317 480881; fax: +31 317 423110. E-mail address: [email protected] (P.S. Bindraban). 0308-521X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.agsy.2009.06.005
198
P.S. Bindraban et al. / Agricultural Systems 101 (2009) 197–199
biofuels to mitigate GHG emissions (e.g. European Environment Agency, 2006) will have to be evaluated in a global perspective because GHG have no national or regional borders. To be more specific; the gross emissions reduction of a global 10% blending obligation in 2020 would be 450–600 million tons of CO2-equivalents (assuming good agronomic management with a 60–80% efficiency in GHG replacement of biofuels relative to fossil fuels). This equals on average 1.1% of total CO2-equivalent emission in 2005. However, these gross gains turn negative if more than 30% of the required land would be obtained through clearing of natural lands (Bindraban et al., 2009). We argue that this is the most likely scenario when ambitious mandatory biofuels mixing rules are in place (see below). Moreover, even for positive GHG emissions savings, the social costs are high—by far exceeding those of alternative approaches to mitigating climate change. Total costs for biofuels range from 960–1700 US$ per tons of CO2 saved, while alternative means of GHG savings exist with costs in the range of 7–22 US$ per ton (OECD, 2008).
favorable ratios of cost to GHG/energy savings. These uncertainties further increase investment risks. It is therefore almost inevitable that in the short and medium term biofuels will continue to be derived from food crops, or from crops that displace food crops. For the mid- and long-term, most studies estimate blending obligations to increase equilibrium food price levels by 10–30% (OECD, 2008; Banse et al., 2008; Von Braun, 2008). Moreover, while linking food and energy markets implies introducing a price ceiling for food crops (potentially contributing to price stability), it is also evident that food prices may become more volatile because of mandatory mixing (von Braun, 2007). Any volatility in energy prices will be transferred to food markets. Also, mandatory blending targets imply extra demand for food crops even if prices are high – contributing to higher price peaks. For example, the high volatility of food prices that was experienced in 2008, was caused by several factors, including biofuels (estimates of the contribution of biofuels vary from 30% and 80% – see Rosegrant, 2008 and World Bank, 2008). As a result of these effects, the food security of poor people is expected to structurally deteriorate (Von Braun, 2008).
3. Competition for resources and biodiversity loss 5. Opportunities for development? The critical question is whether agricultural productivity can be increased to such an extent that sufficient agricultural land can be freed up for the production of energy crops. Most studies indicate that this is unlikely to be the case, and argue that to meet future food demand the global acreage of both arable land and grassland will have to increase (OECD/FAO, 2008; IAASTD, 2008). Moreover, these studies may be too optimistic as they are partly based on extrapolating existing trends, whereas a deteriorating resource base (notably water availability and physical and chemical soil fertility) will limit future productivity increases in biomass production. While measures to mitigate resource degradation and scarcity have been identified, implementation is a complex and time-consuming undertaking, involving agro-technical, institutional and economic innovations. Arguably more rather than less land will be necessary for food production to meet food demand, certainly until 2020 (e.g. Bruinsma, 2003). This implies that the production of biofuels to meet the blending targets in 2020 will imply additional demand for land. It is unlikely that this additional demand for land can be met without a net clearing of natural lands – resulting in carbon emissions as well as a loss of biodiversity. Can we use non-food biomass produced on marginal lands as a sustainable option (e.g. Searchinger et al., 2008)? The use of marginal lands is unlikely to create significant volumes of biomass in the near term. They are beset with a range of difficulties, and overcoming such difficulties will compromise the natural character of the ecosystem (likely implying a loss of ecosystem services and biodiversity). To raise and stabilize yields, increased inputs are needed, and investments in institutions and infrastructure are required. Favorable estimates for biomass yields from low-input, high-diversity grassland for instance (Tilman et al., 2006) appear to be open for discussion (Russelle et al., 2007). 4. Competition with food Many advocates of biofuels have vested their hopes on so called 2nd generation technologies, i.e. the production of biofuels from non-edible plant parts (e.g. EEA, 2008). However, the implementation of such technologies, in terms of timing and volumes, remains highly uncertain until 2020. It has not yet been proven at a (large) industrial scale and its implementation requires investments that exceed food-based biofuels plants by a factor of 10 (Deurwaarder et al., 2007). Moreover, on the longer term strong competition may be expected from alternative technologies, including electrical and hydrogen-driven cars, and solar and wind energy with more
An expanding biofuels sector involves both opportunities and threats for development. Similarly, higher prices of food involve opportunities, for (potential) net producers as well as threats for net consumers. Structurally higher food prices may invite a badly-needed intensification strategy among farmers, contributing to rural economic development with possible positive spillover effects for the rest of the economy (WDR, 2008). However, the set of opportunities for smallholder farmers remains unclear, and will importantly depend on the types of supply chains that eventuate. Small scale initiatives for local use of biofuels may catalyze rural development and facilitate transport or operation of small equipment (irrigation pumps and pressing). However, these initiatives are not likely to contribute significantly to the international trade in biofuels. It is likely that production and processing of biofuels is subject to ‘‘economies of scale”. If so, large-scale commercial farming (plantations of jatropha, sugar cane, oil palm, etc.) may crowd out other activities, possibly displacing smallholder farming. The net development impact will depend on newly created job opportunities, price effects on local (food) markets, and so on. These effects are difficult to predict. 6. Concluding remarks It seems unlikely that large-scale biofuels production will be able to comply with a reasonable set of sustainability criteria before 2020. Imposing a worldwide 10% obligatory blending target of biofuels for transport, would, for instance, claim 85–176 million hectares of fertile land, depending on the fraction 1st or 2nd generation biofuels, the fraction of residues used in the 2nd generation feedstock, the crop mixture as feedstock for the biofuels and the assumed crop yield levels (Bindraban et al., 2009). These lands tied up for biofuels production could produce enough food to feed 320– 460 million people with a diet currently consumed in the EU. It is likely that the additional claim for land will contribute to the loss of biodiversity, result in extra GHG emissions and trigger competition with food and for scarce resources. In light of this knowledge, current biofuels promotion policies appear ill-advised. Acknowledgement We would like to thank Bas Eickhout of the Netherlands Environmental Assessment Agency for his valuable comments on the manuscript.
P.S. Bindraban et al. / Agricultural Systems 101 (2009) 197–199
References Banse, M.A.H., Nowicki, P.L., van Meijl, J.C.M., 2008. Why Are Current World Food Prices So High? A Memo. Wageningen: LEI Wageningen UR, The Netherlands, p. 27. Bindraban, P.S., Bulte, E.H., Conijn, J.G., Eickhout, B., Hoogwijk, M., Londo, M., 2009. Can biofuels be sustainable by 2020? An assessment for an obligatory blending target of 10% in The Netherlands. Report to the Scientific Assessment and Policy Analysis on Climate Change, The Netherlands. Report No. 500102024, p. 94.
199
Licht, F.O., 2007. Licht Interactive Data.