Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change

Searchinger, Timothy D.; Heimlich, Ralph E.; Houghton, Richard A.; Dong, Fengxia; Elobeid, Amani; Fabiosa, Jacinto F.; Tokgöz, Simla; Hayes, Dermot J.; Yu, Tun Hsiang E.

doi:10.1126/science.1151861

Cited by 3,946 publications

(2,763 citation statements)

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“…At a global level, the evidence base has been provided by the IPCC reports (IPCC, 2007a and2007b), but the assumptions made for agriculture at a global level (a closed system) will not hold at a national level, where the farming industry consists of a large number of small-to medium-sized businesses whose carbon emissions will depend both on the natural resources available and their response to technology and markets, with varying levels of imports and exports over time. The volatility of those markets was demonstrated in 2008, when increasing competition for agricultural land between food and non-food uses was highlighted (Searchinger et al, 2008). This has consequences for the evidence base required by the policy community, who increasingly have to balance the need to address climate change with the need to maintain food security.…”

Section: Introduction: the Need To Mitigate Climate Changementioning

confidence: 99%

Mitigating climate change: the role of domestic livestock

Gill

Smith

Wilkinson

2010

Animal

236

175

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Livestock contribute directly (i.e. as methane and nitrous oxide (N 2 O)) to about 9% of global anthropogenic greenhouse gas (GHG) emissions and around 3% of UK emissions. If all parts of the livestock production lifecycle are included (fossil fuels used to produce mineral fertilizers used in feed production and N 2 O emissions from fertilizer use; methane release from the breakdown of fertilizers and from animal manure; land-use changes for feed production and for grazing; land degradation; fossil fuel use during feed and animal production; fossil fuel use in production and transport of processed and refrigerated animal products), livestock are estimated to account for 18% of global anthropogenic emissions, but less than 8% in the UK. In terms of GHG emissions per unit of livestock product, monogastric livestock are more efficient than ruminants; thus in the UK, while sheep and cattle accounted for 32% of meat production in 2006, they accounted for , 48% of GHG emissions associated with meat production. More efficient management of grazing lands and of manure can have a direct impact in decreasing emissions. Improving efficiency of livestock production through better breeding, health interventions or improving fertility can also decrease GHG emissions through decreasing the number of livestock required per unit product. Increasing the energy density of the diet has a dual effect, decreasing both direct emissions and the numbers of livestock per unit product, but, as the demands for food increase in response to increasing human population and a better diet in some developing countries, there is increasing competition for land for food v. energy-dense feed crops. Recalculating efficiencies of energy and protein production on the basis of human-edible food produced per unit of human-edible feed consumed gave higher efficiencies for ruminants than for monogastric animals. The policy community thus have difficult decisions to make in balancing the negative contribution of livestock to the environment against the positive benefit in terms of food security. The animal science community have a responsibility to provide an evidence base which is objective and holistic with respect to these two competing challenges.

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Section: Introduction: the Need To Mitigate Climate Changementioning

confidence: 99%

Mitigating climate change: the role of domestic livestock

Gill

Smith

Wilkinson

2010

Animal

236

175

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“…The impact on food prices could be serious (Clayton, 2008). The negative impacts of the crop-based approach are becoming evident (Clayton, 2008;Rosenthal, 2008;Searchinger et al, 2008). A simple computation illustrates the scale problem using crop-based ethanol.…”

Section: Biomass Options That Cannot Attain Large Enough Scalementioning

confidence: 99%

Opportunities for renewable bioenergy using microorganisms

Rittmann

2008

Biotech & Bioengineering

543

232

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Global warming can be slowed, and perhaps reversed, only when society replaces fossil fuels with renewable, carbon-neutral alternatives. The best option is bioenergy: the sun's energy is captured in biomass and converted to energy forms useful to modern society. To make a dent in global warming, bioenergy must be generated at a very high rate, since the world today uses $10 TW of fossil-fuel energy. And, it must do so without inflicting serious damage on the environment or disrupting our food supply. While most bioenergy options fail on both counts, several microorganism-based options have the potential to produce large amounts of renewable energy without disruptions. In one approach, microbial communities convert the energy value of various biomass residuals to socially useful energy. Biomass residuals come from agricultural, animal, and a variety of industrial operations, as well as from human wastes. Microorganisms can convert almost all of the energy in these wastes to methane, hydrogen, and electricity. In a second approach, photosynthetic microorganisms convert sunlight into biodiesel. Certain algae (eukaryotes) or cyanobacteria (prokaryotes) have high lipid contents. Under proper conditions, these photosynthetic microorganisms can produce lipids for biodiesel with yields per unit area 100 times or more than possible with any plant system. In addition, the non-lipid biomass can be converted to methane, hydrogen, or electricity. Photosynthetic microorganisms do not require arable land, an advantage because our arable land must be used to produce food. Algae or cyanobacteria may be the best option to produce bioenergy at rates high enough to replace a substantial fraction of our society's use of fossil fuels.

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“…En Europe, les études régionales plus détaillées s'accordent sur le fait que le développement des biocarburants de 1ère génération pourra difficilement aller au-delà des 5,75% d'incorporation (Wiesenthal et al, 2006). Il pourrait de plus entraîner la mise sous culture d'écosystèmes naturels (forêts, savanes) ou de prairies permanentes -des conséquences difficile à prévoir et à prévenir, mais qui grèveraient fortement le bilan des biocarburants en termes d'émissions de GES (Searchinger et al, 2008). …”

Section: Disponibilité De La Ressourceunclassified

“…En revanche, la substitution des mêmes céréales par des cultures lignocellulosiques (pour les biocarburants 2ème génération) devrait permettre de réduire de façon substantielle la pression agricole sur l'environnement local. On peut toutefois craindre que la compensation nécessaire au niveau de la production alimentaire, qui aura lieu ailleurs sur la planète, risque elle d'y aggraver l'environnement local (Searchinger et al, 2008). D'où la nécessité de traiter la question des impacts locaux..au niveau global!…”

Section: Bilans éNergétiques Et Environnementauxunclassified

Intérêts et limites des biocarburants de première génération

Gabrielle

2008

J. Soc. Biol.

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Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change

Cited by 3,946 publications

References 10 publications

Mitigating climate change: the role of domestic livestock

Mitigating climate change: the role of domestic livestock

Opportunities for renewable bioenergy using microorganisms

Intérêts et limites des biocarburants de première génération

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