Most of the scenarios in the IPCC’s Fifth Assessment Report that set out pathways to avoid temperature increases above 2C rely on large-scale use of so-called “negative emissions technologies,” with the lion’s share coming from the use of Bioenergy and Carbon Capture and Sequestration (BECCS) options. However, there is increasing concern that BECCS could have serious negative ramifications for food security for some of the world’s most vulnerable populations. A recent study by Tim Searchinger et al., analyzing results from a suite of models assessing changes in land use, crop production and food consumption associated with the production of biofuels, suggests that these concerns are valid, and may have serious ramifications for the use of BECCS in the future.
Among the findings of the study were the following:
- Approximately 25-50% of net calories associated with diversion of corn or wheat to ethanol are not replaced through planting of other crops, but rather is taken out of food and feed consumption. Failure to replace crops reduces greenhouse gas emissions from land use change and direct emissions of carbon dioxide by people and livestock;
- Most analysis of the greenhouse gas emissions implications of biofuel production assume that the emissions associated with fermenting and burning ethanol is offset by carbon absorption by growth of crops diverted to ethanol production. However, this accounting methodology is faulty, because carbon absorbed by crops that would be grown anyway doesn’t constitute a valid offset, because it’s not linked to biofuel production and is not additional.
- The only valid form of crop growth offsets would be either from growth of additional crops to replace those diverted to biofuels production, or increases on crop yields on existing croplands;
- Moreover, converting forests or grasslands to produce additional food crops would also release carbon, “reducing or negating the net offset from producing more crops;”
- One study suggests that approximately 20% of calories diverted by biofuel production are not replaced. “Food reductions result not from a tailored tax on overconsumption or high-carbon foods but from broad global increases in crop prices.”
Among the class discussion questions that might be pertinent to this article are the following:
- What would the food implications be of a large-scale commitment to BECCS?
- What are the prospects to avoid food security issues outlined in this study by techniques such as increasing crop yields or using alternative bioenergy feedstocks, such as algae or cellulosic sources?;
- If trade-offs are indeed inevitable in terms of food production and greenhouse gas emissions, how should the world community make decisions under such conditions?