Bioenergy CCS and Potential Tradeoffs with Food Production

As the Intergovernmental Panel on Climate Change concluded in its Fifth Assessment Report’s Working Group III contribution, “[b]ioenergy coupled CCS (BECCS) has attracted particular attention since AR4 because it offers the prospect of energy supply with negative emissions.” However, as the IPCC report also cautions, BECCS poses serious challenges, among them, the potential threat to food supplies posed by diversion of biomass to energy production. A study, “Global bioenergy potentials from agricultural land in 2050: Sensitivity to climate change, diets and yields,” published a few years ago in the journal Biomass & Bioenergy (subscription required) provides an excellent overview of the potential interrelations between food and energy production, and the potential for projected climatic change to either ameliorate or exacerbate the tensions between food and energy production. The study employed what it termed a “socioeconomic metabolism approach” to formulate a biomass balance model (to 2050) to link supply and demand of agricultural biomass, excluding forestry.

Among the conclusions of the study:

  1. Climate change could have dramatic impacts on available biomass in 2050. If some projections of the CO2 fertilization effects are correct, bioenergy potential could rise by a whopping 45% to 151.7 EJ y-1, or it could decline to 87.5 EJ if CO2 fertilization is completely ineffective.  To put this in context, humans currently harvest and utilize a total of amount of biomass with an energy value of 205 EJ y-1. “This implies that the global bioenergy potential on cropland and grazing areas is highly dependent on the (uncertain) effect of climate change on future global yields on agricultural areas.”
    • However, part of the potential benefits of the CO2 fertilization effect could be obviated by potential decreases in protein content and higher susceptibility to insect pests
  2. There is huge uncertainty in potential bioenergy from forests, ranging from zero to 71 EJ y-1 in 2050;
  3. After taking into account projected food needs, primary bioenergy potential is estimated to be between 64-161 EJ y-1 However, this is “only a fraction of current fossil-fuel use.” Moreover, realizing bioenergy potentials on grazing lands of this magnitude would require “massive investments” in agricultural technologies, e.g. irrigation and could also particularly threaten populations practicing low-input agriculture.

This study demonstrates that BECCs remains a highly contested proposition in terms of potential tradeoffs of food and energy production. Moreover, the “wildcard” of the potential impacts of climate change on biomass production are likely to remain unknown for many decades, making it difficult to determine if large-scale BECCS should be pursued as a policy option.

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WilBurnsBioThumbWil Burns is Director, MS in Energy Policy and Climate Program, Johns Hopkins University & co-founder of the Washington Geoengineering Consortium.