The Paris Agreement establishes the objective of “[h]olding the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels . . .” However, in the negotiations leading up to Paris, and in its aftermath, it has become increasingly obvious that meeting even the less stringent of these two goals may prove extremely daunting.
Policymakers and climate scientists believe the only way to avoid passing critical climatic thresholds, or to address “overshoot” scenarios in which atmospheric concentrations and/or associated temperature increases could temporarily exceed target levels, is to deploy so-called “negative emissions technologies” (NETs) on a large-scale. NETs can facilitate capturing anthropogenically-produced carbon dioxide, through immediate capture at the site of production, direct removal of carbon from the atmosphere, or through engineered enhancement of natural carbon sinks.
The vast majority of mitigation scenarios developed in integrated assessment models under which temperatures are kept to 2°C or below (344 of 400 by the IPCC) contemplate extensive deployment of NETs during the course of this century, with an approach called Bioenergy with Carbon Capture and Sequestration (BECCS) cited as the primary option. BECCS is a process by which biomass is converted to heat, electricity, or liquid or gas fuels, coupled with carbon dioxide capture and sequestration. Feedstocks can include energy derived from woody biomass from forests, energy or food crops, agricultural residues and municipal solid waste.
While proponents contend that BECCS might effectuate sequestration up to 17 gigatons of carbon dioxide annually by 2100, questions about the technology’s economic viability and risks abound. For example, two of the alleged model facilities to demonstrate the promise of CCS, Saskpower’s Boundary Dam Carbon Capture project and Southern Company’s Kemper project have suffered from serious cost overruns and technical problems. Moreover, there are serious questions about whether CCS projects can ever be cost-competitive absent a very high price on carbon. Proponents, on the other hand, argue that learning by doing and economies of scale will ultimately bring down prices and ensure dependability.