Pcic Science Brief: Is Atmospheric Carbon Dioxide Removal a Game Changer for Climate Change Mitigation?

University House 1, PO Box 1700, STN CSC, University of Victoria, Victoria, British Columbia, Canada, V8W 3R4 Phone: 250-721-6236 | Fax: 250-721-7217 | pacificclimate.org Recent work by Kriegler et al. (2013) in the journal Climatic Change finds that removing carbon dioxide from the atmosphere with a combination of biomass combustion and carbon capture, together with the storage of resulting carbon dioxide underground, can improve the feasibility and reduce the costs of achieving climate change goals. Current global greenhouse gas emissions are tracking the upper range of the IPCC’s scenarios. Climate model results suggest that this could lead to changes in the Earth’s climate that would be larger than 2 °C (the range of global temperature change of these upper range scenarios is between 2.4 to 6.4 °C). Despite international consensus on the importance of climate change mitigation, primarily through the reduction of emissions, global emissions are currently increasing. Because of this, there is interest in developing methods for reducing the atmospheric concentration of greenhouse gases. These methods can be broadly broken into two categories: (1) biological methods, that aim to use biological organisms such as trees and algae to remove carbon, and (2) chemical methods, that involve using chemical reactions to reduce carbon dioxide concentrations. Kriegler and colleagues examine one type of carbon dioxide reduction method, which involves using biomass for energy production and to produce biofuels, while capturing and storing the emissions. The overall strategy is as follows. As the biomass fuel source, such as corn, sugarcane or algae grows, it draws down atmospheric carbon dioxide. That carbon is released upon combustion, in a process that is potentially carbon neutral if a small enough amount of fossil fuel was is used for agricultural inputs and processing (tillage, fertilizer and pesticides, harvest transportation and processing). If the carbon from the combustion of the biomass is captured and stored, then the process, in principle, draws down more carbon than it releases and so the process acts as a carbon sink. This is known as Bioenergy with Carbon Capture and Storage, or BECCS. The authors examine the effects of implementing this form of carbon dioxide reduction scheme, over the 21st century, on three sectors: energy, transportation and stationary, non-electric energy use (which is primarily heating). The computer model that they use to do this is one that represents global energy use, the economy and the Earth’s climate system. Such models are called “Integrated Assessment Models.” They find that, using their carbon dioxide reduction method, greater reductions in emissions are achieved than from taxes on carbon emissions alone (see figure) and that the mitigation costs to reach certain target PCIC SCIENCE BRIEF: IS ATMOSPHERIC CARBON DIOXIDE REMOVAL A GAME CHANGER FOR CLIMATE CHANGE MITIGATION?