By Daisy Brickhill, IIASA science writer and editor.

Many of the options proposed for achieving a stable climate rely on ‘bioenergy with carbon capture and storage’ — burning plant matter for energy, capturing the carbon, and storing it underground. However, this technology has hardly been deployed on anything approaching the large scale. Is it a realistic tool for climate mitigation?

Limiting global warming to 2°C above pre-industrial times has long been a reference point for policymakers and researchers trying to reduce the chances of dangerous climate change. The 2015 Paris climate summit went even further, with countries agreeing to try and limit temperature rise to 1.5°C.

However, while there is a strong scientific consensus that we need to aggressively cut greenhouse gas emissions immediately, there is also growing evidence that we may not be able to achieve the necessary reductions in the time available. This means that we may need a way of removing CO2 already in the atmosphere — a process known as negative emissions.

Negative emissions can come in many forms: from simply planting more trees, to crushing rocks that naturally absorb CO2. One widely considered option is using plant matter as a fuel to produce energy, then capturing the CO2 that is emitted and storing it underground. This is known as bioenergy with carbon capture and storage (BECCS).

This latter technology is cited by research as being an important part of restricting warming to safe — or at least safer — levels since it contributes to both carbon sequestration and decarbonization of the energy system. In fact, more than half of the future scenarios that give at least a 66% chance of limiting warming to 2°C, which were developed for the Intergovernmental Panel on Climate Change (IPCC), feature BECCS.

However, the technology remains mostly untested on a large scale and there are doubts about its sustainability in terms of land and water use, and other potentially negative impacts on the environment. With so many IPCC scenarios including BECCS, information on whether it is at all a practical solution is desperately needed.

A recent IIASA study addresses deployment of BECCS in Indonesia, examining whether adapting existing coal-fired power stations so that they can burn a mix of coal and plant waste from agriculture (such as seed kernels or stems that are usually discarded), is more effective than building specific biomass-burning power stations.

Rice paddies in Indonesia. Plant waste from agriculture can be used in bioenergy with carbon capture and storage systems.

The team found that although both options saved the same amount of CO2, the combined stations were more efficient, producing more electricity for the amount of biomass burnt. “More efficiency means that burning biomass in adapted coal-fired power stations would be more economically viable,” says IIASA researcher Ping Yowargana, coauthor of the study. “It is also likely to be easier and cheaper to convert existing coal power stations than build new specific biomass-burning stations. With lower investments and existing infrastructure, policymakers and other stakeholders are more likely to embrace the idea.”

There are limitations: the study results indicate that under the current conditions it is not possible to burn any more than 30% biomass in a combined power station, for instance. There are also uncertainties surrounding whether it is possible to collect enough biomass on the scale needed. “We need to do further work on the logistic and financial feasibility of BECCS,” says Yowargana. “But these results are broadly general, and can be applied to other countries and situations, making them a valuable starting point.”

And while a complete conversion to a decarbonized energy system is needed in the long term, this work points the way to how BECCS might be deployed now to help prevent the damaging climate change we have sown for ourselves.

Reference: Hetland J, Yowargana P, Leduc S & Kraxner F (2016). Carbon-negative emissions: Systemic impacts of biomass conversion: A case study on CO2 capture and storage options. International Journal of Greenhouse Gas Control, 49. pp. 330-342.

Further reading:

Moreira, J. R., Romeiro, V., Fuss, S., Kraxner, F. and Pacca, S. A. (2016) BECCS potential in Brazil: Achieving negative emissions in ethanol and electricity production based on sugar cane bagasse and other residues. Applied Energy, 179. pp. 55-63. Item availability may be restricted.

Smith, P., Davis, S.J., Creutzig, F., Fuss, S., Rogelj, J., McCollum, D., Krey, V., Grubler, A., Jonas, M., Kraxner, F., Nakicenovic, N., Obersteiner, M. and Rogner, M. (2016) Biophysical and economic limits to negative CO2 emissions. Nature Climate Change, 6 (1). pp. 42-50.

Fuss, S., Canadell, J.G., Peters, G.P., Tavoni, M., Andrew, R.M., Ciais, P., Jackson, R.B., Jones, C.D., Kraxner, F., Nakicenovic, N., Le Quere, C., Raupach, M.R., Sharifi, A., Smith, P. and Yamagata, Y. (2014) Betting on negative emissions. Nature Climate Change, 4 (10). pp. 850-853.

Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.

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