Background

Biomass use for energy production in processes such as combustion and gasification, and its use to produce biofuels such as bioethanol, results in emissions of CO₂. This CO₂ produced during combustion is approximately the same quantity consumed during biomass growth; therefore emissions from biomass combustion are considered to be CO₂ neutral (Demirbas, 2009)*.  Capture and long-term storage of these CO₂ emissions would effectively result in net removal of atmospheric CO₂; and Biomass with CCS is potentially one of the few options for ‘negative emissions’ (Figure 1).  Several mitigation scenarios show biomass in combination with CCS is likely to be required to meet low stabilisation concentrations (e.g. as discussed in Lindgren et al., 2006; IEA/OECD, 2008), and as biomass use is expected to increase, the potential application of CCS will also increase. 

The combination of biomass and CCS in energy conversion technologies has many technological similarities with CCS applied to fossil fuel conversion; however there are also several differences such as biomass fuel typically has other combustion/gasification properties, lower energy density and greater variation between biomass types.  Biomass with CCS (BE-CCS) is not restricted to production of electricity or heat, and other production processes such as bio-ethanol production produce pure CO₂ streams as a by-product which can easily be captured and separated.  BE-CCS has many advantages, and consequently there is a need to understand deployment potential.  An overview of global and regional biomass potential mapped with CCS potential has not yet been published, and understanding of global potential, drivers and obstacles which may accelerate or limit BE-CCS implementation is imperative for assessment of this negative emissions mitigation option. 

Conclusions

This study has shown the value of a first order techno-economic assessment of BE-CCS technologies which is currently under wide debate due to its potential for negative emissions.   The global Technical Potential for BE-CCS technologies is found to be large and, if deployed, can result in negative emissions up to 10 Gt of CO₂ equivalent annually; or a more conservative Economic Potential of up to 3.5 Gt of CO₂ equivalent of negative emissions per year; which compared to the IEA ETP (2010) estimate of 43 Gt of global CO₂ emissions reductions required from the energy sector by 2050, shows significant potential.  Given the impact such could have on atmospheric CO₂ reduction targets, it is important IEAGHG continues to expand upon this study to further assess these results. 

The key obstacle to the implementation of the technology is identified as the absence of a price for stored biomass based CO₂, hence an economic value on ‘negative emissions’, in for example the EU ETS; and BE-CCS needs inclusion into the CDM if this option is to be taken up by developing countries such as Brazil where early opportunities exist.  There is therefore, a need for policy developments in this area to assist global take-up of the technology.  This is of course not an area IEAGHG covers directly, and the policy implications of this study will be discussed with the IEA CCS Unit.

The study raises the importance of further definition of what constitutes sustainable biomass, and IEAGHG should ensure to keep abreast of advancements in international efforts to establish sustainability criteria, in addition to further detailed regional and focussed potential assessment of BE-CCS.  IEAGHG should consider a focussed study to provide insight into the economic and infrastructure boundary conditions for CO₂ capture from bio-ethanol production, as bio-ethanol appears to be a route which has short-term opportunities for BE-CCS; consideration of the co-utilisation of biomass and coal in existing and new Fischer Tropsch facilities that are planned or operating worldwide; and additional assessments to include other potential biomass supply options not included in this study, such as aquatic biomass from algae, with a particular emphasis on potential secure sustainable biomass sources.  The study also further highlights the need for consistent and detailed storage capacity estimates and linking any such further assessments to developments in estimates will be necessary. 

Recommendations

There are a number of recommendations resulting from this study, the most important of which highlights the need for an economic incentive for producing negative emissions, without which BE-CCS will not have an economic potential.

• Stored CO₂ originated from biomass will require an economic value to stimulate the introduction of this technology.  CO₂ price in combination with low cost sustainable biomass are the key drivers for BE-CCS.

• Further research should be focussed on assessing the BE-CCS potential per region and in greater detail through regional specific cost supply curves for CO₂ transport and storage, including source sink matching.

• State-of-the-art sustainability criteria should be applied when assessing the potential for BE-CCS technologies, and additional research should verify these results with a more detailed assessment of factors that limit sustainable supply of biomass at a regional level and assess actions to increase this supply, which was out of the scope of this first level assessment.

• Further assessment of the effect of (co-)firing biomass on the performance of CO₂ capture options in pilot/demonstration plants is needed, particularly in terms of potential effects of increasing biomass fractions, and after such any potential technical barriers can be identified and removed to facilitate deployment.

• A BE-CCS option not considered in this study is the co-utilisation of biomass and coal in existing and new Fischer Tropsch facilities that are planned or operating worldwide.  In conjunction with CO₂ capture from bio-ethanol production, this could provide early opportunities for BE-CCS at relatively low cost; and examination of such on a case-by-case basis could be a valuable next step.  Research should be focussed on further insight into the economic and infrastructure boundary conditions for CO₂ capture from bio-ethanol production, using detailed case studies.  This seems to be economically attractive for the short to medium term, and it is likely short-term opportunities exist in Brazil and the USA, which are the largest producers of bio-ethanol with considerable CO₂ storage potential.

• Short and long-term price estimations are pivotal to assessing economic potential and, insights and quantification of key factors influencing trade volume and price of biomass would provide a more robust economic potential assessment.

• Further research should take into account assessments of other potential biomass supply options not included in this study, such as aquatic biomass from algae.