Bio-CCS: Feasibility comparison of large scale carbon-negative solutions

Abstract

Abstract The urgency to stabilize the global temperature rise at 2 °C as highlighted in the IPCC Fifth Assessment Report calls for solutions that can remove CO 2 from the atmosphere. Achieving negative CO 2 emissions by removing CO 2 from the atmosphere is possible by applying carbon capture in processes using biomass (Bio-CCS). Biomass has the capability of withdrawing and storing atmospheric CO 2 . As a result, CO 2 released during biomass combustion can be captured and stored permanently underground, thus depriving the atmosphere of CO 2 . The objective of this paper is to assess the background for most rational deployment opportunities of Bio-CCS from climate and economic point of view; to evaluate what is the best way to use constrained biomass resources by assessing the effects that raw materials types, different processes and end products have on carbon stocks and on the overall GHG mitigation from the global perspective. A concrete example on how more thorough deployment of Bio-CCS could penetrate in near-term markets is given as a Finnish Bio-CCS roadmap with scenarios highlighting the bottlenecks and constrains. The roadmap assessment is based on power plant, industrial plant and emission database calculations with future projections for existing installations. The technical implementation of Bio-CCS in different industrial sectors goes hand in hand with the development of conventional CCS technology deployment. In general, similar solutions are suitable for capturing CO 2 from biomass applications as for fossil fuels. The main differences relate to the size and the location of emission sources (biomass-based installations are often decentralized and of smaller scale compared to fossil-based installations) or to the different kind of impurities in the combustion process, ash and flue gas. However, no principal technical restrictions to the capture of biogenic CO 2 exist in energy generation applications or industrial processes. As a consequence, certain Bio-CCS applications are low-hanging fruits for near future deployment of carbon capture assuming that negative emissions are accounted for. In this paper the potential technologies for Bio-CCS and the feasibility of some solutions are compared both from a sustainability and cost point of view. There are four major biomass conversion routes where Bio-CCS is applicable; biochemical conversion (fermentation and hydrolysis), thermo-chemical conversion (e.g. gasification), power production (gasification and combustion) and industrial processes. In addition to ethanol fermentation the thermo-chemical biomass conversion processes are considered the first-phase targets for applying capture of CO 2 , both from a logistic and cost point of view. The main Bio-CCS technologies assessed in this study are Fischer-Tropsch diesel production, bio-SNG production, lignocellulosic ethanol production, torrefaction and biomass based power production such as co-firing biomass in a coal-based condensing power plant and biomass-based CHP (combined heat and power) production. The most applicable industry sector forintroduction of Bio-CCS is obviously pulp and paper industry but some potential exists also in cement industry, iron and steel industry and oil and gas refineries. The emission reduction potential in different technologies is very much bound to the scale of installations which again is generally limited by the scale of technologies and availability of biomass raw material. The biggest reduction potential for the studied cases per industrial site can take place in iron and steel industry (∼3 Mt/a), pulp and paper industry (∼1.3 Mt/a) and in combined heat power (CHP) production (∼2.5 Mt/a) as opposed to straw ethanol production of smaller scale (∼0.1 Mt/a). However, the CO 2 avoidance potential per unit of biomass raw material utilized is highest in co-firing (20tCO 2 /toe), iron and steel industry (10tCO 2 /toe) and in CHP production (8tCO 2 /toe) whereas straw ethanol has lowest potential also in this category (1.5tCO 2 /toe). The cost estimations show a theoretical economic advantage of Bio-CCS over fossil CCS on carbon prices when the carbon sink effect is accounted for. The total costs for Bio-CCS vary from 35€/ton to 300€/ton CO 2 stored depending on the technology. As the potential of Bio-CCS is bound to the availability and usage of biomass raw materials, the sustainability of the raw materials is of essence. The current biomass flows and potentials set the initial limits for the wider deployment of Bio-CCS. Efficient utilization of constrained resources is an essential question, when the target is to optimize the impact on the system level, from the society point of view. The ultimate objective is to suggest whether deployment of CCS has the desired impact on the atmospheric CO 2 concentration. As biomass can be used in many ways, the primary purpose of utilization and products containing biogenic carbon also adds up to this. When biomass is utilized for products other than energy, the impact to environment and economy differs. The opportunities with these solutions, realistic potential and the main threats related to Bio- CCS are discussed in the light of sustainability and economic potential.