Towards Zero Emissions CCS from Power Stations using Higher Capture Rates or Biomass

Publication Overview

To-date, capture technology developers have largely focused on designing plant for CO₂ capture rates of 85% to 90%, leaving 10-15% of the emissions uncaptured, which are usually referred to as residual emissions. In a “well below 2°C” scenario, it is projected that net zero carbon emissions would be required by early in the second half of this century. A review of the literature indicated that there were no technical barriers to increasing capture rates in the three classic CO₂ capture routes (post-, pre- and oxyfuel combustion) and with the broad suite of CO₂-capture technologies currently available or under development. A techno-economic analysis of a standard PCC process applied to both coal- and gas-fired power plants revealed that, with dedicated process design, the additional costs of achieving essentially zero CO₂ emissions were quite modest in comparison with the costs of achieving 90% CO₂ capture. For coal-fired power stations, the analysis found that using biomass co-combustion (10% biomass) combined with a standard PCC process (90% CO₂ capture) was the lowest cost option.

Publication Summary

To-date, capture technology developers have largely focused on designing plant for CO₂ capture rates of 85% to 90%, leaving 10-15% of the emissions uncaptured, which are usually referred to as residual emissions. In fact, in recent years, a 90% capture rate cap has featured almost ubiquitously, e.g. in integrated assessment models, in advanced project initiatives and FEED studies, as well as in the two large-scale CCS projects operating at present in the power industry. It has been shown, however, that in a “well below 2°C” scenario, it would be virtually impossible to achieve the net zero carbon emissions projected to be required in the second half of this century without substantially higher capture rates. This study was commissioned to explore the potential for the residual emissions from capture technologies to approach zero.

A review of the literature indicated that, qualitatively, there were no technical barriers to substantially increasing capture rates in the three classic capture routes (post-, pre- and oxyfuel combustion) and with the broad suite of CO₂ capture technologies currently available or under development. A techno-economic analysis of a standard PCC process using monoethanolamine (MEA) solvent applied to both coal- and gas-fired power plants revealed that, with dedicated process design, the additional costs of achieving essentially zero CO₂ emissions (99.7% for coal and 99% for gas) were quite modest in comparison with the costs of achieving 90% CO₂ capture.

Importantly, it was also found that, as CO₂ capture rates are increased, indirect emissions from fossil fuel use become significant, i.e. as the direct emissions tend to zero, the indirect emissions become proportionately greater. To maximise the benefits of higher CO₂ capture rates in providing a path towards zero emissions, increasing the capture rate should therefore go hand-in-hand with effective management to reduce overall CO₂ emissions, particularly in the fuel supply chains.

Although biomass is an important source of the world’s primary energy requirements, only a small portion (~4%) of bioenergy is used for power generation globally. Combustion is the dominant and proven technology for (heat and) power generation from biomass. Co-firing biomass in existing coal-fired power plants is a simple and effective way to reduce CO₂ emissions. In fact, for coal-fired power stations, the option of using a combined biomass co-combustion (10% biomass) with a standard PCC process (90% CO₂ capture) was the lowest cost option for effectively achieving zero CO₂ emissions.