Introduction

harmful climate change is now widely accepted. One of the technologies which could help to reduce emissions is CO2 capture and storage (CCS). A high percentage (e.g. ≥85%) capture of CO2 at power stations and other large industrial plants will be essential in the long term to achieve the challenging targets for overall emission reduction, which may for example need to be around 80% by 2050 for developed countries. Some countries are likely to insist on high percentage capture in the near term to put them on track to achieving their long term goals but in some other countries a lower percentage emissions reduction may be considered to be acceptable and a useful contribution in the near-term. An example of this is the requirement in California for coal fired power plants supplying the state to have CO2 emissions no greater than those of natural gas fired plants. Partial capture of CO2 would be a way to satisfy such requirements. In some cases a requirement for partial capture may also
help to facilitate CCS technology demonstration.

This report is a brief review of the technology and costs of partial capture of CO2. The report does not attempt to prescribe policies for mandating CO2 capture and whether partial capture should be part of a policy for reduction of greenhouse gas emissions. IEAGHG provides technical information which can be used by policy makers but it does not intend to be policy prescriptive.

Conclusions

Partial capture of CO2 is not feasible in oxy-combustion power generation units but partial capture can be achieved at multi-units power plants by having some units with high percentage capture and some units without capture.

In a plant with post combustion capture the optimum method of achieving partial capture would be to by-pass some of the flue gas around the capture unit. The resulting cost per tonne of CO2 avoided is expected to be similar to or slightly higher than for high percentage capture.

Partial capture can be achieved in IGCC by reducing the extent of shift conversion. The resulting cost per tonne of CO2 avoided for partial capture (around 50%) is expected to be about the same or lower than for high percentage capture.

Based on current expectations of the relative costs of IGCC and pulverised coal plants, the lowest cost method of achieving partial capture would be to have a portfolio of IGCCs with high percentage capture and pulverised coal plants without capture. Partial capture could be appropriate for power plants with CCS demonstration units.