Carbon capture plants part-fired with wood

If affordable carbon capture and storage technologies can be developed, the prospect is there for 'carbon negative' power plants that burn a mix of coal and wood

Carbon capture and storage (CCS) is the practice of capturing the CO2 emitted by a power station or other industrial site and piping it to an underground storage site – usually a disused oil well or saline aquifer. Scientists believe that these geological formations are capable of storing virtually all the CO2 injected into them for millions of years.

CCS has various disadvantages: the infrastructure is expensive to build; the separation and compression of the CO2 takes large amounts of energy; and there will always be a small risk of leakage from storage sites. Nonetheless, with so many existing and planned coal-fired power stations in the world, a growing number of experts believe that only with the help of CCS will it be possible to reduce global greenhouse emissions to a safe level.

In Manchester, Staffan Gortz, made the case for CCS on behalf of Vattenfall, the Swedish energy giant that has built a pioneering carbon-capture power station in Schwarze Pumpe, Germany. This pilot-scale plant uses the so-called oxyfuel approach to capturing carbon. Nitrogen is removed from the air, enabling the fuel to burn in pure oxygen. This results in a waste stream of virtually pure CO2, ready for capture and storage. Vattenfall and other companies are also investigating two other CCS technologies, known as pre-combustion and post-combustion.

Perhaps the most exciting element of CCS is the prospect of "carbon negative" power plants. These would work by co-firing (burning a mixture of) wood and coal. Since wood is partly made of carbon pulled from the air by growing trees, a CCS power station fuelled by a mixture of coal and sustainably harvested wood could actually reduce the amount of greenhouse gas in the air.


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