Options for Minimising CCS Retrofit Costs to Natural Gas and Coal Power Plants in US Markets

The demand for ‘plain vanilla’ baseload CCS power plants in electricity markets seems to be waning. At the same time, very low, and possibly even negative, average tCO₂/MWh emission levels can be expected for future energy systems.

Since there is underutilised capacity in the national power plant fleet, a CCS deployment strategy based on retrofits is likely to be most cost-effective to meet these requirements, with two classes of retrofit of particular interest:

1. flexible natural gas power plants retrofitted with CCS; and
2. negative emission CCS plants, based on retrofits to coal plants converted to use biomass.

Flexible gas power plants retrofits could use post-combustion capture or hydrogen firing. The preferred option is not simply a matter of average load factors; there is a relatively wide overlap where project-specific factors will influence rational choice.

Biomass combustion in existing pulverized coal plants, cofired with coal or as a 100% conversion, is already a relatively mature technology. The nation’s existing coal fleet therefore represents a huge potential both to produce negative emissions and to support employment in a new industry producing sustainable biomass.

For biomass plants, post-combustion capture is likely to be the preferred route, but again with a number of options available to confer benefits for owners through increased operational flexibility and future upgradeability.

Longer term deployment of CCS power plants retrofits will obviously need to be supported by a range of policy and market changes, not least a recognition of the unique services that CCS can offer. In the shorter term ways of building the first plants are required, using existing instruments such as 45Q as far as possible. Possible routes for reducing the costs of these initial projects, while still retaining their value as reference plants for future large scale rollout, will be discussed.