MIT Report: Technology Options for Existing Coal-Fired Plants Are Crucial

There is no credible pathway toward prudent greenhouse gas stabilization targets without carbon dioxide emissions reductions from existing coal power plants, but the U.S. urgently needs technology options for these plants and policies that incentivize implementation, a new study from the Massachusetts Institute of Technology (MIT) finds.

The report, “Retrofitting of Coal-Fired Power Plants for CO₂ Emissions Reductions,” (PDF) is based on the findings of a March 2009 symposium that focused on retrofitting existing pulverized coal plants with post-combustion capture technology to capture CO₂ from flue gases after coal is combusted. The symposium included 54 subject matter experts from a range of stakeholder groups.

“Once built, coal plants are, in most cases, the cheapest source of base load power generation and will not be phased out absent very high CO₂ prices,” said Professor Ernest Moniz, director of the MIT Energy Initiative (MITEI) and former undersecretary of the U.S. Department of Energy, as he unveiled the report last week. “It’s basic economics.”

The report points out that there are multiple pathways to reduce carbon dioxide emissions from existing coal plants, but that post-combustion capture followed by long-term, large-scale, sequestration is the most direct pathway to avoiding nearly all CO₂ emissions. But efficiency retrofits of existing coal plants could also result in modest reductions of CO₂ emissions per unit of electricity produced, the report said. “This is especially attractive for older, less-efficient plants. There is a range of approaches from boiler to control system improvements. A rough estimate is that 4–5% emission reduction could be realized relative to business as usual if efficiency improvements were introduced at less efficient coal plants. This action has the highest benefit/cost ratio for CO₂ mitigation.”

The symposium also seriously considered biomass cofiring as another retrofit option for net CO₂ emissions reduction, if feedstock were available. “Indeed, if biomass use is combined with CCS there are negative net CO₂ emissions,” it said.

Other options included major rebuilds of existing coal plants. This included a range of possibilities, starting from capturing substantial value from use of an existing site, its infrastructure, and even from existing permits. “Rebuilds are likely to be expensive, but will include large efficiency gains, for example, rebuilding an old subcritical unit to a high efficiency supercritical (SCPC) or ultra-supercritical (USCPC) unit, with or without CCS,” the report said. “More extensive rebuilds include conversion to oxygen-driven combustion or to an [integrated gasification combined cycle] plant with CCS.” Additional options discussed in the background papers include cogeneration and, for gasification plants, poly-generation of fuels and electricity.

Among other key findings of the report are these:

• “Relatively large, high-efficiency coal plants already equipped with desulfurization and nitrogen oxide emissions controls are the best candidates for post-combustion capture retrofit. Such plants make up less than half of the existing fleet. However, specific retrofit projects will need to pass various site-specific screens, such as available space, increased water supply, and CO₂ off-take options. A fleet-wide, detailed inventory of plants and sites is urgently needed to determine which plants are suitable for retrofitting, rebuilding or repowering or for partial CO₂ capture solutions tailored to the current plant configuration. This inventory should inform policy makers about the range of options for significant reduction of CO₂ emissions from operating coal plants in different climate policy scenarios.
• “The primary focus of research and development for existing coal plants should be on cost reduction of post-combustion capture. This is essential if retrofits are to be affordable in developing countries. An expanded R&D program should also include efficiency upgrades, rebuilds, repowering, poly-generation and co-firing with biomass. Consideration should be given to including a component for research on CO₂ capture from natural gas power plants. A robust U.S. R&D effort with this scope requires about $1 billion per year for the next decade (not including support for commercial scale demonstration).
•  “The federal government should dramatically expand the scale and scope for utility-scale commercial demonstration of coal plants with CO₂ capture, including demonstration of retrofit and rebuild options for existing coal power plants. New government management approaches with greater flexibility and new government funding approaches with greater certainty are a prerequisite for an effective program.” Specifically, the report calls for some $12 billion to $15 billion to be spent over the next decade to “dramatically expand” federal government programs to demonstrate large-scale, sustained CO₂ capture-and-sequestration technology for existing plants. At least $1 billion in federal funds should be invested annually for roughly 10 years while creating more flexibility and improved certainty for robust research into advanced technology, efficiency, and repowering or rebuilding options.
• “The world cannot achieve significant reductions in CO₂ emissions, avoiding the most disruptive impacts of climate change, without commitments to reduce emissions from existing coal-fired power plants in the United States and China. Bilateral approaches on climate change should be encouraged and supported as a matter of U.S. policy. Joint R&D programs between the United States and China should be supported and funded.”

Source: MIT