This analysis evaluates the role of coal and biomass co-firing power in the future energy portfolio of the United States. Coal and biomass co-firing power is evaluated with respect to resource base, growth, environmental profile, costs, barriers, risks, and expert opinions. The core of this analysis is the life cycle environmental and cost analysis. The report has been externally peer reviewed. The report is one of a series of Technology Assessment Reports for power production in the United States. A briefing is also included with the report.