Biomass accounts for 3.5% of primary energy use in the OECD region, and 3.1% of final energy consumption. Biomass is the source of 14% of total heat produced in the region. Its role in electricity production (1.4% of total) is much less significant. Most biomass energy is consumed by households (wood burning) and paper pulp and wood industries. The political and public interest in expanded biomass use is based on the supposition that the external costs of this fuel are much smaller than those of coal, oil and gas. Comparison of full social costs are very hard to make, since uniform value measures of the respective external costs do not yet exist. The scattered and limited assessments that are available suggest that the difference between biomass and fossil fuels in this regard may have been exaggerated in policy debates, and may not be sufficient to warrant a large-scale expansion of biomass use.