Environmental impacts of energy use can impose large costs on society. We quantify and monetize the life-cycle climate-change and health effects of greenhouse gas (GHG) and fine particulate matter (PM2.5) emissions from gasoline, corn ethanol, and cellulosic ethanol. For each billion ethanol-equivalent gallons of fuel produced and combusted in the US, the combined climate-change and health costs are $469 million for gasoline, $472-952 million for corn ethanol depending on biorefinery heat source (natural gas, corn stover, or coal) and technology, but only $123-208 million for cellulosic ethanol depending on feedstock (prairie biomass, Miscanthus, corn stover, or switchgrass). Moreover, a geographically explicit life-cycle analysis that tracks PM2.5 emissions and exposure relative to U.S. population shows regional shifts in health costs dependent on fuel production systems. Because cellulosic ethanol can offer health benefits from PM2.5 reduction that are of comparable importance to its climate-change benefits from GHG reduction, a shift from gasoline to cellulosic ethanol has greater advantages than previously recognized. These advantages are critically dependent on the source of land used to produce biomass for biofuels, on the magnitude of any indirect land use that may result, and on other as yet unmeasured environmental impacts of biofuels.fine particulate matter ͉ ethanol ͉ biomass ͉ greenhouse gas ͉ life-cycle analysis

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SignificanceGlobal pollinator declines have raised significant concern over food security, human health, and agricultural productivity. Our work highlights how the Conservation Reserve Program (CRP) has a direct influence on landscape suitability for supporting honey bee apiaries in a region harboring >1 million colonies. Our analysis revealed recent conversion of CRP grassland to annual crops in core areas of the commercial beekeeping industry, thereby reducing forage lands for honey bees at a time when the number of colonies in this region has never been greater. Our land-use scenario models provide policy makers with direct information on how future CRP acreage caps established by the US Congress will affect the environmental carrying capacity for supporting honey bees and the US beekeeping industry.

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