Role of lignin in reducing life-cycle carbon emissions, water use, and cost for United States cellulosic biofuels.

Cellulosic ethanol can achieve estimated greenhouse gas (GHG) emission reductions greater than 80% relative to gasoline, largely as a result of the combustion of lignin for process heat and electricity in biorefineries. Most studies assume lignin is combusted onsite, but exporting lignin to be cofired at coal power plants has the potential to substantially reduce biorefinery capital costs. We assess the life-cycle GHG emissions, water use, and capital costs associated with four representative biorefinery test cases. Each case is evaluated in the context of a U.S. national scenario in which corn stover, wheat straw, and Miscanthus are converted to 1.4 EJ (60 billion liters) of ethanol annually. Life-cycle GHG emissions range from 4.7 to 61 g CO2e/MJ of ethanol (compared with ∼ 95 g CO2e/MJ of gasoline), depending on biorefinery configurations and marginal electricity sources. Exporting lignin can achieve GHG emission reductions comparable to onsite combustion in some cases, reduce life-cycle water consumption by up to 40%, and reduce combined heat and power-related capital costs by up to 63%. However, nearly 50% of current U.S. coal-fired power generating capacity is expected to be retired by 2050, which will limit the capacity for lignin cofiring and may double transportation distances between biorefineries and coal power plants.

The biofuels landscape through the lens of industrial chemistry.

Replacing petroleum feedstock with biomass in the production of fuels and value-added chemicals carries considerable appeal. As in industrial chemistry more broadly, high-throughput experimentation has greatly facilitated innovation in small-scale exploration of biomass production and processing. Yet biomass is hard to transport, potentially hindering the integration of manufacturing-scale processes. Moreover, the path from laboratory breakthrough to commercial production remains as tortuous as ever.