Roadside vegetated filter strips to simultaneously lower stormwater pollution loadings and improve economics of biorefinery feedstocks.

Roadside vegetated filters strips (VFSs) reduce roadway runoff pollution by intercepting stormwater and reducing pollutant loads. VFS maintenance and operating costs can be reduced by designing the VFSs to serve as sites for production of marketable biomass. This biomass can provide feedstock for the emerging bioeconomy producing renewable fuels and biobased chemicals and products. Economic evaluation is needed to quantify the benefit of combining VFS with bioenergy biomass production. This evaluation requires a place-based approach to quantify availability of land, transportation costs, and benefits to sensitive habitats. We evaluated roadside land, within the state right-of-way, in Western Washington, to determine the total area available for implementing VFSs. These data were then used to estimate the volume and cost, of biomass produced on the filter strips, and the resultant reduction in pollutants emitted through highway runoff. The analysis showed that up to 5600 ha were available for roadside VFSs that would be within transportation distance of the theoretical biorefinery location. This space could produce up to 97 dry Gg per year of poplar biomass. The resulting reduction in biorefinery feedstock cost was up to $24 per dry Mg compared to biomass from dedicated tree farms. The results showed that combining roadside poplar with traditional dedicated poplar feedstocks can reduce the feedstock cost of the biorefinery from $76 to $67 per Mg for a biorefinery processing 150 Gg biomass per year. Environmental impact analysis showed that within the study area half of urban roadways and one-third of rural roadways in highly sensitive aquatic areas were amenable to VFS. Construction of VFS in these amenable areas would reduce total loadings to sensitive aquatic areas in urban areas by 26% for TSS, copper, and zinc, and by 10% for phosphorus, and nitrogen and by 21% for lead. The impact for rural sensitive areas was even greater where the VFS had potential to reduce total loadings to sensitive aquatic areas by 38% for TSS, copper, and zinc, by 15% for phosphorus and nitrogen, and by 31% for lead. This research showed an approach combining geographic information system (GIS) mapping and economic analysis to document simultaneous evaluation of cost and environmental benefits when considering use of non-traditional land for bioenergy crop production.

Techno-economic analysis of an integrated biorefinery to convert poplar into jet fuel, xylitol, and formic acid.

BACKGROUND: The overall goal of the present study is to investigate the economics of an integrated biorefinery converting hybrid poplar into jet fuel, xylitol, and formic acid. The process employs a combination of integrated biological, thermochemical, and electrochemical conversion pathways to convert the carbohydrates in poplar into jet fuel, xylitol, and formic acid production. The C5-sugars are converted into xylitol via hydrogenation. The C6-sugars are converted into jet fuel via fermentation into ethanol, followed by dehydration, oligomerization, and hydrogenation into jet fuel. CO2 produced during fermentation is converted into formic acid via electrolysis, thus, avoiding emissions and improving the process's overall carbon conversion. RESULTS: Three different biorefinery scales are considered: small, intermediate, and large, assuming feedstock supplies of 150, 250, and 760 dry ktonne of poplar/year, respectively. For the intermediate-scale biorefinery, a minimum jet fuel selling price of $3.13/gallon was obtained at a discount rate of 15%. In a favorable scenario where the xylitol price is 25% higher than its current market value, a jet fuel selling price of $0.64/gallon was obtained. Co-locating the biorefinery with a power plant reduces the jet fuel selling price from $3.13 to $1.03 per gallon. CONCLUSION: A unique integrated biorefinery to produce jet fuel was successfully modeled. Analysis of the biorefinery scales shows that the minimum jet fuel selling price for profitability decreases with increasing biorefinery scale, and for all scales, the biorefinery presents favorable economics, leading to a minimum jet fuel selling price lower than the current price for sustainable aviation fuel (SAF). The amount of xylitol and formic produced in a large-scale facility corresponds to 43% and 25%, respectively, of the global market volume of these products. These volumes will saturate the markets, making them infeasible scenarios. In contrast, the small and intermediate-scale biorefineries have product volumes that would not saturate current markets, does not present a feedstock availability problem, and produce jet fuel at a favorable price given the current SAF policy support. It is shown that the price of co-products greatly influences the minimum selling price of jet fuel, and co-location can further reduce the price of jet fuel.