Future fuel supply systems for organic production based on Fischer–Tropsch diesel and dimethyl ether from on-farm-grown biomass

The effects of making a 1000 ha organic farm self-sufficient in renewable fuel were studied. Biomass grown on-farm can be transported to large fuel production facilities and the fuel transported back to the farm. Two fuels, Fischer–Tropsch diesel (FTD) and dimethyl ether (DME), produced from either straw or short-rotation willow coppice (Salix), were studied. The environmental impact, land use and energy balance were calculated using life-cycle methodology.It was calculated that the straw-based systems had only 32–39% of the impact on global warming (kg [CO2-eq]) compared to the Salix-based systems. For acidification and eutrophication, the differences between the systems were less significant. The energy balances were 8.9 and 9.6 for FTD and 10.1 and 10.0 for DME, from straw and Salix, respectively.To become self-sufficient in FTD, 108 ha has to be set aside for Salix production or 261 ha of straw collected from the existing crop rotation. For DME the corresponding figures are 38 and 70 ha. The many by-products in the FTD scenarios explain the large difference between fuels.Comparing FTD and DME, the differences in environmental impact were small. Considering this, FTD is a more likely alternative since DME requires a pressurised infrastructure system and engine modifications.