Environmental impacts and costs of woody Biomass-to-Liquid (BTL) production and use -- A review

This article investigates the environmental profile and costs of woody BTL production and use by reviewing existing LCA studies. The findings reveal that BTL from sustainably managed forest biomass and woody waste may have a lower overall environmental impact than fossil diesel. The benefits of using BTL instead of fossil diesel are largely due to savings in fossil energy use, which offer savings in GHG emissions since a large part of the lifecycle CO2 emissions are biogenic. Improvements in the impact category photosmog or summer smog have also been reported. On the other hand, wood based BTL may increase eutrophication and acidification, and increased ozone depletion and toxicity may also be expected. While global indicators like climate change, non-renewable resources and ozone depletion are fairly easy to interpret, the local indicators such as eutrophication, acidification, photosmog and toxicity are site specific, and an LCA will not take into account where, when and at which rate the emissions occur, which are important parameters when estimating local pollution effects. In addition, increased logging or the establishment of short rotation plantations may impact biodiversity, land-use changes and the value of nature. The reported results differed when assessing the same fuel due to differences in methodology and data assumptions. For the methodological part, differences in system boundaries, system completeness and chosen allocation methods contributed to the ranges in results. Differences regarding data inputs, such as plant efficiency and fuel consumption were also important for the differences in results. The most influential or sensitive factors within the reviewed studies were the assumed type of feedstock, plant efficiency and drivetrain. The reported production costs of BTL are in the range of 0.70-1.12 euros per liter. The costs are largely influenced by plant scale, biomass costs and plant efficiency. Biofuels are generally not considered a cost effective climate mitigation means, but there are no other feasible solutions than biofuels for the heavy transport sector in the short to medium term.