Process comparison of biomass-to-liquid (BtL) routes Fischer-Tropsch synthesis and methanol to gasoline

Lignocellulosic biomass is currently seen as a renewable alternative to fossil fuels in the transport sector. There are two possible routes to produce liquid hydrocarbon fuels from biomass via synthesis gas: Fischer-Tropsch (FT) synthesis and methanol to gasoline (MtG). This paper evaluates, based on chemistry and chemical engineering aspects, the process design, the economic feasibility and the process potential for both synthesis routes. FT and MtG reactions can be described under the same overall chemical equation. However, the differences between the two syntheses were found in chemical mechanism, catalyst and product distribution. The material and energy balances do not establish a clear preference for any synthesis route, the market application of the product being a key parameter. The calculated overall chemical energy efficiencies to synthetic liquid hydrocarbons (C-5-C-20) from biomass are 25.8-46.5% for FT and 23.4-44.4% for MtG. The calculated carbon efficiency to synthetic liquid hydrocarbons (C-5-C-20) ranges between 18.6% and 33.5% for FT and 17.3-32.8% for MtG. The production costs for synthetic liquid hydrocarbon fuels are calculated based on the efficiencies given above. They range between 21(sic) and 34(sic) per gigajoule. These values could drop to 18-28(sic) per gigajoule in the medium term based on optimistic predictions (increase of efficiencies and reduction of capital investment). If the prize difference between crude oil and biomass becomes as high as 20(sic) per gigajoule, the production of liquid hydrocarbons from biomass will probably become competitive with petroleumbased products.