Systematic review on the energy conversion efficiency of biomass-based Fischer-Tropsch plants

Biomass-derived Fischer-Tropsch fuels (Bio-FT) represent a promising fossil fuel substitute, but their high production cost is a limitation for their further deployment. This work has systematically reviewed studies on energy efficiency of biomass-based Fischer-Tropsch (FT) plants to identify: (1) which energy efficiency indicators are used in literature, (2) which are the variables affecting the energy conversion efficiency, and (3) whether a correlation exists between energy conversion efficiency, the biofuel production cost and the critical variables, as the Bio-FT process efficiency is a critical contributor to the Bio-FT fuel cost. Using a relevant search string, studies were identified in the Web of Science, Scopus, and ScienceDirect databases. The number of techno-economic assessments reporting on the Bio-FT plant's energy efficiency (24) was small since the Bio-FT process is still under development. The average yearly number of studies published in the past eight years was two and it could rise as the technology matures. 208 plant designs were extracted from the selected studies and six energy efficiency indicators were identified, of which overall efficiency and biomass-to-fuels efficiency were the most common. Plant design features that lead to high conversion efficiency or low production costs are feeding biomass at low moisture content, pressurized gasifiers, FT catalysts with high single-pass CO conversion, using combined cycles for electricity generation and electric self-sufficiency. No correlation was found between the overall efficiency and the biofuel production cost. Still, a moderate correlation was found between the latter and the biomass-to-fuel efficiency.