A techno-economic feasibility study on gas-to-liquid (GTL) aviation fuel produced from feedstocks of bio-methane, CO2, electricity and hydrogen was done. The study assumed the use of steam reforming and Fischer-Tropsch (FT) for methane and reverse-water-gas-shift or co-electrolysis plus FT when using CO2/hydrogen as feedstock.
This production pathway was found to be cost-efficient, area-independent, scalable and globally sufficient, technically mature and ready to implement, and approximately CO2 neutral. Key merits of the pathway lie in its system integration properties. First, it allows the flexibility of shifting between the feedstocks for economic optimization with fluctuating electricity prices and with shifting availability of CO2 from biomass flue gas between summer and winter. Second, the bio-methanation of the CO2 content of biogas and the recycling of any CO2 and CO off-gas emissions from the GTL allow for an almost 100 % carbon conversion efficiency from methane to liquid fuels. Together with using flue gas CO2 and atmospheric CO2 as feedstock, it makes the pathway fully sufficient and a real and globally scalable solution. Third, being based on biogas and CO2, the fuels will be practically CO2 neutral.
The biogas feedstock is further motivated by biogas facilities being attractive agricultural management facilities allowing agriculture to reduce its greenhouse gas emissions significantly and allowing for optimized nutrient management and soil carbon management as well as advanced treatment and value addition to biomass feedstocks. Moreover, storing bio-methane on the gas grid allows for the most cost-efficient balancing of the fluctuating wind and solar power, as gas turbines and motors constitute the cheapest back-up capacity installed, and as such the pathway provides the supplementing service of efficiently and sufficiently storing electricity in the renewable energy system.
Finally, locating electrolysis, bio-methanation and GTL on district heating grids constitute a significant economic advantage of the pathway, and any location allowing the use of the process heat loss from these units will have a high competitive advantage.
Following this pathway, jet fuel was found to be realistically available at costs around 2-3 times today’s fossil jet fuel price. Comparing this to costs of available bio-jet fuels today, the price level is attractive.