With the push to net zero by 2050 accelerating, renewable fuels are being explored and developed to phase out petrochemical fuels. Biofuels are gaining increasing attention as a viable type of fuel for the heavy industry and transportation sectors, and research has focused on manufacturing these types of fuel. A study published online in Frontiers of energy research explored their production from a technical-economic point of view.
To study: Techno-economic analysis of a flexible process concept for the production of transport fuels and heat from biomass and renewable electricity. Image Credit: JH Bispo/Shutterstock.com
The push for renewables and fuels to reach Net Zero
The world is warming due to human activities, facilitating the need to drastically reduce carbon emissions. Various alternative fuels and energy sources have been explored to meet society’s energy needs, including hydrogen, solid-state batteries, and biofuels. Biofuels have proven particularly attractive as an alternative to petrol and diesel derived from petrochemicals.
Operating modes for the hybrid process concept. Image credit: Habermeyer, F et al., Frontiers in Energy Research
In line with the European Union’s Green Deal, major work is being undertaken to increase the share of renewables in the total energy mix to 65% by 2030. Currently, the share of renewables stands at 32%, which means that this figure will have to double during this decade.
This presents significant technical and economic challenges for the energy sector in the European Union. Short-term mismatches between supply and demand need to be corrected. Studies have shown that an approach that uses a combination of energy storage and flexible demand strategies will be needed to achieve an efficient energy transition from fossil fuels to renewables.
The transport sector is a major emitter of greenhouse gases. Electrification is only part of the decarbonization plan for the transport sector, as the energy needs of aviation and heavy transport such as shipping, trains and transport still require liquid fuels with high energy density. Therefore, low-carbon and renewable alternative fuels and associated technologies need to be further targeted and deployed by 2030.
In addition, heating plants and biomass-fired power plants must be developed to fill the energy gap left by the phasing out of fossil fuels. While renewable energies such as wind and solar will provide a significant share of renewable energy generation solutions, there is still room for power generation from biomass.
Flow diagram – blue means the equipment only operated in BA mode, orange means EA mode. Image credit: Habermeyer, F et al., Frontiers in Energy Research
Fuel production processes from biomass: BtL and PBtL
Two processes for the production of renewable fuels have been studied extensively in recent years. These are known as Biomass to Liquid Fuel (BtL) and Power and Biomass to Fuel (PBtL) processes. BtL converts biomass into hydrocarbon chains that can be used to make renewable fuel via the Fischer-Trope pathway. PBtL differs from this process by incorporating electrolytic hydrogen into the BtL process. PBtL has higher carbon efficiency levels than BtL.
The processes for transforming biomass into liquid fuel have been explored from a technical-economic point of view in several studies which have demonstrated its economic potential. The realistic production cost of this process varies from 1 to 4 euros per liter for four hundred MWand factory, with the process showing increasing maturity. Currently, demonstration plants are waiting to go into operation until the promotion of sustainable fuels reaches a point where they can be implemented commercially.
Liquid fuel energy and biomass have an economic advantage over BtL when cheap renewable energy is available. Adding renewable energy to the biomass conversion process increases fuel efficiency, which lowers the cost of production.
Techno-economic analysis of a hybrid model
The study published in Frontiers of energy research took previously published literature on renewable fuels research and development and techno-economic analyzes in the field and presented a hybrid model. A techno-economic analysis was carried out on the commercial viability of the hybrid model.
The hybrid model can switch between biomass-only processes and electrolysis-assisted conversion operational modes depending on demand. Previous studies have demonstrated the feasibility of a hybrid process, with Müller et al. demonstrating the use of hydrogen generated by an integrated wind farm in an FT-BtL process.
Hybrid systems have a higher initial investment cost, but the advantage of these systems lies in their lower operational costs. They can produce fuel at lower cost and at lower biomass consumption levels than a stand-alone BtL process. An additional economic benefit is the ability to temporarily shut down the electrolyser to avoid high electricity prices in a fluctuating market.
Sankey carbon flow diagram for case 1.1 mode BA (A), AE mode (B). Image credit: Habermeyer, F et al., Frontiers in Energy Research
The hybrid process showed an overall carbon efficiency rate of 53.3% compared to 61.1% for the PBtL models and 35.4% for the BtL models. The production costs of the hybrid model were found to be 1.08 €2019/L. Net production costs could be lowered by €0.07.
Although the study found that the most economically viable process given current renewable electricity prices was BtL, changing market forces such as the cost of electricity and biomass, advances technologies and trends towards cheaper electrolysers could make the hybrid model economically feasible in the future. Further studies will be needed in the future on the processes to realize their full potential to bring the world to net zero by 2050.
Habermeyer, F et al. (2021) Techno-economic analysis of a flexible process concept for the production of transport fuels and heat from biomass and renewable electricity [online] Front. Energy Res. | frontiersin.org. Available at: https://www.frontiersin.org/articles/10.3389/fenrg.2021.723774/full