Sustainable Synthetic Fuels

IASS FACT SHEET 1/2014 Institute for Advanced Sustainability Studies (IASS) Potsdam, April 2014 Sustainable Synthetic Fuels Michele Ferrari, Alberto Varone, Stefan Stückrad, Robin J. White The extensive use of fossil hydrocarbons and their derived products in the energy, transport and petrochemical sectors is a major source of greenhouse gas (GHG) emissions and ties our society to ever dwindling reserves. In this context, synthetic fuels represent alternative energy carriers (and in some cases raw materials) that could be easily integrated into existing systems. Based on “Power-to-Gas (PtG)” and “Power-to-Liquid (PtL)” schemes that convert intermittent green power to chemical energy, these synthetic fuels could play a crucial role in establishing carbon neutral energy provision, importantly based on CO2 recycling. Renewable power Total energy Losses Electrolysis and Synthesis Electric PtG PtL Load Losses Figure 1: Final energy carrier mix in a RES/renewable fuels scenario with extensive use of electrolysis and SOECs in particular (adapted from an original illustration from the German Federal Environment Agency). Sustainable Synthetic Fuels What are sustainable synthetic fuels? value of CO2 will be dramatically increased, transforming it from an economic and environmental lia- Sustainable synthetic fuels are liquid or gaseous energy bility to a future energy carrier. Air capture is particu- carriers that are produced using renewable inputs larly relevant, as it has the potential to mitigate instead of fossil feedstocks. They are hydrocarbon atmospheric GHG concentrations. compounds that share the same chemical composition as conventional fuels like gasoline, and as such repre- The fuel synthesis process can be powered by sent convenient substitutes to oil, coal, natural gas and renewable energy. Indeed, the technologies for the all their derived products. Recent technological develop- production of these fuels require energy in the form ments have demonstrated the possibility of combining of electricity and/or heat, which could be supplied by green power and waste carbon (biomass or recycled renewable energy sources (RES) like wind and solar. CO2) to synthetize fuels like methanol (CH3OH), dime- With both renewable power and CO2 recycling, the thyl ether (DME) or synthetic methane. These could be whole fuel cycle becomes potentially carbon neutral. used to replace their fossil-derived counterparts in the transport sector, the chemical industry, and for elec- In this scenario, synthetic fuels also represent a way tricity and heating generation, resulting in greatly of storing surplus power from RES in the more con- reduced greenhouse gas (GHG) emissions and venient form of a liquid or gas. These “power-to- decreased reliance on declining fossil reserves. liquid” and “power-to-gas” schemes would help buffer the natural intermittency of RES and therefore allevi- From this perspective, methanol in particular is a very ate one of the major constraints to their large-scale promising fuel: the concept of a “Methanol Econ- deployment. omy ®” 1 developed by Nobel Laureate George A. Olah illustrates how the use of renewable methanol as the In a recent report, the German Federal Environment main energy carrier could help address both the Agency (UBA) 2 combines all these elements to devise demand for liquid energy carriers and the need to a 2050 scenario where fossil fuels are unnecessary and reduce GHG emissions. renewable power is used to produce synthetic fuels for transport, industry, heating etc. (Fig. 1). The UBA How could sustainable fuels help estimates that this scenario is technically feasible, and reduce CO2 emissions? that it would achieve a 95 % reduction in GHG emissions from the energy sector. The production of sustainable fuels requires a carbon input, which can be obtained from bio- What are the advantages in mass or recycled CO2, thereby utilizing something comparison to the alternatives? that would have otherwise been undervalued or dis- carded. The combustion of synthetic fuels, for Synthetic fuels could be directly integrated into instance to power a car engine, releases CO2 into the existing fuel infrastructures, like filling stations atmosphere, but this is offset by the fact that an for instance, without incurring excessive costs, tech- equivalent amount of CO2 is used in the fuel produc- nical barriers or behavioural changes. This consti- tion process, resulting in an overall reduction in CO2 tutes a more practical approach compared to other emissions. ‘green’ alternatives, particularly the “Hydrogen Economy”. Indeed, while the use of hydrogen (H2) as This CO2 can be captured from large point emit- a final energy carrier is interesting because of its ters like fossil-burning power plants, and in the clean combustion, in practice the storage, transport future from the air itself. This approach builds and distribution of H2 raises many technological and upon the growing technological expertise on carbon safety concerns, and the cost of transforming the capture, while avoiding the difficulties, costs and risks whole energy infrastructure is likely to prove eco- of CO2 storage faced by Carbon Capture and Seques- nomically prohibitive. Similarly, massively convert- tration (CCS) schemes. In this context, the economic ing the transport sector to electric vehicles would be a daunting task. 2_IASS Fact Sheet 1/2014 Sustainable Synthetic Fuels Sustainable Synthetic Fuels In comparison, replacing fossil-derived petrol and While transportation would be the main sector of diesel with methanol and DME in the transport sec- application, synthetic fuels could also replace fossil- tor would only require minimal modifications to derived products in other sectors: account for these fuels’ corrosiveness to certain materials (e.g. aluminium and zinc). The incremental Chemical industry – Higher-rated (cetane and cost to provide flexible fuel capability to a new car octane) fuels can also be synthetically produced, 3 has been estimated to be as low as € 100. while methanol is a flexible C1 platform chemical that can be transformed into a variety of commercially Other advantages of methanol (and DME) as fuel for relevant compounds like propylene, often using conventional internal combustion engines (ICE) already established processes. include: Electricity generation – Methanol and synthetic Safety and engine performance – Many of the methane can be used in conventional power plants to inherent proprieties of methanol, such as its octane generate electricity. Moreover, methanol can be used rating (~ 100), heat of vaporization and flame speed, as a fuel in highly efficient electrochemical cells for translate into enhanced engine performance. In electricity generation (termed Direct Methanol Fuel terms of safety, the lower volatility of methanol will Cells). These cells operate at low temperatures, mak- result in fewer fuel-related fires. However, methanol ing them potentially ideal for mobile electronic (and DME) has only half the volumetric energy devices and, ultimately, even as a replacement for density of petrol. comparatively inefficient ICE vehicles. Cleaner combustion – Compared to petrol, com- Therefore, with the appropriate mix of renewable bustion of methanol in current ICE produces lower fuels, it would be possible to cover all the energy emissions of CO2 and of other harmful pollutants needs of a modern economy. (e.g. volatile organic compounds and carcinogens). Some power train and marine companies, for exam- ple, have shown growing interest in these fuels in order to curb SOx and NOx emissions. Oil Oil Oil Present Scenario: Fossil Feedstocks Figure 2: Transition from a fossil fuel-based to a renewable energy-based supply of synthetic fuels Coke CH3OH H2 coupled with renewable Industrial syn-gas CH4 Olefins electricity storage. production CO2 H2 DME } Gasoline Bio and city waste, black liquor, Biomass Catalysis pulp mill etc. CO Fischer-Tropsch Fuel Electrolysis CO2 CO2 CH Solar 4 H2O thermal Artificial photosynthesis Future Scenario: Renewable Energies © IASS IASS Fact Sheet 1/2014_3 Sustainable Synthetic Fuels Technologies for the production quence of these points, electrolysis and specifically of sustainable fuels: state of research solid oxide cells represent an efficient and flexible way of converting renewable energy and CO2 into a Currently, some synthetic fuels, and especially meth- synthetic fuel, and will therefore play a central role in anol, are already being produced on an industrial future sustainable fuel scenarios. scale, but based on methods that rely on fossil feedstocks (natural gas and coal) and which, in the case of Valorisation of biomass and associated wastes coal, release large quantities of CO2 during the process. The syn-gas required for methanol (and DME) production can also be generated via the gasification of Conversely, in anticipation of a growing demand for biomass and associated low-value wastes. Various synthetic fuels, a number of innovative, sustainable small- to medium-sized enterprises (SMEs) are technologies have emerged and are presently at exploiting this approach to produce synthetic fuels different stages of industrial maturity. cost-effectively. Precursors include lignocellulosic crops (e.g. sugarcane bagasse), municipal solid waste, Electrolysis paper mill wastes (i.e. black liquor lignosulfonates) and biodiesel by-products like glycerol. The main Electrolysis is an electrochemical process utilising a drawback relates to limitations on biomass availabil- direct current

Load more