Decarbonisation Technology - November 2024 Issue

Key to scalable, sustainable hydrocarbon fuels A novel iron-based catalyst and process directly convert CO2 and green H2 from water into jet fuel range hydrocarbons in one step, reducing Capex and Opex

Andrew Symes OXCCU

T o prevent global temperatures from surpassing the critical two-degree threshold, a rapid transition away from using fossil fuels must occur within the next 30 years. This has led some to assume that all refineries and petrochemical plants will have to shut down, but this is incorrect. While they need to change radically, and some may be replaced, they will not all be replaced entirely, as demand for hydrocarbons in certain sectors will remain. Wherever possible, renewable electricity should be used directly due to efficiency, but only hydrocarbons will suffice in some sectors. The critical change will be the inputs. Refineries and petrochemical plants must rapidly move from using fossil fuels as their feedstocks to using a source of recycled carbon with green electricity, as articulated in a recently published paper in Nature ( Vogt and Weckhuysen, 2024 ). Continued need for hydrocarbons Aviation will continue to need hydrocarbon fuels due to its energy density requirements. While some reduction in aviation fuel demand may be necessary, particularly where there is excessive flying – such as short flights – significant demand will remain. It is unrealistic to expect people to stop flying or demand that politicians ban it. In fact, rather than seeking to ban aviation, many want to ensure that flight is available for future generations and people in developing countries. Flights without hydrocarbons remain a distant prospect. Electric or hydrogen planes for long- distance flights face huge challenges with safety, refuelling, and range due to energy density, and lighter-than-air flights (airships) will always be limited in terms of speed.

Additionally, hydrocarbon fuels will always be needed in military operations. With the urgent need to reduce emissions, a source of sustainable hydrocarbon aviation fuel, SAF, will play a vital role in meeting these needs with far fewer emissions. In the same way, hydrocarbons are essential for the production of plastics and chemicals. It is unrealistic to expect a total ban, especially where they are critical for medicine, healthcare, food production, transport, and electronics. Reducing the excessive use of plastic is important, particularly as many unnecessary single-use applications are causing a huge waste problem and the increasing issue of microplastics. Likewise, excessive chemical use should be stopped, as it can contaminate soil, water, and air, harming human health and biodiversity. However, some sectors will need to continue, or even increase, their use of chemicals and plastics to improve life expectancy, human prosperity, and economic growth. These must be made with fewer emissions to reduce their climate impact. To supply these critical hydrocarbons with fewer emissions, fossil carbon, crude oil, coal, or natural gas must be replaced by a source of recycled or surface carbon and varying amounts of low carbon intensity hydrogen, such as that derived from electricity generated from renewable sources. The three options are biomass, plastic waste, or carbon dioxide (CO₂). Despite requiring the most green electricity input via green hydrogen, CO₂-based hydrocarbons are predicted to be the largest component over time due to the challenges with biomass or plastic waste as feedstocks. Feedstock challenges First-generation biomass feedstocks, such as oil