Decarbonisation Technology - February 2025 Issue

Managing corrosion risk in SAF and renewable diesel processes Non-intrusive, real-time monitoring solutions can help manage the unique corrosion risks associated with biofuel feedstocks and processes

William Fazackerley Emerson

A s the world grapples with climate change and seeks to reduce its carbon footprint, the transportation sector has come under increasing scrutiny. Aviation and long-haul trucking, in particular, have faced challenges in transitioning away from fossil fuels. Sustainable aviation fuel (SAF) and renewable diesel have emerged as two promising alternatives that are reshaping the landscape of transportation fuels. However, the shift to these sustainable fuels brings its own set of challenges. The production of SAF and renewable diesel involves complex processes and the use of diverse feedstocks, ranging from used cooking oils to agricultural residues. These new feedstocks and processes introduce novel corrosion risks that threaten the integrity of production facilities. This article explores the evolution of biofuels, delves into the production processes of SAF and renewable diesel, examines the corrosion challenges faced by producers, and discusses the innovative monitoring solutions being employed to mitigate these risks. Evolution of biofuels To understand the significance of SAF and renewable diesel, it is essential to look at the evolution of biofuels over the past decade. Biofuels have gone through several generations, each addressing the limitations of the previous one. First-generation biofuels, popular in the early 2000s, were primarily derived from food crops like corn, sugarcane, and other energy crops. While these fuels offered a renewable alternative to fossil fuels, they faced criticism for competing with land use for food production,

consequentially driving up food prices and deforestation. Second-generation biofuels, which gained traction in the 2010s, aimed to address these concerns by utilising non-food biomass such as agricultural and forestry residues likes wood chips. These fuels offered improved sustainability and reduced the risks of land use change and competition with food production. As these biofuels were not capable of directly replacing their hydrocarbon counterparts, blending limits were imposed, which limited their adoption. Third-generation biofuels, emerging in recent years, focus on waste streams, including municipal solid waste (MSW), sewage sludge, and more advanced feedstocks like algae. These feedstocks promise even greater sustainability and potential for scalability and are available as a direct replacement to legacy fuels without blending limitations. The latest development, sometimes referred to as fourth-generation biofuels, involves engineered organisms and carbon capture technologies to produce fuels with a negative carbon footprint. Sustainable aviation fuel SAF represents a significant leap forward in the aviation industry’s efforts to reduce its environmental impact. Unlike traditional jet fuel, SAF is produced from sustainable feedstocks such as used cooking oil, agricultural residues, and even MSW. The International Air Transport Association (IATA) reports that in 2022, more than 300 million litres of SAF were produced ( IATA, 2023 ). This figure is set to grow dramatically, with more