Skuld’s experiences on biofuels in Marine Insurance P&I Club News 09/06/2026 Biofuels are renewable fuels derived from biological sources, such as agricultural crops, waste, or residues, designed to reduce greenhouse gas emissions. Since we received our first inquiry on the use of biofuels back in the last quarter of 2019, we have seen different kinds of challenges. The first type of biofuels we received questions on was FAME (Fatty Acid Methyl Esters). FAME is a mixture of Fatty Acid Methyl Ester that has similar properties to those of conventional fuel, and this type of biofuel is a good alternative as a ‘drop-in-fuel’. However, FAME is unstable due to either unsaturated products in the fuel or the oxygen in the fuel, causing rancidification over time. FAME-based fuels can increase their instability if alcohol or water is present, and they are susceptible to thermal degradation and degradation if the fuel is exposed to light. It also has poor long-term stability and poor cold-flow properties. When FAME oxidises, the fuel becomes increasingly acidic and viscous, forming solid deposits that can cause operational issues for the engine, such as blocking filters and pipes, leading to fuel starvation and engine problems. So far, from various trials and consumption on board insured vessels, our experience is that FAME is reliable and effective. FAME-based biofuels are reliable ‘drop-in fuels’ that can be readily used with existing ship engines, but of course, with the approval of the engine manufacturer. Another type of biofuels is CNSL (Cashew Nutshell Liquid) which is an example of the explored options for ‘drop-in fuels. CNSL is a byproduct of cashew nuts and serves as a low-cost, renewable fuel alternative. Its characteristics include high levels of acidity, which make it highly corrosive and have poor combustion properties. However, it does improve lubricity and the energy content of the fuel blend. CNSL typically contains phenolic compounds, which have a high c