Influence of advanced biofuel blending on combustion performance, exhaust emissions, and tank-to-wheel environmental impacts for compression ignition engines

Heavy-duty vehicles and off-road machinery primarily operate on compression ignition (CI) engines using diesel and heavy fuel oils. To achieve net-zero targets, lower-carbon fuels are required. The EU REDII and REDIII directives promote the integration of advanced biofuels to reduce the carbon intensity of liquid fuels. It is therefore essential to evaluate how such fuels influence engine performance and emissions to ensure compliance with current and future air quality and greenhouse gas standards.
This study investigated a series of HVO-butyl-based blends designed to model the products of lignocellulosic alcoholysis. These included n-butyl levulinate (BL), di-n-butyl ether (DNBE), and n-butanol (BuOH), with butyl acetate (BA) introduced as a potential coproduct from parallel alcoholysis processes. Physical properties such as miscibility, density, and flash point were measured. All blends remained stable at room temperature, confirming compatibility with current fuel systems. Blends containing BA showed slightly higher densities relative to HVO. All three-component blends met minimum flash point requirements, while BA addition reduced these values to near or below standard limits.
Engine performance tests on a YANMAR L100V CI engine showed that all biofuel blends increased brake-specific fuel consumption (BSFC) and ignition delay (ID) relative to diesel and neat HVO, reflecting their lower energy content and slower ignition characteristics. Nonetheless, emissions of CO, total hydrocarbons (THC), and NOx decreased compared with diesel, and PM2.5, particle number (PN), and elemental carbon (EC) levels were substantially reduced.
Detailed PM2.5 characterisation showed a shift toward more cylindrical particle morphologies with increasing biofuel content. PAH analysis indicated reductions in 3-4 ring PAHs at high load and in lower-weight PAHs at mid-load, suggesting cleaner combustion. Metal concentrations in PM and fuels were negligible. A tank-to-wheel (TTW) life cycle assessment (LCA) using experimental data confirmed lower human health impacts for HVO-based blends. Overall, butyl-derived biofuels demonstrated technical compatibility, improved emission performance, and strong potential as low-carbon, cleaner alternatives to fossil diesel.