B100

B100 is 100 percent biodiesel, made by transesterifying vegetable oils or animal fats with methanol or ethanol to produce fatty acid methyl esters (FAME). Unlike blended biodiesels, it contains zero conventional mineral diesel and no petroleum-derived additives. In the fuel designation system, the number indicates the percentage of biodiesel in the blend, so B100 sits at the top end of the scale, alongside B20 (20 percent bio, 80 percent mineral) and B5 (5 percent bio, 95 percent mineral).

B100 requires a diesel engine designed or modified to run it, and even then only in specific climates and use cases. The fuel has a higher pour point than mineral diesel, meaning it thickens faster in cold conditions; most operators cannot use B100 year-round in temperate or cold regions without heating the fuel lines or switching to a lower blend before winter. It is hygroscopic, absorbing water from air and storage tanks more readily than mineral diesel, which can promote microbial growth and corrosion in fuel systems over time. Fuel filter changes are also more frequent because B100 acts as a solvent, loosening deposits in older tanks.

B100 is used mainly in fleet vehicles and stationary engines in mild climates: municipal waste trucks, buses, and agricultural equipment in regions where it can run year-round without cold-start problems. Some operators blend B100 down to B20 or B50 as a seasonal compromise. The fuel burns cleaner than mineral diesel, producing lower particulate matter and nitrogen oxides in exhaust, which made it attractive for emissions-regulated urban fleets.

Fuel quality is critical. B100 that meets ASTM D6866 (North America) or EN 14214 (Europe) must have viscosity between 3.5 and 5 cSt at 40 degrees Celsius, water content below 500 ppm, and acid value below 0.5 mg KOH/g. Poor-quality B100 from unreliable suppliers can damage injectors and fuel pumps. Feedstock matters: soybean methyl ester and rapeseed methyl ester are the dominant commercial sources in North America and Europe respectively, though used cooking oil (UCO) and animal tallow also appear in the supply chain.

The term B100 emerged in the 1990s as biodiesel blending became commercial practice. The B-series nomenclature (B5, B10, B20, B100) is now standard across industry and regulation. B100 remains niche because its handling and storage demands, cold-climate limitations, and higher cost relative to mineral diesel restrict its use to fleets with the infrastructure and geography to support it. Most regions adopted B5 or B20 as a compromise between emissions benefit and compatibility with existing diesel engines and infrastructure.