A biodiesel truck is any diesel truck that runs on biodiesel, a renewable fuel made from plant oils, animal fats, or recycled cooking grease instead of (or blended with) petroleum diesel. Most diesel trucks on the road today can use biodiesel blends without any engine modifications, which means a “biodiesel truck” isn’t a special type of vehicle. It’s a standard diesel truck fueled differently.
How Biodiesel Works in a Diesel Engine
Diesel engines are compression-ignition engines. They don’t use spark plugs. Instead, they compress air until it gets extremely hot, then inject fuel into that superheated air, causing it to ignite. Biodiesel ignites the same way because it has a similar chemical structure to petroleum diesel. In fact, biodiesel raises the cetane number of the fuel, which is a measure of how quickly and smoothly it ignites. A higher cetane number generally means cleaner, more complete combustion. Biodiesel also improves fuel lubricity, reducing wear on the engine’s fuel injection system.
Because the combustion process is essentially the same, truck manufacturers don’t need to redesign engines for biodiesel. The fuel flows through the same fuel lines, filters, and injectors. This compatibility is why biodiesel has gained traction in commercial trucking, agriculture, and fleet operations where diesel engines are already standard.
Common Biodiesel Blends
Biodiesel is almost always mixed with petroleum diesel in specific ratios, labeled with a “B” followed by the percentage of biodiesel in the blend. The two most common are B5 (up to 5% biodiesel) and B20 (6% to 20% biodiesel). B5 is approved for safe use in any compression-ignition engine designed for petroleum diesel, including light-duty and heavy-duty trucks, tractors, boats, and generators.
B20 is the sweet spot for most truck operators. It offers a good balance of cost, lower emissions, cold-weather performance, and full compatibility with conventional engines. No modifications are needed for B20 or any lower blend. You could fill up with B20 at a truck stop and drive normally.
B100, which is pure biodiesel, exists but is rarely used as a standalone transportation fuel. It’s primarily a blendstock, meaning producers use it to mix lower-percentage blends. Running B100 presents challenges with cold weather performance, fuel system compatibility, and cost that make it impractical for everyday trucking.
What Biodiesel Is Made From
Over 95% of biodiesel worldwide comes from edible oil crops like soybean, canola, and palm oil. The production process, called transesterification, chemically converts these oils into a fuel that behaves like petroleum diesel.
But the feedstock options go well beyond cooking oils. Biodiesel can be made from animal fats like beef tallow and chicken fat, waste cooking oil from restaurants, and non-edible plants like jatropha, castor, and cotton seed. Waste-based feedstocks are increasingly attractive because they’re abundant, cheap, and don’t compete with the food supply. Algae-based and genetically engineered crop feedstocks are also being explored, though they remain a small fraction of production.
The source material matters because it affects the fuel’s physical properties. Different feedstocks produce biodiesel with different viscosity, density, and cold-weather behavior. Castor oil, for instance, has roughly seven times the viscosity of other vegetable oils in its raw form. Transesterification brings that viscosity down to usable levels, but the characteristics of the final fuel still vary by feedstock.
Emissions and Environmental Impact
The main environmental case for biodiesel trucks is lower lifecycle greenhouse gas emissions. Unlike petroleum diesel, which releases carbon that has been locked underground for millions of years, biodiesel comes from plants and waste materials that absorbed carbon from the atmosphere recently. This shorter carbon cycle means less net carbon added to the atmosphere.
The EPA has evaluated biodiesel from multiple feedstocks and found lifecycle greenhouse gas reductions of at least 50% compared to petroleum diesel for sources like rapeseed oil and camelina oil. The exact reduction depends on the feedstock, how it was grown or collected, and the energy used during production. Biodiesel also produces less particulate matter and sulfur during combustion, which contributes to better local air quality around highways and trucking corridors.
Fuel Economy and Range
Biodiesel contains slightly less energy per gallon than petroleum diesel, which means a truck burning biodiesel won’t travel quite as far on a full tank. Standard low-sulfur diesel contains about 128,488 BTU per gallon. B100 drops to 119,550 BTU per gallon, roughly 93% of the energy content. That translates to about a 7% reduction in range on pure biodiesel.
For B20, the difference is barely noticeable. A gallon of B20 contains about 126,700 BTU, which is 99% of the energy in a gallon of petroleum diesel. Most truck drivers using B20 won’t see a meaningful change in fuel economy or how often they stop to refuel.
Cold Weather Challenges
The biggest operational drawback of biodiesel in trucks is cold-weather performance. As temperatures drop, the fatty acid compounds in biodiesel begin to crystallize. This can clog fuel filters and prevent fuel from reaching the engine’s injectors, leaving the truck unable to start.
Three measurements define cold-weather performance: the cloud point (when wax crystals first become visible), the pour point (when the fuel stops flowing), and the cold filter plugging point (when crystals block a standard test filter). Waste cooking oil biodiesel, for example, has a cloud point around negative 3°C (about 27°F) before treatment.
Truck operators and fuel producers manage this in several ways. The simplest is blending with petroleum diesel. Lower blends like B5 and B20 retain most of petroleum diesel’s cold-weather tolerance. Chemical additives can also improve cold flow, with some reducing the pour point by as much as 9°C. A process called winterization removes saturated compounds that crystallize first, pushing the cloud point lower. Combining winterization with additives has achieved cloud points as low as negative 9°C (about 16°F), making the fuel viable in moderately cold climates. In practice, many fleets in northern regions simply switch to lower biodiesel blends during winter months.
Who Uses Biodiesel Trucks
Because biodiesel works in existing diesel engines, adoption has been especially strong among commercial fleets, municipal vehicles, and agricultural operations. School bus fleets, city transit systems, and delivery companies use B20 as a straightforward way to reduce emissions without purchasing new vehicles or installing new infrastructure. Trucking companies running long-haul routes can fill up at any fuel station that carries biodiesel blends, which are increasingly available at standard truck stops across the United States.
For individual truck owners, using biodiesel is as simple as choosing a different pump. If your truck runs on diesel, it can run on B20. There’s no conversion kit, no special maintenance schedule, and no loss of power or towing capacity. The truck itself is identical. The fuel is what changes.