Blue diesel is a renewable, paraffinic diesel fuel made from biological raw materials like waste cooking oils, animal fats, and vegetable oils. It meets the European fuel standard EN 15940 for paraffinic diesel and can be used in most modern diesel engines, either on its own or blended with conventional diesel. What sets it apart from regular diesel is its cleaner burn, higher ignition quality, and lower carbon footprint over its full lifecycle.
How Blue Diesel Differs From Regular Diesel
The most important technical difference is the cetane number, which measures how easily fuel ignites in the engine. Regular low-sulfur diesel has a cetane number between 40 and 55. Blue diesel, classified as renewable paraffinic diesel, reaches 70 to 85. A higher cetane number means faster, more complete combustion, which translates to smoother engine operation, less knocking, and fewer unburned fuel particles leaving the exhaust.
Blue diesel also contains virtually no sulfur (under 5 milligrams per kilogram) and very low aromatic content (no more than 1.1% by weight). Conventional diesel carries significantly more aromatic compounds, which are a major source of soot and particulate emissions. The near-absence of these compounds is what gives blue diesel its cleaner exhaust profile.
In terms of energy, blue diesel holds about 96% of the energy in a gallon of conventional diesel. That small gap means fuel consumption may be slightly higher to cover the same distance, but the difference is modest enough that most drivers won’t notice it in everyday use.
What It’s Made From
Blue diesel is produced through a process called hydrotreatment, where fats and oils are reacted with hydrogen at high temperatures and pressures. This strips out the oxygen and converts biological fats into hydrocarbons that are chemically very similar to the molecules in fossil diesel. The result is a fuel that works in existing engines without modification.
The feedstocks are varied. Waste cooking oil and animal fats like beef tallow are common starting materials, along with non-edible vegetable oils such as camelina. Some producers also use fish oil, algal oils, and even waste coffee ground oils. This flexibility is one of the fuel’s advantages: it can turn low-value waste streams into high-quality fuel. In the U.S. biodiesel market more broadly, soybean oil accounts for about 72% of feedstock, with corn oil at 13%, canola oil at nearly 11%, and animal fats making up the rest.
Blue diesel can also contain up to 7% fatty acid methyl esters (FAME), the compound found in traditional biodiesel. However, it’s important to note that blue diesel and biodiesel are not the same thing. Traditional biodiesel is made through a chemical reaction between oils and alcohol, producing a fuel with different properties and limitations. Blue diesel’s hydrotreatment process creates a purer, more stable product.
Emissions and Environmental Impact
Over its full lifecycle, from growing the feedstock to burning the fuel, renewable diesel pathways typically achieve around a 50% reduction in greenhouse gas emissions compared to fossil diesel. The EPA has verified this figure across multiple feedstock types, including camelina oil, food waste, and cover crops.
At the tailpipe, the benefits are also measurable. The extremely low aromatic and sulfur content means significantly less particulate matter in the exhaust. Soot production drops substantially because the fuel burns more completely, thanks to that higher cetane number. This is particularly relevant in urban areas where diesel particulate matter is a major air quality concern.
Nitrogen oxide emissions are somewhat more complicated. While the cleaner combustion profile of blue diesel can reduce these pollutants, the actual reduction depends heavily on the engine, its exhaust treatment system, and operating conditions. Modern diesel vehicles already use selective catalytic reduction systems (the ones that require a urea-based fluid in a separate tank) to cut nitrogen oxides by up to 90%, and blue diesel works well with these systems.
Cold Weather Performance
One of blue diesel’s practical strengths is its behavior in cold temperatures. The cold filter plugging point, the temperature at which fuel starts to gel and clog filters, is a critical spec for anyone driving or operating equipment in winter. Standard diesel with additives can reach a cold filter plugging point of around negative 20°C (negative 4°F). Blue diesel’s paraffinic structure gives it naturally good cold-flow properties, though the exact performance depends on the specific product grade and any added cold-flow improvers.
Different seasonal grades are available to match regional climates, similar to how conventional diesel is sold in summer and winter formulations. If you’re in a cold climate, check which grade is being sold at your pump or by your supplier.
Storage and Shelf Life
Blue diesel has a notable advantage over traditional biodiesel when it comes to storage. Conventional ultra-low-sulfur diesel has a shelf life of roughly 3 to 6 months. Traditional biodiesel is vulnerable to oxidation (which makes it thicken, turn acidic, and develop a rancid smell) and microbial contamination, where bacteria and fungi can clog filters and degrade fuel quality within days if conditions are poor. Biodiesel also reacts badly with copper, bronze, and brass fittings, and breaks down faster when exposed to sunlight or stored with too much air in the container.
Blue diesel, because of its hydrotreatment process, behaves much more like fossil diesel in storage. It has fewer of the double bonds that make biodiesel susceptible to oxidation, and its low water content discourages microbial growth. Store it in clean, sealed containers away from light and extreme heat, and it will remain stable for a comparable period to conventional diesel.
Cost Compared to Conventional Diesel
Blue diesel generally costs more than standard diesel, but the premium varies widely by region and supplier. For reference, biodiesel blends (which use a different production process but offer a useful price comparison) can range from a few cents per gallon above conventional diesel to roughly $0.15 to $0.45 more per gallon, depending on location. In some markets, renewable fuels are actually priced competitively or even below conventional diesel thanks to tax credits, renewable fuel mandates, and blending incentives.
The price gap has been narrowing as production capacity grows and more governments introduce carbon pricing or renewable fuel obligations that make fossil diesel relatively more expensive. For fleet operators, the lower maintenance costs from cleaner combustion (less soot means longer intervals between particulate filter regeneration, for example) can offset some of the fuel price premium over time.
Vehicle Compatibility
Because blue diesel meets the EN 15940 standard and is chemically similar to fossil diesel, it works in most modern diesel engines without any modifications. However, the standard itself notes that blends containing FAME may not be suitable for all vehicles. Before switching, check your vehicle’s owner manual for compatibility with paraffinic or XTL fuels. Most manufacturers of diesel cars, trucks, and heavy equipment produced in the last decade have approved these fuels, but older engines or specific models may have restrictions, particularly around fuel seals and hoses that weren’t designed for paraffinic chemistry.