Green diesel, also called renewable diesel or hydrotreated vegetable oil (HVO), is a fuel made from biological sources like vegetable oils, animal fats, and waste grease that is chemically identical to petroleum diesel. Unlike biodiesel, which has a different molecular structure, green diesel is a true hydrocarbon fuel. It can run in any standard diesel engine without modifications, meet the same fuel specifications as conventional diesel, and even be stored and transported through existing infrastructure.
How Green Diesel Differs From Biodiesel
The distinction between green diesel and biodiesel trips up a lot of people because both come from similar raw materials. The difference is in the chemistry. Biodiesel (technically called fatty acid methyl ester, or FAME) is made through a process called transesterification, which produces a fuel that contains oxygen atoms in its molecular structure. That oxygen content means biodiesel carries about 7% less energy per gallon than petroleum diesel.
Green diesel takes a completely different manufacturing path. Through a process called hydrotreating, hydrogen is used at high temperatures and pressures to strip oxygen out of fats and oils, leaving behind pure hydrocarbons: just hydrogen and carbon atoms, exactly like the molecules in petroleum diesel. The end product is so chemically similar to fossil diesel that it meets ASTM D975, the same specification petroleum diesel must pass in the United States. In Europe, it meets the EN 15940 standard for paraffinic diesel fuels.
This chemical equivalence is a big deal in practice. Biodiesel is typically limited to blends of 5% to 20% with petroleum diesel because higher concentrations can cause engine compatibility issues. Green diesel has no such blending limit. You can fill a tank with 100% renewable diesel and drive away.
What It’s Made From
Green diesel can be produced from a wide range of fats and oils. The most common feedstocks fall into a few categories:
- Vegetable oils: soybean oil, canola oil, and palm oil are widely used, particularly in large-scale commercial production.
- Waste fats and greases: used cooking oil collected from restaurants and food processing facilities, animal tallow from meatpacking, and other food industry byproducts.
- Non-edible plant oils: crops like jatropha, camelina, and castor that don’t compete with food production.
- Emerging sources: algae-based oils and oils from genetically engineered crops are in earlier stages of development.
The feedstock choice matters for both cost and environmental impact. Waste-based feedstocks like used cooking oil and tallow are considered the most sustainable option because they don’t require new farmland and repurpose materials that would otherwise be discarded. They also deliver the largest carbon reductions, as we’ll see below.
Carbon Emission Reductions
The core appeal of green diesel is its potential to cut greenhouse gas emissions without requiring new vehicles or infrastructure. Life-cycle analyses published in Environmental Science & Technology found that green diesel and biodiesel made from soybean, canola, and carinata oils reduce emissions by 40% to 69% compared to petroleum diesel, even after accounting for the land-use changes involved in growing those crops. Without factoring in land-use change, reductions reach 63% to 77%.
Waste-based feedstocks perform even better. Converting tallow, used cooking oil, and distillers corn oil into renewable fuels achieves 79% to 86% lower emissions than petroleum diesel. These feedstocks score so well because they carry none of the upstream farming emissions that crop-based oils do.
Engine Performance and Cold Weather
Green diesel generally performs as well as or better than petroleum diesel in engines. Its cetane number, which measures how easily the fuel ignites under compression, tends to run higher than conventional diesel. Higher cetane means smoother combustion, less engine knock, and typically lower emissions of particulate matter and nitrogen oxides.
Cold weather performance is one area where renewable fuels have historically struggled. Biodiesel is particularly vulnerable: fatty acid crystals can form at low temperatures, plugging fuel filters and preventing the engine from starting. Three measurements define cold performance. Cloud point is the temperature where wax crystals first become visible. Pour point is where the fuel stops flowing. Cold filter plugging point is where crystals block a standard test filter.
Green diesel handles cold better than biodiesel because its hydrocarbon structure can be tuned during production. Refiners adjust the process to create more branched-chain molecules (called isomerization), which resist crystallization at lower temperatures. The exact cold performance depends on the specific product, but producers can tailor green diesel for winter grades in cold climates, something that’s much harder to do with biodiesel.
Storage and Shelf Life
Biodiesel has a well-known weakness: it degrades over time. Exposure to air, moisture, and heat causes oxidation, which produces acids and gummy deposits that can damage fuel systems. This limits how long biodiesel can sit in a tank, particularly in warm or humid environments.
Green diesel is far more stable. Because it lacks the oxygen-containing ester bonds found in biodiesel, it resists oxidation in the same way petroleum diesel does. Research on fuel blends containing hydrotreated vegetable oil found that even after six months of storage in both highland and coastal climates, the blends maintained robust stability. Acid numbers, which indicate oxidative breakdown, showed only a slight upward trend and stayed well within specification limits. Oxidation stability exceeded standard requirements even at higher blend concentrations.
For fleet operators, this stability means fewer concerns about fuel quality in backup generators, seasonal equipment, or storage tanks that may sit for weeks or months between use.
Where Green Diesel Is Used Today
Green diesel has seen rapid growth in the United States, particularly in California, where the state’s Low Carbon Fuel Standard creates strong financial incentives for low-emission fuels. Major oil refiners have converted several petroleum refineries to produce renewable diesel, and production capacity has expanded significantly since 2020.
In Europe, green diesel sold as HVO is blended into the diesel supply in Scandinavian countries, the Netherlands, and Germany, driven by renewable energy mandates. Finland-based Neste is one of the world’s largest producers.
The fuel is especially attractive for applications where electrification is difficult or decades away: long-haul trucking, marine shipping, rail, construction equipment, and agricultural machinery. Because it works as a direct replacement in existing engines and fueling infrastructure, it offers immediate emissions reductions without waiting for new technology to be built or adopted. For the same reason, municipal transit agencies and corporate fleets have been early adopters, switching to renewable diesel as a straightforward way to lower their carbon footprint.