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Ensuring quality for biodiesel and renewable diesel

For years, biodiesel has become widely available in the U.S., with an average 2 billion gallons used each year, and renewable diesel availability doubled, reaching 1.3 billion gallons in 2021.

Clean Fuels Alliance America represents both fuels. Our work promotes quality control and market acceptance for these renewable fuels, and we anticipate further rapid growth over the coming decade.

What’s the difference?

Biodiesel is a fuel or fuel additive composed of mono-alkyl esters of long-chain fatty acids that meets the ASTM D6751 specifications. It is produced through esterification of free fatty acids and transesterification of glycerides into methyl esters. Glycerin is the primary co-product.

Renewable diesel is a hydrocarbon fuel produced from biomass that meets the ASTM D975 fuel specifications. It is produced through hydrotreatment, a process similar to ultra-low-sulfur diesel refining, with naphtha and propane as co-products.

Both fuels are made from fats, oils and greases (FOG). In the U.S., vegetable oils (primarily soybean and canola), animal fats, recycled cooking oil and technical corn oil (a byproduct of ethanol production) are the predominant feedstocks. The feedstocks are pretreated to remove impurities that can hamper the fuel conversions.

FOGs naturally contain phosphorous, salts and other organic metals that must be removed for the final product to meet ASTM fuel standards. For renewable diesel, these must be removed before hydrotreatment. For biodiesel, they are removed in a final washing stage.


ASTM first published the biodiesel specifications (D6751) in 1999. Clean Fuels Alliance America (formerly the National Biodiesel Board) has worked within the ASTM process as the requirements have been updated to reflect the latest fuel and engine performance research and to ensure quality and reliability.

The diesel fuel specification (ASTM D975) was originally written around the production of petroleum diesel. Over the years, it has changed to allow fuels made from renewable sources, including renewable diesel and biodiesel blends up to 5 percent (B5).

Biodiesel blends from B6 to B20 are regulated by ASTM D7467. However, the biodiesel blendstock is assumed to meet the D6751 specification.

The National Biodiesel Accreditation Program BQ-9000 helps biodiesel producers improve their fuel testing and greatly reduce any chance of producing off-spec fuel. To receive accreditation and consistently ensure fuel quality, biodiesel producers must pass a rigorous review and inspection of their QC processes by an independent auditor.

In the recently proposed Heavy-Duty Engine and Vehicle Standards, the EPA notes that recent testing of available on-road diesel blends by the National Renewable Energy Lab and California’s Air Resources Board shows that biodiesel consistently meets the fuel quality specification.

Quality assurance builds acceptance

As the U.S. market for biodiesel and renewable diesel has grown to more than 3 billion gallons, these fuels have proven their value over millions of miles and hours of use in every type of diesel engine throughout the economy.

As an integral part of the industry’s growth, Clean Fuels Alliance America continues to work with OEMs to ensure fuel and engine compatibility. Most manufacturers proactively support 20 percent (B20) or higher biodiesel blends for their vehicles, including light-, medium- and heavy-duty vehicles, as well as other diesel-fueled applications such as railroads, marine, heating oils and power generation.

Renewable diesel that meets D975 is also approved by most OEMs, either blended with petroleum diesel fuel or used as a 100-percent replacement. However, there are some applications utilizing older compression ignition engine technologies, such as the railroad industry, that only approve use of up to 30 percent (R30).

Biodiesel and renewable diesel can both be used from coast to coast as an effective and immediately available carbon mitigation strategy, providing an average 74-percent reduction in lifecycle greenhouse gas emissions.

For more information on the National Biodiesel Accreditation Program BQ-9000 program, visit For more information on ASTM International’s biodiesel specification, visit

For more information on Clean Fuels Alliance America, visit or contact Scott Fenwick at (800) 841-5849.

Source BIC Magazine May 2022