The Environmental, Social, and Governance (ESG) movement has taken the corporate world by storm in recent years as government regulations and an increasing percentage of consumers demand action to address climate change and global inequity. In response, many companies have made public commitments to address greenhouse gas (GHG) emissions and set detailed plans to achieve them, often establishing short- and long-term goals. To address these goals, a growing list of companies, and in some cases, entire industries, have begun turning to biomass-based diesel (BBD) fuels like biodiesel, renewable diesel, and sustainable aviation fuel for their ability to significantly reduce GHG emissions with little or no modifications.
While increasing demand for biodiesel (BD), renewable diesel (RD), and sustainable aviation fuel (SAF), presents an opportunity for significant industry growth and innovation, it has also created many questions around the differences and similarities between the fuels and the respective markets they serve. These questions are undoubtedly a good thing for the industry, because it means the fuels are growing in market share and popularity.
The Michigan Advanced Biofuels Coalition, a coalition of stakeholders that promotes the use of advanced biofuels, in collaboration with the Michigan Soybean Committee, United Soybean Board, and Clean Fuels Alliance America, are all working to answer questions and clear up any confusion surrounding the growing number of sustainable diesel fuel options available today.
In land, sea, and rail operations, BD and RD help to displace the use of carbon intensive fuels such as ultra-low sulfur diesel fuel (ULSD), the standard for highway diesel fuel in the United States since 2010. In 2021 alone, biodiesel and renewable diesel displaced 3.1 billion gallons of petroleum-based diesel fuel in the United States. By 2030, the industry is expected to displace as much as 6 billion gallons, or approximately 10% of the distillate fuel market in the United States.
Similarly, the introduction of sustainable aviation fuel helps to displace the use of petroleum jet fuel like Jet A, the primary jet fuel used in the United States. Production of sustainable aviation fuel is expected to grow from a few million gallons in 2021 to as much as 3 billion gallons annually by 2030 – approximately 15% of the aviation fuel market in the United States.
Today, around 90% of the fuel used to power planes, trains, automobiles, and ships in the United States is petroleum based. Transitioning from petroleum-based fuels to BBD fuels has been shown to significantly reduce harmful air pollutants and carbon emissions. While the latter lessens the U.S. transportation sector’s impact on the climate and environment, the former improves air quality and helps to protect human health. A recent study by Trinity Consultants showed that a simple switch to cleaner fuels like biodiesel would provide billions in health benefits to local communities.
The low-carbon feedstocks used to produce renewable diesel, sustainable aviation fuel, and biodiesel have historically been the same, comprised largely of soybean oil, distillers corn oil (a by-product of ethanol production), used cooking oil, canola oil, and animal fats. However, new and advancing technologies are creating opportunities for the industry to begin producing BD, RD, and SAF from new feedstocks, like camelina and algal oils. Because of their unique production pathways, there is also growing opportunity to produce RD and SAF from waste products like municipal solid waste and agricultural residues.
While biodiesel, renewable diesel, and sustainable aviation fuel are produced for use in diesel engines, they are distinct fuels with differences from production to storage and handling to end-use. The quality standards and specifications for each fuel or fuel blend also differ greatly.
Biodiesel is a biodegradable and non-toxic advanced biofuel produced domestically from a diverse pool of renewable oils and fats. The finished fuel is produced through a process known as transesterification which combines lipids with methanol in the presence of a catalyst to create fatty-acid methyl esters (FAME), the fuel we know as biodiesel. According to research performed by the National Renewable Energy Laboratory, more than 90% of the biodiesel produced in the United States is of BQ-9000 quality.
The BQ-9000 program is a voluntary program started by Clean Fuels Alliance America (formerly the National Biodiesel Board) and administered by the National Biodiesel Accreditation Council. To receive accreditation, companies must pass a rigorous review and inspection of their quality control processes by an independent auditor. This ensures that quality control measures are met throughout the production process, resulting in the highest quality fuel.
In its pure form, biodiesel (B100) meets the American Society for Testing and Materials’ (ASTM) D6751 standard, while blends up to B5 (5% biodiesel) meet ASTM D975 and blends of B6 to B20 (6-20% biodiesel) meet ASTM D7467. All biodiesel and biodiesel blends consumed in the United States must meet these strict requirements to be considered a legal fuel that is fit for purpose.
As with petroleum diesel and renewable diesel, cold weather can negatively impact biodiesel operations. Because biodiesel has a higher cloud point than most of the petroleum diesel and renewable diesel on the market, it is typically blended with either fuel, or a combination of both, to create an efficient drop-in blend. However, new technologies like the Optimus Technologies Vector System, are enabling fleets to operate on 100% biodiesel year-round. Evergreen Grease Service, a recycler of fats, oils, and greases, currently employ’s the Vector System on three collection vehicles based out of their facility in Adrian, Michigan, with plans to scale up to their entire fleet over time. W2Fuel, a BQ-9000 producer also located in Adrian, supplies Evergreen’s fleet with high-quality soy-based biodiesel.
Biodiesel provides a significant boost to sustainability efforts across the United States. Between 2004 and 2020, the use of biodiesel reduced carbon emissions by 143 million metric tons, which is equivalent to removing 30.6 million cars from the roadways. For reference, there are currently about 5 million registered vehicles just in the state of Michigan.
Biodiesel also benefits maintenance intervals by increasing fuel lubricity and cetane. Studies have shown that adding as little as 1% biodiesel can “fix” lubricity concerns in drier fuels like ULSD and RD. Biodiesel is also known to extend oil change intervals and improve diesel particulate filter (DPF) operations. A recent study from Optimus Technologies found more than a 102% improvement in DPF regeneration intervals and a 32% reduction in ash accumulation when using B100. The same study also saw a 1.3% increase in fuel economy.
Renewable diesel, sometimes referred to as hydrotreated vegetable oil (HVO) or green diesel, is typically made from the same oils and fats as biodiesel but is produced through traditional petroleum refining processes such as hydrotreating, pyrolysis, or gasification. The resulting fuel is chemically identical to petroleum diesel and meets ASTM D975, the standard for diesel fuel. Because the fuel meets the same specification, there are typically no blend requirements or upfits needed to operate diesel equipment on renewable diesel in its pure form (R100). RD is also compatible with existing infrastructure, meaning it can be produced at existing refineries, transported through petroleum pipelines, and stored in tanks at terminals across the country.
The production of RD also produces valuable byproducts like renewable naphtha (a component of gasoline), renewable propane (RLPG), and sustainable aviation fuel. These byproducts can be fed back into the system during the production process or sold on the market. In most cases, like BD and RD, the byproducts qualify for Renewable Identification Numbers (RINs), a credit generated for every gallon of renewable fuel produced under the Renewable Fuel Standard (RFS). The products are also incredibly valuable under programs like California’s Low Carbon Fuel Standard (LCFS).
Sustainable Aviation Fuel
Sustainable aviation fuel is an umbrella term that refers to aviation fuels that are derived from renewable feedstocks through one of seven approved pathways. SAF is intended for use in existing aviation equipment. In its pure form, SAF meets ASTM D7566. Upon blending with petroleum jet fuel, SAF is certified to ASTM D1655and regarded as conventional Jet A or Jet A1 kerosene.
SAF is a key decarbonization strategy for all the United States’ major airlines, including United, Delta, American, Southwest, and more. Seen as a drop-in replacement for petroleum jet fuel, SAF provides upwards of an 80% reduction in carbon emissions when compared to petroleum jet fuels. However, SAF is currently limited to a maximum blend of 50% SAF and 50% petroleum jet fuel due to SAF’s naturally low levels of aromatics, a requirement for efficient operation in most aviation engines.
All of the SAF that is commercially available today is produced through the same process as renewable diesel. The major difference between RD and SAF production is that SAF requires additional feedstock, heat, and pressure. In the end, the production process yields a product called Hydroprocessed Esters and Fatty Acids of Synthetic Paraffinic Kerosene (HEFA-SPK), better known as sustainable aviation fuel.
While HEFA-SPK is the only commercially available product today, other processes currently under development in the United States and Europe include Alcohol to Jet (ATJ), which converts an alcohol (typically ethanol) into SAF, and Fischer–Tropsch (F-T), which transforms gaseous fuels into a liquid and then converts it into a diesel fuel using immense heat and pressure.
SAF production is expected to grow to 3 billion gallons by 2030 and as much as 50 billion gallons by 2050 under an ambitious plan set forth under the U.S. Department of Energy’s SAF Grand Challenge. If the projected growth continues and innovative production processes become reality, the International Air Transport Association (IATA) estimates that SAF could contribute up to 65% of the reduction in emissions needed for the aviation industry to reach net-zero emissions in 2050.
Crush the Competition
In the U.S., the shift toward decarbonization, coupled with corporate ESG commitments and a vast array of new government incentives, is furthering the demand for low-carbon fuels like biodiesel, renewable diesel, and sustainable aviation fuel. On top of expanding domestic BBD fuel production, the movement is sparking investments in new feedstocks and expanded oilseed crush capacity to supplement current supplies. These advancements, coupled with carbon sequestration practices on the farm, are leading a sustainable revolution that is certain to benefit U.S. farmers by providing a robust and growing market for their products.