By Marc Laroque*
Biodiesel vs. Renewable Diesel: Which Is Better for Your Fleet?
Demand for sustainable alternatives to petroleum diesel has surged in the last few years. While biodiesel and renewable diesel (RD) are both viable options, they’re not the same thing — and have different impacts on engines and filtration systems.
When using either biofuel, it is important to understand how they differ from petroleum diesel and how to use them correctly. Key considerations include fuel filter lifespan, engine compatibility and performance, filtration dynamics, efficiency and environmental impact.
What’s Driving Demand for Biodiesel and Renewable Diesel?
Although biofuels are typically more expensive to produce than petroleum diesel, higher crude oil prices combined with governmental incentives have made them cost-competitive.
Both alternatives offer benefits to organizations with sustainability goals and requirements. Carbon dioxide (CO2) emissions from 100% biodiesel (B100) are 74% lower than those from petroleum diesel. A study by the National Renewable Energy Laboratory (NREL) found RD reduced both CO2 and nitrogen oxide emissions when compared with petroleum diesel. California’s Low Carbon Fuel Standard (LCFS) shows RD reduces carbon intensity on average by 65% when compared with petroleum diesel.
Over the years, federal policies and tax credits have helped drive the development and adoption of biofuels. According to the U.S. Department of Energy (DOE), U.S. biodiesel consumption reached nearly 2 billion gallons in 2023 (the most recent year for which figures have been released, as of this writing), making it the third-most consumed biofuel in the U.S. after ethanol and RD. Renewable diesel consumption has also been growing steadily for the past few years, surging from 438 million gallons in 2018 to nearly 2.9 billion gallons in 2023. U.S. RD production capacity surpassed biodiesel in July 2022 and reached just over 2.5 billion gallons in 2023.
Demand for sustainable alternatives to petroleum diesel has surged in the last few years. In 2023 (the most recent year for which figures have been released, as of this writing), U.S. consumption of biodiesel and renewable diesel reached nearly 2 billion gallons and nearly 2.9 billion gallons, respectively.
What Is Biodiesel?
Biodiesel, a form of fatty acid methyl ester (FAME), is a sustainable and renewable fuel produced from vegetable oils, animal fats or used cooking oil (UCO). Pure biodiesel is known as B100, but it’s more often blended with petroleum diesel. The most common blends include:
- B5: Up to 5% biodiesel, typically used in fleet vehicles. In the U.S., the government allows up to 5% biodiesel to be mixed into petroleum diesel without notification.
- B20: 6% to 20% biodiesel, which can be used in many diesel engines without modification.
Many original equipment manufacturers (OEMs) support the use of biodiesel and build engines and filtration systems with compatible materials.
Pros
- Biodiesel is one of the most environmentally friendly diesel alternatives, producing lower emissions than petroleum diesel or RD.
- Biodiesel tends to be less expensive than other biofuels.
- The properties of biodiesel are similar enough to those of diesel fuel that it can be used in existing diesel engines if parts and filtration systems are made from compatible materials.
- Biodiesel is the most accepted form of biofuel and has been in large-scale production for more than two decades.
- Many modern engines and fuel filters are designed to be compatible with petroleum diesel or biodiesel.
Many fuel filters are designed to be compatible with petroleum diesel, renewable diesel and biodiesel. Consult your filter provider to ensure the filters you are using are compatible with your equipment and fuel.
- With properly designed equipment, end users who follow best practices have some flexibility to switch back and forth between petroleum diesel and biodiesel.
- Biodiesel offers high lubricity, which can help extend the lifespan of fuel system components.
Cons
- Biodiesel attracts and absorbs 15 to 25 times more water than normal diesel, which can contaminate fuel and provide a medium for algae and microbial growth. Both fuel system components and the fuel itself can be compromised if water is not separated effectively.
- Service intervals for filters may be shorter because of microbes and other contaminants. Biodiesel is known to have issues with carboxylates (soft contaminants that can form when the fuel reacts with other substances, causing filters to plug faster).
Scanning electron microscopy (SEM) image of filter media plugged with carboxylates.
- The cloud point of biodiesel (the temperature at which it begins to gel and become cloudy) is higher than petroleum diesel. In addition, the fuel tends to degrade when stored for extended periods. Either of these effects can clog fuel lines, injectors and fuel filters. As such, it’s critical to store biodiesel fuels at temperatures above their cloud point and use them within six months of production.
- Biodiesel can degrade O-rings, gaskets, paint, coatings in fuel tanks and fuel system components. Over time, oxidation will also form acids that will make the fuel more corrosive.
- Biodiesel has about 7.5% less energy content on average than petroleum diesel. Although this doesn’t significantly impact engine performance when using a B20 blend, expect fewer miles per gallon when running B100.
What About Renewable Diesel?
Also known as paraffinic fuel or hydrogenated vegetable oil (HVO), RD is made from the same feedstocks as biodiesel, but the end product is chemically different.
Pros
- RD can be used as a replacement fuel or blended with any amount of petroleum diesel.
- Users can switch back and forth between RD and petroleum diesel without ill effects.
- RD has a shelf life similar to petroleum diesel.
- RD is less likely than biodiesel to form filter-plugging contaminants in storage or fuel systems.
- RD has less affinity for water than petroleum diesel or biodiesel. Filter life and water separation efficiency are expected to be comparable among 100% renewable diesel, petroleum diesel or any blend of the two.
Cons
- RD is refined using the same types of equipment as petroleum diesel, making it significantly more expensive to produce than biodiesel.
- The cloud point of renewable diesel may vary depending on the supplier or time of year; it can be adjusted during the refining process. Although most vendors target a cloud point of around 10°F (-12°C), which is comparable to petroleum-based diesel fuel, cold flow additives are less effective in RD.
- RD has about 4% less energy content by volume than petroleum diesel. This can have a slight impact on your mileage per gallon but is easily outweighed by its other benefits.
Best Practices for Biofuels
The right biofuel for any given application should be considered on a case-by-case basis. Biodiesel offers greater cost savings and lower emissions, while RD offers the performance and maintenance benefits of seamless integration with existing diesel infrastructure.
Whichever biofuel you choose, the following practices are recommended:
- Properly clean and maintain all fuel storage and handling systems.
- Equip bulk storage tanks with fuel water separators and bulk filters to make sure water and dirt are removed from fuel before entering vehicle tanks. This is a best practice for any fuel but essential for optimal results with biodiesel.
- Keep vehicles and storage tanks full to reduce the potential for condensation.
- Use biodiesel within six months of production, when possible.
- When using biodiesel, always use a three-stage water separation filter to keep water out of the fuel. Use only biodiesel-compatible filters for other parts of the fuel system. Consider alternatives if your application develops issues with corrosion or high water content.
- Use RD in applications where fuel will sit unused for extended periods, such as in standby generator sets. It’s also better suited to lower-ambient temperatures. Consult your fuel supplier for details about its target cloud point.
- biodiesel fuel storage tank cutaway
Proper maintenance of bulk storage tanks is a best practice for any fuel, but particularly important for biodiesel. Tanks should be cleaned regularly to remove the water, dirt, bacteria and sludge that typically accumulate in them. Equipping storage tanks with bulk filtration systems will help to prevent contaminated fuel from being transferred into vehicle tanks, providing an additional layer of protection for your equipment.
Filtration Science makes it possible to get the most from biofuels like biodeisel and renewable diesel, optimizing performance while protecting your engines and fuel systems. Consult your fuel supplier and filter vendor for assistance with choosing the right solutions for your specific needs to avoid in-service equipment issues.
*Marc Laroque is a senior materials science engineer at Atmus Filtration Technologies. In his role, he selects, validates and approves all materials, including gaskets, plastics, adhesives and metals, for Fleetguard products globally. In addition, he investigates field return issues, analyzes root causes, and proposes solutions. He also conducts materials science training for new Atmus engineers. Marc has nearly 15 years of career experience as a materials science engineer at Cummins Filtration (now Atmus) and earned a master’s degree in materials science and engineering at SUNY Stonybrook.
This article originally appeared in Fleet Equipment: https://www.fleetequipmentmag.com/biodiesel-and-renewable-diesel-differenc/
