As the world seeks to reduce emissions by a variety of means, one alternative fuel source is gaining significant traction in the world of heavy-duty transportation: Renewable Diesel.

Renewable Diesel—more formally called hydrogenation-derived renewable diesel, or HDRD—is gaining market adoption for its advantages over first-generation biodiesel and ultra-low sulfur diesel (ULSD) fossil fuels. As noted by the U.S. Energy Information Agency, “because renewable diesel is chemically the same as petroleum diesel, it may be used in its pure form—called R100 diesel—as a drop-in fuel, or it can be blended with petroleum diesel and/or with biodiesel in various amounts.” This makes it a highly convenient and effective means to reduce carbon intensity on a potentially broad scale, especially as zero-emissions technologies like electrification are a long way from maturity in the heavy-duty space.

As of 2022, there are 11 renewable diesel fuel and biofuel plants in the United States, capable of producing nearly 2 billion gallons of those fuels annually, and about 40 new plants are expected to be constructed in the next three to five years. California is heavily incentivizing their use, as are Washington and Oregon. Meanwhile, the Canadian government is expected to implement similar measures (notably, renewable diesels are suitable for use in cold climates, unlike first-gen biofuels). The numbers only stand to rise in the coming years, and renewables will join conventional diesel fuels as a readily available option for heavy-duty fleets throughout North America.

However, as renewables start to proliferate, it’s important to remember that certain classes of additives are critical to unlocking their full potential and to best enable existing engine hardware to deliver long-term sustained performance. Furthermore, the benefits additives bring to renewable formulation highlights their continued application in conventional diesel formulations—particularly in the United States, where cleaning additives are not mandated in diesel fuel like they are in gasoline. In this article, we’ll explore the benefits additives bring to a diversified diesel fuel market and what fuel formulators should consider into the future.

How Renewables Differ from Conventional Diesels

There are a few key ways that renewable diesels differ from their traditional counterparts. In addition to a significant reduction in carbon intensity, renewables bring a number of inherent benefits to the table, including:

• High natural cetane number, reducing the need for cetane additives in renewable formulations.
• Good low-temperature operability with winter grades, making them well suited for colder climates.
• Cleaner burning, reducing unwanted combustion byproducts.
• Greater oxidation stability compared to traditional bio-diesel fuels.

In an untreated renewable diesel fuel, these benefits come with their trade-offs. One of the most significant is renewable diesel’s inherent lubricity—e.g., the fuel’s ability to help prevent wear in metal-on-metal applications as it travels through the entire fuel delivery system. This is particularly important within a diesel engine’s fuel injection system, where fuel travels through high-pressure pumps and injectors designed to extremely tight tolerances. A good fuel—be it renewable or otherwise—requires certain lubricating properties that prevent premature wear. Such wear can lead to operational issues and potentially costly downtime for fleets.

Additionally, though deposit formation can be slightly reduced with the use of renewable diesel, carbonaceous deposits will still in fact form over the long term. Renewable diesels are, indeed, very clean fuels—but the application of deposit control additives remains necessary in controlling and removing performance degrading deposits. This is borne out in a conventional XUD-9 engine testing, a reliable fouling and cleaning procedure to measure deposit formation. Testing performed by Lubrizol confirms that untreated R100 renewable diesel fuels provide reduced injector flow loss compared with untreated ULSD; however, the addition of cleanup additives is required to eliminate flow loss and maintain optimal performance.

The Necessity of Additives Across All Fuel Formulations

Fuel injector deposits can become highly problematic for any heavy-duty fleet. And though they may form more slowly with the use of untreated renewable diesel, it is important for all fuel formulations to mitigate deposit formation through the application of proven deposit control additives.

Why? First, excessive deposit buildup over time will accumulate on the injector spray nozzles and the interior moving parts of the injectors, potentially causing fuel economy losses as these deposits interfere with fuel spray patterns and even the amount of fuel delivered. Second, excessive deposits will inevitably interfere with a truck’s sophisticated aftertreatment devices, such as diesel particulate filters (DPFs), that are required on the majority of diesel trucks on the road today. Suboptimal combustion caused by deposits leads to an increase in particulate formation that plugs up DPFs, requiring a truck to burn them off through a fuel-intensive process known as regeneration (or “regen”), which can be performed while a truck is still operational (albeit consuming higher levels of fuel throughout the process in order to generate necessary temperatures) or while a truck is idle (requiring costly downtime). Though regens may not always be completely eliminated, cleaner fuels that are treated with the right deposit control additives can significantly reduce the frequency of regens or other forms of time-consuming maintenance, helping fleets save time and money over the long term. And that can add up.

Navigating a Diversified Diesel Marketplace

As noted earlier, the U.S. diesel market does not necessitate the application of cleaning additives in conventional diesel formulations, and their usage in U.S. market fuels is much lower compared to other regional diesel markets. In Europe, for example, diesel fuels with cleaning benefits are widely advertised and available. And within the U.S., gasoline formulations are required to be heavily additized in order to help protect against deposit buildup that can result from the combustion of untreated fuels.

For the discerning end user, this leaves the U.S. diesel marketplace challenging to navigate. Particularly for fleets who typically buy their fuel on contract from a bulk supplier, it is worth opening a conversation about the expected performance levels from fuels, be they renewables or otherwise. Fuels that have been formulated with the right deposit control additives and lubricity improvers can be expected to offer higher levels of performance, which can be majorly beneficial for fleets, especially large ones.

For fuel marketers, there is opportunity to differentiate from the competition by working with the right additive supplier. The right supplier should be able to provide you with the kinds of performance data, backed by rigorous testing, that can help you make performance claims on your fuels that other suppliers can’t. This can be especially beneficial for fuel suppliers who are interested in adding renewable diesels to their portfolios—with the right support, you can be confident in delivering a high-performance product your customers can count on.

Our View

As renewable diesel becomes more commonplace, it remains highly beneficial to use multifunctional diesel fuel additives that restore and maintain optimum performance of diesel vehicles for the end users. Simultaneously, it’s worth a reminder that such high-performance additives can benefit all diesel fuels, conventional or otherwise, in order to best enable modern diesel engine technology to reach its full potential. Fleets have the opportunity to educate themselves on expected diesel performance and seek out high-performance formulations to optimize their operations, while fuel marketers have the opportunity to work with collaborative additive suppliers to differentiate their formulations from the competition.

Contact your Lubrizol representative to learn more about renewable diesel fuels and diesel fuel additives.