Hydrogenation-derived renewable diesel (HDRD)—or HVO (hydrogenated vegetable oil) as it is also commonly known—is an increasingly mature industrial scale alternative to fossil-derived diesel fuel. These fuels can also be derived from waste and residual fat fractions so the acronym `HVO’ no longer describes all sourcing options of this fuel type. In comparison, fatty acid methyl esters (FAMEs) are a so-called first-generation biofuel produced by the esterification of vegetable oils, such as rape, palm, soy and used cooking oil. These fuels have been in widespread use since the 1990’s but do present a number of usability challenges.
HDRD currently offers reductions in greenhouse gas emissions (GHG) up to 83% (Source: Neste Renewable Fuels Handbook) depending on the feedstocks used. Production from waste cooking oil offers the greatest CO2 saving according to the EU Renewable Energy Directive (RED) II which, from January 2021, specifies a minimum 70% reduction in greenhouse gas emissions versus fossil fuels. Suitably-qualified HDRD has been incentivized through Renewable Fuel Standard obligations and fuel tax reductions as in the United States or by RED II in the EU. These measures can partially compensate for higher production costs versus traditional diesel.
Total global HDRD capacity was approximately 5 million metric tons (MT) in 2017 compared to 28 million MT of the more traditional methyl ester type (FAME) capacity in the same year. Growth is also set to increase dramatically in North America where the conversion of unused refining volume is playing a significant role and planned capacity is set to reach 15.6 million MT by 2024. Total worldwide HVO capacity could reach 26 million MT by 2030.
HDRD has much improved oxidation stability compared to many FAME type fuels. It is free of less desirable materials such as unsaturates, as well as sulphur and many other trace contaminants such as metals and phosphorus that may be found in FAME.
Unlike FAME, HDRD can be blended in any proportion with conventional fossil diesel fuel. This has become commonplace in European markets as it is a straightforward way to meet renewable fuel blending obligations without exceeding the typical 7% maximum FAME generally allowed in Europe. HDRD density of around 780 kg/m3 is lower than allowed in EN590 diesel fuel which can limit its use in European standard EN590 fuels to blending levels around 30%. EN15940 is used in Europe to define HDRD and other paraffinic diesels both as a blending component and as a finished fuel.
Unlike the EN15940 standard where only some OEMs permit the use of pure HDRD finished fuel, the corresponding US ASTM D975 diesel standard does not have a density limitation. HDRD can be used as a direct “drop in” in the US market fulfilling the requirements for Grade 2-D, subject to OEM acceptance. Pure 100% HDRD is now accepted as suitable for use by many vehicle manufacturers who will have also considered other equipment compatibility issues. It is increasingly used by fleets to meet local environmental requirements or corporate sustainability goals.
There are several operational benefits to the use of HDRD compared to mineral-derived Ultra-Low Sulfur Diesel (ULSD) and FAME. These include high natural cetane number, good low temperature operability with winter grades, the potential for lower emissions, reduced injector deposit formation and greater oxidation stability. Other properties are similar to ULSD, such as fuel consumption, water entrainment tendency, poor natural lubricity and conductivity.
Summary of Key Properties for HDRD
|Usage||100% recommended, or blend with ULSD||HDRD marketed as "drop-in" replacement for ULSD|
|Cetane||>65 - 70||HDRD has significantly higher cetane than available ULSD|
|CP / CFPP||Winter grades: -20°C to -30°C CP||HDRD can meet winter operability even at 100%|
|Emissions||Reduced GHG, hydrocarbon, CO, NOX, CO2, particulate matter (PM)||Renewable feed reduces CO2 by 50 - 83%. Reduced PM emissions may extend DPF regeneration intervals.|
|Fuel Efficiency||Overall very similar to ULSD||Lower HDRD density counteracts higher heating value|
|Fuel Injector Deposits||Lowered injector deposits compared to ULSD but still present||CEC XUD-9 tests show lower level of deposits compared to ULSD|
|Stability||Good oxidation stability||HDRD paraffinic nature superior to FAME|
|Water Entrainment||Similar to ULSD||Good housekeeping and demulsifiers recommended|
|HFRR Lubricity||Meet specs with added lubricity improver||HDRD similar to ULSD|
|Conductivity||As needed with additives||HDRD similar to ULSD|
Although some of the properties of hydrotreated renewable diesel reduce the need for treatment with certain classes of fuel additive, notably cetane improver, other types are still necessary, such as lubricity and conductivity improvers. It remains highly beneficial to use multifunctional diesel fuel additives that control fuel injector deposits, reduce corrosion, fuel foaming and improve water separation.
To continue to educate end users on this often-complicated topic, we have created a series of articles to share on Lubrizol 360 discussing how to improve the performance of HDRD and more.
For more information on diesel fuel, please contact your Lubrizol representative.