New ASTM Specification for Low Metals Grade of B100

ASTM International has approved a new Low Metals (LM) grade of biodiesel in D6751

ASTM International has approved a new Low Metals (LM) grade of biodiesel in D6751, the ASTM specification for low-carbon B100 biodiesel used as a blend stock with middle distillate fuels such as diesel fuel. The new performance standard bolsters confidence in the fuel for original equipment manufacturers (OEMs), fleets and end-users, providing further evidence that biodiesel fuel quality is high, continually improving and meeting robust quality standards.

Throughout its 30-year history, the biodiesel industry has led cooperative research projects with OEMs and leading research institutions to determine if the ASTM specifications for B100 needed to be modified to ensure that biodiesel blends would perform reliably and effectively when diesel fuel or diesel engine regulations changed. This latest round of research followed that same strategy to test the impacts of B20 on the long-term durability of diesel particulate filters in New Technology Diesel Engines (NTDEs) outfitted with modern Selective Catalytic Reduction (SCR) and Diesel Particulate Filter (DPF) aftertreatment.

Recently completed research by Clean Fuels Alliance America with Southwest Research Institute and the National Renewable Energy Laboratory compared long-term (over 1,000 hours of accelerated aging) impacts of NTDEs running on B20 with a lower level of metals - equivalent to B100 containing a total of 4 parts per million (PPM) for sodium, potassium, calcium and magnesium - to the impacts of conventional ultra-low sulfur diesel.

The results indicated that biodiesel containing a maximum of 4 PPM total metals resulted in ash that was similar to that deposited by the ULSD, exhibited a similar ash cleaning removal efficiency, did not have a negative effect on DPF pressure drop or regeneration rates, and did not appear to have any deleterious physical effects on the DPF substrate. These studies were recently presented at the SAE Congress in Detroit in April and published as SAE Papers 2023-01-0297 and 2023-01-0296.

The work was instrumental in the passage of a successful ballot by the ASTM D02 Fuels Committee to approve a new Low Metals (LM) grade of ASTM D6751 biodiesel with a maximum of 4 PPM total metals (Na+K+Ca+Mg), down from the existing grades which allow up to 10 PPM total metals.

A final contributing factor to the persuasive technical data required to modify ASTM specifications has been the biodiesel fuel quality report published by the National Renewable Energy Lab (NREL). According to the most recent NREL report from June 2022, the current average of B100 total metals (Na+K+Ca+Mg) in the marketplace today registers below 1 PPM total, well below the 4 PPM specification recently adopted in the new LM grade of biodiesel at ASTM.

The rigor of these cooperative research efforts and the positive results, along with the already low level of metals in commercial production in the field, bode well for biodiesel use in the new Ultra-Low Emissions Diesel Engines (ULEDE) coming to market in 2027-2031.

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