|ALLEMAN, TERESA - National Renewable Energy Laboatory|
|CHRISTENSEN, EARL - National Renewable Energy Laboatory|
Submitted to: Fuel
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2018
Publication Date: 12/11/2018
Citation: Alleman, T.L., Christensen, E.D., Moser, B.R. 2018. Improving biodiesel monoglyceride determination by ASTM method D6584-17. Fuel. 241:65-70.
Interpretive Summary: This research revealed that an important standard test method (ASTM D6584) that validates biodiesel quality requires modification to be applicable to biodiesel prepared from increasingly common alternative feedstocks such as field pennycress (Thlaspi arvense) and camelina (Camelina sativa) oils. Implementing the changes recommended by the current study will result in a more accurate determination of biodiesel purity and quality than is currently possible with the standard test method as written. Verification of biodiesel quality is critically important to public acceptance of alternative fuels, so improvements to the accuracy and reliability of standard test methods measuring biodiesel quality are needed. These results will be important to biodiesel producers, distributors, and end-users (customers) because biodiesel quality and purity may now be more accurately determined. This research may ultimately improve market penetration, availability, and public perception of domestically produced agricultural fuels such as biodiesel, thus affording greater independence from imported petroleum-based fuels while simultaneously enhancing rural economies across America.
Technical Abstract: Biodiesels produced from commercial and non-traditional feedstocks were analyzed by ASTM D6584-17 for monoglyceride (monoacylglycerol, or MG) content. It was found that D6584-17 as currently written may not accurately determine MGs from conventional feedstocks due to significant differences in retention time using modern instrumentation. For biodiesel from non-traditional feedstocks, D6584-17 did not sufficiently account for MGs containing fatty acids outside of C16 and C18 species. This led to under- and over-reporting of MGs, as critical components were not accurately measured. Improvements to the method were made through a three-step process. First, a standard mixture of MGs was run to determine the retention time of individual MGs that could be present in the samples from C10 to C24. An additional analysis for the fatty acid methyl ester (FAME) profile was used to determine the major MG species present in the biodiesel samples, using the assumption that the MG profile was proportional to the FAME profile. The biodiesel samples were analyzed by D6584-17, and the MGs were identified using retention time matching, based on the major species expected from measuring the FAME profile. By combining these two methods, the accuracy of MG determination by D6584-17 was improved for biodiesels prepared from all feedstocks.