On-road Measurement Of NOx And CO₂ Emissions From Biodiesel Produced From Different Feedstocks
MetadataShow full item record
Biodiesel has generated increased interest in the US and elsewhere recently as an alternative to petroleum-derived diesel. Because it can be produced from domestic feedstocks such as soybeans, canola oil, and even recycled cooking oil, biodiesel can help reduce dependence on foreign petroleum. Due to its high oxygen content, biodiesel typically burns more completely than petroleum diesel, and thus has lower emissions of hydrocarbons (HC), carbon monoxide (CO), and particulate matter (PM). However, biodiesel may increase or decrease nitrogen oxide (NOx) and carbon dioxide (CO₂) emissions, depending on engine type, test cycle, and biodiesel feedstock. Therefore, the purpose of this study was to compare emissions from biodiesel blend 20% (B20) made from various feedstocks, in an on-road setting using a portable emissions measurement system (PEMS) and a chassis dynamometer setting for a test vehicle (1994 Chevy Silverado). The study tested 4 biodiesel feedstocks (soybean oil, canola oil, waste cooking oil, and animal fat) compared with ultra low sulfur diesel (ULSD) using on-road testing under real-world driving conditions with a Horiba On-Board Measurement System OBS-1300 on a highway route and arterial route, and chassis dynamometer with Urban Dynamometer Drive Schedule. Emissions of NOx and CO₂ were measured second-by-second and compared for each feedstock with ULSD. For the dynamometer only, HC, CO, and PM were also measured. Biodiesel fuel specifications from each feedstock were tested and compared. The dynamometer test results showed statistically significant lower emissions of HC, CO, and PM from all B20 blends compared to ULSD. For CO₂, on-road testing (arterial, highway, and idling) and dynamometer testing showed no statistically significant difference in emissions among the B20 blends and ULSD. For NOx, dynamometer testing showed only B20 from soybean oil to have statistically significant higher emissions. This is generally consistent with the on-road testing (arterial, highway, and idling), which showed no statistically significant difference in NOx emissions between ULSD and the B20 blends. The results above are specific to the 1994 Chevy Silverado tested, and cannot be generalized to other vehicles.