Trend of Biodiesel Feedstock and Its Impact on Biodiesel Emission Characteristics

Feedstock for biodiesel production has changed over time and it varies depending on regions. Reports and journal articles on biodiesel feedstock resources over the last decade from 2006 to 2016 were reviewed in this article. The regional trends still maintain as the USA and the EU still predominantly use soybean oil and rapeseed oil, respectively, and palm oil is the major source of biodiesel in Asia. It is expected that the food-crop based biodiesel will continue to be dominant for the next decade. However, it was found that uses of animal fats and used cooking oil are increasing both in the USA and the EU. Because of the increasing diversity in feedstock inputs to biodiesel, it is necessary to better understand the effects of feedstock characteristics on engine performance and emissions. In this review, we limit the reports on biodiesel emissions to those who used 100% biodiesel combusted in a one-cylinder, four-stroke, direct injection engine set up in a laboratory. All the emission results were obtained from the same or similar engine conditions to fairly compare them. CO, CO2, NOx, and PM emissions are compared between the biodiesels derived from soybean oil, rapeseed oil, palm oil, jatropha oil, used cooking oil, animal fats, and algal oil. It was found that more emission studies are needed for algal biodiesel. More in-depth studies are necessary for PM characteristics including the compositions of trace metals, elemental and organic carbon. (C) 2017 American Institute of Chemical Engineers