Calculation of Heating Value for Diesel Fuels Containing Biodiesel

Biodiesel, a fuel comprised of mono-alkyl esters of long-chain fatty acids also known as Fatty Acid Methyl Esters(FAME), derived from vegetable oils or animal fats, has become an important commercial marketplace automotive fuel in the United States (US) and around the world over last few years. FAME biodiesels have many chemical and physical property differences compared to conventional petroleum based diesel fuels. Also, the properties of biodiesel vary based on the feedstock chosen for biodiesel production. One of the key differences between petroleum diesel fuels and biodiesel is the energy content. The energy content, or heating value, is an important property of motor fuel, since it directly affects the vehicle fuel economy. While the energy content can be measured by combustion of the fuel in a bomb calorimeter, this analytical laboratory testing is time consuming and expensive. It would be more convenient to estimate the energy content from other commonly measured fuel properties. Several standardized empirical methods have been developed in the past for estimating the energy content of hydrocarbon fuels such as gasoline, diesel fuel, and jet fuel. However, with the addition of biodiesel to petroleum diesel fuel, the estimation methods developed for hydrocarbon diesel fuels are not very accurate for use with biodiesel blends. This paper summarizes heating value test results from different biodiesel blends representing the most common biodiesel feedstocks. New lower heating value predictive model equations are proposed for diesel fuel blends containing biodiesel and the results from standardized measurement tests are compared to the calculated values. This paper expands the scope of the empirical equations proposed in the SAE paper 2010-01-1571 for gasoline-ethanol blends to cover diesel fuel blends containing biodiesel.