56.4 Biodiesel, a Carbon Neutral Alternative fuel to Petroleum Diesel

Ihab Farag , Chemical Engineering Department, Chalmers University of Technology, Durham, NH
Biodiesel is an alternative petroleum diesel fuel made from renewable resources such as recycled cooking oils, vegetable oils or animal fats rather than petroleum.  Biodiesel is produced by the transesterification of a vegetable oil or animal fat with an alcohol (methanol or ethanol) in the presence of a catalyst (sodium or potassium hydroxide). Starting material may include: used cooking oil, soybean, corn and canola. Converting biomass feedstock to biodiesel and the use of biodiesel in transportation to replace petroleum diesel supports climate change by reducing the atmospheric CO2 in several ways. Diesel associated emissions are avoided, the CO2 content of diesel remain in storage; and by harvesting new biomass for fuels we provide a mechanism for CO2 absorption by photosynthesis.

Soybean, Canola, and other oil-producing plants tend to be limited to around 100 gallons of Biodiesel per acre of Land. They also require good quality land, thus competing with food crops. Microalgae have a potential to produce 5,000 to 10,000 gallons of Biodiesel per acre of Land. Therefore the UNH Biodiesel Group is investigating microalgae as a potential valuable source of biodiesel feedstock oil. The energy and labor inputs required for growing algae can be substantially less than those for land crops. Microalgae require light, nutrients, and carbon dioxide, and have the ability to grow fast in regular, brackish and salt water. While being grown in a photo-bioreactor, they convert light and produce much more oil per unit area of land compared to vegetable plants. Claims are that some microalgae store over 50% of dry mass of their energy reserves in oil droplets

The UNH Biodiesel group has been studying the growth lipid-rich algae. In addition to nutrients algae require a carbon source.  The carbon source can be CO2-rich flue gas from combustion or aerobic digestion of waste products. The grown lipid-rich algae could then be harvested and used to produce biodiesel. This paper will discuss the UNH Biodiesel Group experience.