Evaluation of Several Horticultural Plants as Biodiesel Crops

Biodiesel is a non-petroleum-based fuel consisting of short chain alkyl (generally methyl or ethyl) esters, made by transesterification of a vegetable oil or an animal fat which can either be used alone, or blended with petroleum diesel in conventional diesel-engine vehicles.  Biodiesel has better lubricating properties and generally higher cetane values than  petrodiesel.  Biodiesel can be produced from any triglyceride, and the predominant feedstock used in the United States is soybean oil, although other vegetable oils, such as corn, mustards, sunflower and peanut can be used.  We are exploring several horticultural crops whose seeds are rich in oil and have potential as biodiesel sources, including coriander (Coriandrum sativum L.), cress (Lepidium sativum L.), meadowfoam (Limnanthes alba Benth.) and flower-of-an-hour (Hibiscus trionum L.).   Compared to soybean oil,  all of the species had higher unsaturated fatty acid levels, with meadowfoam having over 97 % unsaturates.  Flower-of-an-hour oil contained the highest levels of polyunsaturates (which are oxidatively unstable), with coriander having the lowest levels.  Biodiesel was prepared from all four species by reacting the triglycerides with sodium methoxide.  The low temperature fluidity varied among the biodiesels, with coriander biodiesel exhibiting the most favorable cold flow properties.  All four biodiesels had excellent lubricity values compared to petrodiesel, with cress being the best.  Meadowfoam biodiesel was the most oxidatively stable, with coriander biodiesel also having higher oxidative stability than soy biodiesel.  Both flower-of-an-hour and cress biodiesels were significantly less oxidatively stable than soy biodiesel. Our results indicate coriander and possibly meadowfoam show excellent potential as biodiesel crops.