Developing Designer Oils for Biodiesel.

Canola and rapeseed (Brassica napus) crops are adapted to cool northern regions and require fewer heat units than soybean or sunflower to reach maturity.  These crops offer US growers outside the soybean belt an alternative oilseed crop that does well in rotation with other small grain cereals.  Canola and rapeseed crops have high oil content, containing between 40% and 44% of oil on a dry weight basis and many US regions are capable of producing over 900 liters of oil per hectare.  Despite several environmental advantages over fossil fuel, biodiesel use is low and the fuel is too expensive.  In addition, high polyunsaturated fats in feedstock oils results in biodiesel with low cetane number and high NO_x emissions.  NO_x is an important smog precursor in diesel exhaust, and is highly correlated (r=0.91) with iodine number.  Biodiesel feed stocks with low iodine number (related to polyunsaturated fatty acids) will result in higher quality fuels.  This is particularly important considering the latest EPA regulations mandate that acceptable NO_x levels were reduced by half in 2007.  Rapeseed biodiesel (with 21% polyunsaturated fats) already has significantly reduced particulate matter and NO_x emissions compared to soy-based fuel (with almost 57% polyunsaturated fats).  Similarly, polyunsaturated fatty acids in soy and sunflower are 57% and 71%, respectively, and biodiesel from these oils have high iodine value and cetane numbers.  A second and equally important factor of biodiesel feedstock oil relates to high saturated fats which cause biodiesel cold flow problems at low temperatures.  Vegetable feed stocks with very high in saturates fats (i.e. coconut and palm oil) produce biodiesel with very high cold flow pour points, and might be solid at room temperatures.  Similarly, soy oil has 15% saturated fats and cold flow pour point of soy biodiesel is -1^oC, while rapeseed oil has less than 4% saturated fats and cold flow pour point of rapeseed biodiesel is -12^oC.  In general therefore, the best compromise for a fuel oil feedstock with good cold flow and emissions characteristics would be monounsaturated oil.  Production, performance and quality of biodiesel have been under study at the University of Idaho since 1979.  Researchers at the University of Idaho have pioneered the use of canola and rapeseed and mustards (Sinapis alba and B. juncea) as a diesel fuel substitute.  Breeding research at the University of Idaho has developed high oleic acid low linolenic acid (HOLL) oils and high erucic acid low linolenic acid (HELL) oils.  The oil from these fatty acid types has low saturated fats combined with low polyunsaturated fats which could make them highly suitable for high quality biodiesel production.   Using predictions based on fatty acid profile, standard canola and rapeseed biodiesel would fail the US ASTM standards for iodine value and cetane number; although both produced significantly better values than soy and sunflower biodiesel.  Similarly, canola and rapeseed biodiesel have significantly better cold flow pour points compared to other feed stock oils.  Biodiesel from HOLL and HELL oils produce a marked improvement in all three quality parameters.  Results from this study will be discussed in relation to the potential impact of these oil types on the US biodiesel industry.