As demand for petroleum based products are on the high, demand for biodiesel is also on the rise. The more biodiesel we produce, the more we need to look into feedstock issues and diversify the portfolio of available feedstock. The more expansive and renewable the feedstock is, the safer and more secure we can be about a future fueled by animal fat or plant oil.
Demand vs produce in U.S.: The market demand for biodiesel in the United States is on the rise. Though the oil prices have dropped, more and more consumers are taking to biofuel as an alternative source. However, the country is behind Europe where about 2% of road transportation is on biofuel compared to the 0.5% of it in the United States. It has been gathered that biodiesel production has doubled (in fact tripled) in the country starting from 2004. While 2004 saw a biodiesel produce of 25 million gallons, 2005 saw a rise to 78 million gallons and 2006 topped it all with 300 million gallons. Approximately 700 million gallons were produced around 2008. This increased demand has pushed the industry to seek innovative feedstock for biodiesel.
Tallow as feedstock for biodiesel: Though several researches are on, the biodiesel industry has so far found no ’silver-bullet’ feedstock that can meet all the growing demands of the industry. Animal fat like tallow is an appealing feedstock, but it too comes with a lot of ifs and buts, issues and considerations. To make animal fat a potential feedstock, the industry aims to collaborate with the livestock and rendering industry in the proper purification and preparation of tallow fat for biodiesel use. Though filtering impurities would be a major job, other considerations need to be addressed before making animal fat as a continual feedstock for biodiesel industry. Below are a few issues faced by the industry in making tallow fat perfect for biodiesel production:
1. Processing hiccups: Tallow is processed into biodiesel through a process called transesterification. An alkaline catalyst like Sodium Hydroxide is used which is dissolved in methanol and then mixed with feedstock. While animal fat melts between 40 to 50 degree Celsius, methanol boils at 60 degree Celsius. This would mean that there will not be enough methanol for the transesterification of fat into fuel. Due to this, the temperature should always be kept under 60 degree during the process.
2. Soap formation: Since tallow is highly sensitive to the catalysts, it can result in soap formation or the formation of a thick glob. The more the presence of Free Fatty Acids (FFA), the more soap is formed. To avoid this production loss, the amount of FFA in the fat should be reduced using sulphuric acid as catalyst. When the content of FFA reaches less than 1%, the normal alkaline-based process can take place, using methanol and lye as catalyst. Better than all this is to process a feedstock that has lesser amount of FFA.
3. Glycerol sediments: Glycerol which forms as sediment at the base after transesterification cannot be removed from settle tank easily. It takes a special process to remove glycerol from the produced biodiesel and impurities or fat.
4. Higher freezing point: The Cold Filter Plugging Point (CFPP) can be higher in biodiesel produced with tallow than the one produced with vegetable oil. This may cause poor quality ignition in cold weather. To avoid this, it is necessary to blend biodiesel from animal fat with biodiesel produced from plants (like rapeseed oil).