It’s common knowledge to anyone who’s spent time around a kitchen that vegetable oil is flammable. What’s not so commonly known is that when Rudolf Diesel developed his engine back in the 1890s, it was designed to burn multiple fuels, including vegetable oil. He was under the impression that someday farmers would be providing both food and fuel. Now that the fossil fuel heyday is mostly behind us, his prediction is being fulfilled. Somewhere around 2001, I caught the biodiesel bug.
It seemed like the perfect way to offset my energy costs and reduce my reliance on fossil fuel. I had a diesel generator for backup power and was thrilled when my first batch of biodiesel burned with the smell of French fries in the exhaust, providing electricity for my house. All it took was a little time. Okay, it took a lot of time. But the fuel was nearly free and I could hardly resist.
What Is Biodiesel?
B iodi e s e l is v e g e t a b l e oil that has been chemically modified to remove the heavy glycerin portion of the oil. This allows it to flow freely at temperatures down to around freezing, while straight (unmodified) vegetable oil must be heated to 120°F to flow freely through filters, injectors, and burners.
Both vegetable oil and biodiesel can be used in place of diesel fuel, home heating oil, and kerosene for use in diesel engines and oil-fired heating equipment. Using biodiesel requires processing the vegetable oil, but no changes to the vehicle or burner are needed. Straight vegetable oil (SVO) requires modification to the fuel system.
Biodiesel is chemically described as a mono alkyl ester. It can be used in its pure form or blended in any concentration with petroleum diesel. It can be made with vegetable oil, animal fats, or recycled (waste) fryer oil from restaurants. The oil is filtered and mixed with methanol (methyl or wood alcohol) with the aid of a lye (sodium hydroxide) catalyst to complete the chemical process known as transesterification. Transesterification is the chemical transformation of one type of ester to another.
Other alcohols, such as ethanol, can be used in place of methanol, and potassium hydroxide can be used in place of sodium hydroxide. These ingredients are less hazardous to work with, but the reactions are more sensitive, and the biodiesel yield is generally lower. Most commercial biodiesel makers and home brewers use methanol and sodium hydroxide.
