Coffee grounds for biodiesel

By Yun Xie | Published: November 25, 2008 - 01:36PM CT

Used coffee grounds may be garbage to most of us but, to chemical engineers at University of Nevada, they are a versatile source of green energy. Narasimharao Kondamudi, Susanta Mohapatra, and Mano Misra proposed that the solid waste from coffee brewing can do a lot more than act as compost for gardens. They set out to see if they could extract oils from old coffee grounds and chemically convert those oils to biodiesel.

Spent coffee grounds are about 15 percent oil, which is only slightly less than many of the other biodiesel feedstocks. Since the world produces over 16 billion pounds of coffee per year, there is a constant and cheap supply of solid coffee waste. Kondamudi, Mohapatra, and Misra also predict that biodiesel from coffee grounds would be more stable than those from other sources because coffee contains antioxidants that would slow down degradation.

The researchers extracted oils from Starbuck's spent coffee grounds, and went on to perform a standard transesterification process to convert the oil to biodiesel using methanol (a type of alcohol) and potassium hydroxide (a base for catalyzing the reaction). They were able to convert 100 percent of the oil in the grounds into biodiesel; both the extracted oil and biodiesel were stable for more than a month, which is sufficient for industrial applications.

      
Ground Coffee. 

After the oil is extracted, the grounds can still be used for compost or fuel pellets. The authors estimated that, if spent grounds were converted into biodiesel and fuel pellets in the U.S., it’s possible to make about $8 million in profit per year. On a worldwide scale, based on the amount of coffee that is used, 340 million gallons of biodiesel can be produced from spent grounds.

The authors showed that used coffee grounds are much more than a waste product and can be a source of green energy. Of course, to know if this process is truly green, every step of the conversion would need to be analyzed in detail, but the initial results are promising, especially given that the waste products from the process can be used further as compost or fuel pellets.

Source

Coffee beans for biodiesel fuel

A team of Brazilian engineers has developed a way to make biodiesel fuel from coffee beans. The process extracts oil from the beans for use as a diesel additive much like ethanol in gasoline.

Currently, the coffee-derived biodiesel fuel is being used in tractors and trucks on coffee cooperatives. With technical viability established, tests on commercial-scale production are underway at the Federal University of Minas Gerais.