The world produces an insane amount of coffee each year, somewhere around 16 billion pounds. The grounds are soaked in water, that’s the end of their life. They are not really consumed, only used for a small fraction of their delightful oils and stimulating phytochemicals (read: caffeine). If the grounds are lucky, maybe they end up in a garden or compost heap, but too often, they end up in the landfill.
Research shows that spent coffee grounds could become a viable, inexpensive and pleasant smelling source for biodiesel.
The short version of how it’s made
When you make a cup of coffee in the morning, what you’re really doing is dissolving a bit of the bean into water. Water is a solvent and extracts chemicals and oils from the grounds, giving the water that familiar, pleasant taste. After one use, the grounds are no longer good for preparing coffee; however, a significant amount of oil remains in the grounds. It’s just that it cannot all be extracted by soaking them in water.
To make the biodiesel, chemical solvents more powerful than boiling water are used to extract the remaining oil. Then, the extracted oil undergoes a process called transesterification to yield a usable biodiesel. The resulting coffee biodiesel meets the standards for industrial use.
The impact of coffee biodiesel
Currently, the US consumes approximately 40 billion gallons of diesel fuel each year for road transportation. 75 million gallons (approximately 0.2%) of this is biodiesel made from sources like soybeans and restaurant-oil waste.
It is estimated that 340 million gallons of usable biodiesel could be extracted from used coffee grounds around the world each year. While the amount of biofuel coming from coffee grounds is just about 1% of the current annual US usage of diesel fuel, it doesn’t mean that it’s useless. Likely, alternative fuels will have to come from a variety of sources to be truly sustainable.
Is it green?
This is the true question about any alternative energy. To really know, the manufacturing process will have to be analyzed in detail and compared to existing diesel fuel.
Unlike some other biofuels made with soybeans and corn, nothing has to be grown, and fewer resources are used. It’s green in that sense. Also, since fewer resources are used, it’s less expensive. Cost is important as it is a prohibitive issue for biofuels going mainstream – currently, it is cheaper to use petroleum-based diesel.
The grounds’ life-cycle doesn’t have to stop at biofuel either. After extracting the oil, the coffee grounds were shown to still be usable for gardening and composting, and they can also be used to make fuel pellets for homes.
Narasimharao Kondamudi, Susanta K. Mohapatra and Mano Misra, “Spent Coffee Grounds as a Versatile Source of Green Energy,” J. Agric. Food Chem. 2008, Vol. 56, pp. 11757–11760.
Photo credit: Flickr Creative Commons by trix0r