Recycling Coffee Leftovers To Produce Biodiesel, A Big Move To Sustainable Future

Have you ever thought that your coffee leftovers could someday be used to produce biofuel? While the leftovers end up in landfills or are processed as general waste, researchers at Aston University, UK, have produced high-quality biofuel after feeding microalgae (Chlorella vulgaris sp) on leftover coffee grounds. They have discovered that these leftovers provide essential nutrients and a system on which microalgae can grow and flourish. 

Image Credits: Aston University

Extracting biodiesel from coffee leftovers

Traditionally, microalgae are grown on materials, such as nylon and polyurethane foam, that aren’t rich in nutrients. However, growing them on coffee grounds has helped researchers extract enhanced biofuel with low emissions and good engine performance that meets European and US fuel quality standards. Further, they found that growing microalgae on coffee leftovers doesn’t require any extra nutrients. Also, exposing the microalgae to light for 20 hours a day and dark for 4 hours a day created the best biofuel ever. 

“This is a breakthrough in the microalgal cultivation system. Biodiesel from microalgae attached to spent coffee grounds could be an ideal choice for new feedstock commercialisation, avoiding competition with food crops,” said Dr Vesna Najdanovic, the study author. “Furthermore, using this new feedstock could decrease the cutting down of palm trees to extract oil to produce biofuel. In southeast Asia, this has led to continuous deforestation and increased greenhouse gas emissions.” 

Image Credits: Pixabay

Behind the scene

Typically, manufacturers combine coffee grounds with hexane (a petroleum-based solvent used for extracting vegetable oils) and cook the mixture at 60 degrees Celsius for 1-2 hours to extract the essential oils from feedstocks like coffee. Then, the hexane is evaporated, and methanol, an organic solvent used for increasing production yield, and a catalyst, a substance that increases the rate of reaction, are added to produce biodiesel. However, the researchers combined this two-step procedure and eliminated hexane to reduce chemical waste. They discovered that the optimal time to extract the same amount of oil from coffee grounds was reduced to 10 minutes from hours using the combined method. According to them, this technique could help in producing highly efficient biofuel by reducing energy costs and required time. 

“Our method vastly reduces the time and cost required to extract the oils for biofuel, making spent coffee grounds a much more commercially competitive source of fuel,” said Dr Najdanovic. 

The discovery can pave the way to a sustainable future by reducing our dependence on conventional energy resources. 

The research has been published in the journal Renewable and Sustainable Energy Reviews. 

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