Although they have a number of potential uses, spent coffee grounds typically just end up in landfills – or at best, in compost heaps. According to a new study, however, they could soon be utilized to both support and feed biodiesel-producing algae.
First of all, it is already possible to convert discarded coffee grounds into biofuel, without involving algae at any step along the way. It's a fairly complex process, though, reducing the likelihood of it being adopted on a wide scale.
Of course, oils extracted from algae are also already used to produce biodiesel. The algae is usually grown on inert material such as polyurethane foam or nylon, and feeds on nutrients that are added to the water in order to boost its oil production.
In an effort to simplify and streamline things, scientists from Britain's Aston University tried using coffee grounds as both the supporting medium and the nutrient source for Chlorella vulgaris algae. After some experimentation they were successful, obtaining "enhanced biodiesel that produces minimal emissions and good engine performance, and meets US and European specifications."
The best-quality biodiesel was produced by exposing the algae to light for 20 hours each day, followed by four hours in darkness.
"This is a breakthrough in the microalgal cultivation system," said Dr. Vesna Najdanovic, who led the study along with Dr. Jiawei Wang. "Biodiesel from microalgae attached to spent coffee grounds could be an ideal choice for new feedstock commercialization, avoiding competition with food crops. Furthermore, using this new feedstock could decrease the cutting down of palm trees to extract oil to produce biofuel."
A paper on the research was recently published in the journal Renewable and Sustainable Energy Reviews.
Source: Aston University
