Researchers have found a way to produce high-quality methane gas – a main component of the natural gas used for energy – from the coffee grounds left behind after instant coffee production.
The breakthrough was made as part of a pilot project by researchers at the Paul Scherrer Institute (PSI), a member of the Swiss Federal Institutes of Technology Domain, in cooperation with Swiss food giant Nestlé.
Leftover moist coffee grounds from Nestlé’s instant coffee production were subjected to extremely high pressure and temperature conditions (about 450 degrees Celsius) at an experimental PSI pilot facility. This treatment allowed mineral salts contained in the grounds to be extracted and reused, while the remaining compounds were converted to methane gas using a catalyst.
Around 60% of the energy contained in the ‘spent’ coffee grounds was converted to methane – which could potentially be incorporated into Switzerland’s gas grid, or used to produce electricity.
According to Frédéric Vogel, head of the Catalytic Process Engineering group at PSI, the results of the pilot experiment are just the first step, and show that the conversion of coffee grounds to methane is technically possible. The next step, already underway at PSI, is to field test the method to determine its potential for application as an efficient industrial process.
The researchers are also interested in finding other uses for coffee grounds, including generating high-quality fertilisers from the mineral salts extracted during the processing phase, which contain nitrogen.
The process could also be adapted to other kinds of organic waste with a high enough water content. As a nation, Switzerland produces around half a million tons of organic waste every year, about 11% of which is used to produce energy.
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