Wake up and use the coffee: how waste grounds could be turned into fuel

Used coffee grounds usually end up in landfill, but this 'golden waste' could power the future

Dr Gopalakrishnan Kumar and Georgeio Semaan are using coffee grounds to produce biogas. University of Stavanger

A strong cup of coffee is one of life’s simple pleasures – and something that more people in the Emirates are enjoying.

Figures from the International Coffee Organisation show imports into the country more than doubled between 2008 and 2018.

This seems appropriate given that coffee drinking is traced back to the Arabian Peninsula and, specifically, to 15th century Yemen.

But our fondness for the caffeine-rich bean leaves vast amounts of spent coffee grounds. Of the more than 10 million tonnes generated globally each year, much ends up in landfill sites.

It is golden waste. It could be turned into value-added products and could create job opportunities

Scientists in the UAE and elsewhere are exploring other ways to use coffee beans, which are rich in energy – 20 per cent of their content is fats or oils – and contain useful chemicals.

Among those working in this area is Dr Eyas Mahmoud of the department of chemical and petroleum engineering at UAE University in Al Ain.

"Spent coffee grounds have been proven to be a potential feedstock to produce biodiesel, biogas, bioethanol, fuel pellets and bio-oil, besides their promising potential to produce bioactive compounds, adsorbents, compost and polymers," Dr Mahmoud and his co-authors wrote in a 2019 paper in the journal Fuel.

The researchers said processing the grounds offered environmental benefits, created jobs and produced many “value-added” products.

It is a complex picture, though, as shown by a 2020 study co-authored by Dr Vesna Najdanovic, a senior lecturer at Aston University in England, who found several environmental pluses and minuses linked to approaches such as composting, conversion into biodiesel, incineration and using landfill sites.

Dr Najdanovic streamlined the creation of biodiesel from waste coffee, which has typically been a two-stage process.

In the first step, they are mixed with the solvent, hexane, and the concoction heated so the oils are extracted before the solvent is evaporated off.

In the second stage, methanol (an alcohol) and a catalyst are added to produce biodiesel. The remaining solid can be burnt as fuel.

By determining the optimal concentrations and ratios of the substances, Dr Najdanovic created a quicker and cheaper one-step process that eliminated the need for the solvent.

“It decreases the investment needed if you can do everything in one pot,” she said.

Energy costs were also reduced, she said.

More than 10 million tonnes of waste coffee grounds are generated globally each year and most end up in landfill. Franco Borromeo / Three Coffee

While research has been going on for many years and scientists and companies have developed numerous "proof of concept" initiatives showing such technology works – even using the biodiesel to power buses in London – major commercialisation appears to be lagging.

“To the best of my knowledge there’s no large commercial use,” said Dr Najdanovic. “From a scientific point of view, its technical feasibility is proven. It now needs to move to the next technology readiness by uptake by the industry.”

An extra push could come from making more use of some of the more than 1,000 chemicals present in waste grounds for the making of, for example, cosmetics or medicine.

Dr Gopalakrishnan Kumar, of the University of Stavanger in Norway, and his postgraduate researcher Georgeio Semaan are employing anaerobic digestion, where microorganisms process the material to produce biogas.

“We’ve been trying to find the parameters at which it would work best before upscaling – the right temperatures, solid-to-liquid ratio, acid concentration and processing times,” said Mr Semaan.

The method generates methane, a gas that can be burnt to produce electricity or to heat houses, for example, or used in further chemical processes to produce valuable substances.

The solid portion generated, which the researchers are characterising, may require additional processing, possibly involving microorganisms again, to produce, for example, enzymes useful in industry. Generating high-value chemicals is, they say, preferable to burning leftover solid as fuel.

“We’re trying to develop a biological process where we can produce both value-added products and fuel products so it can be cost effective,” said Dr Kumar, who has collaborated with Dr Mahmoud at UAE University.

“Rather than one product, what about three or four? That’s why we’re working with biological processes.”

Government support to companies or investment in research could move the industry further ahead and Mr Semaan, who was raised in Kuwait, hopes the technology sparks interest in the Gulf region.

“Gulf countries in the Middle East are more than willing to invest in new technologies if they see the benefit in it for them in the long term,” he said.

“The idea is to start implementing it and talk about it and raise awareness in these countries.”

Dr Kumar also thinks that over the next five to 10 years, as the technology develops, commercialisation could happen in earnest.

“It’s golden waste. It could be turned into value-added products and could create job opportunities,” he said.