Turning our mountains of food waste into graphene

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The Guardian

Blended cocoa beans, rice, fruit skins, leeks and asparagus sounds like it should be a recipe for a disastrous smoothie. But these are just some of the wasted foodstuffs that are being treated and converted into materials, with environmental benefits.

Scientists at the City University of Hong Kong have found that they can turn coffee grounds and stale bakery goods – collected from a local Starbucks – into a sugary solution that can be used to manufacture plastic. The food waste was mixed with bacteria and fermented to produce succinic acid, a substance usually made from petrochemicals, that can be found in a range of fibres, fabrics and plastics.

Meanwhile, engineers at the Colorado School of Mines have discovered a way to turn banana peels, eggshells and rice husks into glass. By blending, drying and pounding it into a fine powder, and with a little help from the magic of science, they found the mixture could provide some of the metal oxides required in the composition of glass. Ivan Cornejo, a professor at the university, told the Denver Post at the time that such an innovation could reduce the need to mine for silica, one of glass’s primary components.

Food into graphene

Now, a new EU project, PlasCarb, is researching a way to fashion food waste into graphene. It’s perfectly timed, given the recent buzz surrounding the material and its potential to revolutionise the green industry. The material, discovered in 2004, is so super, Bill Gates is even investing in it to develop an ultra safe condom.

The project uses a process known as anaerobic digestion (AD), where waste is converted into biogas. Finding a new lease of life for food waste using AD isn’t anything out of the ordinary. Businesses have been using the process to make energy for some time. Most notably, early last year, Harvest Power, a Brooklyn-based waste treatment plant, built a digester to deal with waste coming from Disney World. More recently, Sainsbury’s partnered with recycling specialists Biffa to launch their first shop powered by food waste collected from the chain’s stores. But PlasCarb takes the process one ambitious step further.

“Together with an innovative low-energy plasma reactor we convert the biogas from AD, which is mainly methane and carbon dioxide, to graphitic carbon [from which comes graphene] and renewable hydrogen,” explains project manager Neville Slack, from the Centre for Process Innovation.

Beyond the science and technicalities of the process, PlasCarb offers a possible dual advantage over how traditional materials and gases are produced: a happier environment and a commercial use for food waste from a range of industries including retail and hospitality.

“The obvious benefit is taking waste destined for landfills and transforming it into raw materials in a sustainable way,” adds Slack. “Graphene is the latest wonder material. Hydrogen has also been identified as a future transport fuel for a low carbon economy.”

Food mountains

According to the PlasCarb, 95% of hydrogen currently comes from fossil fuels. And some bioplastics produced from crops such as corn are beginning to be deemed unsustainable. The belief is that there won’t be an endless supply of crops, but whether we like it or not, there will probably always be a high volume of discarded food. Growing materials from waste streams could also reduce concerns over how corn-based biopolymers may impact on crop prices, land availability and food shortages.

Graphene and hydrogen from surplus food are desirable alternatives, but despite the exciting prospects they offer, Slack and his team aren’t getting ahead of themselves. There is still a question of scalability and how both small and large businesses could access the technology to deal with their waste. He says the project is still in its infancy – it’s in its second year of its three-year duration – and that the economics of it all need to be ascertained. A pilot trial lasting at least a month will see 150 tonnes of food transformed into 25,000 cubic metres of biogas and then on into the graphitic carbon and renewable hydrogen. The results of this will give the team some indication about future market interest and uptake.

There’s no doubt that, if scaled up successfully, PlasCarb could play a key role in helping prolong food’s life cycle. But Slack suggests that it doesn’t take away from the fact that, in an ideal world, there wouldn’t be any waste at all. Even though the EU has steps in place to improve the situation (including a target to reduce waste by about 30%), estimates indicate that more than 100m tonnes of food is thrown away annually across the union, and this could rise to 126m by 2020 if not enough action is taken.

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