Lead researcher, Professor James Clark from the University of York, said that modified microwave technology breaks down waste orange peels into a wide range of useful products, including valuable ingredients used by the food industry, such as pectin, which can then be further refined.
Pectin can also be used to stabilize acidic protein drinks, such as drinking yogurt, and can be used as a fat substitute in baked goods.
The technology uses a large microwave oven to ‘cook’ the chemicals out of the material being recycled, explained the researcher.
His lab is currently building a test system that will process 10kg of waste an hour, but Clarke added that he has also run a system that can handle 100kg an hour. He suggested that a scaled-up, full commercial system could handle as much as 20 tonnes an hour.
The system only needs to work at about 200 degrees, which Clark noted is hot enough to transform the waste and draw off useful substances.
"The unique feature of our microwave is that we work at deliberately low temperatures. We never go above 200C," he said.
Clark said that the idea of the process revolved around exploiting “supply chain residues.” He noted that this could be the waste stream coming from a food-processing plant or a shopping centre, or the high-volume waste materials flowing from mass production agriculture. Orange peels are a case in point, he argued.
"Waste orange peel is an excellent example of a wasted resource. In Brazil, the world's largest producer of orange juice, half the orange fruit is left as waste once the juice has been recovered. This corresponds to eight million tonnes a year of orange peel that can be used," he said.
“We can release the energy and chemical potential of orange peels with microwaves,” he added.
However Clark noted that other potentially valuable waste materials that could be broken down in a similar way include wheat and barley cereal straws, cashew shells, pea pods, apple peels, rice husks and coffee grounds, adding that the ‘green’ approach could help dispose of waste products whilst also turning a profit.
The professor has now set up the Orange Peel Exploitation Company (OPEC). Work is underway scientists in Brazil and Spain to examine ways of extracting value from orange peel, as part of the OPEC project.