Wonderful waste as horse poo can be made into plastic substitute

A method by which horse manure can be converted into a sustainable product that could be a substitute for some plastics is in development – and the early signs are very promising.

Perry Robinson (pictured), who has been removing equestrian muck heaps for years, has been working with Professor Mohan Edirisinghe OBE of University College London (UCL), and his researcher Dr Mehmet Aydogdu, to produce cellulose from manure, thanks to a “waste to wonder” process they hope will solve an industry issue and potentially save horse owners money.

The project is at an early stage but the “pressure spinning” technique Professor Edirisinghe invented can produce films, fibres and sheets of cellulose, which has potential to be used for anything from packaging to clothing.

Mr Robinson told H&H he took over his family’s muck heap removal business about 10 years ago, taking the manure to farmers for muck-spreading.

“Four or five years ago, we ran into a bit of trouble with the Environment Agency, because they wanted to stop spreading manure in autumn, the only time we could drive on fields with a muck spreader,” he said. “I couldn’t collect, and the yards were getting full of manure.

“We spoke to the EA and got it reclassified, which alleviated the problem, but it sparked something; I thought, ‘This can’t carry on as it has been,’ because if anything like that happened again, it would be terrible for yards.”

Mr Robinson looked into other ways manure could be used, and came across Professor Edirisinghe’s work using pressure spinning to obtain cellulose from cow manure.

“Cellulose can be used as a plastic substitute,” he said. “Cellophane, pill coatings, food coatings, fibres in T-shirts. I contacted the professor, we came up with a plan, I took some manure, tested it and made it into cellulose. He said it’s amazing, so much better than cow manure.”

Professor Edirisinghe, the Bonfield chair of biomaterials at the UCL mechanical engineering department, told H&H his passion is in developing sustainable, environmentally friendly, energy-efficient materials.

“It’s far better to get things off the grid,” he said. “This process, the pressure spinning, is off the grid. It can be run via battery, coupled to the grid or charged. And whichever dung you think about, it’s waste. It can be troublesome waste, but it can be converted to something economically profitable. That’s a big issue – that’s why I call it waste to wonder.”

Cellulose is found in plant cells, and helps plants stay stiff and upright. Humans cannot digest it but herbivores can, and Professor Edirisinghe’s analysis has shown that horse manure contains more of it than other species’ dung.

Pressure spinning has many similar processes invented by Professor Edirisinghe; this version involves a drum with many nozzles on the surface, rotating on an axis as the nanocellulose in the drum, from the manure, is put under pressure. The nozzles are directed to a water bath, where the jets form sheets, fibres or films, depending on viscosity, of a biodegradable and sustainable material. The process can be scaled up or down, he said, for smaller to mass-production use.

Large amounts available

“I realised from talking to Perry that there is quite a large amount of horse manure available,”  he said. “And this could help the equestrian industry; it’s wonderful waste. We can get something usable; cellulose for packaging or to wrap something, using dung that can be a problem and is just thrown away.”

Only small amounts have been involved so far; Professor Edirisinghe said the next steps are looking at how much dung is available, and using the process on a larger scale. He wants to generate interest and funding to research and develop the project further.

“The process is proven, but when you discover something, you have to find out more and more about it,” he said. “But I think this is a great step forward for the equestrian industry. If you can convert a muck heap into pounds and pence, that’s a circular economy.

“That’s the way the world is now moving, whatever you want to make. The questions are: is this good for the environment? Is this sustainable? Is it energy efficient? Of course it is. And because it’s cellulose that’s come from a natural source, we hope to recycle it so there’s a complete cycle.”

Mr Robinson added that cellulose is used in rider clothing and horse wear, and a long-term aim, as well as saving money for horse owners, is to investigate whether the cellulose produced this way could come full circle and be used by riders, and the horses who originally produced it.

“That would allow the industry to close the loop on a problem it knows well,” he said. “This isn’t about inventing something new, but potentially supplying materials the horse world already uses in a more circular way.”

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