By 2030, world’s total faecal output is likely to contain 100m tonnes of phosphorus, 30m tonnes of potassium, and 18m tonnes of calcium. These are all valuable minerals which if tapped, could be recycled back into the global agriculture system.
In addition, waste emissions such as methane can be converted into electricity through biogas generators, as recently highlighted by a British inventor who built a street lamp powered entirely by dog poo. “Methane is a very versatile fuel,” Longhurst says. “It can be used to generate electrical power, domestic and industrial heating, and even in transport. In the coming years there’s going to be increased pressure for countries across Europe and beyond, who are concerned about climate change, to control methane emissions from animal waste and make greater use of it.”
Waste could also be seen as a valuable asset, though whether it can be exploited by the majority of farmers remains to be seen. “If you’re living in an urban environment, you may not have the space to install a generator and it could seem easier to let your waste wash away,” says Eric Fevre, professor of veterinary infectious diseases at the University of Liverpool. “It also requires access to financing to invest in a generator. And it requires time and labour to use that waste. But the hope is that the cost benefit is greater than the initial expenditure, and so it starts to happen on a larger scale.”
Exploiting animal poo to produce environmentally friendly energy through anaerobic digesters requires vast slurry stores to hold the manure, which are prone to either leaking or collapsing. Investigations have found that a store big enough to hold all the waste produced by 100 cows costs UK farmers tens of thousands of pounds, meaning that for many it’s more economically viable to pay a fine for illegally disposing waste than buying a new slurry store.
At the more exotic end of innovation, some companies are convinced they can take waste and turn it into furniture, paper and even clothing.
These are unlikely to make a big difference. A systemic approach to safe management of this waste is going to be needed.