Poo to food breakthrough could boost farm to fork security
14 Feb 2020
Phosphate vital for agricultural fertiliser could be produced on an industrial scale from sewage sludge, thanks to new research.
A Sheffield University researcher is developing techniques to enable extractiontoxic heavy metals from sludge, to leave behind phosphate and help alleviate the global demand for the non-renewable, finite resource vital to the world food supply chain.
With the aid of mining techniques, chemical and biological PhD student James Bezzina, is being funded by the university’s Grantham Centre for Sustainable Futures in his attempt to convert waste water and sewage sludge into a sustainable resource with the aid of mining techniques.
Said Bezzina: “We want to answer the question of how you feed a growing and ageing population sustainably. We need to be focusing on long-term, cost-effective sustainable solutions to solve the phosphate crisis so that we can ensure global food security for generations to come.”
His technique involves the use of tiny beads of microplastic, which act like a magnet and attach themselves to the heavy metals particles in the sewage sludge. By sieving the beads out, he can remove the heavy metals simultaneously.
We need to be focusing on long-term, cost-effective sustainable solutions to solve the phosphate crisis
James Bezzina, PhD student, Sheffield University
As the metals burn different colours, Bezzina can then employ flame analysis to distinguish and separate them.
“The recovery of heavy metals such as silver, copper and zinc from sewage sludge could potentially be very lucrative,” explained Bezzina.
“The estimated economic value from a community of 1 million people in the United States equates to around $8million. Therefore, in addition to taking a waste product and converting it into a sustainable resource, my solution also has the potential for economic viability.”
Phosphate use in fertilisers has quadrupled in the last 50 years, due to global population growth. The main source of phosphate for fertilisers is mined phosphate rock, with scientists predicting no more than 370 years’ worth of reserves are left, with no viable substitute.
Human waste and industrial effluent provide sewage rich in phosphate and nitrogen which are both essential for fertiliser, increasing interest in the potential reserves found in sewage sludge and waste water.
Sewage sludge is already reused as fertiliser for some types of agriculture and forestry, but the UK imposes strict regulations against using for crops or animal grazing because of the toxic heavy metals present. This results in most sewage sludge globally being discarded untreated in landfill, which can harm the environment.