Nutrients like nitrogen, phosphorus, and potassium are a double-edged sword. As key components of fertilizers, they are essential for life on Earth, but become a threat to human health and the environment when they are in excess and run off into water courses and wastewater. With half of the world’s food security dependent on nitrogen and fertilizer use, the urgency to find a balance is further exacerbated by the prediction that the world population will reach 9.7 billion in 2050. “We are made of nutrients, we eat nutrients, and we need nutrients to live, but the question is how to do that sustainably,” points out Professor Mark Sutton, Vice-Chair Global Partnership on Nutrients Management (GPNM), and Environmental Physicist at the UK Centre for Ecology and Hydrology. “Our current use of fertilizers is extremely inefficient, wasting a lot of valuable resources and creating a whole load of pollution problems. So, how are we going to carry on feeding the world's growing population healthily, while working towards to a more efficient world with less pollution, and less waste of valuable resources?”

According to the figures of a recent UN report, wastewater is a growing health and environmental threat, “today accounting for almost as many warming emissions as the aviation industry.” Yet, besides tackling pollution and resource depletion, properly managing wastewater could also provide alternative energy to half a billion people and irrigate an area equal to almost the size of Paraguay. “The efficiency of the system is very low,” confirms Sutton. “Take the nitrogen produced in the world, for example: only 20% of it ends up in our food, whilst the remaining 80% gets lost. We're speaking of some 200 million tons, which means some $600 billion in the current prices, tripled following the Ukraine war.” Despite its huge potential, wastewater is currently allowed instead to contaminate the ecosystems we rely on, acknowledged in August, Leticia Carvalho, Principal Coordinator of the Marine and Freshwater Branch of the United Nations Environment Program (UNEP). Hence, her call not to “let the opportunity simply disappear down the drain”: “It’s time to realize the promise of wastewater as an alternative source of clean water, energy, and important nutrients,” she said.

Recovering nutrients from different kinds of wastewater to produce sustainable bio-based fertilizers is indeed the goal of the European project Walnut. “When wastewater is treated, not all contaminants are removed, or at least not sustainably. Compared to current practices, we embrace a circular approach and not only remove but also recover nitrogen and phosphorus,” says its coordinator Francisco Corona Encinas. Low energy-consuming processes and technologies aimed at eliminating waste and reducing the environmental footprint will soon be validated in five pilot plants in Spain, Belgium, Hungary, and Greece. “Two of them will treat industrial wastewater, with one of them focusing on agri-food waste; a third and a fourth one respectively urban wastewater and the brine issued from the demineralization plant, and the last one the sludge obtained by the urban wastewater treatment,” he explains. Yet, the value of wastewater is still largely underestimated, acknowledges Riccardo Zennaro, Program Management Officer at UNEP, in Nairobi, Kenya. “Unfortunately, wastewater is often neglected, and not yet high on the agenda of many governments and institutions. And this is a major issue we suffer from a lot.” Hence, a platform that Corona Encinas and his team have recently launched, to foster the uptake of nutrient reuse. 

“It’s a kind of virtual marketplace where the supply and demand of nutrients and wastewater can meet, together with all the main actors of these value chains: the industries that generate the wastewater, the managers of the treatment plants, the farmers, and the companies that will use and commercialize the biofertilizers,” he explains. According to Maria Kyriazi, Project Manager and researcher at the National Technical University of Athens that developed it, the platform primarily aims at supporting “an industrial symbiosis” of all the stakeholders. “Its role is to get them together and allow them not only to promote a market for wastewater, but also to share knowledge, consulting, and experiences.” Despite being available worldwide, this online tool is especially intended to embrace a “glocal” approach, she says: “Our goal is to extend its scope as much as possible,” says Kiryazi. “Yet, as costs and environmental impact of transportation are very high, the idea is to foster local clusters, thus also reducing the distance between providers and clients, and cutting emissions.”

Nevertheless, costs go considerably down when you increase the size of the processing unit, argues Chris Thornton, Coordinator of the European Sustainable Phosphorus Platform. “So, making hundreds of thousands of tons of fertilizers in one big centralized factory is much cheaper than making a few hundred tons in many decentralized recycling units.” Profitability is indeed one of the major concerns, preventing the sector from adopting such circular practices. “The existing technologies to recover nitrogen have high operational and investment costs, which makes their implementation difficult and expensive,” explains Corona Encinas. “But we will demonstrate that our biofertilizers can be competitive not only from an agronomical but also from an economic point of view.” It will then also be crucial to educate the stakeholders involved, he says: “We need to raise awareness on these new practices. Farmers and other players must all be first informed of what biofertilizers are, and then also about their potential and benefits, compared to traditional ones.” Biofertilizers will certainly not replace synthetic ones overnight, but Sutton is confident that in the years ahead, nutrient reuse will become more and more attractive. “If half the nitrogen waste in the world will save you $300 billion a year, it means that there are markets to be developed. But these markets need investment, and, the more we invest, the more of them will make it to profitability more quickly."

Also for the sake of human health, experts are unanimous in acknowledging that one of the most pressing issues is to finance the infrastructure needed. “When the infrastructure to collect and treat wastewater is not there, it means that that same wastewater will end polluting the environment, with repercussions for human health too,” points out Zennaro, stressing the commitment of the European Union in addressing nutrient reuse and “working towards a more sustainable future”: “The EU directive on urban wastewater treatment currently under revision sets even stronger objectives. It is a great step for Europe and a very good starting point the world could take inspiration from. Yet the question remains: will it be enough on a global level?” Politics will have to play its share, but to put all the odds on our side we need first and foremost a cultural shift: “We need to break the mould and change first our language, because the concept of a ‘waste sector’ is so strongly embedded in European society,” says Sutton. “What we called waste in the past, is a resource for the future.”

Contacts:

Project coordinator:
Francisco Corona Encinas, PhD FUNDACIÓN CARTIF - fraenc@cartif.es
Communication Manager:
Francesco Agresta, ICONS - info@walnutproject.eu

Project website: https://walnutproject.eu/   
LinkedIn: WALNUT
Twitter: @walnut_project