NTPlus - developing the circular economy in agriculture

This project demonstrates the recovery of nutrients from water, decreasing agriculture's dependence on the Haber process for nitrogen fertilisers and the Mannheim process for sulphate fertilisers, helping agriculture move towards net zero. This has the potential to revolutionise nitrate removal, which is carried out where nitrate levels are above safe levels. Nitrate pollution of ground water occurs in regions of intensive agriculture and treatment uses large quantities of salt, producing a brine nitrate waste stream which often has to be tankered to a large waste water treatment works. The salt regenerates the ion exchange resin used to remove nitrate, but the process is typically ~10% efficient. This is an expensive process: in the UK, the structure of the water industry enables the capital and operational costs of plants to be spread over a large customer base, but, in other parts of the world, the water industry is fragmented, prohibiting the wider use of nitrate removal. For example, in the Central Valley in California, over 200 small community water systems have consistently exceeded the maximum nitrate level for over a decade, without a single treatment system being installed.

Most nitrate treatment sites have adjacent farmland - and the farmer applies potash fertiliser, potassium chloride, out of season so the chloride is washed away before the crops are planted. This project will demonstrate regeneration of the ion exchange resin at close to 100% efficiency, producing low-chloride fertigation products containing potassium, sulphate, nitrate, calcium and magnesium, as well as natural fulvic acids (scavenged by the ion exchange system) which improve soil condition and are involved in the transportation of trace minerals in soils. These could be used by a nearby farm in smart (variable rate fertilisation) irrigation, and could become a new product for existing fertiliser manufacturers, enabling them to ship solid complementary additions and make up the liquid products on the farm.

By encouraging the uptake of smart irrigation in the UK, crop yield gains of 10% would be regularly achieved, along with more efficient use of both fertilisers and water. Irrigation use is increasing in the UK to ensure increased resilience to climate change, particularly where irrigation water storage is used, facilitating winter abstraction and the potential to use such facilities for flood mitigation. The amount of nitrate already present in the Vadose layer is substantial (BGS estimate 600 - 1,800M te) and is seen as a 'timebomb' for water sources.

This project turns this problem into a sustainable solution. The products produced have a greater value than the raw material inputs, which enables the potential for exponential growth. Globally, 90 M te of potash is used annually in agriculture. If 10% of this were used to recover nutrients from water, this would reduce chloride inputs to soil and fresh water systems by over 20 M te and reduce CO2 emissions by over 30 M te, with nearly 1,000 M te of CO2 captured in additional crop production.