Securing reactive nitrogen for high value food and feed production in integrated bioremediation and energy generation systems

Nitrogen has been identified as one of the drivers of global food insecurity, therefore proper nitrogen management will be critical to feed a growing global population, estimated to reach 9 billion by 2050. Inefficiencies of nitrogen use occur at multiple levels within the aquaculture and agriculture production chain, leading to net nitrogen loading in the global nitrogen cycle and threatening the sustainability of the planet in terms of reactive nitrogen pollution. Current technologies to treat nitrogen-rich effluent focus on converting reactive nitrogen to back to its inert form, as nitrogen gas in the atmosphere. However, nitrogen is too valuable to be lost, rather than looking to promote technologies for permanent removal of nitrogen, novel, innovative approaches are needed that focus on the recovery of valuable resources to pioneer sustainable food production systems and catalyse a new revolution in the nitrogen cycle.

This research will develop hybrid waste treatment, protein production and energy generation systems to treat nitrogen rich waste from land-based intensive agriculture and aquaculture systems. These innovative systems are designed to re-use and recycle nitrogen, by converting it into high value protein, in the form of commercially valuable deposit feeders such as sea cucumbers, earthworms and marine worms. These organisms are harvested and processed into human food and alternative feed ingredients for livestock feed. The deposit feeders work in concert with microbial communities naturally present in soils and sediments and their guts, to break down the waste and convert it to high value protein. Carbon is added to balance the nutrients and oxygen is excluded to promote the uptake and incorporation of nitrogen into their cells, where it can be upcycled into high value biomass in the form of sea cucumbers and worms. The energy generated by the microorganisms breaking down the waste is harnessed as a sustainable source of electricity, while the addition of carbon sources and deposit feeding invertebrates will enhance the overall energy generation potential of the system.

Our highly sustainable approach upcycles and remediates nitrogen-rich effluent from aquaculture, by pairing carbon-rich waste streams from agriculture, and crucially, preventing nitrogen loss from the system. This approach aligns current priorities to promote nutrient recycling and encourage value-addition of waste streams in both primary industries. Our approach is revolutionary in that we close the nitrogen-loop and by so doing we displace traditional wastewater treatment technologies that seek to permanently remove nitrogen by converting it back to the atmosphere. The research fellow will use excellent science to demonstrate how simple organisms and waste resources, can be cleverly combined and manipulated to engineer low-cost systems, that provide a myriad of solutions to the current global challenges facing the agro-industry sector. This unique approach tackles head-on a burgeoning 'food security-poverty-pollution' nexus and delivers a unique opportunity to finally close the 'nitrogen-loop'.

Furthermore, the systems are designed to be scalable, transferable and adaptable to a range of different environments and industries. During the course of the fellowship, the systems will be developed in tropical (Mauritius) and temperate (UK) environments, in marine (aquaculture) and terrestrial (agriculture) environments , with technology transfer and lessons learned informing and optimising system design. Our low-tech system offers a simple, low cost option to diversify production in the agro-industry sector, increase revenue, and reduce environmental impacts in the UK and particularly in lower income tropical countries. Furthermore, the large-scale dissemination and adoption of this technology has the potential to correct imbalances in the global nitrogen cycle and secure food and feed production systems for generations to come.

The principal target users of the research and innovation are:
1) Members of the aquaculture industry within the UK and in Overseas Development Assistance countries
2) Government and policy makers
3) Wider public

There is an estimated number of 3 249 enterprises in the UK aquaculture industry. The proposed innovation has a wide range of applications for the treatment of solid and particulate wastes (sediments, biofloc sediments, concentrated suspended solids, sludge) from land-based marine aquaculture, including flow-through, semi-closed, re-circulating and zero exchange aquaculture operations. Commercial private sector beneficiaries involved in the operation of recirculating aquaculture systems (RAS) for the production of high value finfish are the target beneficiaries. RAS operators will benefit from the following economic and technical advantages: no cost to transport and dispose of sludge; reduction in the energy costs and surface area required for filtration systems treatment; reduced nutrient levels in effluent prior to discharge; reduced costs for purchase of buffering chemicals; product diversification to high value secondary crops.

In the UK, the overall findings will be of particular interest to government organisations including UK Marine Management Organisation, Centre for Fisheries and Aquaculture Science (CEFAS). Other beneficiaries in the UK involved in regulating the aquaculture industry, include Natural England, Scottish Natural Heritage, the Scottish Environmental Protection Agency, Natural Resources Wales, JNCC and environmental NGOs. Internationally, a number of global and regional organisations, including the WorldFish Centre and the Food and Agriculture Organisation will benefit from the research through a series of policy and knowledge exchange placements, while the WorldBank and African Development Bank will benefit from the fellow's involvement in regional workshops where she has a proven track record. This range of policy makers and stakeholders stand to benefit from tools such as nitrogen credits; best-practices for aquaculture and agriculture and increased awareness on the potential to increase the sustainability of the industry by harnessing reactive nitrogen to produce sustainable feed ingredients.

As a Small Island Developing State (SIDS), Mauritius is presently highly dependent on imported goods, including fossil fuels for its energy needs and feed ingredients to support the agro-industry sector. Mauritius is aiming to develop the Ocean Economy as one of its main economic pillars, with finfish aquaculture production predicted to increase by 20 000 tonnes, with an investment of RS 1.4 billion over the next 5 years. Innovative solutions for wastewater treatment from land-based hatchery and nursery operations will be critical to ensure that the industry develops in a sustainable manner, while preserving the pristine marine environment the country is famed for. In Mauritius, pig farming is an important economic activity it is one of the most polluting activities in Mauritius since waste management is almost inexistent and wastes are frequently released directly in the environment leading to eutrophication. The Government has a Long-Term Energy Strategy to increase the part of renewable energy in the energy mix to 35% by 2025. This project will expand on the government plans to increase waste-to-energy generation by using pairing waste streams from agriculture and aquaculture. Finally, the project will increase the economic revenues from aquaculture and agriculture, by producing high value protein, including sea cucumbers that can be exported to the Far East and decreasing the cost of livestock feed for local farmers through the development of locally produced alternative protein sources. The wider public, including the tourism sector worth an estimated US$ 3 167 million to Mauritius, will benefit from decreased pollution of the marine environment.