We are faced with meeting the agricultural demands of a growing population estimated to reach 9.8 billion people by 2050 on soils depleted of essential nutrients, with declining yields and a projected reduction in future rainfall in key agricultural regions. A circular economy between agriculture and organic waste streams can recycle essential resources for farming through the recovery of water, biomass, and nutrients from sanitation waste solids, effluents, and livestock manure at scale. This offers benefits to agroecological practices in farming by reducing the reliance on chemical fertiliser inputs with multiple benefits that improve soil health, reduce greenhouse gas emissions from farming, and reduce water pollution in drainage from fields.

However, there are potential risks and challenges associated with this solution and these need to be fully understood to enable resource recovery to operate in a safe and sustainable manner in the long term.

Firstly, the gastrointestinal tracts of humans and animals are a source of pathogens to the environment and agriculture food chain. So, reusing these wastes could potentially spread these pathogens to the food crops we consume. Secondly, manure and sewage are sources of veterinary and medical chemicals to the environment; these compounds can enhance a microbe's ability to resist treatment drugs, such as antibiotics. This ability to resist treatment drugs can spread to other microbes important for plant, animal, and human diseases.

Antimicrobial resistance (AMR) is a global public health crisis that is predicted to cause 10 million deaths per year by 2050. Currently, livestock and the environment are recognised as reservoirs of antimicrobial resistant microbes and implicated in the dissemination of these AMR microbes. Science-based methods to assess the environmental, livestock and human health risks of combined exposure to antimicrobial selective compounds and AMR microbes are therefore central to fully realising the potential benefits of a sanitation-agriculture circular economy.

Models, analytical tools, and quantitative assessment methods to understand, measure and assess the impacts of agricultural exposure routes urgently warrant scientific attention. Through understanding the safety risks recycling waste streams pose, new interventions can be devised to minimise these risks, making resource recycling a viable mechanism to increase soil and farm productivity. Working with water utility companies and the National Pig Centre, we will investigate how water and farm waste can be recycled to be used in agriculture. Using laboratory models, we will identify where pathogens and chemicals aggregate along the different waste streams, thus identify where interventions need to be made. Using this information, we will define a risk assessment analysis to tackle pathogen and chemical buildup. We propose to build on the 'one-health, one environment' approach to AMR by acknowledging the connectivity between humans, animals and the environment. This project will support the development of a UK sanitation-circular economy and build a UK-led innovation network with global reach.

The overall aim of the project is to build a community of educational, industry, farming, and government colleagues to increase the capacity of the UK to address global pollution challenges associated with adopting a circular economy to support agricultural production. A circular economy approach is essential in meeting global agricultural needs, especially enhancing the role that farming can play in climate control and our need to move towards Net Zero greenhouse gas emissions. This proposal will pave the way in achieving this goal whilst minimising the impact of utilising waste materials on the environment and animal and human health.

Technical Abstract:
This project addresses the impact of landscape scale transitions from mineral to organic fertilisers, considering livestock and sanitation resources as drivers of antimicrobial resistance (AMR). We must understand the innovation in agronomic practices required to realise agroecology benefits whilst managing any potential risks with appropriate mitigation measures. This project will build new interdisciplinary and cross-sectoral capacity for research and innovation (R&I) benefits to reduce pollution emissions, their associated health and environmental risks, including AMR, and contribute new perspectives to an agricultural net zero. Stakeholders and researchers engaged in key sectors of the circular system (farming, wastewater, food/feed supply, environmental management) will collaborate to translate conceptual models into quantitative analytical tools and risk assessment methods, extending fundamental research horizons beyond the current paradigm of environmental flows. A stronger biological framing of these flows will be developed, working across a molecule to landscape scale. Novel data identifying sources of organic waste, their loads of AMR-drivers and microbial reservoirs of ARGs, processing streams for resource recovery, and their introduction into farming systems will be delivered. This project provides much needed thinking on the flow of antimicrobials and ARGs from the microbiome to the food-chain and wider landscape. Consideration of antimicrobial related risks associated with adopting circularity in agricultural production is currently missing in the UK. Designed to realise impact beyond academia with outputs directly informing challenges faced by stakeholders, outcomes include new demand-led R&I capacity, focussed on novel solutions to enable sanitation-agriculture-food circular economy, contributing knowledge, practice and policy to accelerate the safe development of a sanitation-agriculture circular economy towards net zero food production.