Facilitating the circular economy in India’s food security: the social, economic and agronomic barriers and opportunities of sewage

Project summary
This interdisciplinary project combines social and environmental science to quantify the potential benefits of sewage for Indian agriculture, as well as understanding the social barriers to sewage use, and identifying opportunities to overcome these.

Project background
Human sewage is a rich source of nitrogen and phosphorus nutrients, historically exploited as fertiliser for food production. However, it is also a major medium for disease, and efforts to address this is behind the recent construction of hundreds of thousands of toilets across India. These are mostly connected to cess-pits rather than centralised sewage systems, with no treatment (Fig. 1). Additionally, due to the historic social injustices associated with manual scavenging by Dalits in India, there are major social barriers to using sewage. Consequently, this potentially valuable resource is causing dramatic eutrophication of fresh water bodies (Fig. 2) and coastal environments and, instead of closing the nutrient recycling loop, India has increased dependence on manufactured mineral fertilisers. Now, with the drivers of meeting integrated Sustainable Development Goals by 2030, including Goal 2 (Food Security), Goal 6 (clean water and sanitation), 11 (sustainable cities and communities) and 14 (life below water), nutrient recycling from sewage to agriculture is receiving increasing attention. Nevertheless, despite the apparently obvious benefits of sewage nutrient recycling, numerous technical, economic and cultural barriers have limited its implementation. This project aims to test the feasibility of, and barriers to, nutrient recycling from sewage in India, soon to be the world’s most populous country which generated an estimated 62 billion litres of sewage per day, only 30% of which is treated (Rohilla et al., 2017). Whilst a number of studies have researched sewage recycling to agriculture, they have been concerned primarily with physical water resource and water scarcity, rather than on the nutrient content of liquid and solid sewage components which is the focus of this project.

Key research questions
1. What is the scale and value/loss of nutrients associated with sewage in India?
2. What are the barriers (technical/ economic/cultural) to recycling nutrients from sewage to agriculture in India?
3. What are practicable options for generating a circular economy for nutrients in India’s sewage?

Methodology and timetable
Initial work will generate an understanding of the quantity, value and costs of nutrients in sewage in India through a comprehensive review, synthesis and analysis/simple modelling of the published peer reviewed and grey literature, together with a high level understanding of potential technical options to generate a closed loop for nutrients. This might include: the masses and forms of nutrients and the presence of emerging contaminants in different sewage systems; the pathways by which nutrients in sewage interact with environmental receptors; the value of nutrients as a fertiliser versus the costs of environmental impact as a pollutant; and identification of technical options from relevant economies around the world. The scale of the review - whether India-wide or focusing on specific cities or states - will be decided following a pilot study and through discussion with the Indian partners. The next stage of the project will explore social and technical barriers to recycling nutrients from sewage to agriculture in India within one or more case-study areas selected with the support of the Indian partners (ATREE, Bangalore, and Ajoy Sharma CEO - Punjab Water Supply & Sewage Board and Punjab Municipal Infrastructure Development Corporation). It will be accomplished primarily through structured interviews with relevant stakeholders (e.g. government/state agriculture and wastewater engineering departments, community leaders, householders, farmers) identified through a stakeholder analysis. To support this work, it is anticipated that analyses of sewage materials will be required to characterise nutrient contents and availabilities and the presence of other contaminants. The final stage of the project will build upon the understanding of barriers generated above to propose practical and acceptable options for generating a circular economy for nutrients in India’s sewage. This could be informed by examining successful case-studies within and outwith India and conducting targeted interviews of those involved in current case-studies and future potential schemes. The outcomes could be presented as a range of options appropriate for different urban-rural settings and scales.

Year 1. Literature review and analysis to generate an assessment of nutrient quantity and values/costs in Indian sewage. Target paper in Environmental Research Letters.
Year 2. Select case-study areas in India for multidisciplinary stakeholder analysis. Characterisation of sewage materials and social barriers. Target paper in Sustainability.
Year 3. Multi-sectoral analysis of options to recycle nutrients from sewage to agriculture with expert interviews to validate options. Target paper in Nutrient Cycling in Agroecosystems.