Biosolids hold untapped potential — using them can revolutionise Indian farming

Agriculture in India is a key sector of the nation’s economy, employing approximately 60 per cent of the population and contributing significantly to the country’s gross domestic product or GDP. However, it faces major challenges such as soil degradation, water scarcity and the overuse of chemical fertilisers, raising concerns about sustainability and environmental health.

Biosolids are increasingly being used in agriculture, either formally or informally, as organic fertilisers, particularly in areas where farmers seek cost-effective alternatives to chemical fertilisers. The use of biosolids could help reduce dependence on chemical fertilisers, lower farming costs and improve soil fertility.

This is particularly beneficial in regions where soil degradation is a concern. However, a lack of infrastructure and inadequate regulatory enforcement limit the safe and effective use of biosolids.

Biosolids are a product of the wastewater treatment process. During wastewater treatment, liquids are separated from solids, which are then treated physically and chemically to produce a semi-solid, nutrient-rich material known as biosolids.

Biosolids generated from Faecal Sludge Treatment Plants (FSTP) are rich sources of nitrogen, phosphorus and potassium — the three essential nutrients for crop production worldwide. India relies on imports to meet its demand for phosphorus and potassium, the reserves of which are increasingly depleting.

When treated and processed, biosolids possess high organic matter content, essential nutrients and beneficial microorganisms, making them excellent for soil health improvement. They can enhance soil fertility, improve crop productivity and reduce reliance on chemical fertilisers. The application of biosolids to land not only helps replenish macronutrients but also micronutrients.

India has approximately 1,024 FSTPs. Estimates suggest that these FSTPs generate around 500 tonnes of biosolids daily. The reuse of biosolids from these FSTPs presents a significant opportunity to convert waste into a valuable resource, contributing to sustainable development and environmental stewardship. 

Biosolids are rich in essential nutrients such as nitrogen, phosphorus, and potassium, which are vital for crop production. Given India's heavy reliance on imports for phosphorus and potassium, biosolids offer an eco-friendly and cost-effective alternative, reducing dependence on external sources.

Several key government missions and programmes, such as Swachh Bharat Mission 2.0 and AMRUT 2.0, are instrumental in advancing this vision, with a focus on sustainability, hygiene, and waste management.

The Waste to Wealth Mission further amplifies these efforts by promoting the creation of valuable resources from waste. It aims to drive innovation and technology-led solutions to efficiently convert organic and inorganic waste into usable products such as compost, biogas, and energy. 

The National Mission for Clean Ganga also plays a crucial role in rejuvenating the Ganga River by reducing pollution from untreated sewage and promoting resource recovery from biosolids.

This reuse aligns with the principles of a circular economy, converting waste into a valuable resource and contributing to the United Nations-mandated Sustainable Development Goals, particularly those related to sustainable agriculture and clean water.

The reuse of treated wastewater and biosolids in agriculture has the potential to reduce greenhouse gas emissions by over 2 million tonnes of carbon dioxide equivalent annually by decreasing groundwater extraction and replacing chemical fertilisers.

There are examples of sludge being converted into compost in wastewater and faecal sludge treatment plants, such as those in Devanahalli (Karnataka), Bansberia (West Bengal), and PNP (Tamil Nadu), and subsequently sold to farmers.

The potential applications of biosolids span several sectors, as illustrated in the diagram below, with a major focus on land application, including reuse in agriculture, forestry and horticulture.

Research has shown that biosolids significantly enhance agricultural crop yields. Numerous studies have reported the benefits of using biosolids for soil amendment and crop cultivation worldwide. Findings indicate that the application of biosolids improves overall crop growth and yield while reducing dependence on chemical or synthetic fertilisers.

At the FSTP in Karunguzhi, Tamil Nadu, biosolids are being reused, generating approximately Rs 20,000 in revenue per month. Both biosolids and co-composted manure from the FSTP are sold to farmers as agricultural fertiliser. Farmers report improved crop yields after using this manure. The remaining biosolids, stored in the sludge storage yard, are used for gardening within the FSTP premises.

At the FSTP in Loni, Uttar Pradesh, the municipality plans to sell biosolids at around Rs 12 per kilogramme to farmers in the near future.

Even states like Odisha are leading efforts in biosolids management through initiatives such as co-composting and advanced drying techniques, demonstrating the scalability and effectiveness of biosolids reuse.

By adopting sustainable practices and integrating biosolids into agriculture, multiple challenges can be addressed simultaneously — improving soil health, conserving water resources, reducing pollution and enhancing food security. The use of biosolids in agriculture can also lower the cost of chemical fertilisers.

Additionally, innovative business models, such as public-private partnerships, can generate revenue for local governments and create livelihood opportunities through the sale of biosolids-based products.

India has recognised the potential of biosolids in agriculture and other sectors through various guidelines and schemes. However, comprehensive national policies specific to biosolids reuse are yet to be developed.

The Fertiliser Control Order (FCO) does not include quality standards for the utilisation of treated municipal or faecal sludge. The FCO (2009, updated in 2013) provides standards only for compost quality, covering parameters such as pH, nutrient content and permissible levels of heavy metals.

The Bureau of Indian Standards (BIS) provides several guidelines related to agricultural inputs, including soil conditioners and fertilisers. While bIS does not currently have biosolids-specific guidelines, general quality standards for organic soil amendments — such as heavy metal content and pathogen control — apply to biosolids to ensure they are safe for agricultural use.

The United States Environmental Protection Agency (USEPA) classifies biosolids into two categories based on their application: Class A and Class B. Class A biosolids are treated to reduce pathogens to below detectable levels and are safe for unrestricted use, including direct agricultural application. Class B biosolids contain reduced pathogens but require controlled application with site restrictions to minimise public health risks.

In India, the FCO and USEPA standards are currently followed in the absence of specific national guidelines on biosolids. The Central Public Health and Environmental Engineering Organisation recently highlighted in a workshop that the government is actively working on establishing standards for biosolids reuse in India. Studies are being conducted to assess the feasibility, benefits and risks associated with their application.

With ongoing population growth and urbanisation, biosolids production continues to rise. Recycling biosolids for agricultural use presents a promising alternative for sustainable sludge management, as they are rich in organic matter and essential nutrients. While biosolids offer significant benefits for soil health and sustainable farming, it is crucial to address associated challenges. Developing a robust regulatory framework, ensuring proper treatment processes and fostering public awareness are essential steps towards integrating biosolids safely and effectively into agricultural practices.

At Delhi-based think tank Centre for Science and Environment, we advocate for a circular economy, ensuring that nutrients from faecal sludge are returned to nature through biosolids reuse for horticulture and co-composting.

By embracing this practice, India has the potential to transform a waste challenge into an opportunity for cleaner and greener cities. However, cultural perceptions and public concerns about the safety of biosolids use in agriculture could hinder acceptance. Addressing these concerns through education and transparent communication is essential for successful implementation.