At the recently held Global Soils Conference, senior scientists revealed a startling reality — nearly 90 per cent of India’s topsoil suffers from nitrogen and phosphorus deficiencies, and 50 per cent lacks potassium, underscoring a critical soil health crisis across the nation.
This crisis of soil, characterised by erosion, degradation of topsoil and low soil nutrients as well as carbon in India, has major implications for long-term agricultural sustainability.
This World Soil Day, it is time to shift the focus on the importance of soil health in sustaining ecosystems, food security, and climate resilience. Out of the many strategies envisioned for improving soil health, one that demonstrates multiple benefits is that of nutrient circularity.
Nutrient circularity is the process of collecting, processing, and returning nutrients from urban organic waste back into agricultural soil. A multi-solving strategy, it directly replenishes soil nutrients along with reducing the quantum of waste that needs to be managed. For a country that has inadequate options for managing the enormous quantity of waste it generates, nutrient circularity offers an option to realise circularity at every scale.
However, budgetary allocations for waste management in India show that its emphasis is heavily invested on the waste-to-energy sector. There are two types of waste-to-energy (WtE) technologies in operation, one that uses mass incineration and the other that relies on bio-methanation.
Incineration-based plants dominate waste-to-energy (WtE) technologies, accounting for 81 per cent of the total waste treated.
A striking example is Delhi wherein 7,250 tonnes of the total 11,328 tonnes of municipal solid waste (MSW) generated per day is managed through incineration.
Although touted as a solution to the waste problem, incineration-based plants demand high capex and opex while solely focusing on energy production, neglecting other potential problems such as the hazardous ash and other toxic byproducts they produce.
The plants are also highly prone to failure, out of the 14 incineration plants with a total capacity of 130 MW, half have failed over the past several years.
The reasons for the same range from economic unviability (despite subsidies) and the low calorific value of India’s high-moisture waste. Apart from their failure rate, these plants also have significant adverse impacts on public health and the environment.
A recent study found that incinerator-based plants emit significantly more greenhouse gases (1707 g CO2e/kWh) and air pollutants than any other power source (2.4–991.1 g CO2e/kWh), raising public health and environmental concerns.
What exacerbates this issue is the lack of stringent standards and poor regulatory oversight leading to inadequate monitoring and non-compliance with real-time reporting mandates.
While biomethanation plants avoid these risks, they face other significant challenges.
They have a high failure rate, as seen in cities like Bengaluru, Salem and Lucknow, mainly due to poor waste segregation. The process requires highly skilled maintenance and an uninterrupted supply of high-quality waste. Poorly maintained plants not only risk operational failure but also methane leakages, which have a much higher global warming potential than carbon dioxide.
These challenges of incineration and biomethanation-based plants must also be seen in light of the fact that WtE plants in India contribute to only 0.1 per cent of renewable energy generation as opposed to the share of 26 per cent contributed by other technologies like solar and wind. This is apart from the fact that waste-to-energy plants have largely failed to address the primary problem they were intended to solve - India’s waste crisis.
Considering that 40-70 per cent of the waste is biodegradable, an alternative imagination of waste management, by operationalising nutrient circularity may offer a pathway to not only recycle organic waste but also regenerate topsoil and enhance urban-rural nutrient flows.
The organic waste crisis in India is inextricably linked to the flow of nutrients from the soil in the form of agricultural resources from rural to urban areas.
Restoring nutrient circularity would then entail recovering them from urban areas through the process of composting and transporting them to rural areas, thus effectively closing the nutrient cycle. Although municipal solid waste derived compost has lower nitrogen, phosphorus, and potassium content compared to chemical fertilisers, it is rich in organic carbon (about 20 per cent by weight).
Studies have shown that when used along with chemical fertilisers, it delivers optimal results at two-thirds of the cost per hectare compared to chemical fertilisers. This roughly translates to a reduction in production costs by 15–20 per cent.
This approach thus not only enhances soil fertility but also reduces the reliance on chemical fertilisers.
Nutrient circularity did find favour amongst the policy makers which resulted in the Government introducing a fixed subsidy of Rs 1,500 per tonne of compost sold under the Policy on Promotion of City Compost in 2016.
However, the policy failed as it did not address two critical aspects: improving compost quality and creating public demand. There were no efforts to ensure high-quality compost, and the policy lacked testing standards, sufficient laboratories, monitoring protocols, and certification mechanisms. Instead of addressing these issues and fostering the compost market, policy support was completely withdrawn in 2021, with budget allocations reduced to zero.
Currently, all financial incentives, supports, and subsidies are focused solely on bio-methanation.
While the process of biomethanation can also technically achieve nutrient circularity owing to the nutrient-rich slurry it generates, the large scale of the process, costs, complexity, and most importantly lack of mechanisms for slurry utilisation make it less viable.
Composting on the other hand can be accomplished at different scales at a fraction of the cost.
Models demonstrating the effective use of municipal solid waste-derived compost abound. Several cities around the country have devised projects and institutional mechanisms to streamline the transfer of urban compost to rural areas.
Towns such as Chikkaballapur in Karnataka have initiated a city-farmer partnership for solid waste management wherein 759 tonnes of legacy waste was semi-processed into organic compost and supplied to 109 farmers across 17 villages of Chikkaballapur.
Similarly, Alappuzha Municipality in Kerala is implementing a hub and spoke nutrient circularity model, facilitating the transfer of compost generated from the hub (urban town) area to the spoke (rural villages) areas around the town.
However, all these are isolated cases with their execution and implementation contingent on the will of stakeholders associated with the process. What is needed is a two-pronged push for replicating nutrient circularity in other regions of the country. A top-down policy push must be complemented by a bottom-up demand from the public and farmers. Such policy interventions may also improve compost quality, enabling a gradual phase-out of chemical fertilisers.
Nutrient circularity is not a novel concept, a time-honored and adaptable practice, it was how organic waste was (still is) managed across Indian households and homesteads over the past many decades. All that remains is scaling it up, if needed, according to the context of the neighbourhood/ward or town.
And the compost generated will restore not only the soil in the fields in the peri-urban and rural areas, but also the soil in our community and terrace gardens.
Views expressed are authors’ own and do not necessarily reflect that of Down To Earth
Sruthi Pillai is a researcher working at the intersection of sanitation, solid waste management, and climate change. She is currently working as a Research Scientist at the Indian Institute of Technology Bombay.
Rakendu S is a Research Scholar at the Ashank Desai Centre for Policy Studies, Indian Institute of Technology Bombay. She is a Prime Minister’s Research Fellow.