Precious waste

When Shakespeare wrote, “When the hurly-burly’s done,/ When the battle’s lost and won,” he captured perfectly the sentiments of Bengalis after Durga Puja. The biryani and egg roll excesses of the past week are perhaps returning to haunt weak digestive systems, prompting many households to have avid discussions on it at the breakfast table. Excrement, ordinarily excluded from polite conversation, thus becomes a subject of great seriousness around this time. However, this concern about excrement ends with the push of the flush. What happens afterwards deserves some urgent attention because the economic cost of managing human waste is between 5.2% and 6.4% of India’s GDP.

There is also a serious agricultural reason to pursue the matter. A 2024 study estimates that phosphorus in human excreta is equivalent to 21% of the phosphorus applied through mineral fertilisers in India. This exposes an expensive absurdity: nutrients needed for cultivation are lost in a substance that municipalities must pay to dispose of. Recovering nutrients from sewage for agricultural use could reduce municipal disposal costs as well as farmers’ fertiliser bills. Calcutta has practical experience of this connection. In the East Calcutta Wetlands, nutrients from the city’s sewage support fish farming and vegetable cultivation, providing food and livelihoods through a system that requires careful management of health risks. The World Health Organization has described this as “productive reuse”. Elsewhere, too, human waste is being reimagined as something that should not go to waste. In Dhenkanal, Odisha, a project documented by the Centre for Science and Environment combines treated biosolids with organic waste in a ratio of one to three. The reported process takes 45–55 days, after which the compost is screened, tested and sold to government departments.

Turning human waste into safe fertiliser requires collection, treatment to remove pathogens, testing for contaminants and reliable transport to farms. In 2024, the CSE found that a sample of co-compost treated at Devanahalli, Bengaluru, contained copper at 351.14 milligrams per kilogramme against a listed limit of 300 and zinc at 1,660.17 against 1,000. This establishes a primary concern with turning waste into co-compost. Unless properly treated, the waste can potentially do more economic damage than it does now. If a municipality saves on disposal while a farmer receives contaminated compost, the cost is transferred. Owing to pathogens or excess minerals in the human waste fertiliser, the farmer may face soil damage, reduced productivity or additional testing expenses. Safe recovery thus requires funds for routine testing, rejection of unsuitable batches and monitoring after application.

India must also confront an additional and more significant question: who handles the waste? Even though manual scavenging is legally prohibited in the country, surveys record around 60,000 active manual scavengers, nearly 95% of whom are scheduled castes, scheduled tribes or hail from other backward classes. Human Rights Watch’s investigation has repeatedly documented caste-based coercion, including threats and withheld wages against people attempting to leave manual scavenging. Against that history, discovering commercial value in excrement provides little assurance of progress. Indian society has considerable experience of valuing a service while humiliating its providers — think of the quick-commerce delivery executive. Mechanised handling, enforceable safety standards, fair remuneration and contractor accountability are crucial for resource recovery.

The case for recovering value from human waste ultimately depends on who receives the benefits and who bears the costs. Public investment must make safe treatment and dignified employment integral to “productive reuse” of human waste.