Bangladesh is facing increasing difficulties in keeping its agricultural production levels high because of factors such as an increasing population, soil degradation, higher chemical fertilizer costs, the movement of people to the cities and water pollution. Heavy reliance on chemical fertilisers in intensive farming has resulted in the pollution of the soil by nutrient imbalances and by environmental damage. In various parts of Asia, where amongst them is Bangladesh, night soil has historically been re-used in the process of recycling nutrients. This was achieved through methods including the use of waste which had been composted and open defecation. . Historical records, including Kautilya's Arthashastra, indicate that the agricultural reuse of human waste formed an integral part of pre-industrial nutrient recycling systems in Asia.
Nutrient Value of Human Excreta: The essential plant nutrients can be found in the faeces of humans. Scientific studies show that one person annually produces enough nitrogen, phosphorus, and potassium to grow approximately 250 kg of cereal-roughly the amount required to feed one person for a year. Of all the human waste materials, urine contains a particularly high concentration of nitrogen - a substance which, in fertiliser form, can constitute up to ninety per cent of the nitrogen content of fertilisers used by farmers. Fertiliser made from excreta also contains phosphorus, potassium, organic matter and micronutrients. These help to improve the microbial activity and the physical structure of the soil. Organic nutrients come from natural cycles of the earth and are among the most sustainable sources of plant nutrients available for use. By reusing human waste effluent, nutrient losses in the food production cycle can be reduced, reliance on imported synthetic fertilizers can be lowered, and long-term soil health can be maintained.
Health Risks and Sanitation Constraints: Human excreta, though possessing some nutritional value, is still a risk to health if not treated. Contaminated faeces contains disease-causing viruses, parasites and bacteria. These can cause diarrhoea, cholera or helminthic disease. Lack of a proper system for dealing with faecal sludge in Bangladesh has led to large amounts of such sludge being disposed of in drains, waterways and open ground in an unhealthy way. Densely populated urban and peri-urban areas are particularly exposed to the risks to public health posed by this type of pollution of soil and water. Consequently, the direct application of untreated human excreta is unsafe, making agricultural reuse dependent on effective treatment methods that ensure pathogen destruction and environmental safety.
Co-Composting and Modern Treatment Technologies: One of the most promising solutions involves co-composting where sludge is composted with municipal waste in a controlled atmosphere which is both hot and oxygen-rich. In Kushtia Municipality, a pilot project has shown how urban waste management can include safe nutrient recovery. The first step in this process involves mechanically collecting fecal matter from septic tanks and pit latrines and subjecting it to filtration and drying beds. Compost made from dried sewage sludge is mixed with other garden waste in the right proportions and reaches high temperatures during the composting process which are sufficient to kill off bacteria and viruses.
Studies conducted by the Kushtia project (Kushtia Project implemented by Waste Concern is a well-known pilot initiative in Bangladesh) show that the final compost fulfills Bangladesh's quality standards for pathogens, heavy metals and nutrient content. The treated effluent from this facility is of a standard that it may be used for irrigation. Studies of the finances of such facilities show that revenue from selling compost and collection services for sludge can cover operational costs and more. It also has a positive impact on the environment and health.
Social, Cultural, and Institutional Barriers: In spite of agriculture in the use of human waste being technologically feasible, social stigma and a number of cultural taboos remain major obstacles to its acceptance. Farmers and consumers often view nightsoil as being diseased and dirty, furthered by a lack of knowledge about the treatment processes involved. Worldwide, European countries have also been affected by similar public concerns with regard to the use of sewage sludge in farming, despite the many advantages it offers.
To overcome these obstacles, it is essential to introduce safety regulations, train farmers, and educate the public, with the aid of demonstration projects. Safe sanitation practices require institutions to implement strict standards in order to ensure the community uses safe systems. Furthermore, it is also crucial to invest in the appropriate infrastructure that can treat the sludge produced from human waste.
Role in Sustainable Agriculture and Circular Economy: The recycling of treated human waste in agricultural contexts aligns with the principles of sustainable land use by reconnecting nutrient cycles between agricultural production and urban living. This approach helps to prevent pollution from waste, decreases the pollution caused by the manufacture of chemical fertilisers and improves soil's resistance to drought. In addition integrated waste management systems such as co-composting contribute to a circular economy through the conversion of waste into valuable raw materials. This also creates employment in waste collection, treatment and compost sales.
The utilisation of human excreta in agriculture poses major obstacles but also exciting opportunities for the country of Bangladesh. Night soil which is untreated can pose serious risks to people's health as well as to the environment. However, through the aid of modern technology it is now possible to make the human excreta safe and a nutrient rich manure. This is achieved either by composting or co-composting. In Kushtia, experiments have shown that the successful management of these systems is technically possible, economically sound and environmentally beneficial. In Bangladesh, recycling human excreta after treatment can make a significant contribution to restoring soil health, pollution reduction and long-term food security if accompanied by public education, the appropriate policies and coordinated effort from key institutions.
The writer is Director General (Former), Bangladesh Rice Reseach Institute, Executive Director (Former), Krishi Gobeshona Foundation
