It seems like a no-brainer. Take human waste that is unfortunately far too often buried in landfills or dumped in waterways in the developing world, extract nutrients from it for fertilizer or process it into fuel, and sell the resulting products. Not only would this reduce our reliance on fossil resources, it would also help to clean up the environment and boost local economies. So why has this not happened yet?

Working on the business side

Many municipalities are interested in waste-to-resource processes that can contribute to circular economies, but they often lack the money to co-fund reuse and recycling. To achieve self-sustaining solutions requires a robust business plan, based on detailed feasibility studies and accurate forecasts of supply and demand. However, there is a large knowledge gap when it comes to the business side of waste reuse. “Very often, the technology exists but not the business case for using it,” says Pay Drechsel, leader of IWMI’s Rural-Urban Linkages strategic program.

A pioneer in the field of resource recovery and reuse, IWMI has spent the past few years seeking answers to this challenge and practical ways forward. Following the publication of the book Wastewater: Economic Asset in an Urbanizing World in 2015, the Institute published the report Business Models for Fecal Sludge Management in 2016, outlining institutional and business solutions for managing fecal waste. The report forms part of a series on resource recovery and reuse, published by the CGIAR Research Program on Water, Land and Ecosystems (WLE).

“Five years ago, we undertook a review of the reuse of organic waste and wastewater, and the sanitation value chain [the process from waste production to reuse],” explains Drechsel. “We found many papers on technical solutions but hardly anything implemented and then only if highly subsidized. We identified a big knowledge gap linking the sanitation sector, which manages waste, and the farmers or authorities who might benefit from products derived from it.” In short, there was a significant lack of business models and plans.

Human waste value chains

IWMI subsequently investigated how to bridge this gap. In the developing world, on-site sanitation involving the use of pit latrines or septic tanks has potential to provide a valuable source of organic matter, nutrients and energy. This is unlike human waste in the sewered systems of the developed world, which is often mixed with industrial contaminants.

The new report on business models draws on 44 case studies from Asia, Africa and Latin America. These cover either part or all of the fecal sludge value chain, which encompasses: access to toilets; emptying and transport; treatment; and disposal or reuse. Highlighting opportunities as well as bottlenecks, the report elaborates on the institutional matchmaking required to ensure the fecal sludge service chain works.

With fecal sludge rich in organic carbon and nutrients, the best ways to reuse it are to extract energy from it or process it to make fertilizer. Energy can be recovered in the form of gas (and eventually electricity) using anaerobic digestion, where microorganisms break down biodegradeable material in the absence of oxygen. Alternatively, briquettes can be made from dried sanitized sludge for cooking or industrial use. Producing fertilizers and soil improvers requires sludge to be sanitized through anaerobic digestion or aerobic composting; the resulting material is capable of boosting plant growth and enhancing soil health.

Policy influence

IWMI is applying its newfound knowledge on business models for using waste materials in its host country of Sri Lanka, advising the government on how best to incorporate fecal sludge management into the national sanitation policy. In its original draft, the policy did not pay much attention to on-site sanitation systems. Based on its research, IWMI facilitated a revision of the policy to incorporate sound fecal sludge management as an option that complements sewered systems, helping prevent environmental damage from illegally dumped human waste, while supporting resource recovery and reuse.

To determine the capacity of treatment and composting stations or energy-generating plants requires detailed statistics on the number of households, the volume of waste produced, the sizes of septic tanks and pit latrines, and the number of vehicles needed to transport the waste. However, with 2.7 billion people globally relying on on-site sanitation, the raw material supply need not be a bottleneck, and neither is the potential value of the compost or energy produced in question. The challenge is to balance supply and demand.

“Our target is to assist urban settlements with decision support on institutional and financing options to make fecal sludge management viable in different contexts and at different scales,” says Drechsel. “While resource recovery can support cost recovery, there is nothing wrong with public subsidies, as these are justifiable because of the health and environmental benefits of sound fecal sludge management. Every vacuum truck dumping sludge indiscriminately is equivalent to the open defecation of 5,000 people.”