the price of

a full pit

Problem statement

In dense urban informal settlements, most households use pit latrines or septic tanks, and the unglamorous but decisive sanitation problem is what happens when the pit fills: someone must empty it, transport the fecal sludge, and dispose of it safely at a treatment site. Safe, formal emptying (vacuum trucks or formalized manual services) exists, but in Kisumu, Kenya, fewer than 20% of households were willing to pay the full market price for it — and 62% instead use informal manual emptiers who dig out the pit by hand and dump the sludge in nearby waterways or bury it onsite, recontaminating the very settlement it came from. The problem is a structural gap between what safe emptying costs to provide and what households living on under 100 KES (about $1) a day can or will pay, with cheaper informal operators filling the void unsafely.

Why this matters

Building a toilet is only the first step; sanitation only protects health if the waste is safely managed across its full chain — emptied, transported, and treated — and the emptying link is where the chain breaks for the urban poor. When 62% of households rely on informal emptiers who discharge raw sludge into drains, waterways, and yards, the fecal pathogens cycle straight back into the community via flooding, groundwater, and contact, sustaining diarrheal disease, cholera risk, and child stunting in exactly the settlements least able to absorb them. The scale is large and growing as urban informal populations expand, and the economics are stark: the study estimated that closing the demand-supply gap in one city would require 27.6–40.7 million KES ($276,000–$407,000) per year in subsidy — a sum that, multiplied across the world's informal settlements, defines a major unsolved financing-and-delivery problem in urban sanitation.

What’s been tried and why it hasn’t worked

The dominant assumption — that a functioning private market would emerge if safe emptying businesses were established — has failed on both demand and supply sides. On demand: a single emptying can cost 50–100% of a household's monthly income, and households stated they would pay only about 3,000 KES for manual service against a 7,000–12,000 KES market price, and 2,000 KES for a vacuum truck against 4,000–6,000 KES — so willingness-to-pay sits far below cost, and informal emptiers undercut formal ones by 50–75%, capturing the market by being cheap and unsafe. On supply: vacuum trucks physically cannot reach many latrines down narrow settlement lanes, and refuse to empty pits containing solid waste (trash thrown in alongside sludge), so the formal option is unavailable even to willing payers. And awareness of formalized manual-emptying businesses — the one model that can reach tight lanes safely — was extremely low, so demand never found the safe supply that did exist. The market doesn't clear because cost exceeds willingness-to-pay, the safe technology can't physically serve the terrain, and customers don't know the appropriate-technology option exists.

What would unlock progress

Progress likely requires accepting that pure market provision cannot close this gap and designing a smart-subsidy plus appropriate-technology model: a settlement-scale sanitation plan that channels targeted subsidy to poor households (the study concludes large, ongoing subsidy is unavoidable) while deploying small-bore, lane-accessible manual or semi-mechanized emptying tools that can navigate where vacuum trucks cannot and handle trash-laden pits. The adjacent precedents are smart-subsidy models from rural water and clean-cooking, and appropriate-technology emptying devices (e.g., small pump-and-barrel systems) piloted elsewhere; the unsolved part is integrating subsidy targeting, a viable operator business model, accessible technology, and demand-side awareness into one functioning local system.

Entry points for student teams

An appropriate-technology team could design and prototype a low-cost emptying device that fits narrow settlement lanes and tolerates solid waste in the pit, then cost out an operator business model around it. A market/finance team could design a targeted smart-subsidy scheme — who qualifies, how the subsidy is delivered (e.g., via mobile money), and how it bridges the willingness-to-pay-versus-cost gap — and model the per-household and per-city budget. A behavioral/communications team could tackle the awareness gap, testing how to make households aware of safe formalized emptying and willing to choose it over a cheaper informal emptier. Relevant skills: mechanical/appropriate-technology design, development economics, public health, and behavioral communication.