Viability of a Black Soldier Fly Plant for processing urine diversion toilet faecal waste

Résumé

The eThekwini Municipality (Durban, South Africa) has constructed over 80 000 Urine Diversion Toilets (UDTs) in rural areas of the City. Due to the potential health risks to residents and a precedent of provision of free basic services to poor households, it was decided to provide a safe economically feasible faecal waste emptying service. In 2015 a project was conceptualized by the Municipality to empty UDT faecal waste and bury it on site or use a circular economy approach by transporting the faecal waste to a central processing plant in order to produce valuable products. Black Soldier Fly Larvae (BSFL) technology was selected for the processing plant and a public private partnership was established between the municipality and the technology developer / operator. A preliminary business model based on prior research and certain assumptions was used to design and develop a 20 ton a day processing plant through a grant from the Bill & Melinda Gates Foundation. During the initial planning and design phase it was decided to utilize a relatively low tech approach to the plant in order to reduce capital expenditure, reduce the need for high skill operators and to allow for easier replication. However, when the completed plant started operating in 2017 a number of technical challenges were experienced. Modifications were then implemented to address these challenges which in some cases raised the technology levels being utilized. A market analysis was undertaken and the business model was re-run for the modified process and other new data. Key findings from the amended business model were as follows: A low tech approach is not viable for a large scale processing plant using BSFL technology Legislation does not prohibit the use of human waste as a rearing medium for BSFL but registration and licencing is essential and would be a complex process To achieve viability using the modified process, significant additional CAPEX would be required to upgrade the existing plant Various key model sensitivities were identified which would need to be targeted to reduce opex, increase income and achieve viability For the Municipality the BSFL plant needs to start operating at over $70 per ton profitability before it becomes a more cost effective solution than burial on site. The document provides key lessons from the front end, biology (bio conversion) and back end operations. In addition, the optimized process flow and business model provide an invaluable guide to new players in the BSFL waste processing field. The document illustrates that a circular economy approach initiated by the Municipality requires patience and the use of an iterative learning approach in order to ultimately achieve a sustainable sanitation model.

Citer ce document

Accès au document

Ce document est hébergé sur son dépôt institutionnel d'origine.

Auteur(s)

Statistiques

Consultations : 2

Téléchargements : 0