Economic evaluation of faecal sludge disposal routes
Funded by: Bill & Melinda Gates Foundation
January 2013 – September 2013

Partner organisations: eThekwini Water and Sanitation, Partners in Development, EAWAG

Project description
Given the PRG’s involvement in the Mechanical Properties of Faecal Sludge study, and a WRC funded study on the LaDePa (Latrine Bio-solids Dehydration and Pasteurisation) machine , the Bill & Melinda Gates Foundation (BMGF) contracted the PRG to carry out an economic evaluation of the LaDePa machine and total combustion processes for sludge disposal and/or re-use. This economic evaluation developed a flexible economic model that enables a total cost comparison of the processes to be carried out, from the latrine pit to the point of end disposal or sale of the treated sludge product. The model is intended for decision makers to evaluate the two routes for the management of pit latrine sludge, taking into account different local conditions, e.g. the distances between pits, frequency and cost of pit-emptying, the nature of the sludge removed, transport and processing costs and the local market value of the end product. 

In developing the model, the study accounted for the actual costs of the collection of VIP sludge by contractors in Durban, and the capital and the operating costs incurred by the eThekwini Water and Sanitation LaDePa machine. The input data was sufficiently disaggregated so that the resulting model is usable in situations and circumstances other than those currently prevailing Durban. The project consists of producing an Excel spread sheet model describing the costs of collection, transport, processing and final disposal of faecal sludge from pit latrines. 

The two end-processing techniques were selected: 
  1. pelletizing, dehydration and pasteurisation and
  2. incineration, which could be sold for agricultural or other uses, or disposed to landfill. 

The project activities were divided into five phases. 
  • Phase 1 of the project outlined the process for the development of the model; compiled the currently available data on the LaDePa process; produced a first draft of the input and output fields to the economic model; and compiled the list of required data inputs to the model and sources to be reviewed to provide these inputs. 
  • In Phase 2, the project team further developed the economic model, detailed the logical structure behind the model, and initiated the research to source the required input data for the model. These input data has been derived from sampling and analysis of raw sludge and LaDePa pellets, valuation of the agricultural value of the pellets, and the sourcing of faecal sludge management economic data from outside of the eThekwini context. 
  • Phase 3 involved continued development of the model, including detailed information on the agricultural benefits from the use of LaDePa pellets. 
  • Phases 4 and 5 focus on applying the model to data collected from Dakar, Senegal, which contains much different properties to the faecal sludge collected from VIPs in eThekwini Municipality. The final report was submitted in October 2013.