A key aim of the trials is to prove that by mixing different kinds of waste with human waste, the calorific value of the overall mixture can be made high enough so that pyrolysis generates enough energy for the whole system. The goal is to find the highest ratio of human waste to supplementary waste for each different combination.
Cranfield University has completed a market assessment of the wastes that can be found in developing cities. This concluded that the following list of waste streams are readily available and can be pyrolysed alongside human waste to provide extra energy:
Trials will be carried out in the UK on a sewage treatment works in 2014 using real human waste. The supplementary waste streams will be acquired in the UK and we will ensure that the characteristics of this waste are as close to those found in developing cities as possible.
How were these supplementary wastes chosen?
A list of six study cities was compiled in order to provide a global perspective and address potential regional variations. From the UN regional groupings, it was decided that the study will focus on the regions on Sub-Saharan Africa, Southern Asia, South-Eastern Asia and Latin America as the key regions for improving data records of waste management strategies, and potential locations for roll-out of pyrolysis technologies in the future.
For each city in the study, a qualitative waste availability assessment has been conducted to determine which waste streams could potentially be used for supplementing the faecal sludge feed and improving the energy balance of the pyrolysis process. The different supplementary waste streams were identified as common solid wastes generated globally, and more detail can be found on each stream in the full waste report, which can be downloaded here.
Waste summary table
Three key characteristics were identified for the pyrolysis process: dry solids content, net calorific value, and density. For each waste stream a data search was conducted to gather these characteristics both for the listed study cities, where possible, and also globally to provide reference values where specific city data were not available. The data will then be used for design of the dewatering system and its trials, as well as to create a test matrix for mixing the dewatered faecal sludge with the supplementary wastes for the pyrolysis trials.