Managing Non-Sewered Human Waste Using Thermochemical Waste Treatment Technologies: A Review

Abstract

The utilisation of micro-scale thermal treatment technologies for non-sewered applications has been emerging as a prominent route for the safe treatment and disposal of high water content hazardous feedstock. This study provides a comprehensive review of the technological concepts practiced up to date in commercial/pilot and small scales for various types of solid fuels. The respective challenges are critically described and discussed to aid in the selection of promising technology for on-site sanitary applications. Furthermore, the challenges observed with the nominated (pyrolysis) technology are discussed in detail and addressed. This study suggests rapid energy recovery from by-products primarily made up of the highest yield of syngas with a desirable calorific value. The optimum operating ranges are discussed to ensure a reliable thermal conversion of sludge materials considering the application constraints and technology drawbacks. However, further studies are needed to investigate the uncertainties regarding emissions, energy consumption and overall associated costs.

Development and prototype testing of a novel small-scale pyrolysis system for the treatment of sanitary sludge

“…These technologies are commonly known to be suitable for low-income countries or situations where sewage infrastructure is inaccessible or difficult to access. This work follows the findings from our earlier study [1], on the selection of pyrolysis as the suitable technology for these applications. A review of the available research on sludge management methods has revealed a major gap in the utilisation of thermal treatment methods for on-site sanitation.…”

“…The rationale behind the implementation of the chamber is to allow the batch processing of the waste per day to reduce energy consumption in comparison to a constant operation of the reactor. Finally, upon applying thermal loads, FS undergoes pyrolysis degradation with an aim to maximise the reduction of char, the essential rule for hazardous waste treatment [1], and boost the production of syngas with the highest yield and calorific value. Production of highquality syngas enables the chance of convenient energy recovery through its combustion and limits the energy consumption of this system via recycling of the heat which are suggested for future studies.…”

“…Implementation of thermal treatment technologies for the decentralised sanitation of human wastes has been recently identified as a cornerstone for proper faecal sludge (FS) management [1]. Researchers have extensively investigated the applicability of combustion and gasification processes to provide rapid, energy-efficient and environmental friendly solution to the improper disposal of this hazardous waste [2 3].…”

“…However, the main application of this process in commercial scale is known to be the maximization of the liquid yield [11]. In addition to high heating temperature, heating rate and residence times, the pyrolysis efficiency and product specifications are affected by the raw fuel's characteristics such as moisture content and particle size [1]. Hence, various stages of pre-treatment might be implemented to further reduce the size and moisture content (<10 % wt.)…”

An Overview of Waste Gasification and Syngas Upgrading Processes

“…The next study [7] provides a comprehensive review of micro-scale thermal treatment technologies for non-sewered practices, which are up to date in commercial/pilot and small scales for various types of solid fuels. Furthermore, the challenges observed with the nominated (pyrolysis) technology are discussed in detail and addressed.…”