Pyrolysis of wastewater sludge and composted organic fines from municipal solid waste: laboratory reactor characterisation and product distribution

Abstract

Sludge from municipal wastewater treatment plants and organic fines from mechanical sorting of municipal solid waste (MSW) are two common widespread waste streams that are becoming increasingly difficult to utilise. Changing perceptions of risk in food production has limited the appeal of sludge use on agricultural land, and outlets via landfilling are diminishing rapidly. These factors have led to interest in thermal conversion technologies whose aim is to recover energy and nutrients from waste while reducing health and environmental risks associated with material re-use. Pyrolysis yields three output products: solid char, liquid oils and gas. Their relative distribution depends on process parameters which can be somewhat optimised depending on the end use of product. The potential of pyrolysis for the conversion of wastewater sludge (SS) and organic fines of MSW (OF) to a combustion gas and a carbon-rich char has been investigated. Pyrolysis of SS and OF was done using a laboratory fixed-bed reactor. Herein, the physical characterisation of the reactor is described, and results on pyrolysis yields are presented. Feedstock and chars have been characterised using standard laboratory methods, and the composition of pyrolysis gases was analysed using micro gas chromatography. Product distribution (char/liquid/gas) from the pyrolysis of sewage sludge and composted MSW fines at 700°C for 10 min were 45/26/29 and 53/14/33%, respectively. The combustible fractions of pyrolysis gases range from 36 to 54% for SS feedstock and 62 to 72% from OF. The corresponding lower heating value range of sampled gases were 11.8-19.1 and 18.2-21.0 MJ m, respectively.

Evaluation of Press Mud, Vinasse Powder and Extraction Sludge with Ethanol in a Pyrolysis Process

“…Similar product distributions of biomass wastes through slow pyrolysis were presented by other studies [38][39][40][41][42]. Agar et al [38] converted wastewater sludge and organic fines from municipal wastewater treatment plants (similar volatiles and ash content as our biomass feedstock) in carbon-rich char through pyrolysis in a laboratory fixed-bed reactor at 600 • C and 700 • C. The product distribution of sewage sludge at 600 • C was gas fraction 19%, liquid 33%, and char 48%, while for solid organic fines, the product yields at the same temperature were gas 33%, liquid 14%, and char 53%. Even at 700 • C, the char produced was 45% for the sewage sludge feedstock, while the gas yield increased to 29%.…”

Integrating anaerobic digestion and pyrolysis for treating digestates derived from sewage sludge and fat wastes

“…To date, several thermal technologies, such as pyrolysis, gasification, combustion, and co-combustion processes have been proposed for valorising sewage sludge for obtaining useful forms of energy (Agar et al 2018;Werle and Sobek 2019).…”

Influence of Moisture Contents on the Fast Pyrolysis of Trommel Fines in a Bubbling Fluidized Bed Reactor

“…There are a large number of studies on the effect of moisture on the pyrolysis of different mixed waste streams including MSW [8][9][10], sewage sludge [11,12], organic fines from compost [12] and refuse derived fuel (RDF) [13,14]. Literature shows that organic wastes and other biosolids can be effectively pyrolyzed at moisture contents of below 10 wt% [11,12]. However, there is no information in literature on the effect of moisture content on fast pyrolysis of trommel fines.…”