Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Briens, Cedric

2nd Supervisor

Berruti, Franco

Co-Supervisor

Abstract

The aim of this thesis was to investigate the potential for pyrolysis of solid anaerobic digestate and municipal sewage sludge. Slow, fast, and autothermal pyrolysis experiments were conducted for the anaerobic digestate while slow and fast pyrolysis experiments were carried out for the sewage sludge. Pyrolysis temperatures ranged from 250 to 550 ᵒC. The effect of pyrolysis conditions on the pyrolysis products was examined.

Fast pyrolysis at higher temperatures was favourable for energy recovery in the bio-oil products. Slow pyrolysis was favourable for the biochar products. Lower pyrolysis temperatures favoured energy recovery in the biochar; while higher temperatures increased biochar carbonization and stability. Soxhlet extraction of the biochar with deionized water showed that slow pyrolysis biochar performed better regarding the leachability of nutritive species and stability of heavy metals for the digestate and sewage sludge biochars respectively.

Autothermal pyrolysis increased the heating value of both the dry bio-oil and biochar products compared to traditional fast pyrolysis, but with a decrease in yield.

A new method for the calculation of the enthalpy of pyrolysis was developed and used to create a complete energy balance for the pyrolysis of sewage sludge. An economic analysis was completed for the construction and operation of a sewage sludge pyrolysis plant. An environmental life cycle analysis was completed comparing the environmental effects of incineration and pyrolysis of sewage sludge. Pyrolysis of the sludge with the use of the biochar as a coal replacement was determined to have the greatest environmental benefit.

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