Bioenergy Recovery from Bulk Greenhouse Waste and Raw Sewage Sludge

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Civil and Environmental Engineering


Bioenergy, Greenhouse waste, Sewage sludge







Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


Global political climate has been leaning towards concepts of environmental consciousness, circular economy, and renewable energy. Several provincial governments in Canada have passed legislation that subjects certain municipal and industrial entities to mandates of waste diversion from landfills.

Centralized anaerobic digestion (AD) facilities offer a promising solution to tackling waste management and renewable energy challenges. However, cost implications are typically a challenge with AD projects. This thesis explores two approaches of improving the feasibility of the AD process, namely co-digestion and pre-treatment, particularly for greenhouse crop wastes (GCW) and raw sludge (RS). A batch setup is constructed using the AMPTS II unit to allow the AD to take place at mesophilic conditions. The co-digestion of GCW with RS is first investigated and the methane yield is compared for different mixing ratios. Results reveal that with higher concentrations of GCW in the substrate mix, the methane yield per mass COD of substrate added is improved by 13 – 27% as compared to the mono-digestion of RS. Feedstock availability is found to have no bearing on the synergism/antagonism of the co-digestion. It is also observed that process kinetics favor higher levels of RS in the substrate mixture.

The effect of microwave pre-treatment (PT) on the methane yield and process kinetics of the co-digestion process is then investigated using different MW power levels (480 W and 960 W) and different target temperatures (70oC, 80oC, and 90oC). Nevertheless, due to a deficiency in the buffering capacity (i.e., alkalinity) within the bottle reactors, only a slight improvement in the methane yield is observed in one of the MW PT samples (at 960 W and 70oC) over the untreated sample. Nevertheless, notable improvements in the methane yield and process kinetics are observed at the higher MW power intensity (960 W) in comparison with those at 480W.