Polyhydroxyalkanoate Production from Domestic Sewage Sludge: Environmental Impact Analysis from a Whole Life Cycle Perspective

Abstract

Polyhydroxyalkanoate (PHA) production from wasted sewage sludge has emerged as a promising procedure, offering a sustainable alternative to traditional plastics. In recent years, sewage sludge has gained recognition as a valuable feedstock for PHA production, turning an environmentally challenging waste into a resource. Several technologies have been developed and optimised to increase PHA production, mainly by applying several high energy-demand processes. Still, this procedure will inevitably increase the environmental impact of the adopted solution, which is usually neglected when the PHA production process is applied at the pilot scale. As the demand for eco-friendly alternatives intensifies, understanding the environmental implications of this process becomes pivotal, meaning that a comprehensive assessment of the entire life cycle of PHA production from sewage sludge is essential. This evaluation should encompass key factors such as energy consumption, direct greenhouse gas emission and amount of biopolymer produced, offering a holistic understanding of the process’s sustainability. A life cycle impact analysis of PHA production from 4 pilot plants regarding two individual technologies was conducted herein. The comprehensive assessment of the overall environmental impact in both alternatives indicates that the ADF system exhibits greater environmental sustainability. A detailed comparison of the effects of each step revealed that the primary contributors to the environmental burden in both alternatives are the Selection of PHA Producers and Ammonia Nitritation. These results, derived from life cycle assessments, establish a foundation for promoting environmental sustainability in selecting diverse production processes and optimising individual process routes.