Polyhydroxyalkanoates (PHA) production from biogas in waste treatment facilities: Assessing the potential impacts on economy, environment and society

Abstract

Using the biogas generated from organic waste anaerobic treatment to produce polyhydroxyalkanoates (PHAs) has emerged as an attractive alternative to heat and power generation (CHP) in waste treatment plants. The sustainability of biogas combustion for CHP, biogas bioconversion into PHA and a combination of both scenarios was compared in terms of environmental impact, process economics and social responsibility according to the IChemE Sustainability Metrics. Although PHA production presented higher investment and operational costs, a comparable economic performance was observed in all biogas valorization scenarios regarding net present value (0.77 M€) and internal rate of return (6.4 ± 0.2%) due to the higher market value of biopolymers. The PHA production entailed a significant reduction of atmospheric acidification and odor emissions compared to CHP despite showing higher land, water, chemicals and energy requirements. Job creation associated to biopolymer industry and the increasing public demand for bioproducts were identified as fundamental aspects for enhancing social and local acceptance of waste processing facilities. This study demonstrated that PHA production from biogas constitutes nowadays a realistic alternative to CHP in waste treatment plants and that PHA can be produced at a competitive market price when biogas is used for internal energy provision (4.2 €·kg^-1 PHA).

Keywords: Biogas valorization; Biopolymer; Circular economy; IChemE sustainability metrics; Methanotrophic bacteria; Polyhydroxyalkanoates.