Going beyond conventional wastewater treatment plants within circular bioeconomy concept – a sustainability assessment study

Abstract

Wastewater treatment plants (WWTP) have extensive energy processes that undermine their economic and environmental performance. In this context, the integration of wastewater treatment with other biochemical processes such as co-digestion of sludge with organic wastes, and production of value-added products at their downstream processes will shift conventional WWTPs into biorefinery platforms with better sustainability performance. The sustainability of such a biorefinery platform has been investigated herein using economic and life cycle assessment approach. This WWTP-based biorefinery treats wastewater from Copenhagen municipality, co-digests the source sorted organic fraction of municipal solid waste and sludge, and upgrades biogas into biomethane using hydrogen-assisted upgrading method. Apart from bioenergy, this biorefinery also produces microbial protein (MP) using recovered nutrients from WWTP's reject water. The net environmental savings achieved in two damage categories, i.e., −1.07E−02 species.yr/FU in ecosystem quality and −1.68E+06 USD/FU in resource scarcity damage categories along with high potential windows for the further environmental profile improvements make this biorefinery platform so encouraging. Despite being promising in terms of environmental performance, the high capital expenditure and low gross profit have undermined the economic performance of the proposed biorefinery. Technological improvements, process optimization, and encouraging incentives/subsidies are still needed to make this platform economically feasible.

Methanotroph biotransformation for nutrient recovery: a review of current strategies and future opportunities

“…For the second-generation M-SCP route, methane is sourced from biogas plants, sewage treatment plants, and landfills, thereby avoiding the direct release of these gases into the atmosphere and significantly benefiting the environment. It has been reported that the environmental impact of producing 1 ton of M-SCP, soybean meal, and fishmeal corresponds to −711, 7060, and 3000 kg of CO2, respectively, in terms of climate change (Marami et al, 2022b), showing M-SCP with negative carbon emissions.…”

“…Renewable energy sources, such as wind power and methane CHP, have been extensively studied in the existing assessments. CHP can achieve heat and electricity savings on the biorefinery platform, and while biogas combustion may produce carbon dioxide and result in methane emissions, it is considered biogenic, renewable, and environmentally superior to nonrenewable sources (Marami et al, 2022b). It has been reported that heat substitution from CHP contributed the most to resource savings, accounting for 65% of the total savings (Marami et al, 2022a).…”

“…Based on sensitivity analysis, several more favorable cost-reduction segments have been identified in the past. It has been demonstrated that increasing the yield of pure protein from ammonium nitrogen, replacing conventional reactors with U-loop reactors, improving power efficiency, and reducing labor requirements can potentially increase the gross profit and significantly reduce the investment cost (El Abbadi et al, 2021; Marami et al, 2022b).…”