From purification to energy: Biogas and biomethane production from Schoenoplectus americanus and a mixture of duckweed from phytoremediation of domestic wastewater

Abstract

Anaerobic digestion (AD) is a promising strategy for converting organic biomass into biogas and methane. In this context, plant biomass generated after domestic wastewater phytoremediation represents an opportunity for integrated waste management and energy recovery. This study evaluated the biochemical composition and the biochemical methane potential (BMP) of biomass from Schoenoplectus americanus and a mixture of duckweeds (Lemna gibba, L. minuta and Wolffia columbiana) collected after use in phytoremediation of domestic wastewater. The BMP were determined through batch anaerobic digestion assays. S. americanus exhibited a higher carbohydrate content (71% dry weight) compared to the duckweed mixture, which showed a higher protein content (58% dry weight). Anaerobic digestion was conducted until stable methane production was achieved for each substrate. BMP values were similar for both substrates (146 ± 1.2 and 153.4 ± 3.3 mLCH4gVS for S. americanus and duckweed mixture, respectively). However, the biodegradability was higher for S. americanus (55%) than for the duckweed mixture (40%). These results indicate that, under the applied experimental and biomass preparation conditions, both biomasses have potential as substrates for biogas and methane production, with trade-offs between biodegradability and operational advantages such as rapid growth and continuous biomass availability in duckweed-based systems.