Bioenergy potential and biomass yield of floating macrophytes grown in impacted environments

Floating aquatic macrophytes, particularly duckweeds, are recognized for their phytoremediation capabilities and potential as bioenergy feedstocks. This study investigates duckweed biomass collected from four distinct environments, two natural freshwater ponds, a settling and a polishing pond. Wolffia brasiliensis from the polishing and settling ponds exhibited the highest protein content (∼45%), while Wolffia brasiliensis and Lemna minuta from the natural pond showed the highest carbohydrate content, both exceeding 35%. The highest biogas production under swine manure co-digestion was observed for Wolffia brasiliensis from polishing pond (403.5 ± 8.1 L_Nbiogas kg VS_ad^-1), despite its lower volatile solids (VS) content (560.5 ± 36.1 g kg^-1), indicating high biodegradability. Wolffia brasiliensis from settling pond, with the highest VS content (736.4 ± 2.5 g kg^-1), also showed high biogas yield (400 ± 9.5 L_Nbiogas kg VS_ad^-1). For natural pond, Wolffia brasiliensis produced 450 ± 6.7 L_Nbiogas kg VS_ad^-1 with a VS content of 635.0 ± 44.8 g kg^-1; in contrast, Lemna minuta, despite a high VS content (693.2 ± 33 g kg^-1), yielded the lowest biogas (190.3 ± 3.6 L_Nbiogas kg VS_ad^-1). The findings demonstrate the potential of duckweed biomass, from different aquatic environment, for biogas production including co-digestion based processes.