Life cycle energy and greenhouse gas profile of a process for the production of ammonium sulfate from nitrogen-fixing photosynthetic cyanobacteria

► Life cycle characterization of cyanobacteria as source of (NH4)2SO4 and biogas. ► Open-pond culture of Anabaena sp. provides biomass and exopolysaccharides. ► Harvest and conversion to biogas and (NH4)2SO4 crystals are considered. ► Significant reduction in non-renewable energy use and greenhouse gas emissions. ► Some trade-offs in non-arable land use and fresh water use.