Purification of anaerobic fermentation digestate of dairy manure by Arthrospira biomass cultivated with biogas-CO2 fixation

Single Arthrospira strain was successfully used for synergistic bio-fixation of tail gas CO2 and digestate utilization generated from anaerobic fermentation project of dairy manure, establishing a new model of circular carbon bioeconomy. Digestate addition ratios (0.96-9.6 vol%) and frequency (once initially/in batches for 4 days) were investigated to improve Arthrospira growth rate, which maximizes at 0.58 g/L/d). Daily addition of digestate resulted in a higher biomass yield than addition once initially. Arthrospira biomass growth cultivated with 7.6 vol % ozone-pretreated digestate and 92.4% zarrouk culture medium first increased to a peak at 0.90 g-O3/g-COD, and then decreased with further enhanced ozone concentration. The digestate is confirmed and designed be used for microalgae cultivation without pretreatment based on actual engineering cases. As far as heavy metals and protein content are concerned, it is safe to cultivate Arthrospira biomass in zarrouk culture medium with appropriate digestate addition for animal feed production.