Innovation in valorization of cow manure: Higher hydrolysis, methane production and increased phosphorus retention using UASB technology

•Ca2+ addition doubled the SRT and increased hydrolysis from 29 % to 67 %.•Methanization increased from 20 % to 46 % by adding Ca2+..•Ca2+ effect on methane production depends on Ca:COD (optimum 0.03 – 0.05, limit 0.08).•Phosphorus removal increased from 38 % to 61 % by adding Ca2+ to the UASB reactor.•Ca2+ was captured by bicarbonate, limiting Cax(PO4)y formation and struvite dissolution.