Liquid waste from bio-hydrogen production – A commercially attractive alternative for phosphate solubilizing bio-fertilizer

Organic acids produced by commercial phosphate solubilizing bio-fertilizer (PSB) can chelate the cations of insoluble phosphates (such as Ca3 (PO4)2) present in soil to solubilize the phosphate and make it available for plants. Meanwhile, during H2 production (dark fermentation) different organic acids are produced as unwanted by-products. Interestingly, the acid-rich liquid waste of the process has excellent phosphate solubilizing ability (36.12 folds increase) and it could be considered as a potential alternative for PSB. Studies have demonstrated that biodiesel manufacturing waste (crude glycerol) could be used as a substrate for hydrogen production and the secondary waste could be used as a phosphate solubilizing agent. Thus, this novel approach could: (i) offer a green fertilizer; (ii) improve economic sustainability of bio-hydrogen production and; (iii) could become a financial booster for biodiesel manufacturers by offering them a profitable waste management strategy.