Organic acids produced by commercial phosphate solubilizing bio-fertilizer (PSB) can chelate the cations of insoluble phosphates (such as Ca-3 (PO4)(2)) present in soil to solubilize the phosphate and make it available for plants. Meanwhile, during H-2 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. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.