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Brewery industry liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry wastewater (SIW) have been considered as substrates to produce biobutanol. Efficiency of hydrolysis techniques tested to produce fermentable sugars depended on nature of agro-industrial wastes and process conditions. Acid-catalysed hydrolysis of BLW and BSG gave a total reducing sugar yield of 0.433 g/g and 0.468 g/g respectively. Reducing sugar yield from microwave assisted hydrothermal method was 0.404 g/g from APS and 0.631 g/g from APUS, and, 0.359 g/g from microwave assisted acid-catalysed SIW dry mass. Parameter optimization (time, pH and substrate concentration) for acid-catalysed BLW hydrolysate utilization using central composite model technique produced 307.9 g/kg glucose with generation of inhibitors (5-hydroxymethyl furfural (20 g/kg), furfural (1.6 g/kg), levulinic acid (9.3 g/kg) and total phenolic compound (0.567 g/kg)). 10.62 g/L of acetone-butanol-ethanol was produced by subsequent clostridial fermentation of the substrate.

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Summary Biobutanol has conventionally been generated by fermentation of carbohydrates derived from biomass (starch or sugar‐based feedstock, such as corn) using Clostridia strains (mainly C. beijerinckii and C. acetobutylicum) under anaerobic conditions in batch mode. Under these premises, it has been tough for the acetone–butanol–ethanol fermentation to compete with petro‐butanol production from an energy efficiency and material consumption standpoint. Challenges for butanol production from biomass comprised high cost of feedstock, scarcity of hyper‐butanol producing bacteria and low butanol yield, volumetric productivity and titre, leading to high water usage and separation‐purification costs. This article is an up‐to‐date review on several under explored sections, such as optimization of fermenter feed, microbial culture responsible for solvent production (co‐culture techniques and electro‐biochemical process), latest recovery techniques and the studies integrating in situ continuous fermentation processes. Biobutanol refinery way forward should build upon the use of low‐cost lignocellulosic matter and zero cost organic wastes and by‐products from food, agriculture, forestry, fermentation and paper industries as feedstock; optimized fermentation of such diversified feed with appropriate hyper‐butanol producing strains in biofilm reactors and integration of fermentation step with hybrid high butanol‐selective recovery techniques. Copyright © 2015 John Wiley & Sons, Ltd.

With CO2 free emission and a gravimetric energy density higher than gasoline, diesel, biodiesel, and bioethanol, biohydrogen is a promising green renewable energy carrier. During fermentative hydrogen production, 60-70 % of the feedstock is converted to different by-products, dominated by organic acids. In the present investigation, a simple approach for value addition of hydrogen production liquid waste (HPLW) containing these compounds has been demonstrated. In soil, organic acids produced by phosphate solubilizing bacteria chelate the cations of insoluble inorganic phosphates (e.g., Ca3 (PO4)2) and make the phosphorus available to the plants. Organic acid-rich HPLW, therefore, has been evaluated as soil phosphate solubilizer. Application of HPLW as soil phosphate solubilizer was found to improve the phosphorus uptake of soybean plants by 2.18- to 2.74-folds. Additionally, 33-100 % increase in seed germination rate was also observed. Therefore, HPLW has the potential to be an alternative for phosphate solubilizing biofertilizers available in the market. Moreover, the strategy can be useful for phytoremediation of phosphorus-rich soil.