Enhancing fermentative hydrogen production from sucrose

Potential use and the energy conversion efficiency analysis of fermentation effluents from photo and dark fermentative bio-hydrogen production

Effluent of bio-hydrogen production system also can be adopted to produce methane for further fermentation, cogeneration of hydrogen and methane will significantly improve the energy conversion efficiency. Platanus Orientalis leaves were taken as the raw material for photo- and dark-fermentation bio-hydrogen production. The resulting concentrations of acetic, butyric, and propionic acids and ethanol in the photo- and dark-fermentation effluents were 2966mg/L and 624mg/L, 422mg/L and 1624mg/L, 1365mg/L and 558mg/L, and 866mg/L and 1352mg/L, respectively. Subsequently, we calculated the energy conversion efficiency according to the organic contents of the effluents and their energy output when used as raw material for methane production. The overall energy conversion efficiencies increased by 15.17% and 22.28%, respectively, when using the effluents of photo and dark fermentation. This two-step bio-hydrogen and methane production system can significantly improve the energy conversion efficiency of anaerobic biological treatment plants.

Biohydrogen production from co-digestion of cow manure and waste milk under thermophilic temperature

Biohydrogen production from co-digestion of cow manure (M) and waste milk (WM), milk from mastitis cows treated with cefazolin, was evaluated in a 3×5 factorial design. Organic loading of 20, 40 and 60g volatile solid (VS)L(-1) were tested at temperature of 55°C using M:WM (VS/VS) 70:30, 50:50, 30:70, 10:90 and 0:100. Hydrogen production increased with organic loading and M:WM to a maximum of 59.5mLg(-1) VS fed at 40g VSL(-1) in M:WM 70:30. Butyrate was the main volatile fatty acid (VFA) accumulated in M:WM 50:50, 30:70 and 10:90. Overall reduction of more than 90% of cefazolin resistant bacteria was observed in all the treatments. The reduction was higher at 40 and 60 than 20g VSL(-1) (P<0.05). Inclusion of waste milk enhances hydrogen production from cow manure and could offer added benefit of waste milk treatment and disposal.

Comparative analysis of hydrogen-producing bacterial biofilms and granular sludge formed in continuous cultures of fermentative bacteria

A system for biohydrogen production was developed based on long-term continuous cultures grown on sugar beet molasses in packed bed reactors. In two separate cultures, consortia of fermentative bacteria developed as biofilms on granitic stones. In one of the cultures, a granular sludge was also formed. Metagenomic analysis of the microbial communities by 454-pyrosequencing of amplified 16S rDNA fragments revealed that the overall biodiversity of the hydrogen-producing cultures was quite small. The stone biofilm from the culture without granular sludge was dominated by Clostridiaceae and heterolactic fermentation bacteria, mainly Leuconostocaeae. Representatives of the Leuconostocaeae and Enterobacteriaceae were dominant in both the granules and the stone biofilm formed in the granular sludge culture. The culture containing granular sludge produced hydrogen significantly more effectively than that containing only the stone biofilm: 5.43 vs. 2.8 mol H(2)/mol sucrose from molasses, respectively. The speculations that lactic acid bacteria may favor hydrogen production are discussed.

Econometric models for biohydrogen development

Biohydrogen is considered as an attractive clean energy source due to its high energy content and environmental-friendly conversion. Analyzing various economic scenarios can help decision makers to optimize development strategies for the biohydrogen sector. This study surveys econometric models of biohydrogen development, including input-out models, life-cycle assessment approach, computable general equilibrium models, linear programming models and impact pathway approach. Fundamentals of each model were briefly reviewed to highlight their advantages and disadvantages. The input-output model and the simplified economic input-output life-cycle assessment model proved most suitable for economic analysis of biohydrogen energy development. A sample analysis using input-output model for forecasting biohydrogen development in the United States is given.

Hydrogen production: two stage processes for waste degradation

The dark fermentation process generates hydrogen by biological means. It presents two main advantages: fulfilling requirements for mild operational conditions and gaining benefit from the residual biomass. The process itself may be seen as a pre-treatment step in a complete stabilisation chain, with the aim of attaining the valorisation of residual biomass. However, increasing the yield of H2 production is an imperative task. In this manuscript, a review of recent work in the field of fermentative hydrogen production is presented. As dark fermentation has a maximum yield of 33% (on sugars), a description is also presented of possible second stage processes for the degradation of dark fermentation effluents. Alternatives considered were photofermentation and bioelectrochemical systems (BES) as processes capable of converting fermentation sub-products into H2. Anaerobic digestion as a final stabilisation stage was also considered owing to the wide application of this technology in the treatment of bio-wastes.

Harvesting biohydrogen from cellobiose from sulfide or nitrite-containing wastewaters using Clostridium sp. R1

Harvesting biohydrogen from inhibiting wastewaters is of practical interest since the toxicity of compounds in a wastewater stream commonly prevents the bioenergy content being recovered. The isolated Clostridium sp. R1 is utilized to degrade cellobiose in sulfide or nitrite-containing medium for biohydrogen production. The strain can effectively degrade cellobiose free of severe inhibitory effects at up to 200 mgl(-1) sulfide or to 5 mgl(-1) nitrite, yielding hydrogen at >2.0 mol H2 mol(-1) cellobiose. Principal metabolites of cellobiose fermentation are acetate and butyrate, with the concentration of the former increases with increasing sulfide and nitrite concentrations. The isolated strain can yield hydrogen from cellobiose in sulfide-laden wastewaters. However, the present of nitrite significantly limit the efficiency of the biohydrogen harvesting process.

Evaluation of dairy cattle manure as a supplement to improve net energy gain in fermentative hydrogen production from sucrose

This study evaluated fermentative biohydrogen production from sucrose supplemented with dairy cattle manure at different sucrose:manure ratios. Hydrogen yields found in this study (2.9-5.3M hydrogen/M sucrose) at ambient temperature are higher than literature results obtained at mesophilic temperatures. This study demonstrated that dairy cattle manure could serve as a buffering agent to maintain recommended pH levels; as a nutrient source to provide the required nutrients for hydrogen production; as a seed to produce hydrogen from sucrose; and as a co-substrate to improve the hydrogen yield. Based on an analysis of the net energy gain, it is concluded that positive net energy gains can be realized with non-thermal pretreatment and/or by combining dark fermentation with anaerobic digestion or microbial fuel cells to extract additional energy from the aqueous products of dark fermentation.