Thermophilic bio-hydrogen production from corn-bran residue pretreated by calcined-lime mud from papermaking process

Dark co-fermentation of rice straw and pig manure for biohydrogen production: effects of different inoculum pretreatments and substrate mixing ratio

Biohydrogen produced from agricultural waste through dark co-fermentation is an increasingly valuable source of renewable energy. Rice straw (RS) and pig manure (PM) are widely available waste products in Asia with complementary levels of carbon and nitrogen that together have a high biohydrogen production potential. However, no research has yet determined the ideal inoculum pretreatment method and mixing ratio for biohydrogen production using these resources. In this study, we tested biohydrogen production using three different inoculum pretreatment methods (acid, alkali and thermal) at five RS/PM ratios (1:0, 5:1, 3:1, 1:1 and 0:1, based on total solids). All three pretreatments promoted biohydrogen production with the increase of bioactivity of biohydrogen-producing organisms (compared with a control group), though acid was clearly superior to thermal or alkali. Using acid pretreatment and RS/PM ratio of 5:1 corresponded with a relatively low NH4+-N concentration (655.17 mg/L), a maximal cumulative biohydrogen production of 44.59 mL/g VS_added with a low methane production (<0.1%), a large butyric acid accumulation (1035.30 mg/L) and a biohydrogen conversion rate of 2.12%. The optimal pH for biohydrogen production from co-fermentation of RS and PM ranged from 5.0-5.5.

A Review of the Enhancement of Bio-Hydrogen Generation by Chemicals Addition

Bio-hydrogen production (BHP) produced from renewable bio-resources is an attractive route for green energy production, due to its compelling advantages of relative high efficiency, cost-effectiveness, and lower ecological impact. This study reviewed different BHP pathways, and the most important enzymes involved in these pathways, to identify technological gaps and effective approaches for process intensification in industrial applications. Among the various approaches reviewed in this study, a particular focus was set on the latest methods of chemicals/metal addition for improving hydrogen generation during dark fermentation (DF) processes; the up-to-date findings of different chemicals/metal addition methods have been quantitatively evaluated and thoroughly compared in this paper. A new efficiency evaluation criterion is also proposed, allowing different BHP processes to be compared with greater simplicity and validity.

Integrated Use of Maize Bran Residue for One-Step Phosphate Bio-Fertilizer Production

The development of bio-fertilizer inoculants is important and desirable. Two phosphate-solubilizing Bacillus subtilis strains were inoculated onto maize bran residue (MBR), which was used as bio-fertilizer carrier and a primary source of nutrients in a medium used for semi-solid fermentation. Water holding capacity, swelling capacity, scanning electron microscopy, and shelf-life assays demonstrated that ground MBR had satisfactory properties for a bio-fertilizer carrier. The maximal soluble phosphorus (P) reached 642.7 ± 0.43 mg l^-1 in an orthogonal test under the following optimal conditions: a pH of 7.0, a cultivation temperature of 31 °C, a medium water content of 160%, and a filling capacity of 500 g l^-1. The bio-fertilizer produced by MBR improved the growth of wheat (Triticum aestivum L.) and Chinese cabbage (Brassica rapa pekinensis) with respect to plant height (by up to 18.36%) and the lengths of roots (by up to 34.03%, 27.22%, separately) in a pot experiment. This study integrated the production and storage of a bio-fertilizer to realize the one-step production of a solid bio-fertilizer using MBR.

Improvement of hydrogen production from glucose by ferrous iron and biochar

Effects of biochar (BC) and ferrous iron (Fe²⁺) additions on hydrogen (H₂) production from glucose were investigated using batch experiment. The glucose with both BC and Fe²⁺ additions were incubated at 37°C for H₂ production. As compared with the control group (without BC and Fe²⁺ additions), the synergic effects of BC and Fe²⁺ make the lag phase time decease from 4.25 to 2.12h, and H₂ yield increase from 158.0 to 234.4ml/g glucose. Moreover, suitable concentrations of BC and Fe²⁺ serve to enhance volatile fatty acid generation during H₂ evolution. These results indicate that H₂ production is improved by BC and Fe²⁺ regulations, where synergic mechanisms are described as follows: BC acts as support carriers of anaerobes and system pH buffers, which promotes the biofilm formation and maintains suitable pH environment; Appropriate Fe²⁺ concentration can improve hydrogenase activity in H₂ production.

Enhancement of biohydrogen production from brewers' spent grain by calcined-red mud pretreatment

This paper investigated the utilization of calcined-red mud (CRM) pretreatment to enhance fermentative hydrogen yields from brewers' spent grain (BSG). The BSG samples were treated with different concentrations (0.0-20g/L) of CRM at 55°C for 48h, before the biohydrogen process with heat-treated anaerobic sludge inoculum. The highest specific hydrogen production of 198.62ml/g-VS was obtained from the BSG treated with 10g/L CRM, with the corresponding lag time of 10.60h. Hydrogen yield increments increased by 67.74%, compared to the control tests without CRM. The results demonstrated that the CRM could hydrolyze more cellulose and further provided adequate broth and suitable pH value for efficient fermentative hydrogen. The model-based analysis showed that the modified Gompertz model presented a better fit for the experimental data than the first-order model.