Continuous hydrogen production in a trickling bed reactor by using triticale silage as inoculum: Effect of simple and complex substrates

BACKGROUND: Previous studies have reported that complexity of the substrate, type of inoculum and reactor configuration strongly affect fermentative hydrogen production. Therefore, the aim of this study was to evaluate the effect of simple (glucose, xylose and sucrose) and complex (acid and enzymatic oat straw hydrolysates) substrates on the continuous hydrogen production in a trickling bed reactor. Novel inoculum (triticale silage) and biofilm support configuration (vertically organized PET tubing) were tested. RESULTS: The enzymatic hydrolysate was a suitable substrate for hydrogen production, since its hydrogen molar yield was similar to that obtained with glucose, mean values of 1.6 and 1.7 mol H2 mol-1 sugar consumed were obtained, respectively. In contrast, hydrogen was not produced from the acid hydrolysate. The highest hydrogen production rate (840 mL H2 L-1 h-1) was obtained with glucose at an organic loading rate of 160 g COD L-1 d-1. In spite of the high organic loading rate applied, clogging due to excessive biomass growth was not observed. Finally, PCR-DGGE analysis revealed that bacteria from Clostridium genus were the putative responsible for hydrogen production. CONCLUSION: This work demonstrates that continuous hydrogen production is affected by complexity of the substrate. Furthermore, it also shows the feasibility of using triticale silage as inoculum in hydrogen production systems. © 2014 Society of Chemical Industry

Methane production from acid hydrolysates of Agave tequilana bagasse: Evaluation of hydrolysis conditions and methane yield

Evaluation of diluted acid hydrolysis for sugar extraction from cooked and uncooked Agave tequilana bagasse and feasibility of using the hydrolysates as substrate for methane production, with and without nutrient addition, in anaerobic sequencing batch reactors (AnSBR) were studied. Results showed that the hydrolysis over the cooked bagasse was more effective for sugar extraction at the studied conditions. Total sugars concentration in the cooked and uncooked bagasse hydrolysates were 27.9g/L and 18.7g/L, respectively. However, 5-hydroxymethylfurfural was detected in the cooked bagasse hydrolysate, and therefore, the uncooked bagasse hydrolysate was selected as substrate for methane production. Interestingly, results showed that the AnSBR operated without nutrient addition obtained a constant methane production (0.26LCH4/gCOD), whereas the AnSBR operated with nutrient addition presented a gradual methane suppression. Molecular analyses suggested that methane suppression in the experiment with nutrient addition was due to a negative effect over the archaeal/bacterial ratio. © 2015

Retraction: Evaluation of Co-Digestion at a Commercial Dairy Anaerobic Digester

Co-digestion of dairy manure with off-farm waste has become a common practice on US farms, however, little data at a commercial-scale is present within the literature. In response, a mesophilic, mixed plug-flow reactor co-digesting 16.36% v/v food processing substrates with dairy manure, was monitored for its performance and substrate effects. Co-digestion, as compared to substrate or manure-only digestion, allowed for more preferred levels of key micronutrients, neutral pH, and additional alkalinity while also producing C/N and C/N/P ratios of 28:1 and 112:4:0.5, respectively. Reduction percentages were 45.36, 55.28, 67.72, and 99.87% for TS, VS, COD, and VFA, respectively, while fecal coliform bacteria as an indicator organism showed a 2 log 10 reduction. A manureonly modeled baseline was developed for comparison with the experimental codigestion data with co-digestion resulting in a 110% increase in biogas production and a tripling of gross receipts with 72% of all receipts being directly due to substrate supplementation. Specific methane productivities for the manure-only and co-digestion scenarios were 0.23 and 0.37 m 3 CH 4 /kg VS load , respectively. Addition of substrates tripled project gross revenues and accounted for 72% of all receipts, however, inclusion of substrates led to significant increases in total nitrogen and phosphorous loading to the farm