Pomace Anaerobic Fermentation Of Biological Hydrogen Production

Fossil energy source cannot be renewable and will be exhausted one day, so it is very urgent for the exploration of substitutes. Hydrogen (H₂) energy is a very promising alternative, it has high energy content per unit weight and high combustion value, does not generate any toxic byproduct. H₂ production by anaerobic fermentation has great potential for development because it is rapid, simple and independent of weather condition. Moreover, it can used industrial and agricultural wastes as substrates for H₂ production, which facilitates both waste treatment and energy recovery.The H₂ production from apple pomace by anaerobic fermentation using natural mixed microorganisms in batch process was studied. The river sludge was used as a seed after being boiled for 15 min. A series of batch experiments were conducted to investigate the effects of substrate pretreatments, initial pH value, fermentation temperature, cellulase dosage, ultrasonic time and substrate concentration on the fermentative H₂ production from apple pomace.Firstly, the effect of pretreatment methods on the H₂ production from apple pomace was studied. The results showed as follows: 1. The best ammonia liquor pretreatment condition was to soak it in 6% ammonia liquor at room temperature for 24 h. 2. The best sulfuric acid pretreatment condition was to treat it by ultrasonic irradiation in the sulfuric acid of 0.5% for 1 h. 3. The H₂ production efficiency from apple pomace pretreated by NaOH solution was low.Secondly, we chose the apple pomace pretreated by 6% ammonia liquor at room temperature for 24 h as the substrate to study the fermentation temperature and initial pH value on the H₂ production efficiency. The results showed that an optimal fermentation condition was temperature 37℃and initial pH value 7.0 with a maximum cumulative H₂ yield of 90.06 mL·g^-1-TS, an average H₂ production rate of 6.00 mL·g^-1-TS·#h^-1 and a H₂ percentage of 53.49%.Finally, under the optimal fermentation condition and in the basis of previous studies of our group, we further investigated the effect of enzymatic hydrolysis on H₂ production from apple pomace. After optimizing a variety of conditions, an ideal H₂ production with a maximum cumulative H₂ yield of 134.04 mL·g^-1-TS, an average H₂ production rate of 12.00 mL·g^-1-TS·h^-1 and a H₂ percentage of 62.71% was obtained. By comparing the results of batch experiments, a relatively economic and effective pathway was proposed as follows: 1. Firstly, apple pomace was soaked by 6% ammonia liquor for 24 h at room temperature (the ratio of solid to liquid was 1 g: 10 ml), then the pretreated apple pomace and cellulase were suspended in a aqueous solution of pH value 5.0 with a cellulase dosage of 12.5 mg·g^-1-TS and a hydrolysis substrate concentration 5% (w/v). Lastly, after being treated by ultrasonic irradiation for 20 min, the suspension was hydrolyzed for 48 h at 45℃. 2. The hydrolyzed apple pomace was fermented at 37℃and initial pH value 7.0 with a fermentation substrate concentration of 15 g·l^-1.