菠萝皮厌氧发酵产沼气的研究

介绍了以菠萝皮为原料,在25℃恒温条件下,采用批量发酵工艺,进行发酵产沼气实验,实验结果表明,菠萝皮可以作为沼气发酵原料,未加碱时产沼气潜力为574.81 mL/gTS,604.30mL/gVS,甲烷含量51.34%;而加碱时产沼气潜力为568.66 mL/gTS,597.84 mL/gVS,甲烷含量52.96%。     

牛粪、鸡粪发酵产氢潜力的研究

采用恒温厌氧发酵工艺,用乳酸调控发酵pH值,进行了牛粪和鸡粪发酵产氢的实验研究。实验结果表明,pH为4.7～5.5时,牛粪的产氢潜力为32.33ml/g(TS)和41.39ml/g(VS);鸡粪的产氢潜力为33.58ml/g(TS)和50.88ml/g(VS)。     

活性污泥驯化对棉花秸秆厌氧发酵产氢的影响

采用棉秆厌氧发酵制氢,既可实现农业废弃物的资源化利用,又可获得可再生能源——氢气。以棉花秸秆为发酵底物,以污水处理厂活性污泥为产氢菌源,主要研究活性污泥驯化时间(煮沸时间、培养时间、超声波处理时间)及污泥质量等因素对棉花秸秆产氢性能的影响。结果表明,25g活性污泥未经驯化时,棉花秸秆厌氧发酵产氢性能较低,累计产氢量仅为34.60m L/g。当活性污泥经驯化后,棉花秸秆的产氢性能大幅提高,活性污泥质量为25g、煮沸15min、超声波处理120min、培养12h时,棉秆厌氧发酵制氢效果最佳,最大累计产氢量为51.46m L/g,相比未驯化时提高近50%,平均产氢速率为9.36m L/(g·h),混合气体中氢气物质的量分数为42.12%。污泥驯化后极大地提高了棉花秸秆发酵制氢效率,为低成本、规模制氢技术奠定了基础。     

生物质产氢的研究现状与发展

综述了生物质光合产氢和发酵产氢的研究现状,分析了利用生物质产氢技术目前所面临的问题;评述了把生物质产氢与新能源开发,环境保护相结合的应用可能性和前景展望。     

稻草发酵产氢潜力的研究

以稻草为发酵原料 ,控制发酵料液pH值在 5 0左右 ,采用批量发酵工艺 ,进行了厌氧发酵产氢的研究。实验结果表明 ,稻草的产氢潜力为 5 3.5mL/g·TS和 6 3.6 5mL/g·VS。     

玉米苞皮沼气发酵潜力的研究

本实验以玉米苞皮为原料,采用批量发酵工艺,进行发酵产沼气实验,实验结果表明,玉米苞皮是一种较好的沼气发酵原料,其沼气发酵潜力为506mL／gTS,612mL/gVS。     

预处理温度对活性污泥发酵产氢特性的影响

为寻求适宜的种泥热处理方法,利用摇瓶发酵实验,考察了城市污水处理厂好氧活性污泥分别经65、80、95、110℃热处理30min后,其利用葡萄糖发酵产氢的特性。结果表明:在初始pH=7.0、葡萄糖浓度10g/L、接种量2gMLVSS/L条件下,35℃培养72h,经65℃和95℃处理的种泥表现出较好的发酵产氢性能,其葡萄糖的氢气转化率分别达到1.08和1.11mol/mol,污泥的比产氢率分别为8.36和9.05mmol/gMLVSS;经65℃预处理的种泥发酵体系,表现为丁酸型发酵,其葡萄糖降解率和最大产氢速率分别高达82%和11.29mL/h,而经95℃预处理的种泥发酵体系则呈现混合酸发酵特征,其葡萄糖转化率和最大产氢速率分别仅为76%和4.45mL/h。     

木糖厌氧发酵产氢特性研究

以木糖作为厌氧发酵产氢底物,热预处理(100℃,处理20 min)的厌氧颗粒污泥作为接种物,研究了中温条件(37℃)下厌氧发酵产氢特性.结果表明,当反应进行至50 h时,累积产氢量最大,为81.11 mL;乙酸、丁酸和乙醇是液相末端产物中的主要物质,其中乙酸和丁酸的浓度分别为1290 mg/L和1225 mg/L,发酵类型是典型的丁酸型发酵;反应体系的pH值开始降低,最后稳定在4.40左右,形成一个稳定的缓冲体系.     

链霉素菌渣中温厌氧发酵产沼气性能研究

为实现链霉素菌渣的无害化、资源化利用,文章以链霉素菌渣为原料,在菌渣含固率为2%,温度为30±2℃的条件下进行60 d的厌氧发酵试验。试验结果表明:链霉素菌渣的累积产气量为18.20 L,中温产气能力为364.07 mL/g;在稳定产气阶段,发酵液的氨氮、VFAs含量均维持在较低水平,pH值大于7.0;厌氧发酵结束后,发酵液的VS去除率达64.32%;以金黄色葡萄球菌作为指示菌,在厌氧发酵后的沼液中未检测到链霉素残留。     

热处理对污泥厌氧发酵产氢的影响

通过对污泥进行热处理来提高污泥厌氧发酵产氢的能力.结果表明:热处理是一种有效的污泥融胞方法,热处理对糖和蛋白质的水解效果好,热处理后污泥中可溶蛋白质浓度为原污泥的6.4～8.9倍,可溶糖浓度为原污泥的1.6～7.9倍.75℃热处理10 min效果最好,最大累积产氢量可达20.3 ml,较原污泥提高了19倍;VS最大比产氢率为152.2 ml·(kg·h)-1.并用SGompertz方程对实验数据进行拟合,定量说明在不同的热处理温度和时间下,厌氧发酵的累积产氢量(y)和时间(x)的关系.污泥厌氧发酵产氢前后各指标都发生明显变化,NH4 -N和总挥发性脂肪酸(TVFA)的浓度都增加了,而可溶糖和可溶蛋白质的浓度都降低了.热处理后的污泥在厌氧发酵产氢过程中,主要降解的有机物为蛋白质,发酵后蛋白质可降解20%～41%.     

Nano-Cu catalyze hydrogen production from formaldehyde solution at room temperature

In this paper, high efficient production of CO-free hydrogen from formaldehyde (HCHO) aqueous solution catalyzed by various nano-metal catalysts was reported. It was found that nano-metal catalyst could catalyze formaldehyde into hydrogen and formic acid under room temperature and atmospheric pressure. Among Pt, Au, Ni, and Cu nano-metal particles, nano-Cu catalyst exhibited the highest activity and the long-term stability. The temperature seems influence the reaction significantly. For example, when the temperature was increased from 0 to 60 °C, the rate of hydrogen production increases from 2.34 to 140 mL min⁻¹ g⁻¹ catalyst over nano-Cu catalyst. Hydrogen was produced via the formic acid intermediate. When NaOH concentration was high, Cannizzaro reaction occurred, which resulted in the retardation of hydrogen generation at high concentration of NaOH and HCHO.     

Effect of temperature on fermentative hydrogen production by mixed cultures

Effect of temperatures ranging from 20 °C to 55 °C on fermentative hydrogen production by mixed cultures was investigated in batch tests. The experimental results showed that, at initial pH 7.0, during the fermentative hydrogen production using glucose as substrate, the substrate degradation efficiency and hydrogen production potential increased with increasing temperatures from 20 °C to 40 °C. The maximal substrate degradation efficiency was 98.1%, the maximal hydrogen production potential was 269.9 mL, the maximal hydrogen yield was 275.1 mL/g glucose and the shortest lag time was 7.0 h. The temperature for fermentative hydrogen production by mixed cultures was optimized to be 40 °C. The expanded Ratkowsky models could be used to describe the effect of temperatures on the hydrogen production potential, maximum hydrogen production rate and the lag time during fermentative hydrogen production.     

Thermophilic fermentative hydrogen production from starch-wastewater with bio-granules

In this study, the effects of the hydraulic retention time (HRT), pH and substrate concentration on the thermophilic hydrogen production of starch with an upflow anaerobic sludge bed (UASB) reactor were investigated. Starch was used as a sole substrate. Continuous hydrogen production was stably attained with a maximum H₂ yield of 1.7 mol H₂/mol glucose. A H₂-producing thermophilic granule was successfully formed with diameter in the range of 0.5–4.0 mm with thermally pretreated methanogenic granules as the nuclei. The metabolic pathway of the granules was drastically changed at each operational parameter. The production of formic or lactic acids is an indication of the deterioration of hydrogen production for H₂-producing thermophilic granular sludge.     

Dark fermentative hydrogen production from sucrose and molasses

There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/X_o) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H₂/mol sucrose_added was obtained at initial pH of 7 and COD of 10 g/L. Initial S/X_o values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.     

Continuous fermentative hydrogen production from sucrose and sugarbeet

To produce hydrogen by fermentation of biomass, a continuous process using a non-sterile substrate with a readily available mixed microflora is desirable. This work investigates a simple batch start-up procedure at pH 5.2 and 32°C, using anaerobically digested sewage sludge, and continuous hydrogen production from refined sucrose, pulped sugarbeet and a water extract of sugarbeet. Without heat treating the sludge, and with initial nitrogen sparging, a hydrogen producing culture was established within 5 days and remained stable during two experiments of 45 and 32 days duration. At 14–$\text{15}\text{h}$ retention time ($\text{16}\text{kg}$ total sugar $\text{m}{}^{\mathrm{-3}}\text{d}{}^{\mathrm{-1}}$ organic loading rate) hydrogen yields for refined sucrose and pulped sugarbeet were, respectively, 1.0±0.1 and $\text{0.9±0.2}\text{mol}\text{/}\text{mol}$ hexose converted. With nitrogen sparging hydrogen yields were 1.7±0.2–1.9±0.2 and $\text{1.7±0.2}\text{mol}$/mol hexose converted for refined sucrose and water extract of sugarbeet, respectively. Increasing ethanol concentration during operation on sugarbeet, and in some cases a higher redox potential $\text{(>−150}\text{mV}\text{)}$, correlated with lower hydrogen yield.     

The effect of heat pretreatment temperature on fermentative hydrogen production using mixed cultures

The effect of heat treatment at different temperatures on two types of inocula, activated sludge and anaerobically digested sludge, was investigated in batch cultures. Heat treatments were conducted at 65, 80 and 95 °C for 30 min. The untreated inocula produced less amount of hydrogen than the pretreated inocula, with lactic acid as the main metabolite. The maximum yields of 2.3 and 1.6 mol H₂/mol glucose were achieved for the 65 °C pretreated anaerobically digested and activated sludges, respectively. Approximately a 15% decrease in yield was observed with increasing pretreatment temperature from 65 to 95 °C concomitant with an increase in butyrate/acetate ratio from 1.5 to 2.4 for anaerobically digested sludge. The increase of pretreatment temperature of activated sludge to 95 °C suppressed the hydrogen production by lactic acid fermentation. DNA analysis of the microbial community showed that the elevated pretreatment temperatures reduced the species diversity.     

发酵产氢面临的问题及对策

氢是一种高效、清洁、可再生的燃料，通过发酵的方式产生氢气，已经成为国内外研究的热点。目前，这一新兴技术的研究取得了可喜的成果。文章在综合国内外发酵产氢技术的基础上，通过比较沼气发酵和产氢发酵的技术成果，揭示了挥发性有机酸反馈抑制是制约生物法发酵产氢的关键因素，提出了如何提高氢的转化率和发酵稳定性的措施和对策。     

Effect of enzyme addition on fermentative hydrogen production from wheat straw

Wheat straw is an abundant agricultural residue which can be used as raw material to produce hydrogen (H₂), a promising alternative energy carrier, at a low cost. Bioconversion of lignocellulosic biomass to produce H₂ usually involves three main operations: pretreatment, hydrolysis and fermentation. In this study, the efficiency of exogenous enzyme addition on fermentative H₂ production from wheat straw was evaluated using mixed-cultures in two experimental systems: a one-stage system (direct enzyme addition) and a two-stage system (enzymatic hydrolysis prior to dark fermentation). H₂ production from untreated wheat straw ranged from 5.18 to 10.52 mL-H₂ g-VS⁻¹. Whatever the experimental enzyme addition procedure, a two-fold increase in H₂ production yields ranging from 11.06 to 19.63 mL-H₂ g-VS⁻¹ was observed after enzymatic treatment of the wheat straw. The high variability in H₂ yields in the two step process was explained by the consumption of free sugars by indigenous wheat straw microorganisms during enzymatic hydrolysis. The direct addition of exogenous enzymes in the one-stage dark fermentation stage proved to be the best way of significantly improving H₂ production from lignocellulosic biomass. Finally, the optimal dose of enzyme mixture added to the wheat straw was evaluated between 1 and 5 mg-protein g-raw wheat straw⁻¹.