利用动力学模型探讨底物浓度对生物产氢的影响

运用间歇实验方法,以葡萄糖为底物,在浓度为0-300g／L时,研究了底物浓度对混合细菌发酵产氢的影响．结果表明,在35℃和初始pH7．0时,当底物浓度为0～25g／L时,混合细菌发酵葡萄糖的最大累积产氢量和产氢速率都随着底物浓度的增加而增加．当底物浓度为25g／L时,最大累积产氢量和产氢速率都是最高的,分别为426．8mL和15．1mL／h．当底物浓度为2g／L时,比产氢率和底物降解率最大,分别为384．3mL／g葡萄糖和97．6％．修正的Logistic模型能很好地描述本研究中累积产氢量随时间的变化规律．Han-Levenspiel模型能很好地描述本研究中底物浓度对产氢速率的影响．     

亚心形四爿藻培养和产氢过程一体化平板光生物反应系统

利用整合了燃料电池的平板光生物反应器, 探讨了将亚心型四爿藻高密度培养和产氢两段工艺一体化集成的可行性. 在培养阶段通入体积分数为2%~5%的CO2可使藻细胞迅速增殖, 9 d内即可达到产氢要求的生物量(8.5×106 cell/mL). 通过叶绿素荧光参数分析, 选择2%的CO2培养的藻进行后续的产氢实验. 结果表明, PSⅡ活性和光合电子传递速率均随时间的推移而逐渐下降. 通过对产氢动力学曲线的分析, 计算出最大产氢速率为1.1 mL/(h·L), 持续产氢时间为60 h.     

脱油芝麻饼厌氧发酵生物制氢

在批式厌氧反应器中,以厌氧消化污泥作为天然产氢菌源,通过脱油芝麻饼的厌氧发酵生产氢气.考察了菌种来源、培养时间和发酵反应温度对芝麻饼产氢能力的影响以及生物氢发酵过程中液相组成的变化.在实验条件下,脱油芝麻饼的最大产氢量为24.1mL/g,生物气中氢气的最大体积分数为66.1%,生物气中没有检测到甲烷气体.     

质量混合比对餐厨垃圾厌氧发酵产氢的影响

采用自制的序批式"厌氧发酵产氢反应装置",以餐厨垃圾为发酵底物,污水处理厂剩余污泥为接种微生物,初始pH为7.0、温度为37℃条件下,研究餐厨垃圾和剩余污泥不同质量混合比对厌氧发酵产氢的影响。结果表明,餐厨垃圾和剩余污泥质量比为4∶1时,厌氧发酵产氢效果最好,累积产氢量和单位产氢量(以VS计)最大,分别为252.2 m L和53.3 m L/g,TS和VS的去除率分别为20.9%和13.8%。     

利用高浓度秸秆废弃物发酵产氢

采用高浓度的玉米秸秆(60g·L-1)作为产氢底物,研究了在氢发酵过程中几个关键过程参数对发酵产氢的影响,以期在秸秆废弃物的清洁氢能转化过程中减少发酵废水的生成总量.结果表明,在酸化秸秆浓度为60g·L-1,碳酸氢铵添加量为1.2g·L-1,十六烷基三甲基溴化铵添加量为30mg·L-1,菌株Bacillus sp.FS2011添加量为10%(质量分数),以及初始pH=7.5±0.5、发酵温度(37±1)℃条件下,最大产氢量和产氢速率分别为(79.8±1.5)mL·g-1和3.78mL·g-1·h-1.与使用低浓度秸秆(≤20g·L-1)底物时相比,生成的氢发酵废水总体积减小了约67%.     

双波长分光光度法快速测定利用木糖生产普鲁兰多糖发酵液中的多糖产量与残余木糖量

以间苯三酚-浓硫酸为显色剂,建立了双波长分光光度法同时测定利用木糖产普鲁兰多糖发酵液中产物与底物量的方法。显色剂配方为2%的间苯三酚乙醇溶液与浓硫酸1:1(V/V)混合。木糖的测定波长为444 nm和405 nm,普鲁兰多糖的测定波长为420 nm和465 nm。测定条件为1 m L底物,加入5 m L显色剂,沸水浴10 min,冷却至室温,加入10 m L蒸馏水混匀。葡萄糖与木糖浓度在10~300μg/m L浓度范围内线性关系良好。重复性实验得到普鲁兰多糖和木糖的RSD分别为1.6%和2.5%,加标回收实验得到普鲁兰多糖和木糖的回收率分别在92.5%~100.3%和96.9%~103.8%之间,相对标准偏差分别为3.7%和3.5%。说明该方法适用于发酵液中木糖与多糖含量的同时测定。     

温度对形成MEC阳极膜的影响

为探究温度对MEC(Microbial electrolytic cell)阳极膜形成的影响,本实验采用单池MEC产氢装置,在外加电解电压1. 0V,p H=7的厌氧环境下,利用厌氧活性污泥为接种物,以乙酸钠为底物,分别在温度为15℃,25℃,35℃,45℃,55℃的条件下进行MEC阳极膜的培养及阳极膜的产氢能力验证实验。培养过程中,通过测定电解电流,p H值,氢气含量,电化学活性、膜生物量等指标的变化,以分析温度对MEC阳极膜形成的影响;验证实验中则通过测定氢气含量说明各温度条件下培养的膜的产氢能力。实验结果表明,在温度从15℃逐渐升至55℃的过程中,各实验组产生的最大电流先逐渐增大,而后又逐渐减小,最大电流分别为13. 5mA、17. 9mA、22. 5mA、1. 1mA、0. 5mA,相比之下,高温较低温更不利于电活性微生物的生长富集,而中温(25～35℃)最利于其生长繁殖。其中,在35℃时呈现出较大的电流值,最大电流值为22. 5mA,在35℃时氢气含量也最高,高达24. 49%,所以35℃是MEC阳极膜形成的最佳温度。     

委内瑞拉常压渣油供氢热转化研究

采用高压釜研究了委内瑞拉常压渣油的常规减黏裂化与供氢热转化过程。结果表明,相比常规减黏裂化而言,供氢热转化过程中的供氢剂能够抑制气体产物、沥青质以及焦的形成,后者的气体收率比前者低0.5%~1.2%,生焦率低0.02%~0.98%,残渣油沥青质含量低0.6%~1.3%;在反应温度425℃、反应时间5~20 min条件下,供氢热转化过程的总降黏率、净降黏率变化分别为46.1%~54.8%、10.2%~33.0%;供氢热转化过程的较佳反应条件为425℃、5 min,此条件下供氢热转化生成油斑点实验等级为一级(ASTM D4740),运动黏度(50℃)为185.5 mm²/s,净降黏率为26.4%,满足了船运的基本要求。     

基于光驱动水氧化的有机底物氧化

模拟光合作用分解水制氢是将太阳能转换为化学能的有效途径,基于光驱动水氧化的有机底物氧化是模拟光合作用体系II释氧中心(OEC)的新思路.该反应过程是通过金属催化剂将水分子活化生成以水为氧源的高价金属-氧中间体,随后将氧原子转移给有机底物,在此过程中水中的氢源得以释放.从催化剂的角度总结了近年来光驱动水分子活化的研究进展,同时对基于光驱动水氧化的有机底物氧化与光致产氢结合进而建立新型光分解水制氢的体系提出展望.     

适应多种原料的生物航煤生产技术的开发

为了减少温室气体排放,扩大航煤的原料来源,生物航煤制备技术的开发受到许多国家的重视.中国石油化工股份有限公司(简称中国石化)开发出了适应多种原料的生物航煤制备技术,该技术以多种生物质油脂为原料,采用加氢法生产生物航煤.针对不同的产品需求,可有不同的产品方案,如最大量生产生物航煤方案,生物航煤兼顾生物柴油方案.以动植物油脂为原料,生物航煤质量收率为35%~45%,生物航煤的冰点可达48℃以下,同时还有7%~11%的柴油馏分和23%~29%的石脑油馏分.中国石化已在工业装置上生产出了符合ASTM D7566-11标准的生物航煤产品,并成功进行了试飞.     

Biogasification of Green and Food Wastes Using Anaerobic-Phased Solids Digester System

The performance of a laboratory-scale anaerobic-phased solid (APS) digester system treating food and green wastes was evaluated at thermophilic condition. The APS system comprised of four hydrolysis digesters and one biogasification reactor. The hydrolysis reactors were operated batchwised at a 12-day retention time, while the biogasification reactor was continuously operated at different hydraulic retention times (HRT). The biogas and methane yields from green waste were determined to be 0.438 and 0.252 L/g volatile solid (VS), respectively, with VS removal of 78%. The biogas and methane yields from food waste were 0.596 and 0.379 L/g VS, respectively, with VS removal of 85%. Hydrogen was produced from hydrolysis reactors during the digestion of food waste. Its content was 30.1% and 8.5% of the biogas produced on the first and second day of digestion, respectively. Hydrogen yield from the whole system was determined to be 0.029 L/g VS representing about 4.9% of the total biogas production from the system. The ratio between the volumes of biogasification and hydrolysis reactors (BR/HR) was found to be a factor that affects the process performance and stability.     

Evaluation of Methanogenic Activity of Biogas Plant Slurry for Monitoring Codigestion of Ossein Factory Wastes and Cyanobacterial Biomass

Overall measurement of methanogenic activity of sludge and or slurry is thought as a key for understanding the basic physiology of anaerobic consortia involved in anaerobic digestion process of an alternative biomass. In this study, the methanogenic activity of biogas plant slurry was used to evaluate the anaerobic digestion of ossein factory wastes such as sinews and primary clarified bone waste (PCBW) and cyanobacterial biomass in standard assay conditions. A maximum methanogenic activity was reported here when ossein factory wastes mixed with cyanobacterial biomass in specific proportions in which sinews and PCBW alone also favored to a significant methane yield. Cyanobacterial biomass alone did not give a desirable methanogenic activity. Approximately 48% of total solids were destroyed from these wastes after 30 days. This study gives information on the use of these wastes with suitable proportions for taking an effort in a large-scale anaerobic digestion in an effective way of ossein factory.     

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass was carried out by catalytic steam reforming in a fluidized bed reactor. The effects of reaction conditions such as reaction temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity of the aqueous phase (WHSV) on the results of hydrogen yield, potential hydrogen yield and carbon selectivity of product gases were investigated. The effect of reaction temperature on the carbon deposition on catalyst was also studied. The hydrogen yield of 64.6%, potential hydrogen yield of 77.6% and the carbon selectivity for product gases of 84.3% can be obtained at the optimized conditions of reaction temperature 800 °C, S/C 10 and WHSV 1.0 h⁻¹.     

Industrial Waste Utilization for Low-Cost Production of Raw Material Oil Through Microbial Fermentation

In view of ever-growing demand of biodiesel, there is an urgent need to look for inexpensive and promising renewable raw material oils for its production. In this context, the aim of this study was to evaluate the potential use of industrial wastes for low-cost production of oils through microbial fermentation. Among the strains tested, Yarrowia lipolytica grew best and produced highest lipid when grown on decanter effluent from palm oil mill. When crude glycerol by-product from a biodiesel plant was added into the effluent as a co-substrate, Y. lipolytica produced a higher biomass of 3.21 g/L and a higher amount of lipid of 2.21 g/L which was 68 % of the dry weight. The scale up and process improvement in a 5-L bioreactor increased the biomass and lipid up to 5.53 and 2.81 g/L, respectively. A semi-continuous mode of operation was an effective mode for biomass enhancement while a fed-batch mode was effective for lipid enhancement. These yeast lipids have potential to be used as biodiesel feedstocks because of their similar fatty acid composition to that of plant oil.     

Biogas Production from N-Methylmorpholine-N-oxide (NMMO) Pretreated Forest Residues

Lignocellulosic biomass represents a great potential for biogas production. However, a suitable pretreatment is needed to improve their digestibility. This study investigates the effects of an organic solvent, N-Methylmorpholine-N-oxide (NMMO) at temperatures of 120 and 90 °C, NMMO concentrations of 75 and 85 % and treatment times of 3 and 15 h on the methane yield. The long-term effects of the treatment were determined by a semicontinuous experiment. The best results were obtained using 75 % NMMO at 120 °C for 15 h, resulting in 141 % increase in the methane production. These conditions led to a decrease by 9 % and an increase by 8 % in the lignin and in the carbohydrate content, respectively. During the continuous digestion experiments, a specific biogas production rate of 92 NmL/gVS/day was achieved while the corresponding rate from the untreated sample was 53 NmL/gVS/day. The operation conditions were set at 4.4 gVS/L/day organic loading rate (OLR) and hydraulic retention time (HRT) of 20 days in both cases. NMMO pretreatment has substantially improved the digestibility of forest residues. The present study shows the possibilities of this pretreatment method; however, an economic and technical assessment of its industrial use needs to be performed in the future.     

Waste biomass from production process co-firing with coal in a steam boiler to reduce fossil fuel consumption: A case study

Waste biomass is always generated during the production process in industries. The ordinary way to get rid of the waste biomass is to send them to landfill or burn it in the open field. The waste may potentially be used for co-firing with coal to save fossil fuel consumption and also reduce net carbon emissions. In this case study, the bio-waste from a Nicotiana Tabacum (NT) pre-treatment plant is used as the biomass to co-fire with coal. The samples of NT wastes were analysed. It was found that the wastes were of the relatively high energy content which were suitable for co-firing with coal. To investigate the potential and benefits for adding NT wastes to a Fluidised Bed Combustion (FBC) boiler in the plant, detailed modelling and simulation are carried out using the European Coal Liquefaction Process Simulation and Evaluation (ECLIPSE) process simulation package. The feedstock blending ratios of NT waste to coal studied in this work are varied from 0% to 30%. The results show that the addition of NT wastes may decrease the emissions of CO₂ and SO_x without reducing the boiler performance.     

Codigestion of manure and organic wastes in centralized biogas plants: status and future trends

Centralized biogas plants in Denmark codigest mainly manure, together with other organic waste such as industrial organic waste, source sorted household waste, and sewage sludge. Today 22 large-scale centralized biogas plants are in operation in Denmark, and in 2001 they treated approx 1.2 million tons of manure as well as approx 300,000 of organic industrial waste. Besides the centralized biogas plants there are a large number of smaller farm-scale plants. The long-term energy plan objective is a 10-fold increase of the 1998 level of biogas production by the year 2020. This will help to achieve a target of 12-14% of the national energy consumption being provided by renewable energy by the year 2005 and 33% by the year 2030. A major part of this increase is expected to come from new centralized biogas plants. The annual potential for biogas production from biomass resources available in Denmark is estimated to be approx 30 Peta Joule (PJ). Manure comprises about 80% of this potential. Special emphasis has been paid to establishing good sanitation and pathogen reduction of the digested material, to avoid risk of spreading pathogens when applying the digested manure as fertilizer to agricultural soils.     

Physical Pretreatment Methods for Improving Microalgae Anaerobic Biodegradability

Microalgae may be a potential feedstock for biogas production through anaerobic digestion. However, this process is limited by the hydrolytic stage, due to the complex and resistant microalgae cell wall components. This fact hinders biomass conversion into biogas, demanding the application of pretreatment techniques for inducing cell damage and/or lysis and organic matter solubilisation. In this study, sonication, thermal, ultrasound, homogeneizer, hydrothermal and steam explosion pretreatments were evaluated in different conditions for comparing their effects on anaerobic digestion performance in batch reactors. The results showed that the highest biomass solubilisation values were reached for steam explosion (65–73%) and ultrasound (33–57%). In fact, only applied energies higher than 220 W or temperatures higher than 80 °C induced cell wall lysis in C. sorokiniana. Nonetheless, the highest methane yields were not correlated to biogas production. Thermal hydrolysis and steam explosion showed lower methane yields in respect to non-pretreated biomass, suggesting the presence of toxic compounds that inhibited the biological process. Accordingly, these pretreatment techniques led to a negative energy balance. The best pretreatment method among the ones evaluated was thermal pretreatment, with four times more energy produced that demanded.     

Codigestion of proteinaceous industrial waste

Organic wastes are increasingly collected source separated, thus requiring additional treatment or recovery capacities for municipal biowastes, organic industrial wastes, as well as agroindustrial byproducts. In this study, we demonstrate that anaerobic digestion is preferentially suited for high-water-containing liquid or pasty waste materials. We also evaluate the suitability of various organic wastes and byproducts as substrates for anaerobic digestion and provide a current status survey of codigestion. Biodegradation tests and estimations of the biogas yield were carried out with semisolid and pasty proteins and lipids containing byproducts from slaughterhouses; pharmaceutical, food, and beverage industries; distilleries; and municipal biowastes. Biogas yields in batch tests ranged from 0.3 to 1.36 L/g of volatile solids_added. In continuous fermentation tests, hydraulic retention times (HRTs) between 12 and 60 d, at a fermentation temperature of 35°C, were required for stable operation and maximum gas yield. Laboratory experiments were scaled up to full-scale codigestion trials in municipal and agricultural digestion plants. Up to 30% cosubstrate addition was investigated, using municipal sewage sludge as well as cattle manure as basic substrate. Depending on addition rate and cosubstrate composition, the digester biogas productivity could be increased by 80–400%. About 5–15% cosubstrate addition proved to be best suited, without causing any detrimental effects on the digestion process or on the further use of the digestate.