Design Biogas Production from Mixed Napier Pak Chong I/Food Waste at Thermophilic Temperature by Anaerobic Digestion in Cow Dung and Chicken Dung

AD （anaerobic digestion） is a beneficial and efficient technique for the treatment of agricultural wastes, food wastes and wastes water to produce renewable energy. Solid agricultural are potential renewable energy resoures. Biogas production by co-digestion of mixed Napier Pak Chong I and food waste at thermophilic temperature using anaerobic digestion in cow dung and chicken dung as the seed inoculums were investigated. The total reactor volume of the co-digester reactor was 7.94 m^3, which was equipped with pump, and it was operated continuously for the 20 days as a pilot scale at 50 ℃. The Napier Pak Chong I was cut into 2 mm sections, and the initial VS （volatile solids） was 30%. The initial VS of food waste were 70%. Two pilot-scale digesters filled with Napier Pak Chong I and food waste, which both digesters contained 476 kg of Napier Pak Chong I mixed 305 L of food waste, and 1305 L of water. There were carried out to investigate the optimum C/N （carbon to nitrogen） ratio for effective biogas production. The slurry raw materials provided sufficient buffering capacity to maintain appropriate pH values （between 7.0 and 8.0）. Digester I was designed for 1.98 m^3 of cow dung as the seed inoculum while digester II was designed to establish 1.98 m^3 of chicken dung as the seed inoculum. Gas detector performs analysis gas production. The m^3/day in digester I and 1.86 m^3/day from digester II, resulting in added, respectively. Biogas production in digester I was directly experimental results indicate that total biogas production was 2.19 specific methane yields of 1.26 m^3 CH4/kgVS and 1.07 m^3 CH4/kgVS correlated with temperature.     

Biogas energy from family-sized digesters in Uganda: Critical factors and policy implications

Dependence on fossil energy sources is increasingly becoming unsustainable due to ecological and environmental problems and rapid depletion. Biogas energy could augment these conventional energy sources but despite its advantages and favourable conditions for its production, biogas energy use in Uganda remains low due to technical, economic and socio-cultural impediments. Based on primary data on households in Central and Eastern Uganda and the use of logistic regression, this study analyses factors affecting the adoption of biogas energy in Uganda. The empirical results suggest that the probability of a household adopting biogas technology increases with decreasing age of head of household, increasing household income, increasing number of cattle owned, increasing household size, male head of household and increasing cost of traditional fuels. In contrast, the likelihood of adoption decreases with increasing remoteness of household location and increasing household land area. Policy options and recommendations including educational and awareness campaigns on biogas benefits and successes, the provision of financial and non-financial incentives to households and establishment of an institutional framework could bolster wider biogas energy acceptance in Uganda.     

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)。     

Manure's allure: Variation of the financial, environmental, and economic benefits from combined heat and power systems integrated with anaerobic digesters at hog farms across geographic and economic regions

Several studies have shown that anaerobic digesters integrated with combined heat and power systems (CHP/AD) are a financially attractive way to generate electricity, reduce odor, and improve nutrient management on hog farms; yet only very few systems have been installed to date. Employing published financial, economic, and environmental indicators, this study tests whether the benefits from CHP/AD identified in these studies can be replicated across all major hog-farming regions in the US. The study finds that a modest support of 1 cent per kWh is needed to assure that CHP/AD generated electricity is competitive with current utility rates in many hog-farming states. However, the study also shows that once CHP/AD systems are promoted hog-farming states stand to reap large benefits from CHP/AD, particularly environmental benefits (such as odor control and emissions reductions), economic benefits (in form of job creation), and added generating capacity.     

Biogas from anaerobic digestion processes: Research updates

Anaerobic digestion (AD) is a biological process that can convert organic substrates to biogas in the absence of oxygen. The AD process has been practiced for centuries; however, it is still a research focus in contemporary literature. This mini-review selected papers published in 2015 and summarized the improvement and technological advancement and revealing current research and development trends for the biogas from AD process. A discussion on the challenges and prospects for developing improved AD technologies is provided.     

Popularizing household-scale biogas digesters for rural sustainable energy development and greenhouse gas mitigation

Biogas utilization has undergone great development in rural China since the government systematically popularized household-scale biogas digesters for meeting the rural energy needs in the 1970s. In order to comprehensively estimate the significance of biogas utilization on rural energy development and greenhouse gas emission reduction, all types of energy sources, including straw, fuelwood, coal, refined oil, electricity, LPG, natural gas, and coal gas, which were substituted by biogas, were analyzed based on the amount of consumption for the years from 1991 to 2005. It was found that biogas provided 832749.13 TJ of energy for millions of households. By the employment of biogas digesters, reduction of greenhouse gases (GHG) was estimated to be 73157.59 Gg CO₂ equivalents (CO₂-eq), and the emission by the biogas combustion was only 36372.75 Gg CO₂-eq of GHG. Energy substitution and manure management, working in combination, had reduced the GHG emission efficiently. The majority of the emission reduction was achieved by energy substitution that reduced 84243.94 Gg CO₂, 3560.01 Gg CO₂-eq of CH₄ and 260.08 Gg CO₂-eq of N₂O emission. It was also predicted that the total production of biogas would reach to 15.6 billion m³ in the year 2010 and 38.5 billion m³ in the year 2020, respectively. As a result, the GHG emission reductions are expected to reach 28991.04 and 46794.90 Gg CO₂-eq, respectively.     

Reduced hydraulic retention times in low-cost tubular digesters: Two issues

Low-cost tubular digesters have been implemented in several developing countries. One of the problems reported from field surveys is that biogas generation that does not meet the user’s expectations. This report provides two reasons for the discrepancy between the biogas generation rate estimated in the design phase and the actual rate measured after construction, due to a lower final hydraulic retention time (HRT). The hydraulic retention time is normally determined from the liquid volume calculated from the cylindrical shape of the bag and not from the trench dimensions. The result is a reduction in HRT of 6%-51%, depending on the dimensions of the trench recommended by various authors. Another factor that is not normally considered is the influence of the biogas pressure on the liquid level inside the digester which negatively affects the liquid volume of the digester, reducing HRT by as much as 15%.     

Evaluating benefits of low-cost household digesters for rural Andean communities

Low-cost household digesters are a promising appropriate technology which can help reducing the pressure on the environment due to deforestation and greenhouse gases emissions. The biogas and biofertilizer produced can alleviate poverty, by improving health conditions, increasing crops productivity and saving working time and burden for women and children. The aim of this study is to evaluate low-cost digesters technical, environmental and socio-economic impacts in rural communities of the Peruvian Andes, where a pilot project was developed during the last 3 years. Although the benefits are restricted by the performance of anaerobic digestion at high altitude, the results show that the digesters improve household living conditions and economy, while reducing environmental impacts. Biogas production covers around 60% of fuel needs for cooking, leading to 50-60% decrease in firewood consumption (i.e. deforestation) and greenhouse gases emissions; the annual income is increased by 3-5.5% due to fertilizer savings and potato sales. These values could be improved by enhancing digesters performance and the sustainability of the technology.     

Effect of temperature and retention period on biogas production from lignocellulosic material

The extensive utilization of biogas for energy needs of rural dwellers would reduce their dependence on fossil fuels and fuelwoods and henoe camplement Government afforestation programes. In this investigation, effect of temperature and retention period on biogas production from lignooellulosic material, hereafter referred to as cow dung were studied. Maximum gas production was dotained at thermophilic temperature. The results of the effect of retention period shows that gas production was qotimum at 4th and 7th weeks of production.     

TS对牛粪与有机垃圾联合厌氧消化特性的影响研究

在中温(37℃)条件下,对牛粪和有机垃圾进行了为期90 d的连续式厌氧消化试验研究。结果表明:在CSTR厌氧发酵反应器中,牛粪与有机垃圾等比例连续式联合厌氧发酵,当系统水力停留时间低于12.5 d,且TS含量高于16.89%时,系统反应条件开始受到限制,TS含量越高,反应受限程度越大;反应末期pH下降,主要因为末期TS含量增高,系统有机负荷增加,厌氧消化反应无法正常进行,导致挥发酸积累;TS含量为15%是系统最佳的固体浓度,产气效率最高;挥发性脂肪酸(VFA),COD在一定时候均会达到饱和状态,使得反应高效率进行,而NH3-N成为制约因素,含量随着物料的添加一直升高,最终导致消化系统氨中毒,使得反应无法进行。     

Effect of substitution by Ni in MgAl2O4 spinel for biogas dry reforming

Mesoporous nanocrystalline Mg_1-xNi_xAl₂O₄ (x = 0.10, 0.13, 0.17 and 0.20) with large surface area were synthesized via a simple one-step sol-gel method using nonprecious metals. The prepared Mg_1-xNi_xAl₂O₄ catalysts exhibit good catalytic performance towards methane and carbon dioxide dry reforming reaction. The catalysts were evaluated by various techniques, including XRD, BET, TPR, TPO, EPR, Chemisorption, SEM and TEM. All the Ni incorporated MgAl₂O₄ samples possessed high BET area (296–305 m² g^?1) and pore volume (0.47–0.56 cm³ g^?1) with small pore size (6.4–7.4 nm) in meso region after calcination at 700 °C. The TPR results suggested strong interaction effect in NiMg and the reducibility property of the catalysts improved with the increase of nickel doping. Mg_0.8Ni_0.2Al₂O₄ exhibited the highest activity for biogas dry reforming with 72.6% CH₄ and 80.7% CO₂ conversion at 700 °C. Electron paramagnetic resonance (EPR) results indicated that the incorporation of Ni in MgAl₂O₄ spinel lattice led to the lattice distortion and formed oxygen vacancies which are a benefit for the dry reforming reaction.     

温度和pH值对餐厨垃圾和牛粪混合厌氧发酵的影响

通过序批式厌氧发酵,以产气量、产甲烷量、厌氧发酵过程中pH值以及有机物降解程度为指标,研究了不同温度、不同初始pH值对餐厨垃圾和牛粪混合厌氧发酵的影响。试验结果表明,温度为50℃时,厌氧发酵效果最佳,其单位产气量(以VS计)为722.98 mL/g,甲烷体积分数最高达62.73%.,有机物去除率为67.5%;初始pH值为7时,厌氧发酵效果最佳,其单位产气量(以VS计)为618.23 mL/g,甲烷体积分数最高达62.4%,有机物去除率为66%。     

二氧化碳-氮气混合气体在微粉硅胶中生成水合物的 实验研究

空气中CO₂含量的增加导致了全球气候变暖问题。气体水合物能够有效分离出电厂尾气中的CO₂,对改善环境具有重要意义。考察了微粉硅胶（silica gel）中80mol% N₂与20mol% CO₂混合气体水合物形成特性,选取压力范围为6.0 ~ 8.0 MPa,温度范围为 -20 ~ -5℃。研究发现,N₂与CO₂混合气进入反应釜后,直接生成水合物,诱导时间小于1 min。压力越高、温度越低,生成水合物的相对气体消耗量越大,最大的相对气体消耗量为0.115 (mol/mol),水的转化率最大为77.02mol%,前30 min水合物生成速率与压力无关。水合物气体消耗量越大,反应釜中剩余N₂组分的含量越大,最大为90.95mol%。水合物生成驱动力越低,水合物中CO₂ 组分越高。在6.0 MPa、-5℃下,水合物中CO₂组分最大为65.70mol%。     

Investigation and application of polysiloxane-based gel electrolyte in valve-regulated lead-acid battery

Polysiloxane-based gel electrolyte (PBGE) is prepared and investigated as a new gel electrolyte for valve-regulated lead-acid (VRLA) batteries. PBGE particles, characterized by means of Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV) and scanning electron microscopy (SEM), reveal good stability and their particle sizes are 30–50 nm. The initial cyclic properties of the absorptive glass mat (AGM)–PBGE and AGM–colloid silica gel electrolyte (CSGE) hybrid batteries are investigated by electrochemical techniques, scanning electron microscopy and X-ray diffraction (XRD). The addition of PBGE improves the utilization efficiency of positive active material (PAM) in AGM–PBGE hybrid batteries and thus enhances the batteries capacity compared with the AGM–CSGE reference batteries. Cyclic overdischarge tests show that the AGM–PBGE hybrid batteries have superior recharge and discharge during partial-state-of-charge (PSoC). It is also found that the greatly enhanced electrochemical performance of the AGM–PBGE batteries may be due to higher charge efficiency, good conductivity with lower internal resistance and the open three-dimensional network structure of the polyelectrolyte. The analysis results of SEM and XRD indicate that softening and shedding of positive active material are the main causes of failure for the two hybrid batteries.     

A study of a greenhouse concept on conventional biogas systems for enhancing biogas yield in winter months

A new concept is introduced of using a greenhouse for enhancing the biogas yield from a conventional biogas system in the winter months. If a conventional biogas system is glazed, the trapped solar energy can be used to raise the temperature of the slurry which normally goes low enough to reduce the gas yield appreciably. Numerical calculations have been performed corresponding to the meteorological data on a typical winter day, i.e. 19 January 1981, at New Delhi (India). A comparative study of the performances of conventional and solar-assisted biogas plants using the concept of a greenhouse indicates that the ambient temperature of the slurry can be raised from 18°C to about 37°C, the optimal temperature for anaerobic fermentation.