分散原料沼气集中供气运行分析

我国规模化沼气工程存在原料单一、产气率低、装备落后等技术瓶颈,西南地区沼气原料来源分散、成分复杂,因此需要开发新的多种原料混合发酵的新模式来提高沼气工程厌氧消化效率。本工程通过全混式厌氧发酵两级工艺共同厌氧消化如秸秆和畜禽粪便等分散原料,形成新的沼气和发酵剩余物利用模式。结果表明,在30 d稳定运行期间,600 m³厌氧发酵罐每天可消纳猪粪7.9 t、浓污水8.2 t及农作物秸秆0.2 t,日产气量为900 m³,混合原料发酵的容积产气率达1.5 m³/(m³∙d)。     

Techno - economic analysis of fermentation residues management places a question mark against current practices

Approximately half of the energy produced by biogas combustion engines is in the form of low-grade heat. A plethora of initiatives have been undertaken to utilize this energy source. In commercial terms, only a few technologies have proven to be economically viable in practice. These include: 1) feedstock pre-treatment; 2) drying of agricultural commodities; and 3) low-temperature pyrolysis of the fermentation residues into charcoal or biochar. Whilst low-temperature pyrolysis appears to be the most profitable, current legislation and qualitative standards gives preference to the application of fermentation residues to arable soils. Analyses have shown that if current legislation is not updated, this significant energy source will remain unutilized, which can be interpreted as having a negative impact on the environment.     

施用沼肥对温室内土壤理化性质影响的研究

通过试验研究了混合施用沼肥与化肥对温室内土壤密度、pH值及养分含量的影响,目的是为沼气的综合利用提供理论依据和技术支持.试验结果表明:施用沼肥能有效改善温室内土壤密度、pH值及养分含量,混合施用沼肥和化肥时效果较好,混合施用户用沼气池沼肥和化肥时效果最好.     

Techno-economic considerations: turning fermentation residues into lightweight concrete

To divert from fossil fuels, nearly 20 k of biogas plants have been built in Europe over the past two decades. Although this trend is not closely followed in the rest of the world, it is still represented by other tens of thousands of installations. Since average biogas plant produces some 10 k tones of fermentation residues (hereinafter referred to as FR) annually, many managers and engineers are intensively looking for an economically efficient way to handle this waste. Under the new solution, FRs were pyrolyzed using waste heat from the biogas combustion engine. The obtained charred FRs (hereinafter as CFR) were incorporated in concrete at various dosages. It was revealed that up to a weight ratio of approximately 20%, concrete density decreases without its mechanical properties being degraded. Since the CFR are nowadays highly economical, the above-stated method represents an environmentally friendly and also financially promising solution that is, to our best of our knowledge, the most important contribution of this work.     

Land application of organic waste – Effects on the soil ecosystem

Growing populations and the increasing use of existing resources has led to growth in organic waste emissions. Therefore, a sustainable approach to managing this waste has become a major concern in densely populated areas. Biological treatment is an efficient method for reducing the amount of organic waste, and for producing energy. A large number of biogas plants and compost facilities that use organic waste as a substrate for electricity and fuel production are being built around the world. The biological treatment process in these plants produces large amounts of organic waste, and there is therefore a growing need to find a sustainable use for this material. Organic waste, such as biogas residues and compost can be a valuable fertilizer for agricultural soils. They can serve as a source of plant nutrients and can also improve soil structure and water holding capacity. However, as organic residues are known to contain both heavy metals and organic contaminants there is a need for long term field experiments to ensure that soil and plant quality is maintained. In order to investigate the potential risks and benefits of using organic waste in agriculture, an 8 year field experiment was established in central Sweden. Under realistic conditions, compost and biogas residues from source-separated household waste were compared with traditional mineral fertilizer. We examined crop yield and soil chemical and microbiological properties. The main conclusion from the field experiment was that biogas residues resulted in crop yields almost as high as the mineral fertilizer NPS. In addition, several important soil microbiological properties, such as substrate induced respiration, potential ammonium oxidation and nitrogen mineralization were improved after application of both biogas residues and compost. Moreover, no negative effects could be detected from using either of the organic wastes. In particular the genetic structure of the soil bacterial community appeared to resist changes caused by addition of organic waste.     

Anaerobic fermentation technology increases biomass energy use efficiency in crop residue utilization and biogas production

A biomass energy utilization project (Corn stalk→Cattle→Cattle dung→Biogas digester→Biogas/Digester residues→Soil) was conducted in a typical temperate agro-village of China from 2005 to 2010. The present study focused on two key approaches of the ecological loop: (1) increasing corn stalk use efficiency by improving anaerobic fermentation technology; and (2) enhancing biogas productivity by optimizing fermentation conditions. Our results showed that crude protein and fat of corn stalks significantly increased, while crude fiber content and pH decreased considerably during anaerobic fermentation. The cattle digestion rate, forage consumption and increases in cattle weight were higher in cattle fed fermented corn stalks than in those fed non-fermented corn stalks. The rate of biogas production was higher (78.4%) by using cattle dung as a substrate than using crop residues. Heat preservation measures effectively enhanced the biogas production rate (12.3%). In 2005, only two cattle were fed in this village, with only 1.1% corn stalk utilized as forage. No more than three biogas digesters existed, and the proportion of biogas energy used in total household fuel was only 1.7%. At the end of the 5-year experiment, the number of cattle capita reached 169 with 78.9% corn stalk used as forage. Biogas digesters increased to 130, and the proportion of biogas energy used in total household fuel was up to 42.3%. A significant positive correlation was noted between the increasing rate of farmers’ incomes and the proportion of corn stalks used as forage. Available nutrients were higher in fermented cattle dung than in fresh cattle dung. Our findings clearly suggest that anaerobic fermentation technology is important in enhancing crop residue use efficiency, biogas productivity and soil fertility. Fermentation technology may help reduce the use of fossil fuels and improve the environment in rural areas.     

利用沼肥培育普陀水仙试验

介绍了2年生普陀水仙的施肥试验和结果,认为普陀水仙对养分的需求较高.在其商品球生长期施用沼肥可促进普陀水仙的生长,增大球径,延长开花期,增加其抗病性.结果表明,在普陀水仙生产中可以施用沼肥.     

Analysis and decrease of the energy demand of bioethanol-production by process integration

Process simulation was used to decrease the external heat demand during the production of bioethanol by integration in a network of facilities for heat and power generation. Models for bioethanol fermentation and purification process, the production of DDGS as well as production and utilization of biogas were developed to calculate the heat demand of bioethanol-production and the amount of heat and power generated from residues of the bioethanol process. Depending on the form of biogas utilization (CHP-plant, biogas fired boiler) and the capacity of the bioethanol plant, the conversion of stillage from the bioethanol process to biogas covers a considerable amount of the heat demand necessary for bioethanol-production and purification.     

施用沼肥对生菜生长特性及品质影响的研究

通过沼肥与化肥的混合施用,试验研究了沼肥对生菜生长特性及其品质的影响,目的是为沼气的综合利用提供理论依据和技术支持.试验结果表明：施用沼肥能有效提高生菜产量,改善生菜的植物学性状和营养品质,特别是在喷施沼液的情况下,当沼渣与化肥配比为8：2时,生菜产量最高,品质最优.     

Evaluation of energy efficiency of various biogas production and utilization pathways

The energy efficiency of different biogas systems, including single and co-digestion of multiple feedstock, different biogas utilization pathways, and waste-stream management strategies was evaluated. The input data were derived from assessment of existing biogas systems, present knowledge on anaerobic digestion process management and technologies for biogas system operating conditions in Germany. The energy balance was evaluated as Primary Energy Input to Output (PEIO) ratio, to assess the process energy efficiency, hence, the potential sustainability. Results indicate that the PEIO correspond to 10.5–64.0% and 34.1–55.0% for single feedstock digestion and feedstock co-digestion, respectively. Energy balance was assessed to be negative for feedstock transportation distances in excess of 22 km and 425 km for cattle manure and for Municipal Solid Waste, respectively, which defines the operational limits for respective feedstock transportation. Energy input was highly influenced by the characteristics of feedstock used. For example, agricultural waste, in most part, did not require pre-treatment. Energy crop feedstock required the respect cultivation energy inputs, and processing of industrial waste streams included energy-demanding pre-treatment processes to meet stipulated hygiene standards. Energy balance depended on biogas yield, the utilization efficiency, and energy value of intended fossil fuel substitution. For example, obtained results suggests that, whereas the upgrading of biogas to biomethane for injection into natural gas network potentially increased the primary energy input for biogas utilization by up to 100%; the energy efficiency of the biogas system improved by up to 65% when natural gas was substituted instead of electricity. It was also found that, system energy efficiency could be further enhanced by 5.1–6.1% through recovery of residual biogas from enclosed digestate storage units. Overall, this study provides bases for more detailed assessment of environmental compatibility of energy efficiency pathways in biogas production and utilization, including management of spent digestate.     

大型海藻发酵生产甲烷技术研究

大型海藻发酵生产甲烷属生物质能,是一种碳中性的清洁能源,是重要的海洋生物碳汇。不同种类的藻类发酵产甲烷的潜力是不一样的,其中巨藻含有丰富的甲烷成分,但其自然资源量有限,而人工养殖依然是一个难题,如何持续不断地提供原材料是巨藻生物质能源开发中亟待解决的问题。海藻发酵产甲烷是多种微生物联合作用的结果,从整体上可划分为产甲烷菌群和不产甲烷菌群,它们相互依赖又相互制约,产甲烷菌利用不产甲烷菌的代谢产物H2、CO2等最终合成甲烷。海藻发酵过程的微生物要求具有一定的耐盐性,大体可以利用沼气发酵微生物经过定向培养和筛选而获得。多数人支持将沼气发酵过程分为水解液化、酸化和甲烷化三个阶段的理论,而甲烷形成途径包括菌种间H2的转移和由乙酸产生甲烷。甲烷发酵的影响因素包括原料的预处理、原料的成分和颗粒大小以及接种物、发酵温度、发酵料液pH值、接种率及接种物中对发酵菌活性有影响的物质等,甲烷产率最大化的最主要前提是反应条件要达到最优化。我国在海藻大规模养殖方面具有先天的自然条件及技术和人力优势,为海藻生物质能源开发提供了巨大的潜力,但在技术上还有待突破,特别是在接种物培养、甲烷产率控制等一些特定环节上还需加强研究。     

Integrating animal manure-based bioenergy production with invasive species control: A case study at Tongren Pig Farm in China

Integrated approach and bioresource engineering are often required to deal with multiple and interactive environmental problems for sustainable development at local and regional scales. Pig farming has flourished with fast growing economy and increasing human demands for meat in China. Water hyacinth (Eichhornia crassipes), a noxious invasive species, has encroached into most of the local rivers and lakes. Both the wastes from the booming pig farms as well as the massive plant materials of water hyacinth have caused a range of serious ecological and environmental problems. Here we present an integrated sustainable, ecological and experimental study that was designed to deal with these two problems simultaneously. Our experimental results showed that the mixtures of water hyacinth with pig manure consistently had much higher biogas production than pig manure alone, and that the highest biogas production was achieved when 15% of the fermentation substrates were water hyacinth. Our analysis further revealed that the changing C/N ratio and the lignin content in the fermentation feedstock due to the addition of water hyacinth might be two important factors affecting the biogas production. We also found that the solar-powered water-heating unit significantly increased the biogas production (especially in winter time). Overall, the project proved to be successful ecologically and socially. Through such an integrated approach and bioresource engineering, wastes are treated, energy is harvested, and the environment is protected.     

Assessment of biogas potential hazards

Biogas produced from anaerobic fermentation of organic substances represents an alternative renewable energy source. Its utilization would contribute to substantial reduction of the solid waste volume in land-filling and incineration. Biogas so produced could be utilized on site or it could be injected into the natural gas distribution network. Microbiological and chemical compositions of different biogas types were determined in order to conduct qualitative and quantitative risk assessments of the potential health hazards associated with biogas use for cooking. Biogas types that could be allowed for injection in the natural gas pipelines were listed with recommendations, while outlining the European biogas injection policy. Results indicated that the injection of the processed biogas in the distribution network did not present any additional chemical or microbiological risk to consumers when compared to natural gas, provided that the biogas resulted from the fermentation of non-dangerous waste. However, since this study did not examine the microbiological and chemical composition of biogas originating from wastewater sludges and/or industrial wastes, the injection of this type of biogas into the gas distribution network should not be allowed unless a similar risk evaluation study is conducted for each case.     

Elemental composition of biogas residues: Variability and alteration during anaerobic digestion

Biogas production and the amount of thereby incurred digestates increased remarkably in the last decade. Digestates should be used as soil fertilizers to close nutrient cycles. However, knowledge about the elemental composition of digestates from biogas production and element losses or accumulations during fermentation process is insufficient so far. Intending to enlarge the database for the elemental composition of digestates and to investigate element in- and outputs of biogas fermenters, we measured the concentrations of C, N, P, K, S, Ca, Mg, Fe, Mn, Zn, Cu, Pb, Cd, Ni, Mo and Se of digestates and feedstock (ingestates) of four full-scale biogas plants in Germany monthly over a one year period. Ingestates were sewage sludge, fat and mash (SEW1), sewage sludge and fat (SEW2), pig slurry, treacle and food residues (SL) and maize silage (M). We developed a statistical method to calculate the number of required sampling dates which have to be integrated for the calculation of reliable element budgets between ingestates and digestates for the case when information about the amount and composition of the produced biogas is not available. Our results suggest that two (SEW2), five (SEW1, M) and 10 (SL) sampling dates had to be integrated for reliable balances. All fermenters revealed losses of N, most likely due to volatilization of NH₃. Losses of S (probably H₂S), Mg (precipitation of struvite), Cd and Zn (precipitation of sulfides) could be detected in some cases. Iron and Mn accumulations can be attributed to attrition of the stirrer.     

Sustainability accounting for the construction and operation of a plant‐scale solar‐biogas heating system based on emergy analysis

Domestic heating systems have long been playing a significant role in China's energy structure. The sustainability of a hybrid solar‐biogas heating system (SBHS) under various feedstock fermentation scenarios was evaluated using emergy analysis. Representative emergy indices such as transformities, emergy yield ratio (EYR), environmental loading ratio (ELR), emergy sustainability index (ESI), ratio of waste treatment (%W), feedback yield ratio (FYR), and emission mitigation intensity (EMI; g/10¹⁰ sej) were selected to evaluate the sustainability performance of different feedstock scenarios including cow dung (CD), swine manure (SM), and poultry manure (PM). The results showed that PM fermentation scenario had greater market competitiveness, lower environmental pressure, better sustainability, and self‐organizing ability than the other two options. However, both the emergy efficiency and the CO₂ emissions mitigation intensity of PM scenario were worse than that of the SM and CD. Moreover, compared with other biogas systems and traditional agricultural systems, the hybrid SBHS was proved to be a promising mode for the treatment of rural manure waste with favorable economic benefits and environmental sustainability.     

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。     

Intracellular disintegration by shockwave pretreatment accelerates “dry fermentation”

Dry fermentation refers to the process of anaerobic digestion that does not take place in a mixable liquid environment but in stacks loaded into airtight chambers. Since it is difficult for anaerobic consortia to decompose biomass without operating fluid, the process of dry fermentation is time consuming and considered technically inefficient. However, the construction costs of such biogas plants are significantly lower in comparison to conventional continuous technologies. Shockwave pretreatment is a modern method of intracellular disintegration that occurs purely on the basis of physical forces. It was confirmed for the first time that shockwaves are capable of accelerating methanogenesis, even in technologies that do not utilise a process liquid. This finding opens up new opportunities with regards to the processing of feedstock such as solid biowaste.     

Agricultural waste resources and biogas energy potential in rural areas of Lao PDR

Lao PDR lacks of conventional energy resources, such as oil and natural gas, and 100% of fossil fuels are imported from abroad. Fossil fuel consumption in Lao PDR in 2010 was about 561 million liters and rapidly increased to 716 million liters by 2015. However, Lao PDR has a high potential for renewable energy, especially from hydropower, agricultural wastes, and livestock wastes, in which agricultural and livestock annually produced a large amount of agricultural residues as a favorable renewable energy sources. In 2016, productivity crops were estimated for 24,608,840 ton and these products amount can be generated annual agricultural residues for 12,525,000 ton, which can be estimated to total of energy potential was 197,840 GJ or 55,001 GWh. The majority of livestock in country are buffaloes, cattle, swine, and poultry; large amount of livestock manure produced from each region and can be feedstock as substrate for biogas digester, which these amounts were estimated about 1,583,740 kg TS/day, and equivalent to 439,917 m3/day of biogas production or 658,376 kWh/day of energy generation. Therefore, objective of this paper is unique to promote and research development the agroforestry residues and livestock wastes as renewable energy resources, and its energy potential for biofuel production, including, biodiesel, bioethanol and biogas in each region of Laos.     

餐厨垃圾与农业秸秆的厌氧发酵区别

从能源的可持续发展和资源化利用的角度,介绍了餐厨垃圾和农业秸秆厌氧发酵的处理方法,重点分析了餐厨垃圾和农业秸秆在成分、预处理、厌氧发酵工艺、沼气成分含量、沼液用途方面的区别。