初探德国厌氧沼气工程技术用于中国餐厨垃圾处理的可行性

德国厌氧沼气工程技术用于中国餐厨垃圾处理初探尤宇嘉1 杨军华2北京时代桃源环境科技有限公司北京市海淀区上地东路9号得实大厦三层邮编：100085摘要：介绍厌氧技术及厌氧工程在德国的产生、发展及应用情况。

并以餐厨垃圾处理为例，探讨德国厌氧沼气技术及沼气工程的成熟经验应用于中国餐厨垃圾处理的可行性。

关键词：厌氧技术、沼气工程、餐厨垃圾、1．前言餐厨垃圾是城市日常生活中产生的最为普遍的废弃物，其主要成分包括淀粉类食物、植物纤维、动物蛋白和脂肪类等有机物。

具有含水率高、盐分含量高、有机物含量高等特点，易滋生病原菌、病原微生物，易腐烂、变质、发臭、滋生蚊蝇。

目前我国餐厨垃圾多作为养殖饲料直接使用，未经过任何处理的餐厨垃圾通过食用牲畜重新进入食物链，危及人类的身体健康；同时地沟油也被收集起来重新炼制成为廉价食用油，在市场上再次流通，危害人民群众的身体健康。

在存在问题的同时，餐厨垃圾因其富含有机物也可作为潜在的能源供应体。

利用餐厨垃圾通过成熟工艺技术获取能源不失为合理的解决方式。

寻找合适的处理技术及工艺值得人们深入探讨。

2．德国厌氧技术及厌氧工程2.1．德国厌氧工程的发展状况自20世纪60年代起，厌氧技术在德国就得到初步应用。

至上世纪90年代，厌氧技术的工程使用日益成熟，厌氧沼气工程开始在德国及整个欧洲大规模、广泛投入使用。

根据德国沼气协会数据，截至到2010年，德国境内总共有约5000个沼气工程运行使用，占欧洲全部沼气工程的80%以上。

年发电2000MW，提供的上网电量约占德国全年供电量的2%。

2010年德国政府按照《新能源法》（Erneuerbare-Energien-Gesetz）开始对沼气工程发电进行补贴，进一步促进了厌氧沼气工程的发展。

按照德国政府的规划，到2020年，新能源发电将占德国全年总发电量的43%，替代核能在能源供应体系中的位置。

2.2．德国厌氧沼气工程的分类根据使用原料的不同，沼气工程所使用的工艺及设备也各不相同。

根据处理对象的不同，沼气工程可分为以下几类：处理对象污水禽畜粪便能源作物污泥餐厨垃圾生活垃圾进罐TS 1.5-2% 约5% 约3% 10-20% 20-35% 前处理设备简单简单简单复杂非常复杂技术难点成熟成熟高效反应器垃圾分拣粉碎和高有机负荷率反应器垃圾分拣粉碎，干式发酵工艺以上所有使用有机垃圾作为原料，采用厌氧降解技术的垃圾处理工程都称之为厌氧处理工程，但由于垃圾原料性质的差别极大，工程应用上所采用的工艺及设备也截然不同。

目前技术最成熟、应用最久的沼气工程是处理污水及粪便和能源作物的处理工程。

污水中TS含量极低，不需要前处理工艺，发酵罐体较小，工艺设计较为简单，设备较为简单。

由于秸秆等能源作物TS含量较高，碳氮比较低，单独采用厌氧处理难度极大。

因此加入粪便稀释降低物料的总TS含量，同时调整物料中的碳氮比。

这种处理工艺相对简单，只需简单的前处理即可。

目前在德国约有超过300家企业可从事这两种沼气工程的建设运营。

污泥的厌氧处理主要是降低污泥中COD的含量，达到无害化处理的目的。

污泥的厌氧处理工程工艺比较成熟，在德国约有30家企业开展该领域业务。

目前的技术发展方向是采用高效反应设备，提高污泥厌氧处理效率。

进入90年代后，厌氧工程开始尝试处理以餐厨垃圾和生活垃圾为代表的TS含量较高的垃圾物料，这两种垃圾由于TS含量较高、流动性较差、杂质较多，因此在采用厌氧降解技术时需要经过较为完整的机械式前处理过程。

前处理的目的是使去处垃圾原料中的杂质、减小垃圾原料的颗粒大小、改善垃圾原料的流动性。

由于工程技术门槛较高，目前德国仅有不到10家企业拥有餐厨垃圾、生活垃圾厌氧处理工程的设计、建造、运营能力。

在沼气工程建设时，应根据物料性质、TS含量、杂质含量、输送方式及输送能力、搅拌器搅拌能力、沼气利用方式、发酵后产物处理及利用方式等参数，组合选择合适的工艺技术，确保工程的正常平稳运行。

2.3．德国厌氧沼气工程技术厌氧沼气工程是针对有机垃圾的工业化集中处置工程，主要采用设计、建造、运营三方面技术。

2.3.1 设计技术设计技术是指根据餐厨垃圾原料的特性，选择合理的厌氧发酵工艺，设计相应的配套工艺，选择合适的处理设备，同时考虑到杜绝二次污染。

经过几十年的发展，德国已基本上拥有了多种使用厌氧发酵工艺技术，如中温与高温技术；湿法与干法技术；单相与两相技术；连续与序批次技术等。

厌氧发酵工艺是整个设计工作的核心，必须首先确定厌氧工艺，才能够确定其他的配套工艺，如前处理、后处理等工艺。

前处理等工艺过程全部都是围绕厌氧工艺展开的，都是服务于厌氧工艺的。

例如，当确定了采用湿法发酵工艺时，前处理工艺中必须设计制浆工艺。

如果采用干法发酵工艺，制浆工艺就没有必要了。

此外在设计时应根据物料特性选择合理的设备。

以餐厨垃圾为例，湿法工艺中，当物料的TS含量较高时，物料的输送对管道的要求就比较高，例如管道口径、管道连接处弯头的设计等。

尤其是弯头的设计，由于物料的干物质含量较高，很多处理污水、污泥及生物质原料的企业没有这种能力，仍然按照原有的经验设计，最终导致了管道堵塞等问题。

根据已有的工程案例，德国的管道设计可以满足TS为15%的物料输送，目前国内的只能够输送TS 在8%-10%间的物料。

在考虑实施餐厨垃圾厌氧沼气工程时，一定要考虑到餐厨垃圾原料性质的特殊性，区分其与污水、污泥及生物质能沼气工程的不同。

2.3.2 建造技术对于厌氧沼气工程来说，由于发酵后产生的沼气为易燃气体，同时厂区内设有发电机、锅炉等设备，稍不注意，会酿成安全事故。

因此厂区内设备与建筑的合理布局尤为重要。

建造技术的特殊之处在于厂区整体设备的设置摆放，管道排布走向，厂区内防暴、防雷区域的设置等。

合理的布局会提高沼气工程的安全性，同时减少工程占地面积，降低成本，减少初期投入。

目前德国已经形成完整厂区布局概念，处理厂内布局紧凑，既照顾到设备间及建筑间的安全距离，也方便工艺流程进行，做到安全合理。

2.3.3 运营技术运营技术包含两方面内容。

一是建成后调试启动运行的技术；二是运行后的维护及管理技术。

厌氧发酵是个复杂的生物过程，参与厌氧过程菌类种类繁多，特性不一。

工业化的工程使用时难度更高。

如何培养及驯化菌类，使其能够适应高强度工业化生产的要求，成为厌氧沼气工程启动的关键。

要求承建单位拥有较为丰富的厌氧沼气工程调试运行经验，才能够保证调试运行的顺利进行。

运行后的维护与管理能力往往被忽视，但实际上只有能够长期、平稳、正常运行的厌氧沼气工程才是合格的沼气工程。

如上文所述，厌氧发酵是个复杂的生物过程，如果在运行过程中出现了运行不稳、控制不当从而导致厌氧系统崩溃，需要耗费较长的时间（数月）重新建立厌氧发酵体系，对于日处理上百吨垃圾的沼气工程来说，会带来灾难性的后果。

维护与管理技术主要体现在：-- 运行的自动化监控技术-- 运行操作技术-- 应急处理技术-- 劳动保护技术3．中国餐厨垃圾处理3.1．中国餐厨垃圾处理的独特性随着政府对于食品安全问题的重视，2010年开始，国内陆续出台了一系列针对餐厨垃圾处理的指导性政策文件，推动我国餐厨垃圾处理事业的进一步发展。

与国外餐厨垃圾相比，我国的餐厨垃圾处理具有自身的特点：1)垃圾原料中杂质含量高由于餐厨垃圾产生源头管理不规范，餐厨垃圾中通常会混有较多的杂质，造成前处理难度增加2)垃圾原料中含水量较高。

含水量高会影响输送方式及输送设备的选取，厌氧降解工艺的选择范围较小。

3)垃圾中油脂部分的利用方式由于目前新能源发电存在上网较难，补贴较少等问题，而回收废弃油脂制取生物柴油获利较多，因此更多的业主希望能够将油脂分离出去制取生物柴油。

4)发酵后产物的利用发酵后产物制肥料的社会接受程度不高，对发酵后产物的再利用造成负面影响。

这种情况下，需要考虑到产物的无害化处理问题。

3.2．德国厌氧工程技术针对我国餐厨垃圾处理的可行性针对中国餐厨垃圾原料的特性以及处理后产物利用情况，目前中国餐厨垃圾处理项目采用的技术以制取饲料、生物柴油为主。

沼气发电项目不多，更多是利用处理过程中的沼液发酵产气，供给处理设备自身使用，严格来讲，并不是真正的餐厨垃圾厌氧沼气工程。

在此情况下，引进国外先进成熟工程技术及经验，处理中国餐厨垃圾成为可选的解决方案。

厌氧沼气工程的最终目的是能够保证处理厂的正常平稳运行，在此之前的所有工作都应围绕这一目的进行。

有机物厌氧沼气工程是生物、机械、管理等多学科交叉组合的综合性工程，合理的处理工艺、可靠的设备性能、丰富的运营管理经验在这其中起着至关重要的作用。

以处理工艺为例，目前国内厌氧工艺多以高温、单相为主。

这种工艺的优点是初期投资较小、产气速度较快、平稳运行时产气较多。

但存在容易出现酸化、难以平稳运行等缺点。

尽管德国在沼气工程上积累了多年的运行控制经验，但是目前在德国境内的厌氧沼气工程一般上还是采用中温、两相技术，目的就是能够较好地控制厌氧降解过程，保证处理厂的平稳运行。

在我国餐厨垃圾原料物性复杂、处理经验不多的情况下，采用比较稳妥的工艺路线，保证处理厂正常平稳运行不失为是可取的解决方案。

经过多年的工程实践，德国的相关企业已经积累起十分丰富的有机垃圾厌氧处理工程技术经验，可以针对不同特性的有机垃圾，给出相应的处理建议方案，设计合理的前处理工艺，选择可靠的设备，提供丰富的运营管理经验，保证厌氧沼气工程的顺利实施。

4．结语餐厨垃圾处理在我国是个新的课题，尽管对于厌氧降解的研究已经进行了很多年，但多数都停留在科研阶段或中试阶段，目前在国内还没有能够稳定运行的餐厨垃圾沼气工程。

因此，实际上国内没有任何可以借鉴的实际工程经验。

经过数十年的发展及工程实践，德国在厌氧沼气工程技术上积累丰富的实际经验，依托强大的设备制造，结合先进的工艺设计，完全能够保证厌氧沼气工程项目的顺利实施。

结合中国餐厨垃圾特性，借鉴德国厌氧沼气工程的技术与经验，合理设计工艺、选取设备、引进工程建设及运行经验，才能够保证中国餐厨厌氧沼气工程的顺利建设、平稳运行。

Practicability Study on Adopting the Anaerobic Biogas Technology of Germany to Treat China’s Food WasteYOU, Yujia 1 YANG, Junhua 2Beijing Fairyland Environmental Technology Co., Ltd3rd Floor, Deshi Building, No. 9 East Road, Shangdi, Haidian District, Beijing 100085 P.R.CAbstract: This article aims to introduce the emergence and development of the anaerobic technology as well as its applications on biogas plants in Germany, taking the food waste treatment as an example, to discuss the feasibility and practicability of adopting German mature technologies and experiences with regard to anaerobic biogas-plant to treat food waste in China.Keywords: Anaerobic Technology, Biogas-plant, Food Waste1.IntroductionFood waste is the most common waste produced in human’s daily life in cities. Its major ingredients are organic matters such as food starch, vegetable fiber, animal protein and tallow etc. Characterized with high water, salt and organic matter content, food waste is perishable and spoilable where the pathogenic microorganism and bacteria as well as mosquitoes and flies are breeding and growing, and the bad smell is also releasing at the same time.Currently in China, without a further processing, most of the food waste is directly used to feed animals and enters into the food chain endangering human health. Meanwhile, the waste oil dumped in the gutters is also collected to refine edible oil which is circulating in the market and jeopardizing people’s health.However, in spite of these seamy sides, the food waste also contains a great many organic matters that are potential suppliers for energy. It is a reasonable solution using the mature technologies and processes to utilize the food waste to generate energy. It is worthy of discussing to find a proper way to treat food waste.2.The Anaerobic Technology and Biogas Plant in Germany2.1 Development of Anaerobic Biogas Plant in GermanySince 1960s, the anaerobic technology has begun to be applied to practice in Germany. By the time of 90s, the anaerobic technology and engineering had been growing mature and then the large scale biogas plants have been erected and been widely in use in Germany and even in Europe.By 2010, according to the statistics from Germany Biogas Association, there were more than 5000 biogas plants in Germany, making up over 80% of all the biogas plants in Europe. The electricity generated yearly by them amounts to 2000MW comprising of 2% of the annual power supply in Germany. In 2010, pursuant to the New Energy Law (Erneuerbare-Energien-Gesetz), the German government has begun to subsidize the biogas power generation which has further promoted the development of anaerobic biogas plant. According to the programme of German government, by the time of 2020, the amount of electricity generated by new energy will constitute 43% of the total amount of electricity in Germany, replacing the place of nuclear power in energy supply system.2.2Classification of Anaerobic Biogas Plant in GermanyThe processes and equipments used in the biogas plant are varied to accommodate the differences of its raw materials. According the differences of the treating objects, the biogas plant can be divided into following categories:Treating Objects SewageAnimal Dungand EnergyCropSludge Food WasteDomesticRefuseTS to be treated 1.5-2% Around 5%Around3%10-20% 20-35%Pretreatment Equipments Simple Simple Simple ComplicatedVeryComplicatedTechnical Difficulties Fully-fledgedFully-fledgedHighperformancereactorSegregation andcrash of the waste,reactor with a highorganic loading rateSegregation andcrash of thewaste, DryfermentationAll the processes mentioned above select the organic waste as raw materials. The waste treatment projects using the anaerobic digestion technology are called anaerobic treatment project. However, due to the distinctive properties of the raw waste materials, the technical processes and equipments are also different in various project applications.With the fully developed and the most mature technologies, the oldest biogas-plants still in operating at present are those projects with regard to the treatment of sewage, excreta and crops. Because of the extreme low level of TS content in sewage, the technical processes of this kind of projects are relatively simple and no pretreatment process needed, while the equipments are also uncomplicated and the digesters are small.Due to the high TS content and the low level of carbon hydrogen ratio in the energy crops like straws, it is difficult to treat them with just anaerobic technology alone. So the TS content of the materials should be diluted through adding excreta in while the carbon hydrogen ratio also shouldbe adjusted in the meantime. This technical process of the treatment is fairly simple, completing with just a simple pretreatment process. In Germany, currently there are over 300 companies which can engage in the construction and operation of these two kinds of biogas-plant.At the time of constructing a biogas-plant, the selection and combination of the proper technical process should be in line with the parameters such as the material properties, the TS content, the impurity content, the conveying approaches and capacities, the blenders and their capacities, the utilizing way of biogas, the treatment of the product after digestion and its utilization etc. to ensure a stable operation of the project.2.3．The anaerobic technology of biogas-plant in GermanyAnaerobic biogas-plant is an industrialized and centralized disposal project on organic waste mainly adopting three technologies in respect to engineering, construction and operation.2.3.1Engineering technologyEngineering technology refers to the selection of the proper anaerobic digestion process, the designing of the corresponding completing treatment processes and the appropriate treating equipments as well as taking the secondary pollution into account to avoid from it, based on the material characteristics of the food waste.Through decades of development, there are several anaerobic technologies, such as mesophilic and thermohphilic digestion, wet and dry methods, single-phase and two-phase processes, continuous and sequential batching processing etc, have been used in Germany. It is the anaerobic digesting process that is the core of the entire designing and should be firstly decided, and then the other relevant completing processes like the pretreatment and the post treatment will be chosen accordingly. The overall treatment processes including the pretreatment should be developed focusing on and working for the anaerobic digesting process. For instance, as soon as the wet digestion process being decided, the pulping process must be designed in the treatment process, whereas it is unnecessary in the design for the wet digestion process.In addition, the selection of the right equipments in the designing shall also subject to the properties of the materials. Taking food waste as an example, in the wet process, if the TS content is higher, the requirements for the conveying pipe, i.e. in the designing of pipe diameter and the bend connection of pipe, are also stricter to facilitate the transportation of the substrate. Especially in the designing of the pipe bent connection, due to lack of this ability, many companies dealing with the sewage, sludge and biomass materials have designed the bent connection based on their previous experience, because of the high TS content, resulting in a plugging in the bent.According to the previous project cases, the pipe in Germany can meet the requirements for conveying the substrate with TS content of 15%, while the pipe in China only can transport substrate with TS content between 8%-10%. Therefore, as planning a biogas-plant project for foodwaste disposal, we must take the material characteristics of food waste into account and find out its distinctions from the sewage, sludge and biomass materials.2.3.2Construction technologyIn the anaerobic biogas-plant, because of the flammable biogas be produced after anaerobic digestion as well as the generators and boilers which also easy to cause a fire, it is liable to cause a safety incident. Therefore, it is very important for a reasonable layout of the buildings and equipments in the plant. The specialties of the construction technology lie in the placing and distribution of equipments, the piping arrangement, the setting out of protection areas from rain and lightning etc. in the plant. The reasonable layout and distribution will lead to an improvement of safety, reducing the foot print of plant, lowering the cost and decreasing the initial investment.At present, in Germany, the concept of overall plant layout has been formed. In the compacted layout of plant, safely and reasonably, not only is the safe distance among the equipments and the building considered, but the implementing of the processes is also facilitated.2.3.3Operation technologyOperation technology contains two aspects: one is the technology of commissioning and start-up upon completing of project; another is the maintenance and management technology in operation.Anaerobic digestion is a complex biological process with wide varieties of bacteria possessing different properties involved in the anaerobic process. It is more difficult to be applied to the industrialized project. The issues of how to train and domesticate the bacteria to enable them adapt to the requirements of high intensity of commercial process has became the key of starting an anaerobic project. It demands the construction company having rich experiences regarding the commissioning and start-up of an anaerobic biogas plant to ensure a smooth progress of the commissioning and operation.Generally, less importance will be put on the maintenance and management during the operation. However, as a matter of fact, only those biogas plants with a stable and normal operation for a long run are of the qualified biogas-plant. As mentioned above, the anaerobic digestion is a complex biological process and the anaerobic system is easy to collapse, resulted from the unstable operation and improper control in the running process, and will cost a long time, at least several months, to reestablish the anaerobic digestion process. The consequence is a huge disaster for a biogas plant treating more than one hundred tons of food waste every day.The technologies regarding maintenance and operation are mainly as follows:-- Automatic monitoring technology-- Operating technology-- Emergency handling technology-- Labor protection technology3. The treatment of food waste in China3.1 The distinctive characteristics of the treatment for China’s food wasteWith more and more importance being attached on the food safety by government, since 2010, there are a series of policy documents issued to instruct the treatment of food waste in China, which have further promote the business of food waste treatment. Compared with the food waste abroad, the treatment of food waste in China has its distinctive characteristics:i.With high impurity content in the waste materialsDue the informal management of the food waste sources, there are great varieties of impurities mixed in the food waste increasing the difficulty for pretreatmentii.With high water content in the waste materialsThe selection of the conveying approaches and the transporting equipments are subjected to the high water content resulting in a smaller range of option for anaerobic digestion process.iii.The utilization patterns of the oil in the wasteFor the electricity generated from new energy, it is hard to combine with the power grid and there is just a small amount of subsidy for it. Whereas, refining biodiesel from the collected waste oil is more profitable. Therefore, there are a great number of the employers who hope that the oil will be separated from the waste substrate to produce biodiesel.iv.The utilization ways of the product after digestionIt is not widely accepted by the public to use the post digestion product to produce fertilizer, giving rise a negative impact on the reutilization of the product produced after digestion. In this case, the innocent treatment of the product is taken into consideration.3.2 The practicability of using German anaerobic technology to treat the food waste in ChinaAccording to the characteristics of China’s food was te and the utilization of its treatment, currently the treatment technology for food waste in China is mainly targeted to produce fertilizer and biodiesel. There are not many biogas plants in China; and most of them are using the biogas slurry produced in the process of treatment to generate gas which will be used for heating the treatment equipments. Strictly speaking, they are not the true anaerobic biogas plants. In thissituation, it is a rational option to introduce overseas advanced mature engineering technology and experience to deal with the food waste in China.The final goal of a biogas-plant is to ensure a stable operation and all of the previous efforts should focus on it. For anaerobic biogas plant, it is a comprehensive project combining disciplines like biology, mechanics and management and so forth requiring a reasonable treatment process, a reliable equipment function and the rich experiences regarding operation and maintenance, all of them are essential for a project.Taking the treatment process as an example, at present the thermophilic single phase anaerobic process is leading a dominant place in anaerobic processes in China. Although holding the advantages of a less sum of initial investment, a faster gas production and a greater amount of gas produced in a stable running, its defects, i.e. it is liable to be acidified and hard to keep a stable operation, also can be found in this process. Over years of experience of operation and control regarding biogas plant as being accumulated, in Germany, the mesophilic two phase anaerobic technology still in wide range of use to make the process of anaerobic degradation being under well-controlled to make sure a stable operation of biogas plant. Facing the problems of the complexity of food waste materials and lack of the relevant experience, it is a sensible solution to choose a stable process to ensure a stable operation.Through years of engineering practice, the relevant companies in Germany have accumulated rich experiences and the engineering and construction technologies in the disposal of food waste. As a result, they can offer an appropriate solution, including the design of a reasonable pretreatment process, the selection of the reliable equipments and the rich experience in operation and management, according to the characteristics of the food waste material, to make sure a favorable implementation of the project of biogas plant.ConclusionIt is a new subject for food waste treatment in our country. Although the study of the anaerobic digestion has been conducted for many years, but most of them are still staying in bench-scale or pilot-scale. At present, there is no any successful biogas plant in a stable operation in China and we do not have any real project experience to provide a reference.Over the years of project practice and development, the practical experiences with regard to the biogas plant have been gathered. Based on its powerful manufacture ability in mechanical equipments and combined with the advanced technical process, a smooth and favorable implementation of project regarding anaerobic biogas plant can be completely guaranteed by them.To ensure a favorable construction and a stable operation of anaerobic biogas plant in China, we must combine the advanced technologies and experiences learned from Germany with the characteristics of China’s food waste to design a reasonable process, select the proper equipments as well as to incorporate their experiences regarding construction and operation in our project.11。