Centralized Biogas Plants Research Articles

The feasibility of a centralized biogas plant treating the manure produced by an organized animal farmers union in Turkey

The aim of this study is to evaluate the feasibility and the energy recovery potential of mesophilic (30-35 °C) anaerobic digestion of animal wastes (manure) at a centralized biogas plant (CBP) for 35,000 cattle. The proposed CBP is composed of an equalization tank followed by pasteurization and 3+[1/2] modules; i.e. each module consists of four completely mixed anaerobic reactors with a capacity of treating the manure from 10,000 cattle. The effect of maize silage loading, as the co-substrate, both on biomethane production and feasibility of the system was also evaluated. Besides, the transport fuel substitutes of the produced biomethane with or without co-substrate were also investigated. Results of the proposed CBP indicated that biomethane production increased ca. 1.65 fold with co-substrate addition and pay-back periods for one module treating 10,000 cattle manure are calculated to be ca. 11 and 7.0 yr without and with silage addition, respectively. Besides, considering the potential revenue when replacing transport fuels, about 74 heavy goods vehicles or 1,560 cars may be powered per year by the biogas produced from the proposed CBP where the co-digestion of manure and maize silage is applied.

The economic performance of combined heat and power from biogas produced from manure in Sweden – A comparison of different CHP technologies

Interest in the generation of biogas from agricultural residues is increasing rapidly due to its climate benefits. In this study, an evaluation of the economic feasibility of various technologies, also on different scales, for the production of combined heat and power from manure-based biogas in Sweden is presented. The overall conclusion is that such production is not profitable under current conditions. Thus, the gap between the calculated biogas production cost and the acceptable cost for break-even must be bridged by, for example, different policy instruments. In general, efficiency of scale favors large-scale plants compared to individual farm-scale ones. However, a large, centralized biogas plant, using manure from numerous farms, is not always more cost efficient than a large, farm-scale plant treating manure from a few neighboring farms. The utilization of the produced heat, electricity prices, and political incentives, all have a significant impact on the economic outcome, whereas the value of the digestate as fertilizer is currently having a minor impact. Utilization of heat is, however, often limited by the lack of local heat sinks, in which case the implementation of a biogas process operating under thermophilic conditions could increase the profitability due to a more efficient utilization of reactor volume by using more process heat. The results from this study could be utilized by policy makers when implementing policy instruments considering biogas production from manure as well as companies involved in production and utilization of biogas.

Exploring the Local Sustainability of a Green Economy in Alpine Communities

Abstract This article aims to contribute to the analysis of the complex relationship between sustainable development and green economy in mountain areas by focusing on a conflict over the building of a centralized biogas plant to produce renewable energy from livestock manure in an Italian Alpine valley. The case study shows that the project for a large-sized biogas plant promoted by the local political institutions as environmental modernization of local agriculture, and supported by the most important professional organizations, became increasingly controversial at the local community level and was eventually abandoned. By drawing in particular on the literature concerning the social acceptance of renewable energies, the article highlights how this conflict raises issues of distributional justice and procedural justice with regard to the implementation of the green economy model, and it points out the need to embed green economy technologies in the local context and conditions. These concerns should be ...

Economic viability and geographic distribution of centralized biogas plants: case study Croatia

Current promising increase of agricultural investments in Croatia not only leads us to the implementation of new technologies and procedures but also leads to an increase of public awareness toward modern agricultural production. As a side effect, renewable energy sources, with special emphasis on biogas, are quickly coming under the loop. Because of this effect, a question of total biogas potential for the farming sector in Croatia becomes very important. One of the biggest obstacles in utilizing biogas on Croatian farms is its geographical displacement and small size. Through this paper economic viability and geographical distribution, as key parameters in determining realistic biogas potential on family farms, will be presented with special emphasis on the two most promising farming sectors: cows and pigs. As already mentioned, one of the biggest barriers in utilizing biogas in Croatia is the relatively small size of farms that are not capable of having economically viable biogas production. That is why community biogas plants will be important in increasing biogas utilization in Croatian farming sector. Presented methodology represents basics for regional analysis of biogas potential of a farming sector with Croatia as a case study with cost assessment of community biogas power plants considering transport distances, transport costs, and size of the power plants and family farms involved in community biogas production. The value of finding Croatia’s farming biogas potential is also important since farms are high-volume energy consumers in their everyday operations and part of that energy consumption can be compensated from renewable energy sources like biogas.

Anaerobic digestion of macroalgae: methane potentials, pre-treatment, inhibition and co-digestion

In the present study we tested four macroalgae species--harvested in Denmark--for their suitability of bioconversion to methane. In batch experiments (53 degrees C) methane yields varied from 132 ml g volatile solids(-1) (VS) for Gracillaria vermiculophylla, 152 mi gVS(-1) for Ulva lactuca, 166 ml g VS(-1) for Chaetomorpha linum and 340 ml g VS(-1) for Saccharina latissima following 34 days of incubation. With an organic content of 21.1% (1.5-2.8 times higher than the other algae) S. latissima seems very suitable for anaerobic digestion. However, the methane yields of U. lactuca, G. vermiculophylla and C. linum could be increased with 68%, 11% and 17%, respectively, by pretreatment with maceration. U. lactuca is often observed during 'green tides' in Europe and has a high cultivation potential at Nordic conditions. Therefore, U. lactuca was selected for further investigation and co-digested with cattle manure in a lab-scale continuously stirred tank reactor. A 48% increase in methane production rate of the reactor was observed when the concentration of U. lactuca in the feedstock was 40% (VS basis). Increasing the concentration to 50% had no further effect on the methane production, which limits the application of this algae at Danish centralized biogas plant.

Integration of centralized biogas plant in cold-snowy region in Japan

A centralized biogas plant was built in Shikaoi town, Hokkaido, Japan to treat manure from 1320 cattle heads. The biogas plant was designed to operate at a feeding amount of 85.8 t/day, a hydraulic retention time (HRT) of 37 days and at a digester temperature of 38 ?C. In this study, the operational performance of biogas plant, utilization of digested slurry and economic balance were investigated. Since the working conditions of the plant became stable, the biogas production was 2,687 m3/day, 92% of produced biogas was consumed in power generation. Average methane concentration in produced biogas was 57.7%. The hydrogen sulfide (H2S) concentration was decreased to below 140 ppm as a result of bio-desulfurization and dry-desulfurization. The average power generation was 3,737 kwh/day and from that 54% of produced biogas was consumed in the facility operation, while 46% was sold to Power Company. About 20,260 t of digested slurry were applied onto 602 ha grassland and agricultural fields. From the results of the operational performance of the plant and the economic balance evidence, it is evident that the centralized biogas plant has a positive effect on the local economy.

Effects of setup of centralized biogas plants on crop acreage and balances of nutrients and soil humus

An increasing number of biogas plants (BGPs) based on digestion of dedicated energy crops have been implemented in Germany. The objectives of this study were to assess the changes in (1) the acreage of different crops (silage maize, cereals, etc.) related to the setup of the BGP, (2) nutrient flows and budgets (N, P, K) due to the implementation of the BGPs, and (3) to assess the effluent N in the overall crop N supply. Data from 14 farmers before the setup of the BGPs were compared with data after implementation. Due to the setup of the BGPs, the acreage of silage maize greatly increased and there were significant negative effects on the weighted soil humus budgets, no effects on the weighted mean N and P budgets, and a negative trend regarding the K budgets. Results concerning the N release from organic manuring to maize crops showed that one third of the farmers considerably over-fertilize maize, indicating an underestimation of short- and long-term N supply of manure N. The implementation of centralized BGPs established very intensive nutrient cycles and, in the long-term higher risks of nutrient losses and environmental pollution are expected. One very effective measure to compensate for negative effects on the soil humus budgets and nitrate leaching is an enlargement of cover cropping, which will also offer economic revenue by providing aboveground biomass for digestion. If the amounts of effluents returned to a single farm or field are not adapted to the nutrient composition of the substrates delivered to the BGP, large nutrient imbalances can result. An effective measure to get a better allocation of the available nutrients is a solid-liquid separation of the effluents, enabling a more targeted allocation of the nutrients.

Substrate inputs, nutrient flows and nitrogen loss of two centralized biogas plants in southern Germany

In Germany, centralized biogas digestion plants (BGP) have been recently constructed. BGPs purchase the substrates from surrounding farmers and, in return, farmers receive the effluents. Substrate inputs, nutrient inputs and outputs were studied for two BGPs with effluent liquid–solid separation. Additionally, the path of the nitrogen (N) during manure handling was assessed. Silage maize (65–75% of the dry matter (DM) inputs) and grass (ca. 20% of the DM inputs) were the main inputs in both BGPs. During manure handling, it is estimated that 20–25% of the N in the effluents was lost via gaseous N emissions. From an environmental point of view the two main challenges are to reduce these gaseous N losses, and to provide N via the effluents mainly for spring manure application, and less so for autumn application. In solid effluents, gaseous N losses during storage are the main potential N loss pathway, whereas for liquid effluents gaseous N losses during and after field spreading are of great relevance. Current management indicated that approximately 50% of the N in the effluents was available for spring application and approximately 30% in autumn due to cleanout of stores before winter. Calculations show that the use of substrates with high DM content during autumn and winter would reduce the demand for storage capacity, thus reducing the demand for store’s cleanout in autumn. This leads to effluents with higher nutrient concentration that are very suitable for application to spring sown crops. Furthermore, some substrates like cereal grains and grass lead to effluents higher in N, whereas silage maize and other substrates lead to effluents low in N. An adapted substrate management would allow more N for spring application. The cycles of P and K are closed, enabling a complete replenishment of the P and K outputs.

地域的な家畜ふん尿処理・利用システム検討へのLCA適用例：共同型メタン発酵施設の導入に伴う温室効果ガス排出量と費用の試算

地域的な家畜ふん尿処理・利用システム検討へのLCA適用例：共同型メタン発酵施設の導入に伴う温室効果ガス排出量と費用の試算

Codigestion of manure and industrial organic waste at centralized biogas plants: process imbalances and limitations

The present study focuses on process imbalances in Danish centralized biogas plants treating manure in combination with industrial waste. Collection of process data from various full-scale plants along with a number of interviews showed that imbalances occur frequently. High concentrations of ammonia or long chain fatty acids is in most cases expected to be the cause of microbial inhibitions/imbalances while foaming in the prestorage tanks and digesters is the most important practical process problem at the plants. A correlation between increased residual biogas production (suboptimal process conditions) and high fractions of industrial waste in the feedstock was also observed. The process imbalances and suboptimal conditions are mainly allowed to occur due to 1) inadequate knowledge about the waste composition, 2) inadequate knowledge about the waste degradation characteristics, 3) inadequate process surveillance, especially with regard to volatile fatty acids, and 4) insufficient pre-storage capacity causing inexpedient mixing and hindering exact dosing of the different waste products.

Enhanced biogas recovery by applying post-digestion in large-scale centralized biogas plants

The main objective of this study was to investigate the degradation efficiency of centralized biogas plants and provide guidance for the design of more efficient digester and post-digestion systems. These centralized biogas plants in Denmark digest manure together with organic waste from the food industry to generate biogas, which is used for electricity and thermal energy. A total of 20 such plants are currently active in Denmark, most of which were included in the investigation. From the plants, samples were obtained from various steps of the process. Samples were analysed and the residual biogas potential determined by batch post-digestion at various temperature levels. Results were correlated with plant characteristics and production statistics in order to judge the efficiency of various digestion concepts. A simplified model based on a two-step biogas production process was developed and experimental data were used to determine kinetic constants. Experimental results and analysis combined with model simulations showed that the residual biogas potential in the main digestion step effluent is originating mainly from undegraded particulate matter in the biomass. For thermophilic plants 93% of the residual biogas potential was originating from particulate matter and 88% for the mesophilic biogas plants. This indicates that the residual biogas potential is mainly due to insufficient retention time in the main digestion step for hydrolysis of particulate material and that the hydrolysis step is the methane yield limiting factor, while conversion of soluble material such as VFA is the rate limiting factor critical for achieving a stable process.

Effect of operating conditions and reactor configuration on efficiency of full-scale biogas plants

A study on 18 full-scale centralized biogas plants was carried out in order to find significant operational factors influencing productivity and stability of the plants. It was found that the most plants were operating relatively stable with volatile fatty acids (VFA) concentration below 1.5 g/l. VFA concentration increase was observed in occasions with dramatic overloading or other disturbances such as operational temperature changes. Ammonia was found to be a significant factor for stability. A correlation between increased residual biogas production and high ammonia was found. When ammonia was higher than approx. 4g-N/l the degradation efficiency of the plant decreased and as a consequence, the residual methane potential was high. Decrease of the residual methane potential with increasing hydraulic retention time was found. Digestion temperature was very important for effective post-digestion. Post-digestion for recovering the residual methane potential at temperatures below 15 degrees C was very inefficient.

Evaluation of Centralized Biogas Plant in Dairy from Economic Point of View

Evaluation of Centralized Biogas Plant in Dairy from Economic Point of View

Centralized biogas plants combine agricultural and environmental benefits with energy production

The concept of centralized biogas plants has been developed in Denmark. At present, 10 plants are in operation with capacities ranging from 50 to 500 tonnes of biomass per day. The biomass consists of approximately 80% manure co-digested with 20% organic waste from abattoirs and various food industries. The effluent is returned as nutritionally defined fertilizer, partly to the farms that supply fresh manure, and partly to other crop farmers. The plants are sited to ensure that the energy can be utilized, mainly for CHP generation. The heat is used for district heating of urban communities. Operational experience shows considerable increases in gas production primarily due to co-digestion of the manure with organic wastes. Possibilities of process regulation have been revealed, and stable thermophilic digestion has been achieved. A two-step process has turned out to be advantageous, the second step being lower temperature post digestion. Environmental and agricultural benefits include savings for farmers, improved fertilization efficiency, less greenhouse gas emission, and cheap, environmentally sound waste recycling. The working economy of the centralized biogas plants has improved, but there is still a need for further reductions in running costs if financially competitive plants are to be created without public investment grants.

Serum myosin light chain in in patients with Kawasaki disease detected by immunoradiometric assay

Currently, geographic information system (GIS) models are popular for studying location-allocation-related questions concerning bioenergy plants. The aim of this study was to develop a model to investigate optimal locations for two different types of bioenergy plants, for farm and centralized biogas plants, and for wood terminals in rural areas based on minimizing transportation distances. The optimal locations of biogas plants were determined using location optimization tools in R software, and the optimal locations of wood terminals were determined using kernel density tools in ArcGIS.The present case study showed that the utilized GIS tools are useful for bioenergy-related decision-making to identify potential bioenergy areas and to optimize biomass transportation, and help to plan power plant sizing when candidate bioenergy plant locations have not been defined in advance.In the study area, it was possible to find logistically viable locations for 13 farm biogas plants (>100 kW) and for 8 centralized biogas plants (>300 kW) using a 10-km threshold for feedstock supply. In the case of wood terminals, the results identified the most intensive wood reserves near the highest road classes, and two potential locations were determined.