Design and Implementation of Biogas Plants Geographic Information System

[Objective] A kind of biogas engineering geographic information system was designed and realized.[Method] Based on the data of the investigation of the large and medium-sized biogas projects in Beijing,the system user＇s need and function demand were studied.Sub-system function was divided.By using SuperMap IS.NET,C# and SQL Server 2005 as the database and WebGIS frame,the system spatial and attribute database were designed so as to realize the WebGIS software of biogas project in Beijing.[Result] The system provided application platform for the distribution of biogas project information.User can realize the submission and inquiry the feedback of biogas project information based on system application right etc,so as to visually,fully and precisely inquiry project data.Based on the comprehensive analysis of data,the current state of biogas project and change trend were studied and decided.[Conclusion] The system provided convenience and services to relevant departments＇ planning and management of biogas project.

The Research on Optimization of the Multiphase Flow Field of Biogas Plant by Using CFD Software

The inner flow field of a biogas plant can be optimized by agitating the feedstock to be evenly distributed for a rising biogas production rate. A hydraulic agitator can be installed in the digester with outlets far above the bottom. Hydraulic mixing is essential in a solid-liquid two-phase flow process, in which large solid particles can be found at the initial stage and turn to being high-concentration viscous liquid （non-Newtonian fluid）. A 0.75 m3 digester was taken as a case study with CFD （computational fluid dynamics） software. The basic pattern was simulated by using water as the medium and the pattern of pseudo plastic fluid state was simulated by the Euler-Euler Model, then the effect of optimized design with bottom inflow and high dispersed outlets could be verified. Viewed from the mixing effects, the velocity of 0.6 m/s is better than l m/s for water medium, while 1 m/s better than 0.6 m/s for pseudo plastic fluid medium.

Ecological analysis of a typical farm-scale biogas plant in China

The aim of this work was to present the common anaerobic digestion technologies in a typical farm-scale biogas plant in China. The comprehensive benefits of most biogas plants in China have not been fully assessed in past decades due to the limited information of the anaerobic digestion processes in biogas plants. This paper analyzed four key aspects （i.e., operational perfor- mance, nonrenewable energy （NE） savings, CO2 emission reduction （CER） and economic benefits （EBs）） of a typical farm-scale biogas plant, where beef cattle manure was used as feedstock. Owing to the monitoring system, stable operation was achieved with a hydraulic retention time of 18-22 days and a production of 876,000 m3 of biogas and 37,960t of digestate fertilizer annually. This could substantially substitute for the nonrenewable energy and chemical fertilizer. The total amount of NE savings and CER derived from biogas and digestate fertilizer was 2.10× 10^7 MJ （equivalent to 749.7 tee） and 9.71 × 10^5 kg, respectively. The EBs of the biogas plant was 6.84× 10^5 CNY.yr^-1 with an outputs-to-inputs ratio of 2.37. As a result, the monitoring system was proved to contribute significantly to the sound management and quantitative assessment of the biogas plant. Biogas plants could produce biogas which could be used to substitute fossil fuels and reduce the emissions of greenhouse gases, and digestate fertilizer is also an important bio-product.

Inventory analysis of carbon footprint on greenhouse gas emission of large-scale biogas plants

Inventory analysis of greenhouse gas emission for large-scale biogas plants using carbon footprint method still needs to be improved.Based on the life cycle theory,the application of carbon footprint on four large-scale biogas plants was analyzed in this paper,which comprehensively considered project progresses of civil engineering construction,operation and comprehensive utilization of residues and slurry.Also the greenhouse gas emissions during the construction and waste removal stages were analyzed and estimated.The carbon footprint of those plants was analyzed in different types and scales.The results showed that the larger scale plant will produce relatively lower carbon footprint.The greenhouse gas emission of energy production,utilization during the period of anaerobic digestion accounted for more than 96%of the entire life cycle emission.The proportion of greenhouse gas emissions on equipment,demolition recycling and transportation phases was smaller,which was less than 1.5%and should be simplified in calculation.The greenhouse gas emission of building materials production can be ignored.

Empirical analysis of mass flow and operation performance of a full-scale biogas plant for human feces treatment

With the rapid development of urbanization in China,the existing municipal network cannot cover all areas and solve all human waste treatment problems.Biogas plants,as an important nationally developmental strategy for cleaner energy production and environmental protection,have been widely used in many industrial and agricultural fields.This research analyzed the mass flow and operation performance in a biogas plant treating human feces at a practical rather than laboratory scale.The biogas plant operated on mesophilic semi-continuous mode at the organic loading rates(OLRs)of 0.56 kg volatile solid(VS)/(m³·d)and average total solid(TS)contents of 3.50%.Results showed that the average biogas production and methane yield were(145±10)m³/d and(471±17)m³CH4/(t VS),respectively.Annual total feeding amount was 2555.0 t.Among these,there were 58.04 t biogas and 2496.97 t digestate,including 43.07 t solid residues and 2453.90 t liquid digestate.For the full-scale biogas plant,anaerobic bacteria could acclimatize to high total ammonia nitrogen(TAN)concentration(3659 mg/L)and tolerate high free ammonia nitrogen(FAN)concentration of 561 mg/L.It also had strong autoregulation for adapting the large range(2.02-15.18 g/L)and high concentration(15.18 g/L)of influent volatile fatty acid(VFA).In order to achieve its sustainable development and high efficient operation,it is very important to improve the feeding concentration,using digestate to dilute raw material and adding some high C/N raw material in human feces.In conclusion,the biogas plant was an excellent alternative technology for treating human feces.

Environmental impacts concerning flexible power generation in a biogas production

Combined heat-and-power units(CHPUs)of biogas plants can be operated at partial load or in intervals to respond to market conditions or interventions by the grid operators.In this study,we present calculations for the specific greenhouse gas(GHG)emissions of electricity from biogas driven CHPUs in dependence of engine load.Following the methodology of life cycle assessment and using measured data from five real-world biogas plants in Bavaria,we investigated the following scenarios for the operation of the CHPU:(1)full load,(2)80%load response and(3)60%load response.Our system boundary included the whole biogas production chain,starting from the production/supply of the input materials and ending at the supply of electricity(functional unit:1 kWh of electrical energy fed into the grid).As electrical efficiency and engine load are positively correlated,partial-load operation results in higher specific GHG emissions of electricity from biogas.The impact of decreasing efficiency of the CHPU under partial load on overall specific GHG emissions turned out to be higher than the influence of methane slip from the engine.Furthermore,the increase of further efficiencies such as higher yields,efficient use of synthetic and organic fertilizers,as well as minimization of fuel consumption and the use of regenerative fuels also lead to further decrease of GHG emissions.

Effects of temperature,pH and O_(2) on the removal of hydrogen sulfide from biogas by external biological desulfurization in a full scale fixed-bed trickling bioreactor(FBTB)

Hydrogen sulfide(H_(2)S)is a critical component of biogas formed under anaerobic conditions by sulfur and sulfate reducing bacteria from animal manure and renewable energy crops.H_(2)S causes high corrosion in equipment,has a negative environmental impact,inhibits the biogas formation process and is furthermore odorous and toxic.Although several methods for internal and external desulfurization found their way into practice and had been explored at laboratory scale,no data were available on the performance of such methods in full scale practice,especially for an external fixed-bed trickling bioreactor(FBTB).The effects of temperature,pH and air ratio on H_(2)S removal efficiency(RE)were studied.The study was conducted at a research biogas plant with a given output of 96 m^(3) biogas per hour,and an H_(2)S concentration ranging between 500 ppm and 600 ppm(1 ppm=1 cm^(3)/m^(3))on average.The FBTB column has been designed to hold a packing volume of 2.21 m^(3) at a gas retention time of 84 seconds being loaded at an average of 32.88 g H_(2)S/(m^(3)·h).The highest H_(2)S RE of 98% was found at temperatures between 30℃ and 40℃.A major decline in RE to 21%-45%was observed at temperatures from 5℃ to 25℃.The results clearly showed a temperature optimum range for sulfate reducing bacteria.The results reveal that RE is little affected by different pH values and air ratios.During the experimental period,the practical suitability of the FBTB system could be proved while avoiding the disadvantages of internal biological desulfurization methods.