Digestion anaerobic

Processes of Biogas Production Anaerobic Digestion and Thermal Gasification 

Another important global challenge is the certainty of energy supply, because most of the known conventional oil and gas reserves are concenttated in politically unstable regions. 

There exists significant and increasing interest in the utilization of biogases for their energy value. 

Turco et al., Treatment of Biogas for Feeding High Temperature Fuel Cells, Green Energy and Technology, DOI 10.1007/978-3-319-03215-3 l 

Biogas is a versatile renewable energy source, which can be used for replacement of fossil fuels in power and heat production, and as gaseous vehicle fuel. Methane-rich biogas (biomethane) can also replace natural gas as a feedstock for producing chemicals and materials. 

Add the plastic sample in the form of powder or small pieces to a concentration of 100-2000 mg/L of TOC with activated sludge or active soil in a test flask. 

Anaerobic digestion is a process where food and agricultural waste can be converted to methane and carbon dioxide in a thermophilic reactor. Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen (NNFCC 

Renewable Fuels and Energy Factsheet Anaerobic Digestion 2013). It is used for industrial or domestic purposes to manage waste and/or to release energy. 

Standards are necessary to monitor the performance of biodegradable plastics in an aerobic digestion reactor. The anaerobic decomposition takes place under high solids (more than 30% total solids) and static non-mixed conditions. The biodegradation process usually requires 1-2 weeks of dwell time. Table 8.5 hsts the biodegradation standards for anaerobic digestion. 

ASTM D5511-02. Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materiais under High Soiids Anaerobic-Digestion Conditions 

Several applications based on biodegradable plastics that end up directly in soil after their useful life are under development and experiencing rapid market growth. Examples are mulch films, strings, hooks and clips, slow release pheromone dispensers and drip irrigation pipes. Furthermore, mature industrial compost, obtained from a feedstock that includes biodegradable polymers, also ends up in soil because of its application as a soil improver. 

Soil is a heterogeneous matrix influenced by the combination of several climatic and 

The main factors influencing the presence of microorganisms and their biodegradation activity in soil are briefly discussed below. 

---

The performance of anaerobic digestion processes varies according to the type of unit, throughput, and feed concentration, but such processes are typically capable of removing between 75 and 85 percent of COD. ... 

In attached growth film) methods, as with aerobic digestion, the microorganisms can be encouraged to grow attached to a support medium such as plastic packing or sand. In anaerobic digestion, the bed is usually fluidized rather than a fixed-bed... 

Anabaena azollae Anabaena cylindrica Anabaena flos-aquae 0-anabasine [494-52-0] Anabasine [494-52-0] Anabolic steroids Anaerobic digestion Anaerobic treatment Anafranil... 

Ana.eroblc Digestion. Methane can be produced from water slurries of biomass by anaerobic digestion in the presence of mixed populations of anaerobes. This process has been used for many years to stabilize municipal sewage sludges for purposes of disposal. Presuming the biomass is all cellulose, the chemistry can be represented in simplified form as follows ... 

Fig. 4. Microbial phases in anaerobic digestion A, hydrolysis B, acidification C, methane fermentation.

Gasification. Conversion of biomass to gaseous fuels can be accompHshed by several methods only two are used by the biomass energy industry (ca 1992). One is thermal gasification in which LHV gas, ie, producer gas, is produced. The other process is anaerobic digestion, which yields an MHVgas. 

Table 37. Potential Methane Production from Commercial U.S. Anaerobic Digestion Systems...

R. L. Wentworth, "Anaerobic Digestion in North America," paper presented at Symposium Anaerobic Digestion and Carbohydrate Hydrolysis of Waste, sponsored by Commission of the European Communities, Luxembourg, May 8—10,1984. 

J. H. Ashworth, Y. M. Bihun, and M. La2ams, Universe of U.S. Commercial-Scale Anaerobic Digesters Results of SERJ/ARD Data Collection, Solar Energy Research Institute, Golden, Colo., May 30,1985 J. H. Ashworth, Problems With Installed Commercial Anaerobic Digesters in the United States Results of Site Visits, Rev. ed.. Solar Energy Research Institute, Golden, Colo., Nov. 6, 1985. 

The microorganisms grow in response to the food source suppHed in the wastewater and produce more biological sludge than is needed to maintain the process. This excess sludge must be wasted from the process and is usually treated by dewatering and aerobic or anaerobic digestion. 

Anaerobic ponds are loaded such that anaerobic conditions prevail throughout the Hquid volume. One of the major problems with anaerobic ponds is the generation of odors. The odor problem can frequentiy be eliminated by the addition of sodium nitrate at a dosage equal to 20% of the appHed oxygen demand. An alternative is the use of a stratified facultative lagoon, in which aerators are suspended 3 meters below the Hquid surface in order to maintain aerobic surface conditions, with anaerobic digestion occurring at the lower depths. 

Sludge Stabilization. Organic sludges need to be stabilized before ultimate disposal except in the case of incineration. This is usually achieved by either aerobic or anaerobic digestion. In aerobic digestion, the degradable volatile soHds are Hquefted and oxidized to CO2 and H2O. In anaerobic digestion the soHds are Hquefted and fermented to CH and CO2. 

Fig. 3. Process components for the activated-sludge process, with aerobic digestion at plants <473.1 m /h and two-stage anaerobic digestion at plants...

Sludge is destroyed by microorganisms and the kinetics of their life processes is temperature dependent. Short anaerobic digestion detention times are obtained at 35°C. Even shorter detention times are possible at 52—54°C, but detention in this range is costly. An increase in detention time occurs at 35—43°C and then a progressive decrease takes place until 52—54°C. This variation is caused by a change in character of the dominant process organisms. 

Stabilization (Anaerobic Digestion, Aerobic Digestion, High Lime... 

---