Anaerobic digestion process temperature

The monitoring scheme carried out on 5 Mi-scale plants, 4 demonstrative ones and an experimental one, shows high biogas yield (m3.Kg VS.d ). The anaerobic digestion process is shown to be stable, even when there are falls in digestion temperature, or breaks in the mixing and feeding process. Considerable problems were noted, however,... 

Complete Mix Digester - A type of anaerobic digester that has a mechanical mixing system and where temperature and volume are controlled to maximize the anaerobic digestion process for biological waste treatment, methane production, and odor control. 

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. 

Anaerobic digestion, like pyrolysis, occurs in the absence of air. But, the decomposition is caused by bacterial action rather than high temperatures. This process takes place in most biological materials, but it is accelerated by warm, wet and airless conditions. It occurs naturally in decaying vegetation in ponds, producing the type of marsh gas that can catch fire. 

After aeration for 3-5 days, flooding with heated excess liquid the charge will be heated to 55-60°C. The feeding orifice then will hermetically be closed and the anaerob digestion lasting 3-4 weeks will be started. During this process the temperature of the biomass will be reduced daily by 1-1°C, while at the end of digestion it will reach 30-... 

Methanation. The formation of methane and CO2 from biomass is a classical example of chemical disproportionation of the zero-valence carbon in biomass. The reaction is mildly exothermic and is the natural decomposition reaction of wet biomass in the absence of oxygen (anaerobic digestion of biomass). The reaction also proceeds at elevated temperatures (up to 400 °C) in supercritical water as a reaction medium [29]. Alternatively the reaction can be carried out in a two-stage process ofgasification ofbiomass to synthesis gas, followed by catalytic methanation at T < 400°C (BioUaz). 

Thermochemical liquefaction of biomass is basically a simple process whereby it is heated with alkali under pressure at temperatures up to 400 C. This simple procedure converts the biomass to a mixture of gas (2-10%), char (5-40%), and oil (up to 40%), on a weight basis. It is one of several methods available for conversion of biomass to potential liquid fuels, the others being direct heating of dry matter (destructive distillation, pyrolysis) (1), fermentation (or anaerobic digestion) ( ), and gasification (partial oxidation) ( ) followed by liquefaction to methanol. There are variants on all of thesb processes. 

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