The Urban Farming Guys have just released a great video showing how they built a DIY biogas digester using little more than some tanks, piping, rubber seals and a grinder. Look for information about these plans and a lively discussion of biogas construction online at www. What is the production capacity of a biodigester? Go to the Directory. Video Case Studies. Learn about anaerobic digestion from these compelling videos.
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The amount of waste that will be digested, and whether or not this will need to be diluted, will determine the size of the digester needed. The amount of waste loaded into the digester will vary according to the species of animal and the waste handling methods used. Digester Start-up To speed up the digestion startup process, methane bacteria can be added to the digester before the first load of waste is loaded. The acid forming bacteria and methane forming bacteria are in balance, with the former only producing as much organic acids that the latter can utilize.
When environmental conditions are not optimal the digester can become too acidic as the acid forming bacteria are hardier than the methane forming bacteria and quickly outnumber the latter, producing more organic acids than what the methane producing bacteria can handle. Should this happen, a temporary solution to control acidity is to add an alkaline substance — lime is commonly used to counteract the acidity in such scenarios.
However, in order to maintain gas production, the cause of the problem needs to be addressed to prevent reoccurred. Digester Construction: Things to Consider Now that we have covered some of the key elements of digester design, lets focus on the construction. The key points to consider when constructing a biodigester is that Biodigesters need to be airtight and well insulated, they must be able to be heated, and they must be able to have the waste contents inside stirred at regular intervals.
Insulation: Because methane is only produced at optimal temperatures it is essential that heat is conserved within the digester. To save costs, this can be achieved by making use of the insulating properties of soil — In a well drained site, the digester tank can be buried; alternatively soil can be piled in a mound around the sides of the digester tank to aid insulation and prevent heat from escaping. Heating: To achieve a temperature of 95F necessary for methane production year-round in all seasons, a heat-exchange is typically installed.
This involves a system of hot water piping installed within the biodigester. Hot water, heated by an external methane powered water heater, flows through the pipes to maintain the desired temperature.
For optimal results, it is recommended that waste is preheated before it is added to the digester. Stirring: It is important that waste is mixed inside the digester so that the bacteria are able to get to the waste to do their job, and that gas is removed from the liquid contents. Waste can be mixed continually or stirred times a day. Mixing can be achieved in one of three ways: Mechanically, using a mixer or agitator — this method is effective, but it is important that the digester is airtight to prevent exposure to atmospheric oxygen which poses a risk of explosion.
Using a compressor to recirculate collected gas back into the digester liquid via a diffuser or open pipe at the base of the tank to create turbulence. By providing equipment that will offer environmental benefits, as well as cost benefits to those pursuing alternative energy solutions, we hope to do our bit to lessen the impact of energy production on our environment and climate.
Biogas Digester Design & Construction
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