Anaerobic digestion is an alternative to waste incinaration and landfilling
Garbage processors earn on the recycling tariff and on what they extract from the garbage. Biogas is just what else can be extracted from garbage in addition to plastic, glass, metal and paper.
In addition, a biogas plant allows to reduce the amount of garbage and save on fees for landfilling. Fermentation of organic matter in a biogas plant is more environmentally friendly than incineration.
Methods for municipal solid waste processing
Pre-sorted municipal solid waste is processed into biogas in one of the following ways:
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landfilling where wells are drilled in buried waste
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biogas digestion where the waste is processed “fresh” immediately after garbage sorting
Biogas plants are more productive than landfill sites and their life spans longer. In landfills gas ends in 3-7 years. And biogas from biogas plants can last more than 50 years.
Technologies for MSW recycling in biogas plants
Several technologies are used for MSW recycling in biogas plants:
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Classic technology:
For using classic technology, a good sorting, hydro-separation, or presses are required, and it doubles the cost of the project. Therefore, we do not like this method in the case of MSW.
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Dry digestion with a rotating reactor:
The technology is interesting but also very expensive. The disadvantages are energy consumption and maintenance of the engine rotating reactor.
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Dry digestion with garage type reactors with mixers:
The gas output with and without mixers is not significantly different. Therefore, we consider the costs of the mixers unjustified. The disadvantages are energy consumption and maintenance of the engine rotating reactor mixer.
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Dry digestion with batch garage type reactors:
The optimal choice for the processing of polluted solid waste is batch type garage reactors. Inorganic inclusion in a wet reactor poses problems, but for a dry reactor, this is the solution. Such inclusions act as a scarifier allowing percolate to penetrate deep into the waste, so mixers are not required.
The disadvantage of this method is period action and scale. Biogas plants and the amount of waste must be large in order to accommodate not one but several reactors which are required to equalize biogas production over time.
NGE Biogas participated in 3 projects using the dry method in India and Russia.