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PowerPedia:Anaerobic digestion

Lasted edited by Andrew Munsey, updated on June 14, 2016 at 9:23 pm.

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Anaerobic digestion (AD) is the harnessed and contained, naturally occurring process of There was an error working with the wiki: Code[2].

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Introduction

Anaerobic digesters have been around for a long time and they are commonly used for There was an error working with the wiki: Code[3] or for managing animal waste. Increasing environmental pressures on There was an error working with the wiki: Code[4] disposal has increased the use of AD as a process for reducing waste volumes and generating useful byproducts. It is a fairly simple process that can greatly reduce the amount of organic matter which might otherwise end up in There was an error working with the wiki: Code[5]s or waste There was an error working with the wiki: Code[6]s .

Almost any organic material can be processed in this manner. This includes There was an error working with the wiki: Code[7] materials such as waste paper, grass clippings, leftover food, sewage and animal waste. Anaerobic digesters can also be fed with specially grown There was an error working with the wiki: Code[8]s to boost biodegradable content and hence increase biogas production. After sorting or screening to remove There was an error working with the wiki: Code[9] or hazardous materials such as metals and plastics, the material to be processed is often shredded, minced, or hydrocrushed. to increase the surface area available to microbes in the digesters and hence increase the speed of digestion. The material is then fed into a airtight digester often with extra water added depending on the digestion process and feedstock.

Stages of anaerobic digestion

There are two conventional operational temperature levels:

There was an error working with the wiki: Code[10] which takes place optimally at 37°C or at ambient temperatures between 20°-40°C with There was an error working with the wiki: Code[11] bacteria

There was an error working with the wiki: Code[12] which takes place at elevated temperatures up to 70°C with There was an error working with the wiki: Code[13] bacteria

The residence time in a digester varies with the amount of feed material, type of material and the temperature. In the case of mesophilic digestion, residence time may be between 15 and 30 days. In the case of mesophilic UASB digestion hydraulic residence times (1hour-1day) and solid retention times (

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