What is wet Anaerobic Digestion?

 
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Wet anaerobic digestion systems are designed to process biodegradable feedstock into a digestate slurry with typically less than 15% total solids. For feedstock with high total solids, the mix is diluted with either fresh water, re-circulated process water, or another organic waste with a lower total solids percentage to the incoming waste stream (i.e. co-digestion).

The differences in wet anaerobic digestion and dry anaerobic digestion are that in wet AD, the feedstock is pumped, heated and stirred (5-15% solids) and in dry AD it can be stacked (over 15% solids), with leachate sprayed over the top of it which percolates through the material, breaking it down over a longer retention time . Wet systems have a successful track record in treating low solid materials such as human sewage and food  waste. 

In QUBE's wet AD systems, the feeding process is continuous, with digestion requiring organic matter to be added in stages to the digester, with the size of the digestion space determining the retention time (usually 30-35 days).

The main advantage of wet AD and the continuous process is that it produces higher biogas production over a shorter time period. The liquid state of the digestate within the digester increases the rate of biogas production as the substrates in the feedstock are readily available for the anaerobic bacteria to feed from, resulting in methane production. 

A wide variety of feedstocks can be processed through in a wet anaerobic digester, and the digesters can be designed to suit each site's requirements and budget.

As an example, our bioQUBE wet anaerobic digester can process feedstocks including waste from food manufacturers, restaurants and canteens, breweries and distilleries. 

The compact and lightweight quickQUBE wet anaerobic digester was designed to provide sanitation and energy generation from sewage and local food waste.

The miniQUBE is our simplified, scaled down manual wet anaerobic digester for remote or off-grid locations in developing countries and is suitable for small quantities of food waste, sewage and animal manures in countries with warm climates.

 

 
Alice Bayfield