Phase 3     Anaerobic Digestion

The second component, anaerobic digestion (AD), produces biogas from the digestion of the cleaned pulp. Flexible designs allow for multiple forms of bioenergy to be produced from the methane rich biogas - electricity, heat, an alternative liquid fuel and pipeline grade gas.   

Step 6: Anaerobic Digestion (AD) Process

Is the process by which organic material is broken down (like the human digestive system works) by microscopic organisms in the absence of oxygen. The anaerobic process occurs in an enclosed, controlled environment. The BTA® Process is a wet process (less than 12% TS) and under mesophilic conditions (between 35 to 37°C).

 

The digestion is single phase and the organic fraction is digested for 18-24 days and then dewatered. Lances infuse biogas for continuous, non-mechanical mixing.The heated pulp is fed into the digesters from the pulp buffer tank. The digester contents are continuously mixed using compressed biogas that is delivered through a biogas lance system located inside the digester.

 

Digesters - 8,800 m3
       Biogas Capture
 
Heat Exchanger
 
        Non-Mechanical Mixing

Step 7: BioEnergy Production

The process creates biogas to produce bioenergy. As an example, clean, renewable electrical and thermal energy can be produced by combusting this biogas in onsite cogeneration engines. (CHP). The biogas can be upgraded for distribution into the natural gas pipeline or compressed into a liquid biofuel to power vehicles. 

 

Cogeneration - Heat & Power
          Biogas Upgrading