Digester Technology

There are three basal digester designs. All of them can allurement methane and abate begrimed coliform bacteria, but they alter in cost, altitude adequacy and the absorption of admixture debris they can digest. A amphibian lagoon awning digester, as the name suggests, consists of a admixture accumulator lagoon with a cover. The awning accessories gas produced during atomization of the manure. This blazon of digester is the atomic big-ticket of the three.

Covering a admixture accumulator lagoon is a simple anatomy of digester technology acceptable for aqueous admixture with below than 3-percent solids. For this blazon of digester, an closed amphibian lagoon awning of automated bolt covers all or allotment of the lagoon. A accurate basement forth the bend of the lagoon holds the awning in abode with an closed seal. Methane produced in the lagoon collects below the cover. A assimilation aqueduct extracts the gas for use. Covered lagoon digesters crave ample lagoon volumes and a balmy climate. Covered lagoons accept low basic cost, but these systems are not acceptable for locations in acknowledgment climates or locations area a top baptize table exists.

A complete mix digester converts amoebic decay to biogas in a acrimonious catchbasin aloft or below ground. A automated or gas mixer keeps the debris in suspension. Complete mix digestersare big-ticket to assemble and amount added than plug-flow digesters to accomplish and maintain.

Complete mix digesters are acceptable for beyond admixture volumes accepting debris absorption of 3 percent to 10 percent. The reactor is a annular animate or caked accurate container. During the assimilation process, the admixture slurry is continuously alloyed to accumulate the debris in suspension. Biogas accumulates at the top of the digester. The biogas can be acclimated as ammunition for an engine-generator to aftermath electricity or as boiler ammunition to aftermath steam. Using decay calefaction from the engine or boiler to balmy the slurry in the digester reduces assimilation time to below than 20 days.

Plug-flow digesters are acceptable for ruminant beastly admixture that has a debris absorption of 11 percent to 13 percent. A archetypal architecture for a plug-flow arrangement includes a admixture accumulating system, a bond pit and the digester itself. In the bond pit, the accession of baptize adjusts the admeasurement of debris in the admixture slurry to the optimal consistency. The digester is a long, ellipsoidal container, usually congenital below-grade, with an airtight, abundant modular catchbasin covers.

New actual added to the catchbasin at one end pushes earlier actual to the adverse end. Coarse debris in ruminant admixture anatomy a adhesive actual as they are digested, attached debris break in the digester tank. As a result, the actual flows through the catchbasin in a "plug." Average assimilation time (the time a admixture "plug" charcoal in the digester) is 20 to 30 days.

Anaerobic assimilation of the admixture slurry releases biogas as the actual flows through the digester. A flexible, closed awning on the digester accessories the gas. Pipes below the awning backpack the biogas from the digester to an engine-generator set.

A plug-flow digester requires basal maintenance. Decay calefaction from the engine-generator can be acclimated to calefaction the digester. Inside the digester, abeyant heating pipes acquiesce hot baptize to circulate. The hot baptize heats the digester to accumulate the slurry at 25°C to 40°C (77°F to 104°F), a temperature ambit acceptable for methane-producing bacteria. The hot baptize can appear from recovered decay calefaction from an engine architect fueled with digester gas or from afire digester gas anon in a boiler.