Every digester is a serious piece of highly technical civil engineering. The Gold Series Digester is based on a simple concrete tank, rectangular in section and finished with portholes, fittings and insulation. This can be built by professional concrete engineers with local labour in under a month from our detailed plans which must be purchased from Practically Green - usually after a site survey. Typically the bottom of the tank is 2 meters or 2.5 meters below soil level and the top 1 meter is above soil level. This reduces the stresses on the structure.
Onto this tank is placed (without bolts) a simply- fitted array of fibre reinforced polymer lids.
These technical lids have features derived from decades of development, are highly insulated and provide the means to enable the insulated, gas tight tank to be used for any digestion or treatment process requiring
- odour - tight aerobic treatment
- biogas tight anaerobic treatment,
- mesophilic or thermophilic temperatures,
- digestion
- storage
- aeration
- sequential batch reactions
- settlement
- High or low solids feedstocks
- Gas extraction
indeed the construction can be used where any tank contents needs temperature and headspace gas control and where there is a need for easily maintainable roof mounted equipment at more or less ground level.
Gold Series Digesters are designed as systems or component digesters in larger systems to meet the needs of each individual site. However, over the past decade or so we have found it necessary to provide a rule of thumb which will enable the potential owner to determine whether or not a full design study is required. We include such a calculation here.
Gold Series Digesters correctly designed on wastes that are seen prior to the design being finalised will give exceptional performance for many decades, however, it is crucial for the owner to realise that it is the feedstock that produces the biogas not the digester. The digester only protects the bacteria and maintains the process by managing the effluent transport. Typical outputs are given in the table at the foot of the 'size and performance' page.
The technical components are supplied in sea containers by Practically Green and assembled by local labour under supervision from the manufacturer. The system is highly refined, largely boltless and much of the work is done by solvent welding and the use of high strength polymer bonding agents - engineering by paintbrush! This is achieved by a high degree of pre assembly in the factory. The control system is a highly refined PLC driven system and commissioning and safety instructions are included in the support package. We can also arrange training in - house and also on- site prior to purchase, or post purchase.
Completed digester with inlet (front) gas storage bags, separation tower and compost storage.
The construction components required for standard digesters are in a table.