1. Estimate how much feedstock you have for the digester. The more you have and the more solids in a cubic meter (i.e. the less washing and rain water) the better for gas production. Calculate the size of the digester and the volume required.
2. Estimate the gas volume and the electricity or heat you could produce from your effluent.
3. If the numbers look interesting, call Practically Green and get a survey of the site, the effluents, and the products required (electricity, compost, liquid fertiliser, biogas, odour control, weed seed destruction, extra grass growth, greenhouse fertigation, hot water etc.). The survey will also give you the costs of the plant and include such factors as the power supply available etc.
4. If the numbers still look good and the proposed plant meets your needs agree a price for the delivery of components and supervision and training services. The costs of the survey may be deducted from the costs of the components as these have a design fee built into the cost.
5. Order the drawings and sign the stage payments and confidentiality agreements. (one month)
6. Drain the site with a land drain below the base level of the tank and build the tank (two months)
7. Place on the tank the lids and technical components on the digester, plumb and wire the system. (two months)
8. Connect the electrical supplies and other services. (one month plus paperwork from the electricity supply company)
9. Get safety training.
10 . Fill the digester using the Practically Green rapid start system and start producing biogas in less than a week. (1 week)
11. Watch the bacteria acclimatise to your wastes and tune the performance for maximum economy. (up to 6 months).
Total time to design, build and commission - 12 months for small to medium systems, 15-20 months for very large systems.