Anaerobic Digestion (AD)
Anaerobic
digestion refers to the biological breakdown of organic material in the
absence of oxygen. It is a net energy-producing process as it generates
substantial quantities of 'biogas' which consists mainly of methane and
carbon dioxide. Biogas is then used as a fuel to produce both electrical
energy and heat. Excess renewable electricity can then be exported to
the national grid, or for use within your own facilities. By using biogas
as a fuel the system is displacing the use of fossil fuels, thereby reducing
the emissions of carbon dioxide into the atmosphere.
An anaerobic digestion plant can typically take material from numerous sources of organic food stock such as:-
- Farm by-products (pig slurry, manure etc)
- Source-separated food waste
- Food processing waste
- Abattoir waste
- Energy crops
Wet AD
Wet
anaerobic digestion has developed to be the state-of-the-art process for
bio-waste treatment and stabilisation in Europe. In direct contrast to
composting, it is performed in the absence of air, which offers numerous
benefits such as:-
- Low energy requirement – high value electrical renewable energy exported to the grid (when biogas produced is utilised with a CHP (Combined Heat & Power) plant)
- Carbon neutral – extracts volatile carbon and methane for energy production
- Low space requirement (build upward rather than out)
- Little or no water required after start-up, a closed loop process
- Low operating cost; low manpower requirement, low maintenance requirement - piping and pumping
- Less expensive than composting for plants larger than 50,000t/a (tonnes per annum)
- Closed, hygienic, very low odour process with significantly less foul air to treat than aerobic systems
- After-treatment stage produces a high quality end product
- Sustainable technology with one of the highest deliverable biogradable waste diversion rates
- Can be used to expand local renewable energy production via use of energy crops like maize or fodder beat.