Anaerobic digestion is the natural biological process which stabilizes organic waste in the absence of air and transforms it into biofertilizer and biogas. It is a reliable technology for the treatment of wet, organic waste. Organic waste from various sources is biochemically degraded in highly controlled, oxygen-free conditions circumstances resulting in the production of biogas which can be used to produce both electricity and heat. Almost any organic material can be processed with anaerobic digestion.
Anaerobic digestion is particularly suited to wet organic material and is commonly used for effluent and sewage treatment. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste. The exception to this is woody wastes that are largely unaffected by digestion as most anaerobic microorganisms are unable to degrade lignin.
There are many advantages associated with anaerobic digestion process which may be classified into three groups viz. environment, energy and financial:
- Elimination of malodorous compounds.
- Reduction of pathogens.
- Deactivation of weed seeds.
- Production of sanitized compost.
- Decrease in GHGs emission.
- Reduced dependence on inorganic fertilizers by capture and reuse of nutrients.
- Promotion of carbon sequestration
- Beneficial reuse of recycled waterProtection of groundwater and surface water resources.
- Improved social acceptance
- Anaerobic digestion is a net energy-producing process.
- A biogas facility generates high-quality renewable fuel.
- Surplus energy as electricity and heat is produced during anaerobic digestion of biomass.
- Anaerobic digestion reduces reliance on energy imports.
- Biogas facility contributes to decentralized, distributed power systems.
- Biogas is a rich source of electricity, heat, and transportation fuel.
- Anaerobic digestion transforms waste liabilities into new profit centers.
- The time devoted to moving, handling and processing manure is minimized.
- Anaerobic digestion adds value to negative value feedstock.
- Revenues can be generated from processing of waste (tipping fees), sale of organic fertilizer, carbon credits and sale of power.
- Anaerobic digestion plants increases self-sufficiency.
Many industries in the Middle East produce liquid and solid wastes that are suitable for anaerobic digestion, such as food processing, pharmaceuticals, organic chemicals, paper manufacturing and tannery industries. Some of the wastes might be difficult to digest as a sole substrate, but they can be biochemically degraded in combination with manure or sewage sludge. The combined digestion of different wastes is called co-digestion.
The relevance of biogas technology for the Middle East lies in the fact that it makes the best possible utilization of industrial organic waste as a renewable source of clean energy. Diversion of industrial waste from landfill sites and taking it to plants which can turn it into biogas and biofertilizer will ensure that it is treated in such a way that it becomes a useful product instead of a harmful one.