Why
Anaerobic Digestion?
There are essentially
three main options for dealing with organic wastes:
§ bury it
- which means landfilling
§ burn it
- which means incineration, gasification or pyrolysis
§ bio-digest
it - which means either anaerobic digestion or composting
Technology
|
Sustainable
|
Impact on the environment
|
Energy recovery
|
Fertiliser output
|
Water recovery
|
Heavy metal recovery
|
Landfill
|
![]() Unsustainable waste of resources |
![]() Some CH4 to atmosphere, leachate problems |
![]() Partial if landfill gas extracted |
![]() No fertiliser outputs |
![]() Lost in leachate |
![]() Not possible |
Composting
|
![]() Energy required |
![]() Damage to ozone layer, also leachate problems |
![]() None |
![]() Incomplete pathogen kill |
![]() Lost to atmosphere |
![]() Not possible |
Incineration
|
![]() Fertiliser loss negates any energy gain |
![]() Toxic ash |
![]() Some but Energy wasted |
![]() Some P&K output, but N destroyed |
![]() Burnt off |
![]() Secondary waste |
Pyrolysis
|
![]() Fertiliser loss negates any energy gain |
![]() Toxic ash, emmissions regulated |
![]() Some but Energy wasted |
![]() Some P&K output, but N destroyed |
![]() Burnt off |
![]() Secondary waste |
Gasification
|
![]() Fertiliser loss reduces energy gain |
![]() Pollutants locked in slag |
![]() Some but Energy wasted |
![]() Some P&K output, but N destroyed |
![]() Burnt off |
![]() Controlled not recovered |
Anaerobic digestion
|
![]() Carbon neutral |
![]() Total recovery of energy as CH4CO2 & fertiliser |
![]() Maximum overall energy |
![]() Clean NPK fertiliser and trace elements |
![]() 100% |
![]() Heavy metals can be recovered from digestate |
Anaerobic digestion is
the only system for dealing with organic waste which is sustainable, recovers
the maximum energy, is a completely closed system with no emissions to air or
land, which retains the fertiliser and water content, and facilitates the recovery
of heavy metals.
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