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Annex A: Assessing the diversion of biodegradable municipal waste in mixed waste compost
This Annex sets out the additional data that SEPA would need in order to assess the amount of biodegradable municipal waste in mixed waste compost sent to landfill, where no loss on ignition analysis is available. The ultimate judgement on the biodegradable diversion is for SEPA, and in certain circumstances this calculation may not apply.
The WasteDataFlow system collects two information on materials sent for mixed waste compost, and the destinations of the treated material. Please follow guidance on where to insert data carefully.
The BMW content of mixed municipal waste sent for composting will be assessed as the BMW proportion of residual waste as calculated from the data. In order to estimate the BMW content of the material sent from composting for disposal, information is needed about the progress through treatment of the weight of material originally sent for composting.
Table: estimating the biodegradable content of mixed waste compost sent to landfill
| Measured weights | Biodegradable content |
|---|
Sent for composting: | x | Residual waste BMW% of x |
Non biodegradable materials (such as metal or glass), separated before composting | y | 0 |
Weight of material entering composting system | (x-y) | Residual waste BMW% of x |
Non biodegradable materials (such as metal or glass), separated after composting | v | 0 |
Weight of material exiting composting system | z | Either the figure given by Residual waste BMW% of x - (x-y-v-z)* Or a figure established by sampling and testing |
Weight of this material disposed of to landfill (including uses at landfill that are not considered recovery) | w | w/z times the figure above |
* (x-z-y-v) is the weight loss due to the composting process
A numerical example is given in the next table.
Table: estimating the biodegradable content of mixed waste compost sent to landfill - a simple numerical illustration
| Measured weights (tonnes) | Biodegradable content (tonnes) |
|---|
Sent for composting: | 1,000 | Assuming a 60% residual waste percentage = 600 |
Non biodegradable Materials (such as metal or glass), separated before composting | 100 | 0 |
Weight of material entering composting system | 900 | 600 |
Non biodegradable Materials (such as metal or glass), separated after composting | 50 | 0 |
Weight of material exiting composting system | 450* | 200 |
Weight of this material disposed of to landfill (including uses at landfill that are not considered recovery) | 450 | 200 |
BMW recycled or composted | | 400 |
* this is a figure purely for illustration, the actual weight of material leaving a system would have to be measured.
In this example, all of the compost is disposed of at landfill, with a biodegradable content of (200/450) = 44.4% BMW, and so the reduction factor would be 44.4/60 = 0.74
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