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4. The calculation of BMW landfilled
The framework for the calculation methodology is set out in regulations 13 and 14 of the 2005 Regulations.
The data for the calculation shall be taken from WasteDataFlow.
4.1 Calculation of total BMW in collected municipal waste
The first stage of the calculation is to calculate the total amount of BMW in collected municipal waste (regulation 13).
The calculation set out in the regulations applies a factor of 63% of the total collected municipal waste for all authorities to determine the amount of BMW they have under their control for the purposes of the landfill allowance scheme.
Some councils may wish to carry out a waste compositional analysis to gain a better understanding of the waste and so further their recycling plans. The Executive and SEPA have developed guidance on methodology for waste analysis. This guidance is intended to ensure that results produced by individual councils are comparable, as the differences would be caused by differences in the waste, rather than by differences in methodology.
The Scottish Executive needs to have defensible data in particular to support the mass balance calculation for the first target year of 2009/10. Depending on the number of councils that come forward with analyses, we may need to commission analysis, in co-operation with local authorities, nearer the target year. It may be possible that, in light of that analysis, the Executive could consider amending the Regulations to change the 63% figure.
Councils who carry out a waste compositional analysis should be aware that there is no provision in the regulations for the mass balance calculations of individual councils to be based on a figure other than the 63% that is set for all councils.
4.2 Calculation of BMW diversion
The second stage of the calculation is to subtract from the total amount of BMW in collected municipal waste an estimate of the BMW diverted as a result of waste sent for treatment. The calculation is set out in Regulation 14.
For each element of waste sent for treatment, the calculation requires a weight from the returns, and a figure for the percentage BMW content.
The regulations specify that an amount of separated municipal waste is comprised only of those types of waste which it is the purpose of the process of separation to separate (see regulation 13(3)). Implicitly, therefore the waste would otherwise be regarded as mixed waste.
For some separated elements, the percentage biodegradable content is given in the Schedule to the Regulations. This is reproduced in the SEPA guidance.
Where no figure is given in the Regulations, a figure will have to be assumed by SEPA. The local authority shall have to demonstrate evidence to SEPA of the nature of the material that has been separated, the type of process that has led to its separation, and its biodegradable content.
4.3 Calculation of BMW reduction when treated material is sent to landfill
Where an element of municipal waste, counted as 'diverted' (under the process described above in section 4.2) as it is sent for treatment, is subsequently landfilled, the quantity of biodegradable waste has to be assessed . This will, in particular, include material sent to landfill for use as 'daily cover'.
The proportion of waste sent from treatment to landfill that is biodegradable will depend on the composition of the waste that was sent for treatment and the nature of the treatment that it has undergone. The local authority is in the best position to understand and monitor its treatment processes, and therefore it is for the local authority to take measurements and present SEPA with an evidence-backed estimate of the biodegradable content of waste that is being sent from treatment to landfill.
4.3.1 Residuals and process waste
The provision in the Regulations, at Regulation 14(3)(c), to add back to the estimate of BMW sent to landfill quantities of material separated for treatment, but subsequently sent to landfill, is not intended to count reject rates at materials reprocessors once a volume of separated waste, such as waste paper, waste textiles, etc, has entered the recycling or recovery process. However, the rejection of waste at a pre-treatment stage prior to it entering the full recovery process, and so sent to landfill by the authority or its agent, has to be counted as disposal.
Where waste that is not separated (ie "mixed waste" in terms of the Regulations) is sent for sorting and processing, such as in a MRF or MBT plant the proportion of this waste that is landfilled should still be recorded as landfill by the local authority (landfill "in pursuance of arrangements made by the local authority" in the words of the Regulations). This should be the case whether the facility is run by the local authority, by a PFI partner, or by a private company. This is consistent with the position on how SEPA and the Executive measure recycling.
The organic output from mechanical biological treatment will be considered to be 100% biodegradable unless the local authority concerned can demonstrate that it contains non-biodegradable material, or that it has been subject to a composting process (see next section).
4.3.2 Issues raised by composting
Composting of biodegradable waste plays an important part in the diversion of BMW from landfill. A number of issues are raised by the range of composting activities that councils carry out. This section gives guidance about how these activities should be reported for the purpose of the landfill allowance scheme. The SEPA guidance includes information on how it makes its assessments on when the use of compost can be considered as recovery.
There are, broadly, four types of composting activity:-
(1) Composting of mixed waste with intention to landfill (including as daily cover). The main purpose of this activity is to stabilise the mixed waste, so that there is a lower weight of BMW sent to landfill.
(2) Mixed waste can also be composted with the intention that the resulting "biowaste" is recovered through use in licensed land restoration, including on closed landfill sites or another use that is judged to be recovery.
(3) Composting of separately collected green/kitchen waste in a process without PAS 100 certification.
(4) Composting of separately collected green/kitchen waste with PAS 100 certification
In order to think about how these activities should be reported for the landfill allowance scheme, it is useful to consider two questions.
(a) when is it diverted from landfill for the purpose of the landfill allowance scheme?
(b) when is waste recovered, and so no longer subject to waste controls?
Both diversion and recovery can be reversed - diversion is reversed if the material is sent to a landfill, recovery is reversed if a recovered material is subsequently discarded.
Generally, recovery occurs later than diversion. This is true for other wastes - for example, a batch of waste paper is diverted when it is sent to the reprocessor, but only recovered when it completes the process. As stated in section 4.3, whole batches of segregated waste that are sent to landfill, or any elements of unsegregated waste sent for reprocessing that are sent to landfill, are deemed to be landfilled by the local authority under the landfill allowance scheme. The additional complication with compost is that there can be long time lags of several months between the diversion of material with the intention for it to be composted and recovered, and the ultimate action that will either ensure its recovery or lead to its disposal.
Essentially, if waste is sent into a composting process with the intention that it should eventually be recovered then, as with other waste processes diversion for the purpose of the landfill allowance scheme, it should be counted at the point that the waste enters the process. However, local authorities must ensure that they have adequate systems in place, both for their own treatment processes, and for processes run by third parties, to ensure that they gain information should composted material that is intended for recovery be ultimately sent for disposal. The SEPA guidance sets out the methods by which the loss of BMW will be assessed should composted material be sent to landfill.
The table on the following page gives more information for the four types of composting activity set out above.
| Mixed waste compost for landfill | Mixed waste compost intended for recovery | Green waste compost (not PAS 100 certified) | Green waste compost ( PAS 100 certified) |
|---|
Diversion | Calculated for stabilisation of material at time of landfill | If a local authority has an operational plan for the recovery of the compost, diversion should be counted when material sent to process. | If a local authority has an operational plan for the recovery of the compost, diversion should be counted when material sent to process. | Diversion should be counted when materiel sent to process |
Recovery | Never | When compost used for restoration/ other purpose. | When compost used for restoration/ other purpose. | When reaches end of PAS 100 certified process and there is a definite market for it |
Reversal of diversion | -- | If sent to landfill, diversion reduced to that calculated for the stabilisation of the material. | If sent to landfill, diversion reduced to that calculated for the stabilisation of the material. | If subsequently disposed of to landfill (including excessive use of material) Diversion reduced to that calculated for the stabilisation of the material. |
Reversal of recovery | -- | Spreading can only take place under appropriate licence or permit | Spreading can only take place under appropriate licence, permit or exemptions | If subsequently disposed of to landfill (excessive use of material is, effectively, an unlicensed landfill operation) |
Information/ data | Never leaves the scope of waste controls Data and evidence submitted for LAS | Only leaves scope of controls when recovered in use. Volumes diverted submitted for LAS - need reconciliation with use | Only leaves scope of controls when recovered in use. Volumes diverted submitted for LAS - need reconciliation with use | Leaves scope of controls when recovered at end of process if there is certainty of use. Need for interim period information from councils to reconcile compost created and used |
4.4 Illustration of a simple mass balance calculation
The mass balance calculation is carried out in specially designed spreadsheets that draw down data from the WasteDataFlow system. A simple illustration of the calculation is:-
| Tonnes | Percent BMW | Tonnes
BMW | |
|---|
collected municipal waste | 200000 | 63% | 126000 |
|---|
sent for treatment | |
|---|
Paper | 6000 | 100% | 6000 | |
|---|
Textiles | 2000 | 50% | 1000 | |
|---|
Wood | 3000 | 100% | 3000 | |
|---|
garden waste | 10000 | 100% | 10000 | |
|---|
Metals and glass | 3000 | 0% | 0 | |
|---|
total separate waste sent for treatment | 24000 | | 20000 | |
|---|
residual waste | 176000 | 60%* | 106000 | a |
|---|
mixed waste sent for composting | 1000 | 60%* | 600 | b |
|---|
mixed waste compost sent to landfill | 450 | 44%** | 200 | c |
|---|
total sent to landfill | | | 105600 | a-b+c |
|---|
* the residual waste BMW percentage is calculated from the weights remaining after separated elements of waste are taken from total waste (in this example 106000/176000 = 60%), this is then applied to any uses of residual waste in that authority.
** this figure could be discovered by the loss on ignition test procedure set out in SEPA guidance. Alternatively, where no such results exist, SEPA will estimate the loss of BMW from the composting process on the basis of weight loss from the data available in the WasteDataFlow system. An outline of this calculation, with an example consistent with the example about, is set out at Annex A.
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