Agency does u-turn on MBT guidance

The Environment Agency has performed a u-turn on how it will measure the amount of biodegradable waste diverted from landfill by mechanical-biological treatment (MBT) plants.1 Biological rather than loss-on-ignition tests will be used - much to industry's relief.

Under the landfill allowance trading scheme, local authorities have to lower significantly the amount of biodegradable waste they send to landfill.

Many local authorities have turned to MBT to achieve this, and so have been anxiously waiting to find out how the Agency will monitor diversion rates from such plants.

In its final guidance on monitoring MBT processes, the Agency says that biological tests - namely biochemical methane potential (BMP) and dynamic respiration index (DRI) tests - will be used to measure the amount of biogas produced by the inputs and outputs of each plant. The difference between them will then be used to calculate diversion rates.

This testing regime contrasts to that put forward in the Agency's original consultation, issued last year (ENDS Report 359, pp 46-47 ).

Back then the Agency proposed using loss on ignition tests to calculate diversion rates. Such tests represented "the most robust and reproducible solution", the consultation said.

Industry, however, disagreed, stating that LOI tests did not give an accurate representation of the amount of waste a plant diverts.

Such tests, it was claimed, cannot distinguish between biodegradable wastes and the biodegradability of wastes. Plastics, for example, would not count as being diverted from landfill even though they take thousands of years to degrade.

Terry Coleman of the Agency insists such concerns were unfounded, but admits a change had to occur. "People didn't see LOI tests as giving a fair representation of their plant's performance, and we had to have a solution that people accept as well as one that's consistent."

The new guidance outlines the sampling, testing and reporting requirements for MBT plants.

Plant operators must submit a site-specific monitoring plan to the Agency before sampling begins.

Inputs to MBT plants will undergo compositional analysis six times a quarter. Samples will also undergo dry matter, loss-on-ignition, total organic carbon and total nitrogen tests three times a quarter, alongside the biological tests.

The outputs from the plant will face the same set of tests - bar the composition analysis - six times a quarter.

A "critical part" of the sampling plan will be describing the timing of tests to ensure there is a link between the inputs and outputs that are being sampled.

Results must be submitted to the Agency on a quarterly basis. It "may" be possible to reduce the frequency of testing after the first year if the plant is producing consistent and reliable results.

  • The Agency has also issued summary guidance on the use of outputs from MBT plants.2It confirms that the fine soil-like fraction from MBT plants may only be spread on land where this results in agricultural benefits or ecological improvement (ENDS Report 359, pp 46-47 ). However, no more than 20,000m3 of such material can be used per hectare.

    It is "unlikely" such outputs will be suitable for spreading on agricultural land as they do not come from source-segregated wastes, but they could be used for land reclamation.

    The use of such materials in landfill engineering or daily cover would not count as diversion from landfill. However, where the materials are used in landfill restoration, and this can be shown to result in agricultural benefit or ecological improvement, the process may be classed as "recovery" and so be considered a form of landfill diversion.

    The summary guidance also outlines when each of MBT's outputs - including glass, metals and refuse-derived fuel - cease to be wastes. RDF is deemed to be waste at all times, but there are moves at EU level to amend this policy (see pp 44-45 ).