The regulator has issued two studies looking at the quality of input and output material in MBT plants and the human health risk posed by the compost-like outputs (CLOs) they produce, which have traditionally had a narrow avenue of use due to the presence of contaminants such as plastic and metals.
In the two studies, which were made available to letsrecycle.com last week, the Environment Agency found that there was considerable variability between the composition of CLOs – both from plant to plant and in the same facility over time.
It also found that the use of CLOs on land could pose an environmental risk, and, as such, called for sites where the products were going to be used to be assessed to establish how contaminated they were both
Outlining the purpose of the research, the Agency said that, with uptake in MBT and MHT increasing, the volume of CLOs produced is also set to increase.
It said that the research “continues to strengthen the Environment Agency's knowledge of MBT processing and the quality and safety of CLOs. It will use the findings of this study to begin to draw up policies on the regulation of CLOs and a framework for compliance monitoring”.
Studies
In the two studies the Environment Agency took CLO samples “regularly” from four MBT/MHT plants over a five-month period.
This was with a view to answering questions raised in a 2008 screening report relating to the concentration of chemicals in CLOs and improving the accuracy of time limits for workers to be exposed to the material.
Research into the input and output quality of CLOs was said to have made it possible for more reliable ‘limit values' to be calculated for direct toxicity and secondary poisoning caused by several chemical present in CLOs, which arise from the plastics in the municipal waste treated by the MBT.
It also claimed the closer a CLO was to natural soil, in terms of its carbon-nitrogen ration, the better it would be at increasing grass growth, and it also found that the capacity for CLOs to act as a fertiliser varied significantly between different treatment plants.
The study found that there was “great variability” between MBTs in the composition of CLOs produced, and also a variance in the quality of CLOs within a single plant over time.
Human health
Work on the human health risk posed by CLOs was said to be hampered by “ambient background concentrations of chemicals” – meaning the amount of metals or pollutants already in the soil that the CLOs were being applied to.
Despite the uncertainty, the research states that the use of CLOs on land may pose an environmental risk and called for individual sites intended for CLO use to receive assessments to establish existing levels of contaminants before and after their use.
Consultation
The Environment Agency is currently attempting to perform large-scale trials to assess the impact of using CLOs on agricultural land, with the intention of issuing bespoke waste management licences to participants (see letsrecycle.com story).
A consultation seeking to determine the best practice for the trials is open to interested parties until January 22 2010.
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