What is Compost-Like-Output?
When mixed Municipal Solid Waste (MSW) is biologically treated in Mechanical Biological Treatment (MBT) plants or autoclave systems, the output is known as a ‘compost-like-output’ (CLO).
This material can be landfilled and has the benefit of lower greenhouse gas emissions compared to raw waste. It is also claimed by some that CLO has agricultural benefits and can be used as a soil improver.
Households use their residual bins to dispose of any objects not collected at the kerbside through source-separated recycling schemes. This can include items like batteries, paints and mineral oils. These items and many others contain Persistent Organic Pollutants (POPs) and their sub-products. The toxins have a number of adverse effects on flora, fauna and the food chain.
It is estimated there are more than 30,000 hazardous substances that end up in residual waste.
The environmental impact and effect on human health is still being investigated today. The biological processing of MSW in MBT reduces the biodegradability of the waste and lessens the potential for methane production (another impact on climate change). But unless the harmful substances are physically extracted, the process does not lower the risk of harm to humans or animals if ingested.
Due to the plethora of substances that can be found in MSW, it is difficult to perform a quantitative risk assessment and give assurance that the use of CLO as a soil conditioner is safe. Concern over a build-up of contaminated material by the spread of CLO on land has been expressed by the Environment Agency. They feel it must be regulated and trialled under the ‘precautionary principle’ and have issued a consultation to consider public opinion.
In the consultation document, the Agency states there is currently insufficient knowledge to assure the spreading of CLO does not incur risks to the population.
MBT of residual wastes is an industrial process that can only extract and treat a percentage of contaminants. MBT extraction efficiencies vary between 60-80% and the remaining contaminants can end up in the final organic product.
If the concentrations measured in the final CLO product are low it is only because the MBT process is effectively ‘diluting’ the contaminants with other substances. If applied to land the contaminants will accumulate and may enter the food chain.
Veolia Environmental services does not support the use of CLO in soil. We believe it should only be used in some applications such as land restoration and reclamation on clearly defined sites. These restrictions will prevent crops or livestock being exposed to possible contaminants.
All CLO should be produced to a pre-defined specification that limits the potential for contamination.
We fully support the
rigorous testing regime proposed by the Environment Agency, and the overall approach to restrict the use of CLO on agricultural land. However, we suggest that permits for land-spreading CLO should be bespoke and specific, relating only to the location concerned.
Quality of a product can only be guaranteed by tight control of the inputs and a rigorous sampling regime of outputs to ensure the process meets approved standards.
If contaminants are accepted because they can be diluted, it defies the fundamental principles of hazardous waste treatment and could lower environmental standards.
We support adherence to BSI Publicly Available Specification (PAS) 100 on composting. The introduction of a lower quality product in the compost market will affect public confidence in all waste-derived products, including those from green waste and food. This will have an adverse impact on local authority landfill avoidance.
It has taken over 15 years to develop a market for such composts and assure the end user it is a consistently safe and beneficial product. Suggesting CLO has the same properties as compost from source-segregated green and food wastes will inevitably lead to a loss of credibility.