De-packaging Food Waste in the UK
Anaerobic Digestion plants being built in the UK to treat food waste are all facing the same key challenge when it comes to dealing with the waste. The levels of packaging are proving to be far higher than those seen in other parts of Europe; in fact the levels can be up to 20% by weight of plastic, card, glass and cans. Similar food waste in Germany for example has packaging contamination of around 5-10%.
Supermarket waste generally contains the most packaging contamination; this is due to a number of factors. Firstly, food manufacturers are competing for shelf space and therefore making their product more attractive to the eye than competitors, this often results in higher levels of packaging. If you consider the packaging on some well known brands where there is a tin foil tray inside a plastic try inside a cellophane wrapper inside a card box. Secondly, most supermarkets backhaul out of date food waste back to distribution centres, this involves placing the out of date stock into as many as three plastic bags in some cases.
The reality at some waste producer sites is segregated waste streams quite often end up contaminated with items such a stones, batteries, concrete blocks and other general waste; as experienced at a Monsal built anaerobic digestion facility in Cumbernauld, Scotland.
When the food waste is delivered to an anaerobic digestion plant it requires some form of mechanical treatment to remove the packaging and other contamination prior to the anaerobic digestion process. The de-packaging equipment is one of the most important components of an anaerobic digestion facility; an insufficient facility will lead to downstream issues within the anaerobic digestion process. Most food waste de-packaging systems have been developed in Europe to deal with lower levels of packaging contamination, and this has led to issues at some UK anaerobic digestion plants. The high levels of packaging can cause de-packaging equipment to have blockages and for screens to be blinded leading to downtime of the equipment, as well as carryover of the packaging into digesters and even into the final digestate product which will affect the operator obtaining the PAS110 accreditation.
Despite all these issues in dealing with the UK’s contaminated food waste, Monsal has installed its fully automated state of the art separation technology at a 30,000 tonne anaerobic digestion food waste plant in Cumbernauld, Scotland within the last 12 months. The separation technology can achieve high levels of organic removal where conventional waste processing plants with manual or semi-automatic screening/sorting can only achieve low separation of organic components.
The plant now successfully deals with over 20 different waste streams from supermarkets and food processors, of which some can contain as much as 20% packaging by weight. The plant in fact has been able to treat all waste delivered to the site, as the Monsal separation equipment has the capacity to process the most difficult of contaminated food wastes.
In an ideal world food waste would be de-packaged at source and arrive at anaerobic digestion facilities with no contamination; however in reality this is unlikely to ever happen so the UK needs to adopt more advanced separation technology in order to deal with higher levels of contamination in UK food waste.
Due the success of the advanced separation technology at the Cumbernauld plant, Monsal is now in receipt of further orders which are currently in design and construction.
Written by: Shaun Flynn, Monsal Ltd
Article featured in LAWR April issue:
http://content.yudu.com/A1rw9k/LawrApril2011/
