07 February 2023
With contamination never higher on the organic waste agenda, one of the most important items of equipment in the AD operator’s arsenal is the de-packaging machine. Harry Waters, Commercial Director at Agrivert Ltd, explores the options
Talk to a wide range of food AD operators and they will probably tell you that one of the most important processes to get right is de-packaging. Failure of this process can result in the doors closing to feedstock, downstream issues in the digesters and detrimental effects on product quality. A key question to ask, then, is what is required of de-packaging equipment?
Firstly, de-packaging equipment must be robust. In terms of contamination, there is no such thing as ‘designer’ food waste and operators must expect the worst. In short, if it can’t cope with sledgehammer heads on a regular basis it is probably not up to the job, because that is exactly what will come through the door. Contaminants must also be able to be swiftly removed from de-packaging machines. More than 20 minutes downtime can result in queuing trucks on busy sites and if you are working with local authorities this is probably in breach of contract.
De-packaging equipment must also be able to process a wide range of wastes. Too many machines cannot process changes in waste type and contamination within the waste stream. This can result in plants being restricted on the feedstock they can process and therefore commercially disadvantaged. When selecting de-packaging equipment, try it on pineapple tops or 25 per cent contamination: if it comes to a grinding halt it is the wrong machine.
Speed of processing is also important; equipment unable to process swiftly without interruption will result in backlogs in the reception building that could elevate odour and extended tipping times. Whilst operating Agrivert’s food waste plants, we were always amazed at how many times a driver turned up at one of our plants advising they had been diverted because they had been waiting too long to tip elsewhere. Operators should not forget that haulage costs are normally the largest component of total organic disposal costs and as such, keeping trucks off the road while queuing will quickly drive customers to competitors’ plants.
The equipment must also be able to separate food from contaminates effectively. Contamination disposal is normally one of the top three plant operating costs and therefore excess organics carry-through is expensive. Ideally, organics carried through with contaminates should be less than one per cent, but many machines are allowing well in excess of six per cent. At this level it equates to a disposal bill of around £7 for every input tonne received. So for a 40,000 tonne plant this is a potential £300,000 contaminants disposal bill, most of which is unnecessary if better equipment is utilised.
A de-packaging machine must also properly extract the contaminants. Too many plants suffer from floating layers of contamination, which can cost many thousands of pounds to rectify or clean out. If there is contamination in the digesters it will also be in the digestate, compromising product quality. Poor end product will make it more difficult to secure payment for the digestate, resulting in a loss of income confidence in the product. Eventually it will also cause problems with the Environment Agency.
“Overly complex systems often look good on paper, but they seldom perform in line with the sales brochure”
Like most machines, the simpler they are the less there is to go wrong. Reliability is essential to provide a consistent service to the customer and feed for the biology. Therefore, it is wise to select a machine that is robust and able to be serviced and maintained by site operators. Overly complex systems often look good on paper but seldom perform in line with the sales brochure. There is a huge range of equipment to choose from; sadly, much of it does not work well. Agrivert would always advocate that spending money on robust, well understood, de-packaging equipment is probably the best money you will spend, as the cost of failure quickly outweighs the capital expenditure associated with securing quality equipment.