New Anaerobic Digester could improve Aberdeen’s household wastes collection system
The proposal to build an anaerobic digestor (AD) plant to digest food waste and create biogas offers an excellent opportunity for Aberdeen to improve its waste collection system.
AD plants like good quality, uncontaminated, food waste. This is best collected in small compost bins, similar to those used by Aberdeenshire council. These can be put out weekly, by both house and flat dwellers alike. Unlike Aberdeen’s street-located food bins, in Aberdeenshire waste collection staff can check for any contamination in these compost bins and leave them unemptied if contamination is present. The waste collection team is in control.
The second benefit from this approach is that it is less likely that food waste will end up in the residual waste bin, especially if periods between these general waste collections are extended. If residual waste is to be burnt in the proposed Energy from Waste (EFW) plant at Altens, food waste only serves to reduce the energy generated from the burning of the waste; try burning potato peelings, cabbages and left-over sprouts if you don’t believe me.
The third benefit from the AD plant is that the biogas produced can be fed into the natural gas main, which already exists. Unlike the EFW plant that needs an expensive hot water distribution system to be installed to heat homes, the gas network already exists.
The fourth benefit is that this food waste does not have to be mixed with green (garden) waste, as in the present brown bin collections. The presence of food waste in these bins means that for bio-security reasons all this waste must go through an in-vessel composting plant. This may cost £60 per tonne. Green waste in contrast can be composted in open windrows for £12-20 per tonne. Significant savings can then be made (sorry Grant).
Operators of EFW plant like waste that has high quantities of food and low-calorific value waste in it. Their plant’s throughput is limited by the heat it can absorb from burning the waste. The lower its calorific value, the greater the tonnage they can put through the plant. As they get paid by the tonnage of waste throughput, more waste means greater income. The downside is that it is us householders who must pay these fees.
A significant addition to the proposed AD plant is Aberdeenshire Council’s aim to extend general waste collections to three-weekly. Paper and cardboard collections will be collected one week, and metals, cartons and plastics the next. Food waste will continue to be collected weekly. This would mean that the contamination of paper with broken glass in comingled systems is minimised, with good quality paper and plastic the result.
The drive to build an EFW plant at Altens is partly to meet Zero Waste Scotland’s directive to ban food and biodegradable waste going to landfill. As this organic waste emits methane that contributes to global warming it is right that it should not go to landfill. EFW is seen by the waste industry as a failsafe solution that hides the fact that Aberdeen’s general (residual) waste has food in it. It is also likely to be used to get rid of contaminated recyclable material. The blame for this contamination and poor recycling must be shared between the system of collection chosen and the willingness of residents to properly separate their waste.
On the one hand we have the forward-looking developments in AD and quality recycling and on the other we have an inefficient, chuck-it-out and dispose of it approach of the EFW plant. In my opinion the district heating system for the Alten’s EFW plant will never be built. It is just a sweetner to bring councillors on side. If this is what the residents of Aberdeen want, it is their choice.