Waste: IVC or AD

Glos Friends of the Earth Network made a very useful contribution to a Cabinet meeting looking at waste - in reply to a question from a Cabinet member they were asked for details of the green waste collection at St Arvans.

Photo: View across to Doverow Hill and Severn from Paganhill

Basically St Arvans is already reaching very excellent targets but they need to be looked at closely as they pick up green waste - and as I've noted on this blog many times that is not the best way forward...In April 2007 their recycling/ composting rates were :- Recycling 22%, Green waste 55% (including cardboard and food) Refuse 23%.

Basically green waste collections at St. Arvans are collected with cardboard and food because this collection is taken for In Vessel Composting. FoE in their letter said they understood "that green waste is needed for the efficient performance of In Vessel Composting systems (IVC)."

See my email to Officers and councillors in response re IVC and AD (anaerobic digestion):

Just a note regarding the FoE letter re St Arvans -green waste is not, as suggested by the letter,needed for 'efficient performance in IVC's- infact many view them as a poorly performing option in terms of the carbon footprint. The EUNOMIA report expands on this in detail - their findings are consistent with my understanding of SDCs current position ie that green waste should not be collected -if you have a big enough garden to produce it, you have a big enough garden to compost it in - the best environmental option by a long way.

Howeverwhere it has to be collected[for reasons of political expediency mainly] it should be windrowed - it doesn't need to be IVC'd, and you add anextra carbon burden if you do.

Also, the food waste doesn't need the green waste - after all, green wastecarries a far lower gate-fee, and you don't need to ensure the pathogen kill that you do with food waste - so why tie up expensive infrastructure treating a material that doesn't need treatment to that standard?

Food waste is best AD'd -infact I have seen figures that 30kt of food waste sent to IVC means a net avoidance of 450 CO2 tonne equivalent emissions whereas AD means 6,450 tonnes. Given that collection arrangements are the same AD offers a considerable CO2 saving.

I understand St Arvans may use the Wormtec facility at Caerwent which some consider is not a 'bona-fide IVC' - it uses time and lowest temps possible and probably need the green waste to sop up liquid coming off food waste? However purpose built plants do not do this.

GCC have already signed a contract woth Cory for IVC. What room, if any, is there for SDC using AD? All the best - Philip