I work for a national retailer, we have recycling manager who knows the ins an outs but I'm aware of the basic recycling processes.

We send no food waste to landfill (landfill is the most expensive method of disposal and we have our company environmental objectives to achieve).

Disposal via Anaerobic Digestion (AD) is very popular these days, we have 8 warehouses and all 8 send the vast majority of food waste to AD. It may depend on who collects the waste and what plant it goes to, but we are not required to remove the packaging. Presumably further processing occurs, and presumably because we don't remove the packaging we have to pay more (or get less £££ per tonne of waste).

The only waste food that is not sent to AD is bread and cakes and Fruit and Veg, the process varies from site to site but these either go to a farm for animal feed or a rendering plant for pet food.

For food identified at the warehouse that is still safe to eat but past best before we pass to localised charities. Due to business processes, we can't do that for similar waste from the stores.

Despite not required to remove packaging, it's still a messy task!

Ooh my companies name is quoted on their website! (which is unusual as the standard policy is to not give consent..!)

Many thanks to those who have responded with information. Especial thanks to AlanD with your direct knowledge of anaerobic digestion (AD) plants, including how foodstuff residues are extracted by the washing of packaging materials after most of their contents have been extracted by the shredding and squeezing processes. In view of the volumes involved it's understandable that refrigeration of putrescible waste foodstuffs is considered too costly. With experience during my time with HSE of visits to rendering plants for animals and fish I sympathise about the stenches which pervade AD plants and also people and their clothing while working in/visiting such premises AND for some afterwards.

During the 1980s my work with HSE included various paper mills, including some which had facilities for processing waste paper so that it could be combined with raw supplies of woodpulp. Such facilities were able to remove metal staples, bookmaking cord and other unwanted components ('foreigns') during the shredding and pulping of the waste paper. As local councils in some areas including mine now collect mixed loads of all types of paper, card and waxed cartons from households it seems that paper and cardboard recycling nowadays is very sophisticated and can cope with a wide range of unwanted components including glues, inks and various types of plastic such as the transparent film used for window-type envelopes. Therefore, it should be no surprise if food waste recycling is equally sophisticated nowadays.

p.s. The newspaper report mentioned in my opening post included a note that specialist meat suppliers experienced an unexpected rise in demand for horse meat late last week. Apparently the beefburger scandal prompted some adventurous Brits to find out what horse meat tastes like! Although one supplier reported a "tenfold increase" in demand for horse meat, there's no indication of the normal level of demand. It could have been just one or two orders or several hundred or more per week!

AlanD76 interesting posts with regard to the process, You said you end up going home stinking on a Friday. I always thought the process was sealed and the smell could not get out ?. or is only the digestion part sealed and the process before it open to atmosphere etc. Would the smell be limited to the plant or did it also inevitably make its way outside ?

Alan

Thanks for the response, I knew the purpose of AD was to produce methane to power a turbine and produce electricity. So could not see how the smell got out as you would not want the methane getting out.

Are the turbines noisy from a H&S point of view for employees and pubic nearby? I can't get the idea out of my head that these will make the same noise as a jet engine?

HAHA just thought if they use horse burgers to produce methane, which in turn produces electricity, which then fuels an electric car, we will have gone back to horse power. Just as well stuck with horse and cart and you still got fertiliser as a by-product. The only polymer needed would be in the shovel handle.

Chris

You've hit a topic of interest with me so I'm happy to waffle on with this thread ;)



A CHP is essentially a modified diesel generator, so yes they create a lot of noise (I can't remember exact figures but it is incredibly uncomfortable being near one without adequate hearing protection).
Depending on the engine, they are usually built into an adequately insulated engine room, or with newer models such as Jenbachers (other CHP models are available), they come supplied as a pre-assembled unit built into a sound-proofed container and are dropped into position ready to connect (which is pretty impressive).



I can only speak from personal experience on this one but I do think there is a correlation between exposure to waste-streams on AD plants and illness; since working with AD i've reignited my childhood asthma, and had a minimum of two chest infections per year (of which i've developed pneumonia once and been hospitalised twice).
I've been working in a none-AD environment now for a year and seen a marked improvement in my health... coincidence? maybe...

I think to assess the health implications on AD the broader picture has to be looked at: the waste stream for example – sewage treatment brings the obvious biological hazard of contact with faecal matter, contact with syringes (you wouldn’t believe how many syringes you find in the inlet screens of a sewage plant!) can lead to some life-changing diseases.
Food waste AD, although eradicating these hazards does bring its own: unknown mold spores, contaminants (why was the food rejected in the first place?), and pest infiltration, and as mentioned previously the putrification process of a stockpile of waste food.

The digesters themselves have the previously listed hazards of asphyxiants, flammables and toxins, as well as the biological content of the digesters. Also, if food waste isn’t pasteurised pre-digestion there are likely biological hazards still present here.

There’s also chemical usage; usually sulphuric / hydrochloric acid, caustic soda, sodium hypochlorite etc in H2S removal (pre-CHP) and odour scrubbing

Then there’s the mechanical hazards…

Not trying to be downbeat regarding AD (it's a fascinating process), just trying to show that behind the pictures of a shiny Digester there are a huge amount of hazards to contend with that aren't always obvious.

Alan

Non-explosive methane!?

LB

Yes that is what he said in response to my question about possibility of explosions and affected area. This was at a public consultation and was introduced as a technical expert. Made me wonder if this rubbish was also given to Local Authority (pun intended).

No problem Chris, good luck :)

I won't get started on Flash Pyrolysis too much as this thread already has too much of me on :P
In a nutshell tho it's a case of waste product in (doesn't matter whether organic/inorganic so long as there is a good calorific value), heated to around 850 degrees in an oxygen free environment which effectively atomises the waste into hydrogen and methane (generally 60% / 40% respectively), then gas is cooled and a generator powered from it, waste product is char (8-10%) - in theory anyway, it has its own unique issues! :)

Alan