September 9, 2010

Beer and biogas

The other day I had the chance to have a good nose around the new Adnams biogas plant behind their super-eco warehouse outside Southwold. I declare an interest: having a family connection to the company and been a fly on the wall (and occasional adviser/critic) of their projects over the years, I am immensely proud of the culture of innovation they have created - an over-used phrase that for once is entirely appropriate. This is another groundbreaker: the first anaerobic digestion plant in the UK to put gas directly back into the mains, through a unique partnership with British Gas.

The premise is simple: take the brewery waste yeast (which currently goes to feed cows) and the food waste from the Adnams pubs and hotels, as well as waste on contract from other local hospitals, schools and so forth; chomp it up and boil it into a safe slush; let bacteria digest it in a series of giant plastic stomachs buried underground; take off the gas created, clean it and put it into the mains while the remaining liquid can be used for fertiliser. The cleaning of the gas removed CO2 which will be pumped into algae tanks, growing algae that can be fed to the digester as well.

The plastic stomachs are truly huge - up to 80m long. Unfortunately I had a broken camera the day of my visit, but here's a photo from the web:

What is very interesting is both the innovation of a plant that isn't just about creating gas to use on-site (a relatively small proportion of the gas will be used to power the plant itself, with plans to use more in the future to power vehicles) but puts it back into the mains, and the evident enthusiasm of British Gas for the idea. There is even a hint of panic about meeting renewables obligations about the fact that BG have, on their own initiative and cost, also installed a massive photovoltaic array next to the plant in order to generate electricity. The whole project will both save money (waste disposal is a cost to the company) and actually make money as the plant benefits from the gas equivalent of a feed-in tariff.

Architecturally, there isn't much to say except for the very neat construction of the building that stores the waste food prior to its digestion. The only consideration is air- and water-tightness: as food may sit in there for up to 2 weeks, the gases are going to be quite a stink. So the structure is a giant tent with aluminium frames over which a reinforced rubberised fabric is stretched and sealed. The entrance door rolls up and down almost like a zip in a sleeve. The whole thing came over from the Netherlands (I think) and was erected in 6 days. Clever, economic and not at all bad looking either (not that you can tell from this terrible photo!)

Next time I have the chance, I'll try for an update on how the plant works in practice - when I was there they were just digesting the first loads of material and building up the population of bacteria in the plant. But it looks to be a great example of using simple, appropriate technology to do the right thing. I wonder what Adnams will think up next.

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