WE stood staring in fascination at several tons of heaped-up rubbish.

Identifiable among its murkier constituents were a great many rotting prawns and enough dry mix doggie dinner to feed a pack of hounds, not to mention shredded paper, stale loaves and ominously bulging, slimy plastic bags.

At least we couldn’t smell the repulsive mixture from our vantage point behind a window.

‘We’ were a group of environmentallyminded types from Salisbury Transition City, on a fact-finding mission to the Malaby Biogas plant near Warminster.

This is where they do a quite miraculous thing, transforming food waste into enough energy to power a community of 2,000 homes.

I’m no scientist, so I won’t delve too deeply into the details, but try to give you what someone is bound to criticise as a grossly oversimplified explanation.

It’s all about anaerobic digestion, a process in which solid and liquid rubbish, reduced to a gloopy soup, is broken down by bacteria in huge tanks.

These give off methane gas, which is burned in something called a CHP (combined heat and power unit), producing electricity that goes into the grid.

The residue can be pasteurised and used as fertiliser, cutting the use of nasty agro-chemicals and saving farmers money.

And any solid junk that is separated out such as plastic, tin, batteries – apparently they get plenty of cutlery! – goes off to an RDF (refuse-derived fuel) plant.

So zero waste at the end. We’re all winners.

Domestic food waste isn’t collected separately in Wiltshire. Malaby’s intake comes from Bath and northeast Somerset.

The time may not be far off, however, when it will handle food waste from our city centre eateries, if a deal can be set up.

It’s amazing what else finds its way there – we saw stacks of past-its-date canned pineapple, sacks of petfood that had been contaminated with rubber – not to mention unsold supermarket stock.

According to Malaby’s director Thomas Minter, sometimes goods never even make it onto the big stores’ shelves because they arrive from a distribution centre too close to their use-by date to have a realistic prospect of sale.

So much that we never give a thought to – chicken skins from a poultry processor, unusable dairy produce, blood from abattoirs, liquid potato waste from a crisp factory - arrives in tankers, along with leftovers from school dinners, hospital kitchens, even prisons. Yuck, yuck, yuck! But all of it is put to good use.

Separating food from packaging is something that takes up a disproportionate amount of the staff ’s time. Not to mention contamination.

Unlike the responsible Germans, apparently, we’re not much cop at sorting our rubbish, and there’s a display at the plant of random detritus that’s turned up – metal chains, batteries, even a child’s sandals – which all have to be dealt with. I don’t know how we make people care more about this kind of thing.

Since it opened in 2012 the plant has processed 66,000 tons of food waste, sent out 61,000 tons of fertiliser, and produced 23million kilowatts of electricity.

Rolled out nationwide, the technology – more reliable than solar or wind power – could meet five per cent of our energy needs.

Food for thought, indeed.

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