THE song of the curlew and the sight of the sailing craft may have you thinking you’re 1,000 miles from industry when you’re beside the waters of Kielder and Selset.

Amid this rural serenity, though, the story is different. For years now Northumbrian Water has operated England’s biggest hydro plant at Kielder Water, and this year Selset reservoir near Middleton in Teesdale has similarly started delivering electricity for the company.

A third hydro project is on the way for Mosswood at Derwent reservoir in north west Durham. And beyond that Northumbrian Water, in partnership with a supplier, has in the pipeline – pardon the pun – plans to create further, albeit smaller, hydros with other companies.

This way, Northumbrian Water is further contributing to greener energy gathering and reducing carbon emissions in the UK. It is doing likewise in urban areas, with its introduction of waste-to-energy plants.

These combine the modern technology of thermal hydrolysis with age-old feeding habits of bugs to give calories from organic waste and even more green electricity.

For more than a year Northumbrian Water has been running Europe’s largest such conversion plant at Bran Sands on Tees estuary. Now a second plant, a £34m investment, is coming up at Howdon, North Tyneside.

Building is ahead of schedule and it will be running a year from now, using the micro- organisms in similar fashion to break down the biodegradables in sewage sludge.

Each half a million tonnes-plus of sludgy residue from treated domestic sewage and industrial effluent – waste from an equivalent of one million people – will be reduced to about 60,000 tonnes to generate 4MW of green electricity.

Heidi Mottram, chief executive of Northumbrian Water, says: “We were first in the country to get into this in a big way, and I think we’re still the UK’s biggest producer of power through this anaerobic digestion.

“For now we use the power for ourselves – to reduce our own carbon emissions. But opportunity exists to scale up and contribute to the national grid.”

The process is like that of a pressure cooker. After intensely-heated sludge has been depressurised and cooled, it is deposited in large concrete containers where the bugs banquet. Their resulting methane fuels gas engines which then give out the renewable electricity. Digested sludge “cake” left over provides farm fertiliser.