Fat lot of good down the sewer
Fat gets a bad press. It's blamed for obesity, clogs up drains and is disagreeably slimy.
But Costing the Earth is about to cast it in a new light, after producer Anne-Marie Bullock and presenter Tom Heap went down a London sewer.
The Radio 4 duo were guests of Thames Water in the drains beneath London's theatreland where they hunted for fatbergs formed from discarded cooking grease from the area's many restaurants.
The unwanted lumps of lard used to be sent to landfill, but a new scheme will see them turned into fuel to heat 40,000 homes.
It's a good news story, but not exactly a glamour assignment.
'Some of the team get to go to foreign countries,' sighs Bullock. 'I got to go down a sewer. It was one of our grimmer location recordings. You're prepared for the smell but it's a horrible atmosphere down there which Tom described as 'wet dog'.'Don't look down
Fat deposits coated the pipes, collected on the tunnel's walls and lurked just beneath the surface of the water.
Despite being well protected in overalls, waders and hard hat, Bullock found it revolting - 'I concentrated on sound quality and didn't look down'. Her presenter was less squeamish.
'You have to engage in the gross,' believes Heap. 'Many of our stories take us to new and interesting places, whether we're in the Gulf of Mexico looking at fish or under the streets of London looking at poo and fat coating the walls of a drain. Both are fascinating.'
He had a 'good hack' at the congealed fat which came off surfaces in chunks the size of a loaf of bread. Likening it to thick, grey plasticine, Heap couldn't resist squeezing it through his fingers.
'It's yucky and obviously horrid,' he concedes. 'But burning fat is answering two of the big environmental questions - where we get our fuel and what we do with our waste.'Sausage rolls
The pair also visited a fat recycling plant in Hull where fat is recovered from food waste to be used for biofuels and industrial lubricants.
'It takes in things like pork pies, sausage rolls, and 'fryer sludges' from the processing, as well as the remains of rotisserie chickens and massive ten litre tubs of mayonnaise and chipotle sauce,' says Bullock.
'They even take the fat out of individual butter pats,' adds Heap. 'It's extraordinary and all driven by ingenuity, the price of fuel and the need to get rid of our waste.'
He was particularly struck by what he alluringly describes as a paddling pool of pork fat with a few pork scratchings floating on the top.
'After a few pints I might have dived in,' he laughs.
Costing the Earth: Burn that Fat, Radio 4, Tuesday, September 24 at 9pm