Sewer Fat – The Other Energy Source

I noticed my sink was draining rather slowly the other day and on checking outside the house, I could see the cause – the grease trap had clogged with, well, grease.

I had only cleaned the grease trap about 12 months ago and even got a nod of approval from the septic tank dude who inspected my work. I don’t cook with a lot of oil or fats; so I was surprised by the blockage.

I obviously need to follow my own advice a bit more closely and dose with Actizyme more frequently; which is an environmentally friendly enzyme/bacteria based preparation. There’s nothing like seeing (and smelling) some of the remnants of a thousand meals to drive that point home.

Anyway, as I scraped off the solidified chunks of gunk (and battled to keep my breakfast down), I was reminded of a recent story on a related topic.

In April, the UK’s Thames Water announced it would be using ‘sewer fat’ and waste grease and oil from various food establishments to power Britain’s largest sewage processing facility.

The stuff will be fed into what will be the world’s largest fat-fuelled power station; situated at Beckton in East London.

When liquid fats go down the sink; some of it is caught in grease traps – if they are in place and working properly. What isn’t captured cools in sewers, creating fat “bergs”; which are a serious problem in Thames Water’s 100,000km of pipes. Half of the 80,000 blockages that Thames Water clears each year are attributed to fat, oil and grease (FOG).

Adding to the problem are so-called “disposable” wipes that don’t breakdown which get caught up in the fatty mess.

Through the initiative, approximately 30 tonnes a day of FOG will be harvested – enough to provide half the fuel the power station needs to generate 130 gigawatt hours (GWh) a year of electricity. That level of production can supply the electricity needs of over 39,000 average-sized homes.

Gross sewer fat trivia: 25% more fat, oil and grease (about 500 tonnes of the stuff) goes down London’s drains in December than at any other time of the year due to festive season meals.


How Sewage Wastewater Is Treated