Saturday, 13 April 2013

Fat and fantasy

Energy Live News has a lightweight piece about Thames Water and its attempts to solve the old problem of congealed fat causing sewer blockages.

Because the fat and cooking oil tipped carelessly away by homes and local restaurants which ends up as congealed gunk contributes to the 80,000 blockages that Thames Water deals with every year. At a million pound a pop to solve, that’s a big old spend.*

Hmm... 80,000 x £1,000,000 = £80 billion. So fat blockages cost Thames Water £80 billion a year? I don't think so. Why don't reporters check these things? In fact it's not a million pounds a pop, but a million pounds a month - source.

We are also told.

In a stroke of recycling genius, some bright spark has found a use for the yucky goo: a fat-fuelled power station. So along with energy firm 2OC, they’re going to collect that grease from restaurants in the city with ‘fat-traps’ and truck it out to a new plant in Beckton.

While it will cost £60million to build the plant, it’s going to save Thames Water an awful lot of money on energy bills – they’ve agreed to buy 60% of the electricity. With energy prices going the way they are (i.e. ever upwards) I think we’re going to see more and more like this classic example of waste not, want not.

I'd take that with a large pinch of salt too. 

Fuel used in collecting fat from fat traps and trucking it out to the generating plant. Refining the collected gunk into some kind of fuel and turning it into electricity at a profit and without a big juicy subsidy. 

No, I don't think I believe that one either. Maybe I'm a cynic.

* Update 14/04.
The original article has been corrected to - At a million pounds a month to solve, that’s a big old spend.


Anonymous said...

Being a sad b'stard I ran some numbers. The power plant does about 15MW (130GWh/year) which would cost between say £2000/hour to £1330/hour to buy. The feedstock is sewer fat plus bought-in (cheaply?) waste fat & oil. At Brent Crude price to make 15MW would take say 13 barrels/hour (60% effy) costing about £870/hour plus the interest on capital - say £240/hour. So add in a few subsidies and tax breaks and this could make sense if a continuing supply of cheap feedstock comes gurgling in.

The question in my mind is just how much of that 13 barrels/hour oil-equivalent will be sewer fat - cleaned up and de-watered etc etc.

Sam Vega said...

"With energy prices going the way they are (i.e. ever upwards) I think we’re going to see more and more like this classic example of waste not, want not."

Absolutely true. The fat greasy Londoners will not be able to afford takeaways, and thus the problem will be solved.

Anonymous said...

One niggle, the source article refers to 40,000 fatbergs/year blocking the system, now let us say 25Kg/berg and 100% recovery. In oil equivalent this amounts to 1 million Kg of fat or about 7000 barrels of oil (assume burns the same....) which will last the power plant about 17 days. Even if they recover twice as much fat from effluent the fat source looks a bit iffy. Further, they will be a bit of a hostage to the waste oil suppliers and as Sam says Londoners may not nosh the same for the next 20 years. Maybe this is all a good excuse to build an oil-fired power station on the back of a green agenda/subsidy stream.

A K Haart said...

Roger - interesting calculation. A lot of sewage fat is emulsified or absorbed within solid matter. It mostly ends up as methane from the sludge digestion process.

At Beckton this is methane is already used to generate electricity. It all sounds a bit iffy to me.

Sam - and if food prices rise too, this project is subject to a double whammy.