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Wondering why BioGas is not promoted

 
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Wood Burners, Biomass, Small Scale, Biofuels & Other Heating Alternatives
Last Post by ChickenBig 3 years ago
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 ChickenBig
(@chickenbig)
Honorable Member Member
Joined: 3 years ago
Posts: 292
15/05/2022 9:13 am  
Posted by: @robl

I think an anaerobic digester has to run warm, and it uses some of the available organic material to keep itself warm.  For that reason, it works better at larger scale in the UK.  Maybe you could get scraps from other households to help out!

Dale Vince, cool founder of Ecotricity, has a great blog - saying the UK could create enough biogas to run most of our housing stock, assuming it was upgraded a bit and using most grazing land in the UK to make grass fed to biodigesters.  As gas prices are now so high I'm sure this is being worked on.  I think he said ~1/2 acre of grass makes enough biogas for his average "improved" house:

ECOTRICITY.CO.UK "https://www.ecotricity.co.uk/our-news/2021/ecotricity-explains-making-gas-from-grass"
Ecotricity explains: Making gas from grass | Ecotricity
Right now, we’re working on a really exciting project, the first green gasmill in Britain – turning grass into gas that can be used in standard boilers to heat our homes and fight the climate crisis.

   

The headline figure of 5MW to power 5,000 homes is not so helpful for understanding where it fits in, given the strong seasonal demand for heating. They must be able to dial gas production up and down according to demand, which may take a time to achieve, so I wonder what this lag is like and what the upper limit on the power output is.

I did find the Green Gas Mills fact sheet made for interesting reading on the subject of heat pumps; "Sounds like a magical energy making machine", "And in the cold weather the COP of a heat pump will be 1 - meaning one unit in and one unit back out." and "It’s very difficult to find an annual average COP for an air source heat pump -real world figures. I’ve not been able to" stand out.


   
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 Derek M
(@derek-m)
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Joined: 4 years ago
Posts: 4427
15/05/2022 9:53 am  

Hi @chickenbig

One of the benefits of gas is that it can be stored in bulk for later use, which is not yet the case with electricity.


   
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 ChickenBig
(@chickenbig)
Honorable Member Member
Joined: 3 years ago
Posts: 292
16/05/2022 1:48 pm  

@derek-m Regarding the quantity of gas used in the winter, I found this page interesting; eyeballing the embedded figure, I think average power from gas is around 100GW in the winter (and 150GW during the Beast from the East), although this also includes non-domestic usage. The proposed 3,000 5MW mills is a factor of 6 away from covering the winter average. Storing large amounts of gas is difficult; the now defunct Rough storage facility could hold approximately nine days' supply of gas, although it looked to have quite a bottleneck as it could only supply 10% of the actual demand. Perhaps turning it into LNG would help with the volume, but no doubt there are other costs associated.


   
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