Gas for sale AD.

[wasted years]

Would harvesting the gas from slurries etc be economic?
I have often thought that there must be 000's of farmers who could never have full AD through planning or grid connection issues but could simply harvest the gad=s to bottles/tanks and sell it.
I had contact with a gas company ythat said they would buy it as they had to have so much 'green ' gas per year to comply with rules and regs.
It would help to put an end to the climate change lobby around methane from housed cattle.

 

[Digester Man]

Nice idea in theory, it would be more efficient than transporting slurry to the AD plants. But hard to know whether the capital cost for the farmer would high and the resulting gas would be hard to sell at a competitive price.

 

[sjt01]

Marches Biogas were promoting their Agridigestore, which was basically a roof for a slurry store with a bit of heating to convert to a simple digester. Not sure how many they installed, if any.

 

[thesilentone]

The problem is the cost of compressing the gas. Biogas is mostly methane and CO2. However the logistics and risks of compressing CO2, make it uneconomical. (why transport 30-40% of nothing)

However methane compressed to CNG is a good option, if your plant is big enough to justify cleaning and compressing the gas. Then of course you need the right trucks to transport the compressed CNG, one to fill, at least one in transport, and one being used at the destination, and at least one spare. (each trailer is over £100k)

Looking to the future of electricity grid connections and demand (and the difficulty of getting a reasonable capacity), spare capacity at existing plants, and of course the elephant in the room, transport fuel (where we are years behind) there is a good future for CNG (maybe if the Government takes the brakes off and allows the market to develop).

But I agree with Rob AD, it is much more economical and a different model to have one large plant and everyone takes the slurry to it, or it is collected like milk.

This business model is very slow to develop in the UK, I think it is mainly due to our unwillingness to work together.

If we want small units, we need a complete change in technology to allow the £££'s to add up.

 

[DGC1]

moving slurry from farm to a central AD plant would be very costly
not enough gas in the slurry to justify the haulage costs
1t slurry has ?? cu gas in it
1t rye/maize has ??? cu gas in it
same cost to haul both!
--
slurry ? dry matter
rye 40% dm
--
slurry = too much low dm material going through valuable digester space
--
low dm feedstock = high volume of digestate to handle vs gas output
all adds up
imo the sums don't add up unless the slurry is on-farm or possibly umbilical pumped but the minute tankers are introduced?? --
and then even if they did could a big gas to roadfuel plant pass sus-cri once all carbon footprint captured.... could be a complex calculation.
--
if slurry coming from multiple farms then to pass QMS then the digestate going back to these farms would need to be pas110 and pasteurised
and some would need to go back

 

[Sharpy]

Surely the gas should be used to generate electricity with on farm generators at peak times? Zero waste miles and a ready made distribution network.

 

[DGC1]

agree but there are no FIT's available these days to pay for the gas engine / other capex required
very much doubt gas from slurry stacks up these days given the high capital cost of AD with little or no support mechanisms. engine needs to run most of the time as digesters produce the gas 24/7 and unless its used it needs flared or stored.... more capex!
.gov missed a trick as a small/medium sized digester in a medium/large dairy farm is the ideal marriage but there was no lasting incentive once FIT's started to be cut and a lot of the gas2grid rhi money poured into the arable regions with hardly any g2g rhi in the livestock regions
imo there should have been a specific scheme relating to slurry based system

 

[wasted years]

Surely the gas should be used to generate electricity with on farm generators at peak times? Zero waste miles and a ready made distribution network.

In my situation, looking at small scale AD (less than 250 cows) and robotically milked there is no peak time use, unless the gas was stored to fuel a Peaking, STOR type engine that may only run a few hundred hours per year.

 

[Sharpy]

@DGC1 @wasted years
Thats a great pity, although I was meaning to export the electricity at peak demand times as for example a fattening unit or pig unit wouldn't have the surges in use of a conventional dairy.

 

[thesilentone]

moving slurry from farm to a central AD plant would be very costly
not enough gas in the slurry to justify the haulage costs
1t slurry has ?? cu gas in it
1t rye/maize has ??? cu gas in it
same cost to haul both!
--
slurry ? dry matter
rye 40% dm
--
slurry = too much low dm material going through valuable digester space
--
low dm feedstock = high volume of digestate to handle vs gas output
all adds up
imo the sums don't add up unless the slurry is on-farm or possibly umbilical pumped but the minute tankers are introduced?? --
and then even if they did could a big gas to roadfuel plant pass sus-cri once all carbon footprint captured.... could be a complex calculation.
--
if slurry coming from multiple farms then to pass QMS then the digestate going back to these farms would need to be pas110 and pasteurised
and some would need to go back

In theory you are correct, however if you look at the whole life cycle, the slurry (as a liquid) is very bulky and is mostly water, so of course the first consideration is separation. Also, the liquid element is to deal with also, so the balance of sustainability is slurry transported to AD/energy production/returning nutrient v slurry transported to spreading/unbilical.

Slurry alone is not a consideration, however there is plenty of waste in form of silage, muck (beef) and/or any other from C&I production (milk/food/meat).

Of course pasteurisation would be required, however this could only be positive.

It is already happening in other Countries.

http://www.lemvigbiogas.com/GB.htm

https://www.bioenergy-news.com/disp...watt_biogas_plant_in_germany_now_operational/

https://waste-management-world.com/a/300-000-tpa-farm-waste-to-biogas-facility-opened-in-denmark