Anaerobic digesters

Boomerang · Jun 24, 2019

I get the principle of using them to make use of a waste byproduct and turn this waste into energy , But what I don't get is the now thousands of acres of maize grown specifically to feed a digester, I've heard of an outfit running 2 foragers 20+ tractors and trailers, as well as a number of trucks to harvest and transport the maize to the digester. The fossil fuel usage must be huge.
How much energy is being used to sow ,grow , harvest and transport the maize , compared to the energy that is being extracted by the digester.
Does this only work because of subsidy ??? Or do I not fully understand the process.

Bill the Bass · Jun 24, 2019

I don’t understand the process either, but when cattle are fed soya shipped around the world and grass and maize grown in the uk is being ‘digested’ to make subsidised energy you do have to wonder...

Werzle · Jun 24, 2019

SIABOD50 said:
I get the principle of using them to make use of a waste byproduct and turn this waste into energy , But what I don't get is the now thousands of acres of maize grown specifically to feed a digester, I've heard of an outfit running 2 foragers 20+ tractors and trailers, as well as a number of trucks to harvest and transport the maize to the digester. The fossil fuel usage must be huge.
How much energy is being used to sow ,grow , harvest and transport the maize , compared to the energy that is being extracted by the digester.
Does this only work because of subsidy ??? Or do I not fully understand the process.

Its a con that helps the government meet its green energy targets. It wouldnt pay a shilling if it wasnt for the subs .

uztrac · Jun 24, 2019

SIABOD50 said:
I get the principle of using them to make use of a waste byproduct and turn this waste into energy , But what I don't get is the now thousands of acres of maize grown specifically to feed a digester, I've heard of an outfit running 2 foragers 20+ tractors and trailers, as well as a number of trucks to harvest and transport the maize to the digester. The fossil fuel usage must be huge.
How much energy is being used to sow ,grow , harvest and transport the maize , compared to the energy that is being extracted by the digester.
Does this only work because of subsidy ??? Or do I not fully understand the process.

Massive acreage of Maize & Rye grown around this part of Norfolk to feed 2 very large AD plants.Fleets of tractors and lorries common sights keeping up with the foragers.

holywell farmer · Jun 24, 2019

SIABOD50 said:
I get the principle of using them to make use of a waste byproduct and turn this waste into energy , But what I don't get is the now thousands of acres of maize grown specifically to feed a digester, I've heard of an outfit running 2 foragers 20+ tractors and trailers, as well as a number of trucks to harvest and transport the maize to the digester. The fossil fuel usage must be huge.
How much energy is being used to sow ,grow , harvest and transport the maize , compared to the energy that is being extracted by the digester.
Does this only work because of subsidy ??? Or do I not fully understand the process.

Don't digesters put energy back into the grid ?

Shep · Jun 24, 2019

A friend of mine works for Ofgem, his view is that they are a waste management solution, rather than an energy generation solution.

teslacoils · Jun 24, 2019

A lot of the economy doesn't work without the tax breaks or the subs tbh.

Boomerang · Jun 24, 2019

holywell farmer said:
Don't digesters put energy back into the grid ?

yes but how much energy has been consumed to extract it , is my point , it dosn't stack up. As said above its a government con to meet so called green energy , but green its most definitely not .

holywell farmer · Jun 24, 2019

uztrac said:
Massive acreage of Maize & Rye grown around this part of Norfolk to feed 2 very large AD plants.Fleets of tractors and lorries common sights keeping up with the foragers.

Do different crops produce different amounts of energy from the digester?

Suffolk Serf · Jun 24, 2019

holywell farmer said:
Do different crops produce different amounts of energy from the digester?

Yes. Just like feeding livestock.

Al R · Jun 24, 2019

holywell farmer said:
Do different crops produce different amounts of energy from the digester?

YES!!!! Silage needs to be Holstein quality not suckler quality, many AD plants are on 6 grass harvests a year.

See the second chart about yield from rye from different growth stages.

holywell farmer · Jun 24, 2019

Al R said:
YES!!!! Silage needs to be Holstein quality not suckler quality, many AD plants are on 6 grass harvests a year.

See the second chart about yield from rye from different growth stages.
View attachment 813714 View attachment 813716

Cheers

holywell farmer · Jun 24, 2019

Suffolk Serf said:
Yes. Just like feeding livestock.

Do think there more to develop with ad units ?

Al R · Jun 24, 2019

holywell farmer said:
Do think there more to develop with ad units ?

That doesn’t make sense?

holywell farmer · Jun 24, 2019

Al R said:
That doesn’t make sense?

Meant maybe get more output from them, i.e. Make them run effectively

Al R · Jun 24, 2019

holywell farmer said:
Meant maybe get more output from them, i.e. Make them run effectively

They need managing meticulously from what I’ve seen, the ones doing it well are doing well and are strict on the diet formulations, imagine running a 1000+ Holstein herd. The AD operators that have problems are the ones that are slap dash and will take in produce because it’s cheap/free.. I remember going to 1 and i asked how it was going and they said it was going well for 3 years until a lorry load of bananas had tipped on the motorway and they said they’d take it, AD plant onstop for months while they emptied it all out and had to re import good bacteria as they killed all their old bacteria with 29t of bananas in 1 day instead of doing 2t for 15 days.. it cost them a fortune in time and loss of income!

Werzle · Jun 24, 2019

I was told you have to feed it as if it was your best cow.

Norfolk Olly · Jun 24, 2019

Werzle said:
I was told you have to feed it as if it was your best cow.

And just as temperamental. A good friend of mine runs the maintenance side of things for one. They are putting 70 tons per day through it and requires alot of attention keep it running efficiently after numerous issues with the generators initially. He will very often be woken in the middle of the night by a text alert with an issue that needs sorting. Then theres the by products, we receive 22000 tons of digestate on a muck for straw deal which our crops seem to have improved with since applying

Tarw Coch · Jun 24, 2019

Werzle said:
I was told you have to feed it as if it was your best cow.

They put chicken sh!t in digesters, I wouldn’t want to feed that to my poorest cow.

TripleSix · Jun 24, 2019

Tarw Coch said:
They put chicken sh!t in digesters, I wouldn’t want to feed that to my poorest cow.

Cattle do really well when fed poultry litter.

Until you get botulism...

Anaerobic digesters

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100% I’ve had enough of farming!

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