Grass silage for AD

[Warnesworth]

Looking to make grass silage this year for AD. I cannot find any recommendations regarding best time to cut, i.e. grass growth stage, wilt time, additive etc.
Any advice gratefully appreciated.

 

[The Son]

Make the best quality you can, so grass should all be shut up by now, and you should be looking to cut early May, ideally before heading starts, then cut, ted and get it dry, 28-30% DM, then chop nice and short and consolodate well in the pit, the day you finish spread digestate, then six weeks later repeat, we got 4 cuts last year.

I use grass in our AD plant and like it as a feed, it compliments maize as it gives a better quality of gas for us allowing us to get to 54-55% methane, the main downside is the dm of the digester tends to go up, the separator slows down, and you can get a nasty crust if you are not careful.

 

[Great In Grass]

Sow a blend of Italian and Westerwolds ryegrass, cutting can be expected in 10 - 12 weeks after sowing. Late cut silage of grass that has gone to seed can produce 20% less gas than if cut in the vegetative state. I think optimum yield/gas production is between 45/55% ear emergence. Wilt to get a dry matter content of 30%. Chop length should be between 2.5-5 cm. Rapid regrowth for subsequent cuts.

 

[Warnesworth]

Great stuff so far, that's what I thought, not too much stem and therefore lignin.
I understand this is a 'how long is a piece of string' question, but, given reasonable weather conditions (no rain) how long would you wilt for? 24hrs ?

 

[Warnesworth]

Make the best quality you can, so grass should all be shut up by now, and you should be looking to cut early May, ideally before heading starts, then cut, ted and get it dry, 28-30% DM, then chop nice and short and consolodate well in the pit, the day you finish spread digestate, then six weeks later repeat, we got 4 cuts last year.

I use grass in our AD plant and like it as a feed, it compliments maize as it gives a better quality of gas for us allowing us to get to 54-55% methane, the main downside is the dm of the digester tends to go up, the separator slows down, and you can get a nasty crust if you are not careful.

I suppose you counteract the higher DM by feeding more water? Do you find that the H2S also goes up when you feed grass?

 

[Great In Grass]

12 hours should do it if favourable weather conditions. Also it pains me to say so as I sell the stuff no need to inoculate.

 

[Warnesworth]

12 hours should do it if favourable weather conditions. Also it pains me to say so as I sell the stuff no need to inoculate.

Really!? I would have thought that it would still be necessary to get the fermentation going rapidly to preserve as much 'energy' as possible.

 

[mushnt grummmble]

Looking to make grass silage this year for AD. I cannot find any recommendations regarding best time to cut, i.e. grass growth stage, wilt time, additive etc.
Any advice gratefully appreciated.

think of it as making top quality silage for milking cows

 

[Great In Grass]

If you can wrap up the cutting and ensiling process very quickly also cut when sugar content is high you should preserve most of the quality.

 

[Warnesworth]

Cheers. Thanks for all the comments.

 

[The Son]

Yes, H2S does rise slightly using grass, but we have a carbon filter, and blow more air into the roof to counteract, we are running at 7ppm H2S at the moment on 10t of grass silage a day.
We wilt first cut for upto 48 hours, but this does reduce on subsequent cuts down to 24 hours.

 

[Warnesworth]

That's a very low H2S level. Are you also using ferric containing products to control the H2S? A 48hr wilt must produce some very dry grass. What gas volume are you producing on a maize/grass feedstock per tonne?

 

[The Son]

We are not only maize and grass, other items are going in as well, but as a rule of thumb we are using 200m3 per tonne on the grass, and 180m3 per tonne with maize, and I don't think that is far out.
We have just changed the ferric oxide to a new product called S con, and we put in 6kg a day, it is in a soluble bag so what we actually do is bung in one bag every three days.

 

[rjs15t]

What chop lengths do you use for your Maize and grass?

 

[it's not over]

if the made silage was high in nitrogen due to too much fert/slurry how would it preform in the digestor. cows certainly will not eat

 

[Warnesworth]

What chop lengths do you use for your Maize and grass?

Maize 7-10mm. As @Great In Grass says above grass we have been advised to aim for 25-30mm

 

[Warnesworth]

if the made silage was high in nitrogen due to too much fert/slurry how would it preform in the digestor. cows certainly will not eat

High N (NH4-N) products in a digester do not go well, you really have to watch the C:N ratio

 

[The Son]

We chop our maize to 4mm, grass 25-30mm

 

[Merlo 40.7]

What would a crop of grass be worth feed to a digester? Weather it be £/t or £/Dm

 

[Exfarmer]

I know nothing about AD plants, but I am interested.
Why are you looking to put high protein grass into them (as silage)?
I would have thought ( in my ignorance) that bulk in the form of carbohydrates is what they would require.
Cutting grass relatively young ie. early May is surely missing out on yield.
Further by going for multiple cuts is costing more in harvesting terms