AD - fresh Grass Clippings causes Gas drop?

[GreenerGrass]

Our AD has been running a little over a month and is up to full output and is going well. It's fed on slurry, and primarily grass silage, with a little whole-crop. We have a fair amount of lawn mowings and just started to feed these into the tank. However, with the tank running pretty level gas generation, this addition of mowings really caused a noticeable drop in gas, in fact we increased the feed rate to get over it and get the levels back up - which kind of defeats the point!

I've read a fair bit about feeding fresh grass clippings, and the majority seems to be positive. As I see it they must be digested in the tank (and thus produce gas) at some point - but perhaps it is slower breakdown, or different bugs?

Would be keen to include them in the ration (perhaps at a lower rate) as it will generate gas from a product that costs us nothing, but does anyone have any experience of this? Also wondered about feeding freshly mown grass from our silage fields to take a wee bit of pressure off silage space, but with this experience of the clippings now have reservations.

Would appreciate if anyone has experience or advice relating to this.

 

[Digester Man]

You should start getting biology analysis done (I use FM Bioenergy, very happy with their advice), when things like this happen you have a direct line to advice which can be invaluable. There are a few people successfully zero grazing for digesters so I would not be scared to put fresh grass in mine. But without analysis and commentary on your own plant it will be hard to say for sure what caused the drop in output

 

[The Son]

What happened to your methane content, on my plant that is a good indicator as to how things are going, if it went higher than your normal reading, then bugs are hungry, and you need more feed, if it dropped lower than your normal reading then you are over feeding, its a crude but usefull indicator.

Just because your gas yield has dropped it does not automatically follow that you are under feeding, it may be that the grass clippings are a better feed than you think..

As suggested above get a biological analysis done, but also as you gain more experience you will get a feel for how the bugs are working.

Good luck

 

[Will Wilson]

Quick Q could the grass clipping have been contaminated with anything?

Ensiling kills most nasty's - feed fresh and they will still be there.