We're just finalising our plans for our 'Animal Centre', which will incorporate a milking parlour, cattle accommodation, pony stables, hay store, and so on, plus of course a midden.
We're not in an NVZ, but I've been reading up the NVZ papers looking for guidance on volumes of muck. I've found figures for volumes of 'solid excreta' but can't fathom what multiplicand I should use for the straw. I found something that said to use a factor of 1.3 by weight - but as straw is very light and voluminous, I'm not sure that's helped me much :/
Also, we expect to deep bed the cattle, not mucking out much unless necessary until after the winter, so a lot of their effluent will not be in the midden for most of the housed period. However they'll be free to loaf around in the yard during the day, which will be scraped daily, so I guess that perhaps half of their poo will in fact get into the midden during the winter.
The ponies' stables will be picked out daily and rebedded as necessary to keep them on clean dry footing. They too will have some loafing time in the yard.
My calcs of the expected total 'solid excreta' give 21-25 m3 on current predicted usage, possibly up to 40 m3 if we increase the size of the dairy herd. (This is for four months housed, which would be a really bad winter for us. They were in for three months two years ago, but usually it would be two months / 10 weeks, I think.). The surface area of our midden as currently designed is just under 22 m3, and I'm told that will hold 32 m3 in a 's**t pyramid' !
So I thought I'd ask whether anyone could offer practical advice from their own experience.