The environmental impact of farming is not just big news, it gets turned into regulations. Ammonia from livestock sheds is something we've been reading more about and is another reason for keeping no more than a dozen cattle in a shed together. When I came across the Danish company JH Agro's small stand which claimed to have sorted the ammonia problem out, there's a good article for the magazine. They have around 100 installations on farms in Denmark, also Germany and one in N Ireland. The system is to mix sulphuric acid with the slurry, and that changes the NH3 gas - ammonia - to NH4 liquid - ammonium. Plus a measure of usable sulphur. So there's 10% or so more usable N in the slurry, clean air in the shed making for increased health, and ammonia emissions that are pretty much elimiinated. Storing and messing around with concentrated sulphuric acid is not a DIY job, but they seem to have the safety part sorted. The economics is the big question. There's value in the plant nutrients, and the clean air in the shed, and there look like grants as well. The system is mainly retrofitted to existing sheds but of course can be built in. And what was missing? I searched for a compost turner, and also a grass aerator, and found none.