Scaling up

My pal the Lion of Punjab came with another (smaller) parcel of mushrooms Agaricus bisporus [prev parcel] which I accepted gratefully. In an excess of enthusiasm for his work, he suggested that we should bring our undergraduate students to visit the Ashtown Teagasc Food Research Centre, where he works. I said that was unlikely to happen because the external visit rota was more or less set in stone. But the suggestion reminded me of a 1992 field-trip we made with undergraduates from TCD to a mushroom farm. Those field trips were quite the opposite of set in stone: over the 3 years when I was a designated driver ferrying students round the country we visited a stud farm (Equus caballus); an AI centre (Bos taurus); a fish farm (Salmo trutta); a brewery (Saccharomyces cerevisiae); as well as the mushroom farm in Edenderry, King's County.

It was really interesting to see how things scaled up in order to supply tonnes of mushrooms to supermarkets rather than going out into early morning fields and woods with hope and a basket. Edenderry was picked as the site because it was conveniently close to The Curragh of Kildare where there are more equine stud farms and livery stables than pubs and petrol stations. Horse shit is the gold standard for growing Agaricus bisporus; as you will know if you have been mushroom picking where horses have grazed. Horses are not ruminants and have a relatively short digestive tract, so they produce prodigious quantities of dung.  I'm guessing that fungal spores pass through unscathed. I've spent a bit of time recently making compost . . . with a garden fork and a sieve. If you're in the business of raising horses, especially if you are buying in hay and nuts, then the horse-shit is going to overwhelm the ability of your paddocks and gallops to absorb it. In 1992, I think the mushroom farm / stud farm relationship was cost-neutral: by turning one man's dross into gold.

• Every few days, a forty tonne truck would do the rounds of the stud-farms and take their dung-heaps back to Edenderry. 
• The dung was emptied into a large concrete area surrounded by a block wall 2m tall. 
• There it was actively processed by tractors with front loaders - shovel and turn; shovel and turn - until it had been considerably reduced in bulk [huge invisible plume of CO₂ and methane] by microbial action. 
• I am assuming that aerobic bacteria worked their wonders more efficiently than leaving the material around in anaerobic heaps. 
• When that digestion was judged to have finished; the compost was loaded into wooden trays 2.4 x 1.2 x 0.6 m in size and loaded into a steam sterilising oven. 
• The trays were emptied into hoppers, mixed with mushroom spores and dispensed into 40kg sacks. 
• The sacks were left in super-cleansed black plastic poly-tunnels until the bag was run through with fungal mycelia and the fruiting bodies started to emerge on the top of each sack.
• It was like pop-corn popping - first one, then a few, then a barrage, then the rate trailed off . . .
• In 1992 the mushrooms were harvested by local people. Nowadays all the workers are probably from East of the Oder-Neiße line: PL LV LT EE RO etc

Back in 1992, they used to give the 'spent mushroom compost' away to anyone; although much of the nutritional value had been shipped out as mushrooms; there was still enough mulchy material remaining to give body to a garden or a raised bed in a garden. Mushrooms were still being produced but not at a sufficiently high rate to justify house room in a commercial concern: a meal's worth over the next week??

I guess, as a source of food, spent compost was worth having but not worth making a distant trek to obtain.