In Mineral Spring’s sterile lab, the growing process begins with vials containing mycelium, or the white rootlike strands found underground from which mushrooms grow in the wild. A sterile culture containing the mycelium of a mushroom species and a growing medium are combined to create spawn (essentially mushroom seeds). The spawn, combined with sugar and yeast, eventually are injected into blocks of sterile oak sawdust or rye seed. The blocks are placed in sealed plastic bags, about two gallons in size, and allowed to incubate.

They are then placed in the greenhouses at 50 to 60 degrees and within 10 to 17 days will begin sprouting mushrooms.

All the used growing matter – straw, sawdust and grain – is trucked to Mineral Spring President Andrew Smith’s farm in Thorndike as compost.

By spring, two new conventional greenhouses will be placed on the end of each mushroom greenhouse to catch the heat created by the growing fungi. Smith said he will grow lettuce and other salad greens in those structures, capturing the lost heat and creating another product.

He is also looking at shifting from oil heat to biodiesel, even for his delivery vehicles, and installing windmills to supplement electricity costs.