The rice in these trays is being fermented with aspergillus oryzae (or Koji), after which process it can be used to make a number of tasty things, miso and amasake being the most popular transformations around here.
Got to keep a close eye on the temp
The grain is bought unhulled, in bulk, to be hulled and sorted here, the most economic way. Economy of scale can be a real advantage, as you might imagine, when a large group of people buys food as a unit. It also helps, of course, if they share a common diet.