Instructables user anthony_p1234 writes:

This is my first Arduino project aimed at helping me with my other hobby which is growing oyster and shiitake mushrooms indoors. In a nutshell, the controller takes in two temperature readings, 1 Humidity reading and 1 Co2 reading and triggers a set of four relays connected to mains power. Intended to be connected to the mains are two heating pads, a sonic humidifier and an air pump (although the choice isn’t limited to these of course).

Arduino-powered mushroom environment controller