I would like to start a small-scale vertical urban farm that produces mushrooms in an old factory building. How important is floor drainage in this type of enterprise?

Answer: There is a lot of interest in urban mushroom farms that include indoor production. Many of these farms are utilizing local resources for their growing substrate and are also creating value-added by-products from the mushroom production that particularly can be utilized in crop production. Indoor mushroom production requires creating and maintaining certain environments specific to the varieties being cultivated. An indoor mushroom farm requires a dark, temperature-controlled room for the mushrooms to grow. A separate, smaller, temperature-controlled room with humidity control for sterilizing the substrate is often used in commercial production.Temperature, moisture/humidity, and oxygen levels must be monitored not only for the production of the mushrooms but also to prevent any possible contamination. Unfavorable conditions in indoor mushroom production can create unwanted odors, bacteria, and mold that can not only harm fungus health, but also compromise the health of farm workers and others who may be in the building.Sterilization is a key component of indoor mushroom production. Home-scale and commercial sterilization systems can be purchased but can also be homemade. These systems are generally made up of an autoclave that holds in the environmental conditions. Steam is often utilized to sterilize the mushroom substrate, which would require a boiler system. Water is also needed for controlling the moisture levels as well as washing/cleaning equipment and infrastructure used in the production, harvesting, and packaging of the product. While an old factory building may be an ideal location for starting an indoor urban mushroom farm, the absence of drainage is going to create several obstacles. This is not just an issue for production purposes, but more importantly, it will most likely be a food-safety issue as indoor commercial operations may be required to have proper drainage. The specifics depend on local zoning and food-production regulations and it is recommended that you contact your local health inspector as well as the state department of agriculture for further information. It is also important to discuss the specifics of the operation with the building owner and/or manager so that none of the structural integrity of the building is jeopardized. For more information on mushroom production, see ATTRA publication Mushroom Cultivation and Marketing, available at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=77.