Though indoor farms have been used since ancient Rome - allowing Emperor Tiberius to enjoy cucumbers year-round - the first major report on their safety has arrived late 2025.
Dr. Keith Warriner
"Indoor farming was thought to be safer than outdoor crops given that plants are grown in a protective environment," says Dr. Keith Warriner, a University of Guelph food scientist.
However, product recalls remain a major concern, Warriner says. As the industry has grown, outbreaks and recalls linked to pathogens such as salmonella and listeria are becoming more common.
A food safety researcher and the developer of award-winning sanitation technology, Warriner is the co-author of the new report released by the Food and Agricultural Organization (FAO), a United Nations agency that establishes global standards and guidelines in the field.
There are currently few regulations tailored for indoor farms, as it was assumed the same guidelines for outdoor farming could apply. However, researchers discovered that pathogens can grow and persist as in systems used in sprouted seed production.
"Indoor farming needs separate guidelines that balance food safety, plant health and economic benefits," says Warriner, with the Ontario Agricultural College.
If not taken seriously, these safety risks could lead to a loss of consumer trust as indoor farms ramp up in scale.
"Their potential ranges from increased sustainability to a method of growing that is less sensitive to the effects of climate change," Warriner says. He adds that over $100 million is being invested in Canada's indoor farming to make the country more self-sufficient in fruit and vegetables, as 80% of commodities such as lettuce are imported.
To prevent setbacks in this promising sector, such as costly recalls and foodborne illness, food safety considerations are needed to ensure the global role that indoor farms can play in feeding future generations.
Indoor farms favour survivability of pathogens
"The conditions of indoor farms are constant and ideal for plant growth, but that stable system supports the growth and persistence of pathogens," Warriner says.
Seeds and water are among the top hazards for such farms, he notes.
With moist, warm and nutrient-rich conditions, indoor farms are at risk of harmful bacteria that flourish in germinating seeds, as they aren't routinely screened for pathogens and are often grown with recirculated water. Many of the current cleaning methods also do not fully remove pathogens from seeds.
And though indoor farms are encouraged to sanitize facilities, that necessary practice also removes protective and beneficial bacteria, he adds.
To that end, one of Warriner's research projects uses a hydroxyl-radical process to disinfect seeds, remove harmful pathogens and stimulate germination, which can boost a plant's defenses and greatly improve the shelf life of food.
Outdoor farms, on the other hand, have more dynamic conditions, such as hot, cold, dry or saturated weather, which causes pathogens to die off over time. The conditions within indoor farms, such as their enclosed spaces, recycled materials and stable environment all promote pathogen survival and dissemination.
"Bottom line: keep hazards out and contain them," Warriner says.
He emphasizes strategies such as disinfection of inputs, use of biological controls and post-harvest decontamination treatment as effective risk management options.
Beware of over-regulation
Although safety risks are a concern, Warriner urges the dangers of over-regulation on indoor farms.
"Indoor farming works on very low profit margins," Warriner says, noting they do not see profits until about year five or six of operation. "In some countries, they require government subsidies to keep operating. Any regulation must consider the cost to implement."
Any decontamination methods also need to provide tangible benefits such as increased productivity or shelf life, Warriner says.
"Heavy sanitation should be done with caution, as you want to keep the good microbes."
Though these risks need to be met with new standards, Warriner says, addressing them may unlock the potential of indoor farms in addressing global food security and fostering the growth of the sector.
