Natural gas has long been the fuel of choice for commercial greenhouse operators—for several reasons. It’s affordable. It burns efficiently. Combustion by-product CO2 can be captured and redirected to feed the plants. The plants combine the carbon dioxide with water and light through photosynthesis to make carbohydrates, nourishing their growth.
“When we think of photosynthesis, light and carbon dioxide are the key drivers in plant development and making food grow,” says Aaron Coristine, Manager Science, Regulatory Affairs and Government Relations at Ontario Greenhouse Vegetable Growers (OGVG), a not-for-profit organization formed in 1967 representing approximately 220 members who grow greenhouse tomatoes, cucumbers and peppers on nearly 4000 acres in Ontario. Areas of its focus encompass research, food safety, energy, environment, market performance, and marketing.
That produced CO2 serves to boost what plants normally get in an outside environment. “Ideally on a warm sunny day you’d have CO2 levels around 200 to 400 ppm [parts per million],” explains Coristine. “Whereas inside the greenhouse we could have levels upwards of 1200 ppm, and the plants would consume all of it and produce oxygen as a by-product- which helps with the growth and development and the efficiency of food production.”
“So really we operate as sustainably and as close to net-zero as possible considering we are a large consumer of natural gas,” he adds. “As a matter of fact, if we could further that, what we do know too is that we can utilize natural gas to sustainably produce electricity with cogeneration to power our farms. So really when we use natural gas in the greenhouse sector we’re using everything.”
Cogeneration, or CHP (combined heat and power) is common in the industry, especially in areas with little extra electricity. It allows greenhouse operators to come off the grid and free up electricity that goes to residential, industrial and manufacturing and allows farms to operate self-sustainably. It’s really a win-win: cogeneration can boast of energy efficiencies above 90%, lower costs and lower emissions than with separate heat and power generation systems, and often surplus electricity can be sold.
Other advantages of greenhouse growing include the smaller footprint over traditional farmers’ fields. Coristine offers an illustration: “Depending on the farming practice, you would need 13 to 16 acres of field cucumber for one acre of greenhouse,” he says. “Generally, it’s around 15 times more efficient to grow in a greenhouse than in the field.”
Pest control can be more environmentally friendly too. “We use a lot of biological control,” says Coristine. “So, we use good bugs to eliminate the bad bug population. We’re not having to use much pesticide at all. We use bumble bees for pollination, and we use various species of mites to go in and eat the organisms that are detrimental to crop growth.”
So, all-round the role the greenhouse industry plays in food security, affordability, sustainability, and climate change is significant. “It’s the way of the future and the best way forward because we are not susceptible to hailstorms, drought, heat waves,” says Coristine. “We are extremely efficient. We use very little water. We recirculate our water, we treat it on site, we reuse water, we regulate temperature. It’s probably the most sustainable form of farming that’s available.”
But offsetting many of these greenhouse positives are concerns like vulnerability to natural gas price increases. “We see gas prices increasing including their effect on prices of things like fertilizer and building materials,” says Coristine. They try to buy forward but it’s a publicly traded commodity so “when there’s a shortage the price goes up – we have no choice. We can try diesel but that’s a short-term answer.”
With that risk, why is natural gas still the best energy source for greenhouse operations? “Just because it’s the most efficient, the most environmentally friendly the way we use it and in Ontario specifically there is not enough electricity to power or electrify the sector,” says Coristine. He feels it’s not feasible presently to put in electric boilers or electric heat pumps because of the lack of electricity availability. “But if gas prices aren’t kept in check, greenhouse farming could become unfeasible and we would see more imports.
Energy savings can be improved in various ways. For example, energy-saving curtains trap heat in low-light conditions during cloudy days and at night. Multiple curtains across different crop types significantly increase savings and offer greenhouse operators greater flexibility in managing their climate. New and more efficient designs and materials are currently under development.
New crops in new areas using new technologies are now developing too. For example, strawberry production in Alberta: Sunterra Greenhouse, northeast of Calgary, recently built a 20-acre greenhouse facility for tomato and strawberry production with plans to expand to 70 acres. According to Amanda Hehr, Sunterra’s president, they’re the third greenhouse in North America to implement the more efficient lift gutter system for strawberries. This makes better use of growing space and higher plant density, so their next expansion may be almost exclusively strawberries.
And local wind farms are another option being eyed as a potential carbon-free solution. “We have a project to examine the feasibility of using wind power electricity to create hydrogen which we can then blend with natural gas to reduce our carbon footprint even further,” says Coristine. The HIGH (Hydrogen Integrated Greenhouse Horticultural) Energy project partners OGVG with the University of Windsor and Kruger Energy to investigate using existing wind turbines. A commercial facility would take the locally captured wind energy, turn it into electricity and hydrogen for greenhouses that grow tomatoes, peppers, cucumbers, strawberries, and other crops.
Going forward, the greenhouse industry builds on its stellar reputation with developments like these to meet a critical supply and affordability need. “I think it’s certainly the key component to a resilient supply system of Canadian produce as we navigate the future,” says Coristine. “It’s an extremely forward-thinking sector.”
Graham Chandler spent a decade in energy corporate finance and marketing management. As a full-time freelance writer, he has specialized in energy topics for the past 20 years.