The greenhouse domes use naturally hot water drawn from a geothermal well in Pagosa Springs, Colorado. Photo / Nina Riggio, for the Washington Post
Much about the spring that gives the mountain town of Pagosa Springs its name remains a mystery.
It is certified by the Guinness Book of World Records as the deepest geothermal hot spring. But the plum line measurement instrument ran out at 1002ft (305m), before it hit the bottom.
“People have no idea how deep it is or exactly where it comes from,” resident Laura Hamilton said. “It’s pretty magical.”
Hamilton is on the board of a non-profit that is harnessing the power of the Colorado town’s hot underground reservoir to perform a sort of magic.
It’s creating the capacity to grow food year-round in a region where winter temperatures routinely dip into single digits.
“We have harsh winters and extremely short growing seasons, which make it hard for people to grow their own food,” she said as we walked through one of the three geodesic domed greenhouses run by her group, the Geothermal Greenhouse Partnership.
We passed an herb bed brimming with cilantro, thyme, parsley, oregano, rosemary and basil. A lush fig tree extended its branches towards the translucent roof, which filtered soft diffused light.
What’s most distinct about the greenhouses is under the pathways between the planting beds.
An agreement with Pagosa Springs enables use of naturally hot water drawn from a town-owned geothermal well.
In cold-weather months, heat from that geothermal water is used to elevate the temperature of conventional water, which runs in a separate closed-loop system and is pumped beneath the pathways to warm the space.
“The idea was to make a sustainable agricultural system that would support the community,” Hamilton said.
Indoor farming is an established way to extend growing seasons, insulate food systems from climate volatility, reduce transportation costs and address local food insecurity.
But the industry is energy-intensive, and standard greenhouse operations have a significant carbon footprint, typically relying on fossil fuels to power supplemental heating and lighting.
Researchers estimate that growing tomatoes indoors is responsible for six times the planet-warming emissions of field tomatoes, even considering that greenhouse-grown produce may not require long-distance transport.
Geothermal greenhouses like the ones in Pagosa Springs can avoid CO2 emissions. And the water used for heating can be continually recycled.
“Geothermal greenhouses offer a more sustainable solution by using the Earth’s natural heat directly for warming, greatly reducing overall energy use and carbon footprint,” said Gina Marie Butrico, co-author of the article Greenhouse Agriculture in the Icelandic Food System.
Iceland is a global leader in geothermal agriculture.
For hundreds of years, farmers there have planted crops in areas heated directly by geothermal steam, using the robust natural resources of the Nordic island nation.
By 1924, Iceland had begun using geothermal energy to heat greenhouses and extend the short growing season. Today, geothermal greenhouses are an integral part of the food system, producing 90% of Iceland’s tomatoes and other produce.
Turkey also has several large geothermal greenhouses, including one that spans more than 27,870sqm and is dedicated solely to tomato production.
“The United States has similar potential, especially in states with abundant shallow or deep geothermal resources,” said Marit Brommer, chief executive of the International Geothermal Association.
Residential and other fairly small-scale geothermal systems tend to rely on energy from heat stored in the soil. Some geothermal greenhouses work that way, too. And those can be built pretty much anywhere.
Geothermal systems that draw energy from underground water or steam are more specialised in terms of where they can be located.
They can have broad applications - heating whole business districts and keeping footpaths clear of snow.
While there are favourable conditions for geothermal agriculture throughout much of the western US, geothermal greenhouses remain scarce.
According to Brommer, there are only about 44 in the country. And beyond greenhouses, less than 0.5% of US energy comes from geothermal sources.
That’s primarily a matter of cost, industry experts said.
The Inflation Reduction Act passed during the Biden Administration included tax credits for geothermal power sources, and those have survived even as other clean energy incentives were cut in the big budget bill US President Donald Trump signed this month.
“This policy stability is unprecedented for the geothermal sector, and it gives developers the confidence to build long-term, cost-effective projects, including in agriculture,” Brommer said.
Congress, though, voted to end residential tax credits for geothermal heat pumps. And Trump’s tariffs may increase the cost of drilling equipment and heat exchangers.
It took years for the Pagosa Springs greenhouse partnership to get enough financial support to install geothermal - and that’s even in a town with pre-existing infrastructure.
“The reason most people don’t take advantage of it is because it’s really expensive,” said Garnette Edwards, a third-generation geothermal farmer in Boise, Idaho.
In 1926, her grandfather dug a 1300ft (400m) well and built what would become the first commercial geothermal greenhouse in the US.
“It’s a family myth that my grandfather found the well with a divining rod,” Edwards said, referring to the magical forked stick used to locate wells.
The family grew watermelons, onions, sweet potatoes and hothouse tomatoes.
“True tomato flavour in the off season,” said Garnette, who as a child would tag along with her father as he made deliveries to Boise grocery stores.
“There wasn’t much connection between agriculture and geothermal back then,” Edwards said. “It was pretty forward-thinking.”
It was also cheap. The cost per foot to dig the geothermal well nearly 100 years ago was just US$1.50 a foot. Garnette said a recent quote for another well came to US$100,000.
“The problem is that labour costs for putting these systems in are very, very expensive,” said John Bartok, an agricultural engineer and extension professor emeritus at the University of Connecticut.
“Most people can’t put in a system if that payback is more than 10 or 15 years.”
Geothermal advocates note that once systems are in place, heating is free.
“Heating can account for 50 to 80% of greenhouse operating costs, and geothermal cuts this dramatically,” Brommer said.
Hamilton, with the greenhouse non-profit, said the expansion of geothermal agriculture can build food security and support sustainable agricultural practices in Pagosa Springs and elsewhere.
Rural food insecurity in the US has increased steadily over the past decade. In Pagosa Springs, more than one in 10 residents lack access to food.
“We see so much fear in people’s faces. People are scared because they can’t buy food,” said Katherine Solbert, president of a food pantry that feeds more than 3000 people a month. “And our lines just keep getting longer.”
Kelle Bruno, a teacher whose students attend biweekly classes at the greenhouses, said some families have to make hard choices between healthy foods and other necessities.
“Because we only have two grocery stores, prices are high, and getting fresh local food is a struggle for a lot of families,” she said.
The greenhouse project offers some help.
One of the domes has been operating since 2017, with a cadre of volunteers growing produce for local food pantries, senior citizen centres, schools, and other community partners in Pagosa.
Two newer domes, which are in the midst of some upgrades, are dedicated to a community garden, where groups of residents can grow and harvest vegetables at market rates, and to aquaponic and hydroponic experiments.
“This is a pathway for small farmers and tribal nations to increase yields and diversify crops, even in northern states like Alaska and Montana,” Brommer said.