Building sustainability for the MHA nation with a vegetable greenhouse heated by waste gas

Controlled environment agriculture (CEA) will soon supply leafy greens and vine vegetables year-round for the nearly 17,000 members of the Mandan, Hidatsa, and Arikara (MHA) Nation, whose leaders intend to power and heat a commercial greenhouse with natural gas now burned off as waste at the wellhead. In this article, Tony Barendregt with Prospiant tells us more about the project.

Called Native Green Grow (NG2), the greenhouse project is a step toward creating a stable food system and jobs. MHA Nation Chairman Mark Fox envisions the project as a way to restore crop production by and for the people who live on the Fort Berthold Indian Reservation in Central North Dakota.

Key to the plan's success is capturing waste gas from nearby oil well fields that the MHA Nation leases to private companies.

Instead of burning off or flaring the natural gas, it will be used as fuel for a new combined heat and power (CHP) facility. The CHP will generate electricity for the MHA Nation. The heat from the generation process will be directed to keep plants warm in a growing facility scheduled to open toward the end of 2022.

Fox read an article about sustainable greenhouses in the Netherlands, which efficiently grow healthy vine crops and lettuce along with other leafy green vegetables. Indoor agriculture enabled the Netherlands to become the world's second-largest exporter of food after the United States. That insight led the tribal leaders in 2019 to travel there. What they saw and learned convinced them to agree to fund the construction of a $26 million CHP and greenhouse complex.

Rethinking how to bring tribal leaders' ambitions to life
Fox and the Tribal Council hired general contractor Woodstone Inc., which in turn has partnered with Prospiant to help the MHA Nation make its greenhouse dream a reality.

"Site preparation is underway; Prospiant has ordered the fabrication of steel posts and trusses at one of its Canadian production facilities. We're now deep into the engineering phases of heating, lighting, irrigation, and growing systems for the greenhouse."

"In early 2021, Prospiant had been invited to bid on parts of the greenhouse project along with other companies. We reviewed 600 pages of bid documents — and respectfully declined the opportunity. We can best help growers by providing complete, end-to-end greenhouse structures and advanced growing systems that are proven to optimize CEA. We simply believe there is a better way to design and build the best possible facility for the MHA Nation."

In May 2021, tribal leaders and their consultants agreed and asked Prospiant to help them redesign plans for a greenhouse and systems that better matched their growing ambitions and financial objectives.

Deciding what really had to be accomplished
Throughout the summer of 2021, our team of greenhouse and CEA specialists worked alongside the MHA Nation Tribal Council members and their consultants to revise drawings, plans, and budgets. We recommended critical revisions to the project to enable the MHA Nation to enhance operational efficiency and productivity and build and open the greenhouse on time and within budget, such as:

  • Building one large greenhouse structure instead of subdividing it into multiple rooms
  • Sizing irrigation and heat storage systems large enough to not just meet immediate needs but to support future greenhouse expansion
  • Streamlining the list of specified equipment and suppliers to ensure that proven products from reliable manufacturers were selected in order to minimize the initial capital expenditures, lower costs for operations and maintenance, as well as avoid unplanned downtime
  • Redesigning a planned retail store with a smaller footprint or perhaps moving it to a future phase in the greenhouse project

"Our produce-growing specialists helped the MHA Nation to select the business model, structures, equipment, and processes that we deemed best for what the Tribal Council set out to accomplish."

"In September 2021, they agreed and accepted our recommendations. Based on how thoroughly and quickly we answered their questions and provided technical information during all the plan changes, MHA Nation and Woodstone Inc. chose Prospiant to move with them into the construction and commission phases of their greenhouse project."

What it takes to keep plants warm
Building a commercial greenhouse on tribal land in the middle of North Dakota is not without unique challenges.

"The first, of course, is integrating the structure and growing equipment with the CHP plant to take full advantage of the electricity and heat it will produce. To enable the MHA Nation to realize its goal of converting waste natural gas into a sustainable energy source, we reviewed the CHP plans to determine that enough heat would be available to support crops in a North Dakota winter when temperatures can drop below 0 oF for extended periods."

Additional considerations that we designed solutions for include:

  • The greenhouse roof would need to support the weight of snow at least 2 feet deep.
  • Water supply, drainage, and sewers would have to be constructed to serve a remote site.
  • Electricity for lighting and growing systems is to be supplied by the new CHP plant, as well as the surplus heat from the power generator. So we had to make sure that the greenhouse was designed to easily connect to feeds from the CHP.

"And since the MHA Nation intends to grow crops year-round, a way to store heat was needed to sustain vegetables at night or whenever the CHP might be offline. So we sized tanks to hold enough hot water to keep the plants warm overnight but also to support future greenhouse expansion."

Designing to grow simply and efficiently
"To reduce the initial capital expenditures and optimize growing operations, we approached the MHA Nation project like we would for large-scale commercial operators of greenhouses covering dozens or hundreds of acres. We're helping the tribal leaders to maximize their investment by simplifying plans that originally called for four separate growing areas, each with its own systems and equipment to create microclimates."

Now the overall greenhouse structure is engineered to support a heavy snow load. That also makes the posts and trusses in one large room strong enough for hanging growing systems for vined vegetables such as tomatoes, peppers, and cucumbers. Lettuce and other leafy green vegetables will be grown on rack systems attached to the greenhouse floor.

"We're designing smarter and efficient lighting solutions that will combine high-pressure sodium fixtures with light-emitting diode (LED) lighting."

A system will capture rain and snow to supplement other water sources — and contribute to achieving the goals for sustainability and self-sufficiency set by the Tribal Council.

Working with a greenhouse partner instead of a supplier
Important to the future of the MHA Nation is the ability to expand its greenhouse operations. By redesigning the greenhouse structure from what had been a highly specialized, custom facility to one that's standardized like a commercial growing facility would be, the MHA Nation can more easily add greenhouses on the site. There's room and infrastructure — especially for water storage and irrigation — to scale up to 15 acres under glass.

"We also convinced the Tribal Council to increase the foundation size in preparation for an expansion of the headhouse as vegetable packing increases. It will cost less to do the work now so that the MHA Nation is ready to grow."

"In our role as greenhouse partner rather than simply a supplier, Prospiant also is working alongside the MHA Nation leaders and their consultants to implement a growing chamber in which lettuce plants can be germinated and matured to a certain size before being transplanted in the greenhouse. This approach can reduce the growing cycle from 42 to 35 days, which means that the MHA Nation can increase its vegetable yield beyond the designed capacity of the greenhouse."

On track to grow healthy vegetables this year
The NG2 project is on schedule for construction through the summer; Prospiant will install growing, climate control, irrigation, and lighting systems into the fall. The greenhouse should be commissioned and ready to turn over to the MHA Nation by Dec. 1.

Tribal leaders are still considering which vine crops and leafy green vegetables they'll grow indoors. They plan to hire as many as 25 MHA Nation members to tend to the plants.

On its land, the MHA Nation will begin to use natural gas that's now wasted to generate heat to warm its climate-controlled greenhouse. As a result, vegetables will be grown indoors 365 days a year to help the MHA Nation develop a sustainable ecosystem that yields healthy nutritional and economic benefits for tribal members.

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