Built with Straw
Marcus and Jessie Koenig may have the only large potato storage in the world using straw-bale insulated walls. You’ll find them in southwestern Ontario, about an hour’s drive north from Port Huron, Mich.
Their system doesn’t rely on stacking the bales and then covering them with plaster.
Instead, the walls were built in sections or panels flat on the ground and then assembled.
The straw walls were made using a technology developed by Ian Weir, one of the owners of NatureBuilt Wall Systems Inc.
“By building in this manner, we are able to build a more consistent product, in climate- controlled conditions with much flatter wall surfaces at a more cost-competitive price,” Weir said.
“Another advantage is that because the walls can be built off-site, they can be built in advance and installed as soon as the foundation is ready, greatly speeding up construction time.”
The Koenigs see other advantages to the system they built, which cost about the same as a conventional potato storage. For one, they were able to use their own straw for the walls. While that resulted in a three- month construction process, they saved money by using their own labor.
Ten panel sections were made at a time and then assembled once the plaster — a mixture of lime and cement — had set.
“It didn’t make sense to make an ecological wall and then truck it halfway across Ontario,” Marcus Koenig said.
The storage is part of a larger building they put up in 2009. More than half of the facility — the section where the roof peaks — is used to store hay for the Koenigs’ cattle.
Normally with straw bale construction, plaster-coated bales provide the structural strength. With this building’s expansive roof, steel beams were required.
The wall panels themselves are extremely strong, however. They were made in wooden forms laid flat on the ground. The first step was to pour the lime/cement plaster mixture to a depth of about 1.5 to 2 inches. Next, the straw bales were laid on top and followed with a second layer of plaster, which was leveled by hand.
On their own, neither the bales nor plaster have much strength. Bonded together, they do.
The finished panels were put into place between the steel beams with a telehandler and secured.
Cellulose insulation — recycled paper — was blown into the ceiling and used around the steel wall beams. Koenig feels the overall insulation value of his storage is anywhere from R-40 to R-50.
The straw bale section of the building is 130-by-40 feet and divided into three parts: a large workshop and two storage sections with a combined storage capacity of about 800 tons.
Humidity and temperature levels are controlled the same as in conventional potato storage systems in North America. The Koenigs plan to add automation.
According to Neeraj Jain, another NatureBuilt owner, there are now about 1,000 straw buildings in Canada. The majority were built by stacking the bales and then coating them with plaster.
This has limited straw-bale construction primarily to small buildings, since the plastering is a labor-intensive process,
he said. With the NatureBuilt system, forming the walls lying flat allows for gravity to help create the flat wall surfaces.
The Koenigs grow certified organic potatoes. With about 60 acres in production, they’re a large organic potato producer by Canadian standards, but small when compared to conventional producers.
Most of the family’s 500 acres is used for pasturing cattle. Koenig follows the holistic principles developed by Alan Savory, founder of the Savory Institute.
After four years of pasture, potatoes are grown. In the following year, small grains under seeded to pasture are planted.
Much of the land has a high sand content. Koenig feels the system, which includes intensively grazing small sections of pasture with high numbers of cattle, has been good for the land.
“It doesn’t blow anymore,” he said. “We’ve seen a big increase in the water-holding capacity.”
--By Jeffrey Carter, Spudman corresopndent
Photos: Marcus Koenig stands inside his straw bale potato storage facility. Divided into two for bulk and bin storage, it has room for about 800 tons of potatoes. Photo by Jeff Carter.