With the price of imported vegetables skyrocketing, consumers are seeking affordable alternatives. In the summer and early fall, our own local produce competes, in price and quality with Mexican and southern USA crops, but by mid-October, only root crops remain competitive.

Root crops, however, are not suited to greenhouse growing, as they are not cost effective. That leaves tomatoes, short-season crops, some peas and other legumes and leafy vegetables grown locally in greenhouses to help ease the impact of shipping from southern regions. By November, those crops, too.

The major costs for greenhouse operations used to be heating and lighting. Today, with inexpensive LED lighting, only heat remains the major barrier to greenhouse operation.

Historically, off-season greenhouse production costed four times what it would cost to field-grow crops in the south. Some enthusiasts in Canada’s north (northern Manitoba and the northwest territories) found that they could cut costs by growing in abandoned mines, where temperatures remained relatively constant. Others, in urban areas, experimented with empty warehouses, but heating costs and retrofitting remained prohibitively expensive.

In examining these lessons, many of which were failures, a window of opportunity opened for rural greenhouse initiatives.

There are a number of factors at play that provide an advantage for rural greenhouses.

The movement away from synthetic chemicals means that an organic approach, relying on animal fertilizers, favours the country over the city.

Shipping costs from a hundred kilometres away is much less costly than fuel costs to ship from Texas or California.

Manitoba’s hydro resources means that cheap electricity for lighting is even cheaper, with LED lighting.

Our abundant supply of water is an advantage over California’s system of canals and waterways for irrigation.

Our ability to develop networks among easily reached communities, producers, grocers and local buyers means that we can establish and maintain a symbiotic network that acts as a barrier to imported goods.

Significantly, our ability to design cost-effective structures for greenhouses, using earthen bale designs, or bermed buildings significantly reduces capital costs.

But, most importantly for economical ongoing operating costs, we are able to tap into extremely low-cost heating resources. This means that we now can compete on a dollar-for-dollar basis with many of the imported vegetables coming from the southwest.

Of course, many citrus or delicate fruit crops remain unviable for production in the north, as do space-demanding crops like corn, long-season root crops and low-yield crops. But all leafy vegetables, tomatoes, some vegetable vines such as cucumbers, Asian crops like choy, and even most legumes can be grown as cheaply as southern crops whose prices spike in winter.

Those heating costs also provide revenue streams for farmers where none existed before.

Biomass (all green sources of mass)

Wood chips, old bales of hay and straw, remnants from forestry and even barnyard waste can be used as a biomass source for heating greenhouses. Abandoned buildings made of wood, deadfall and other ignored sources of lignin make viable heating materials, without contributing significantly to environmental degradation.

Hemp stalks, pressed into logs or nuggets, offers a high-fuel source. There even is residual value in tailings from biodiesel and ethanol production, potato tailings and waste, and so on. These may be burned, used as a gasifier source or converted into biofuels and the waste then used as heat, as well as the biofuels.

Manure, once it has been processed into biogas, still has usable and burnable mass for the furnaces that can heat a greenhouse.

Passive (and Active) Solar

The concept of using earth and bale construction as a backdrop (and back wall) for a greenhouse has two origins. First, it is an economical construction method, used in housing designs of the 1980s, known as “spaceship” housing. Second, it involves using the bales to store solar heat collected either actively or passively. Combined with a “stucco” type finish, it also provides a solid, permanent wall. By strategically applying a dark colour coating to the portions of that wall where the sun strikes in autumn and winter, solar heat is gathered more effectively.

The same concept works by using packed earth, or berming, to build this rear wall. Often, pipes are interwoven in the mass to distribute and recover the stored heat, which costs nothing to collect. On more northern latitudes, this rear, or north wall, may extend to the northwestern and northeastern sides, creating a more energy efficient building.

Then, by using thermal blankets inside or outside on the glazed roof, more energy is trapped in cold seasons. In the summer, the earthen, bale, or earthen bale walls give up cooler air to moderate the temperature inside the structure.

Biodiesel

Small scale biodiesel operations are missed opportunities, so far, in rural Canada. Estimates place lost oilseeds crops due to sprouting, heating or other degradation at 1 to 3 percent of total crop production. These waste crops generally are abandoned, deemed unfit for human consumption and undesirable for animal consumption. Yet, they produce biodiesel of as good quality as food-grade canola, mustard and soybean. Other sources of feedstock can include animal renderings (including poultry waste, industrial oil waste, and restaurant oil recovery. That biodiesel can fuel numerous greenhouses, and the production equipment purchased for as little as $12-15,000.

Biogas

Another missed opportunity, biogas can be readily produced from manure, whether it is chicken, cattle or hogs. When a greenhouse is collocated on a livestock operation, that biogas can be produced in a few simple steps, with no storage or transportation costs. And the waste from the biogas production can be used in other greenhouse operations. Infrastructure and equipment costs are nominal.

Geothermal

Geothermal heating is not new. In fact, it is merely passive solar heat collection: using the heat stored in the ground. While well-to-well geothermal is regulated by Water Stewardship, horizontal and vertical ground loop geothermal is not. With the abundant space on most farms, a horizontal loop geothermal system is relatively inexpensive to install and maintain, and its only cost is the cost of operating the heat pumps and in-building fans.

Gasifier

Gasification involves heating a biomass (e.g. bales of straw or wood debris) from below and burning the off-gases produced by this heating It is environmentally friendly, efficient and inexpensive. It also is a great way to use straw bales that have been standing for years when there is no market for them.

Storage of Heat

Heat storage requires developing the mass that holds the heat. For instance, a heavy salt water brine, in storage tanks, holds heat longer than water alone. A tank buried in insulative material, such as mulch, may hold heat for weeks. Simple heat exchangers can recover heat from what appears to be cold air or water. Storing heat for weeks extends the growing season in a greenhouse inexpensively, before the need for more intensive heating emerges as the autumn progresses.

The ability to store heat is demonstrated by new building regulations that require a basement or foundation to have rigid insulation extending four feet beyond the footing, to keep frost from penetrating below the footing and causing shifting. That same insulation can hold the heat in a ground-based reservoir at depths just below the frost line.

Insulation Ideas

Creative insulation ideas include curtain walls, reflective surfaces that direct sunlight toward dark, dense masses such as an inner concrete wall, earth and straw shored up against the east and west walls of a greenhouse in spring and autumn, dead air spaces between layers of light-penetrating fabric, and so on.

Co-located buildings and heat recovery

An on-farm  manufacturing facility, such as are found on many Hutterite colonies, a barn heated for livestock, or other heated buildings may share heating and cooling resources.

One seniors facility, planned for a rural community, was designed to share geothermal with its neighbouring curling rink, with one needing heat when the other needed cooling, and so on. This meant that one building could be heated with the waste air from cooling the curling rink, in winter.

Another location pumped the excess heat in summer from his hog operation into underground insulted heat sinks, where the heat was used by his machine shop in the autumn.

These creative ideas for heat generation and storage offer cheap ways to operate local greenhouses, making them much more viable than standalone operations.