We’re building a walipini greenhouse with earth bags this fall (you can join us for free workshops). Walipini are in-ground greenhouses. They use the thermal mass of the earth to keep the temperatures regulated in the summer and winter. We’re using earth bags (woven plastic bags filled with clay, sand, and binder) for the walls. This week we’ve started preparing the site and gathering materials.
The greenhouse will be located behind our garage in what is now the temporary chicken run. We’ve had to clear raspberry canes, black locust suckers, and other new growth. Next, the 13-×-18-ft footprint was marked out with corner stakes. The actual greenhouse will be smaller: 6 in of drainage scoria surround the walls, which are 16 in wide, thus the interior dimensions are 9.5 × 12.5 ft at ground level. Below is a photo of the site as well as a quick mock-up of the finished product.
One could buy bags new, but woven plastic bags are ubiquitous in the grain industry: 55-lb (25-kg) bags are the standard and work perfectly for earth bags. Luckily Wisconsin has a strong beer industry and local breweries have agreed to donate used bags to our project. Today I picked up 175 bags from Wisconsin Brewing Company and Hop Haus Brewing Company.
I was surprised by the amount of bags generated in a week. I did not have a tarp to hold them all in the truck bed, so I had to cram 175 bags into the cab. Once home, the bags were cleaned out, stacked, and organized into bundles of 25. These will be hung up from the rafters to keep the mice away from the remaining bits of grain in these sacks.
My favorite bag was that of Rahr Malting Company (from my home state of Minnesota), which had a dinosaur crossed out and “Fossil-Free Malting — Made with Renewable Energy” emblazoned on the bag. I think it is fitting to use these bags to build an environmentally friendly structural wall.