If it’s not obvious from the picture, then a scratch-and-sniff option for the blog would help you identify the stuff that’s loaded on our trailer. That’s right, horse manure. The folks at Capital Area Theraputic Riding Association (CATRA) have a limitless supply of it, and are happy to load it for me. Back at the farm, the manure is used to make hot beds, which heat our germination greenhouse.
Here’s how it works. We used some old twin-wall polycarbonate (though cinder blocks or plywood will work, too) to build boxes under two of the tables in the greenhouse, about 3 feet high, 3 feet wide, and 8 feet long. The horse manure goes in the boxes, gets watered well, and topped with a layer of finished compost, straw, or leaves. Surrounded by friends, with room to dance and lots to drink, the microorganisms in the horse manure start to party, generating a lot of heat in the process. That heat radiates slowly from the hotbeds, warming the germination greenhouse enough to keep our tender plants from freezing. When the microorganisms have run out of oxygen, the party’s over. After the hotbed has cooled, we can use the composted manure as fertilizer and we go back out to CATRA for another load of fresh manure.
It’s not a perfect system of heating a greenhouse, but it’s worked for us (with the help of the strong backs of Messiah student volunteers!). Most growers use gas heaters, which can be easily adjusted and require less physical labor. Our system is somewhat dependent on the weather–we are getting a late start in the greenhouse because the trailer was snowed in–and requires additional heat when we have extended cold spells (temps in the 20s or lower). We still use some fossil fuels to transport the manure. On the plus side, there is some evidence that plant growth is enhanced by the enriched CO2 levels. In case you’re curious, the smell is almost minimal, due to the filter of straw we put on top. It’s nice to have relatively weed-free compost to use when it’s done, and it’s kind of fun to find alternative uses for waste. Taking the temperature of the hotbed is one of the highlights of my day. I’m not really sure what that says about me. Maybe since I’m not the sort to be the life of the party, it’s fun to know that the party lives!