Home Heating with Horse Manure
Various means were tried to determine the simplest and most expedient method for forming and drying the waste biomass in preparation for burning. Three ways were tested:
A. Compression – waste was taken from manure pile, mixed with water sufficient for binding and compacted in a wooden lever press. It was presumed this would be the default method of forming but the process is sensitive to the moisture content of the mix and it is inherently slow, yielding only a single brick per cycle (a gang press could be employed to increase this), and as well is unnecessarily messy. A limited number of bricks were made this way and when dried were also prone to a sort of de-lamination making them difficult to handle.
B. Frames – In the same fashion as adobe brick, the moistened and mixed biomass was tamped into a frame having three compartments, each creating a nominal 6” x 9” x 4” block. The frame being pulled from the blocks left them in place on whatever surface was chosen for drying (a palette was used for this). This process is simple, rapid, and each cycle results in as many blocks as the frame has compartments. Dry time in clear, ~75 degree F conditions was approximately three days. Many of these bricks were made and burned at varying points to refine the process. This became the preferred method of production.
C. Cutting – Skipping over any kind of mixing altogether, we instead cut directly into the lower level of the manure pile where the waste had been naturally compressed and composted. From this layer blocks could easily be cut with a spade in a manner identical to peat. It was then sun-dried. This method is fast but because of the high moisture content the dry time is very long (>5 days). Due to weather and incomplete drying these bricks were unable to be tested.
It was found that any of these can also be wrapped in a layer of newspaper while still moist, and this helps contain any loose matter once they’ve dried and additionally gives a ready-to-light surface.
Several test burns were conducted with both the dried blocks and cured wood as a control. The fuel was loaded in 8 lb. batches in a cold stove, lit and the temperature monitored for an hour and a half over ten minute intervals using an infrared thermometer. As anticipated, the peak temperature of the biomass is less than that of wood, it reaches it more rapidly, but surprisingly burns evenly for just as long. The odor is that of burning grass, comparable to a controlled prairie burn.
Results thus far have been positive. Despite knowing that something works, doing it and seeing that it does for yourself is both satisfying and a bit surprising! The combustibility of the biomass bricks exceeded expectations and it is simple to light. Needless to say our experiences have enforced the idea that preparation can be time-consuming, though no more so than the various steps required for wood. We plan to estimate comparative times for this since we will be using both fuel sources this year.
One major issue is the arrangement of drying the bricks. As they need to be sun-baked, this leaves them exposed to the elements. In the often sudden turns of weather present while one may be at a day job, this means an entire batch can be washed away by rain, or at least soaked and productivity lost. This occurred several times. Likewise, a dry, covered area is required for storage.
A couple dozen bricks were set aside during the winter to see if they would dry through dessication enough to be used. They did not, despite the extended cold weather.
I’ve also not built a website in about a decade, so there has been a bit of re-learning curve there and it is overall more time consuming than making the fuel!
WORK PLAN FOR 2014
This year will be spent amassing as many formed and dried bricks as possible in preparation for the next heating season. We plan to construct a solar dryer to accelerate the curing process and have already collected materials for this. In keeping with the low-level of technology of this project it is something easily manufactured from scrap with basic tools. It should solve two issues – decreasing dry time, and reducing the threat held by rain as mentioned above.
A website has been started (http://Horse2Hearth.Weebly.com) to compile and reference the collected information. I have also inquired with The Backwoodsman magazine (http://www.backwoodsmanmag.com/) about writing an article and have their approval. The Backwoodsman has a circulation of some 200,000 so this would be significant distribution to a community which embraces the idea of making something from nothing. Previous recent articles have discussed the making of paper-based briquettes for burning.