In general, we are trying to make the best fuel brick for the purpose of burning in a wood stove or fire place for heat or for cooking, documenting all work and publishing the results so that other interested farmers and homeowners with a beautiful abundance of livestock manure can make their own press.
We began with several trial runs. Mixtures of different amounts of dry manure with bedding, fresh manure and water to make the manure briquette. The measure of excellence is that the briquette must hold together so that it can be handled and set to dry. If too moist they will not survive the pressing, if too dry, or not well mixed, containing pockets of dry and wet, they will crumble during handling as they exit the press.
Trial runs and results (note that measurements were not exact or perfect, but approximate.)
6 shovels of dry manure/bedding
6 shovels fresh manure
1 gallon water
Mix together in a wide mouth feed bucket and stir until you have a well blended mix.
This trial made us aware of the importance of water in the mix. The water should be enough to hold the briquette together but not more. The drying happens after the briquette is pressed and set to dry. That is an important point because too little water will cause the brick to crack and break.
Result: these bricks held together fairly well although they appeared too loosely knit for the drying period. Also we did not use full compression.
Two briquettes were made.
4 shovels of dry manure/bedding
1.5 shovels of fresh manure were wetted down with with additional water prior to adding to dry.
1 gallon of water.
The mixture was hand formed before dropping into the hopper. Then we used almost 100% compression.
This pressing was wetter than the first one and we were made aware of issues with the manufacturing of the press. Where the top of the expulsion door of the press meets the mold box, there is a space that should have been filled in. Because we moved we could not ask Steve, our fabricator to weld a piece to tighten up the hole, so we began to improvise using wood and plastic objects to block the space so the manure mix would stay in the box and not squish out. We also started covering it with a tarp as we pressed because a manure shower was not so welcome!
Same mix as in #2.
Wood shims were put into the hole on the press. Less compression. The briquette did not hold together well. Too much moisture. We lost much of it through the intentional spaces of the press designed to let out moisture.
3 shovels dry manure/bedding
2 shovels fresh manure
1/2 gallon water
We made one large briquette with this trial. It did not hold together well due to size and lack of water. We realized during this trial it is better to make a briquette 4” – 5” thick rather than 7” – 8” thick. Easier to form and handle. The down side of this is that the briquette will not have as much burn time.
Sifted dry manure/bedding and mixed with water: 1 to 1 ratio. Mixed well . Add to fresh manure in this trial was a few days older than previous trials.
I put on my gloves and mushed it all together as if making bread. It was important to make sure all moisture touches all dry ingredients so no cracking and breaking.
A mechanical mixer would be great for this process to expedite mixing. There are mixers available. They are typically used in animal feed production. I found some available online, but only sold in other countries.
Mixing thoroughly all ingredients is important to getting a good consistent briquette. Moisture must touch all ingredients leaving no dry contents.
Mashing the ingredients of the briquettes is also important, our best results were when the contents of ingredients were thoroughly mashed. When doing large volumes of material it is advisable to use a mixer.
We ran one trial with half a batch and it was too moist. So we added more dry and fresh manure. The second batch and got a really nice small briquette.
Because in all these trials we were hesitant to use full compression because of the fault in the expulsion door area allowing too much mixture to escape, we tried putting the contents of the mixture in a plastic bag to contain it and prevent lose of moisture. It formed better briquettes that held together better.
The plastic bag has limitations in that air pockets form and pop, defeating the purpose of containment.
We tried fabric screening with better results.
After several attempts to wrap each briquette in a fabric screening, the best result we achieved was to place the screen across the end of the press to trap the solids inside the pressing chamber and also allow the excess liquid out of the press.
Fabric screen holds in solids, removes liquids effectively, compensating for the spaces in the press that would be improved by anyone building the press. Fabric screen and closed door with a piece of composite shingle to keep solids in liquids out. The results were considerably more consistent and the quality of the briquette was denser and more uniform.
Drying the briquettes can take many forms. Ideally you want good air flow, sunshine for drying and no rain interfering with the process. We set up the wet briquettes on a screen so that they had air flow from beneath as well as on the sides and top. The weather was very dry during the drying periods at first. This was excellent and produced very dry results. We had difficulty when the weather changed. We covered the bricks with a tarp to keep them out of the rain and figured that would be sufficient to keep them dry until sunnier days arrived, but unforeseen issues arose when we checked the briquettes after a few weeks during the rainy period. They did not get wet, but because we placed the rack to close to the ground, approximately 1 ft. above the ground, we had an infestation of red ants, grubs, centipedes, as well as mushroom spores and other microbial growth. That was a shock! We savaged the best samples to send off for testing. Moral of the story is: put your briquettes up high to dry, preferably dry them in a greenhouse or hoop house if you can away from moisture, and turn the often.