What we did:
This week we pressed the material that had been sitting in the bucket to rot for the past week. The bucket had a solid layer of dried material and mold which had formed on the top. Upon puncturing this layer, a repulsive odor reminiscent of sewage and sauerkraut. Based on the recommendations of our team biologist Kelly, we all gloved up for the remainder of the day’s work to avoid contact with the mixture.
Using the newly finished die, we pressed a briquette made from rotting fruits and vegetables. Once the briquette was removed from the die, it quickly lost its shape and fell apart. The rest of the briquettes produced that day were made from either only rotted bucket material or rotted material with freshly gathered paper products added. While the new die provided the ability to fabricate larger briquettes, there were issues of material being blown out of the bottom due to the high pressure. This could have created briquettes which had sections with less compression and cohesion when removed from the die. We also added blast plates to the press, which we learned was necessary after nearly being blasted with briquette juice several times.
The other portion of the time was spent testing the burning quality of the briquettes that were produced in the previous lab. We worked with the rocket stove team and added our briquettes to their fire. The briquettes were removed periodically to investigate how they were burning. After 25 minutes, we observed that they were behaving similarly to charcoal briquettes in that they were not burning with a flame and formed an ashy coal. They also burned at a temperature noticeably lower than charcoal, although actual values are not known.
What we learned:
Although letting material rot in the bucket created a finer pulp, the addition of odor and possibly hazardous mold or microbes made the fabrication of briquettes an extremely unpleasant experience. Compared to the fresher pulps of past labs, the rotted pulp did not have any better shape retention. We have not burned the rotted material briquettes yet, but as of now, we have decided to not pursue rotted material further and will focus on how to effectively use the briquettes and what materials work best.
What’s next (2/18/14):
We will be shifting our work towards developing quantifiable metrics for recording our results. These will include burn temperature and time, among others. We will also be treating the briquettes like regular bbq briquettes in terms of burning methods instead of placing them in a rocket stove.