Lignocellulosic wastes in Costa Rica are often not optimally managed. When disposed in a landfill, such wastes shorten its useful lifetime, imply transportation and management costs, and emit greenhouse gases without first having rendered their energy or other products they can yield. One option of valorization for lignocellulosic wastes is carbonization. A low cost, simple-operating, portable carbonizer was designed and built at the Instituto Tecnológico de Costa Rica. It can be replicated at any metal-mechanics workshop, mostly constructed with widely available re-used materials. It is able to process up to 50 kg feedstock batches, and it minimizes smoke emissions as compared to local traditional methods, by burning the pyrolytic gases to maintain the temperature required in the process. This model is very much within reach for small farmers, but may as well serve for SMEs interested in valorizing their wastes. To assess its performance, two locally common wastes were carbonized in it, namely construction waste-wood and waste-wood from a palette factory consisting exclusively of Gmelina arborea wood. Variables as moisture content, heat content, densities, color, odor, mechanic resistance, sonority, volatiles content, ash content, germination inhibition, and earthworm avoidance, were assessed in the feedstock, in the charcoal, or in both materials. The tests were selected in view of the two main uses foreseen for the charcoal: to obtain clean heat, and as a soil amendment. The palette factory waste showed excellent yields between 30 % and 33 % w/w of a sonorous, lustrous and very slightly odorous charcoal, all traits of good quality. Its moisture after stabilizing for at least 3 weeks in air was 5 % to 8 %, apparent density was 140 kg/m3 to 170 kg/m3 density was 210 kg/m3 to 310 kg/m3 heat content varied from 29.5 kJ/g to 30.7 kJ/g, and volatiles from 10 % to 33 %. Results for other wastes will be shown at the conference. The time per batch was 5:25 hours to 7:10 hours. Firewood needed to initiate the process was 33 % to 38 % of the total per batch, and can be sensibly reduced by combining 2 carbonizer reactors. The performance of the carbonizer is, so far, outstanding, and improvements are foreseen.

Performance of a low-cost portable carbonizer for the valorization of lignocellulosic wastes

249th National Meeting (2015)

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