Dusan Vergara Alemán turns corncob into biochar and earns the laureate distinction
His undergraduate thesis in Agro-industrial Engineering shows that pressing corncob into pellets and carbonising them slowly yields a biochar whose properties can be tuned to its end use. The examining committee granted it the laureate distinction.
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After harvest, corncob is usually left in the field or burned. It is light, bulky and hard to transport, the opposite of what a good fuel needs. The thesis on pelletised biochar production from corncob by slow pyrolysis, supervised by Eduardo Arroyo Dagobeth and co-supervised by Daniel Otero Meza, tackled the problem in two steps, first pressing the residue into pellets and then carbonising them slowly.
Pelletising markedly increased the density of the material, its strength and the energy packed into each cubic metre. Slow pyrolysis at 400 °C and 500 °C then produced biochars with yields of 25.8% to 36.0% and higher heating values of 23.7 MJ/kg to 25.7 MJ/kg, comparable to several mineral coals. At 500 °C the material lost more oxygen and gained fixed carbon, a sign of a more stable solid.
The most striking finding concerns the reactor atmosphere. When pyrolysis runs in a self-purging atmosphere, without the nitrogen laboratories usually require, the biochar is denser and more thermally stable, an advantage for use as a solid fuel. With nitrogen, by contrast, it develops more pores and surface area, useful for environmental applications such as adsorption. Tuning temperature and atmosphere therefore makes it possible to design the material for its end use.
Self-purging pyrolysis is on the agenda of INGEBIR's thermodynamics and kinetics line, and Dusan Vergara Alemán remains in the group as an early-career researcher.