Physical and Compression Properties of Pellets Manufactured with the Biomass of Five Woody Tropical Species of Costa Rica Torrefied at Different Temperatures and Times

Abstract

The purpose of the biomass torrefaction and pelletizing processes is to increase its energy properties, be environmentally friendly, decrease shipping costs, and make handling easier. The objective of the present work is to evaluate the density, internal density variation by X-ray densitometry, moisture content, water absorption, and compression force of torrefied biomass pellets of five wood species (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea) under three torrefaction temperature conditions (light, middle, and severe) and three torrefaction times (8, 10, and 12 min). The results showed that the bulk density of the pellets was 0.90–1.30 g/cm3. The density variation of the pellets was higher with torrefaction at 250 °C. The moisture content decreased with increasing torrefaction temperature from 3% to 1%. Water absorption was lower in the pellets torrefied at 250 °C. The compression force was lower in the pellets torrefied at 250 °C with approximate loads of 700 N. Based on the above results, it was concluded that pellets made with biomass torrefied at 200 °C have better energy properties and evaluated properties. According to these results, pellets fabricated with the torrefied biomass of tropical species can be used in stove, gas, and hydrogen production because the pellet presents adequate characteristics.