Abstract
Agroforestry industries, such as sugar-alcohol, food, and logging, produce large quantities of waste, used to generate energy from direct burning. The application of other processes, such as torrefaction and briquetting, can increase the profits from the use of agro-industrial waste for energy generation. Briquetting is an alternative for using these wastes, allowing the compaction of the biomass, generating a biofuel with high energy density, and which is more homogeneous and easier to store and transport. The objective of this study was to evaluate the physical and chemical properties of four biomass types (wastes from sawed eucalypt and pine wood, coffee pruning wastes, and sugarcane bagasse) torrefied at 300 °C and compacted (briquetting) at pressures of 6.21, 8.27, and 10.34 MPa. The torrefaction increased the fixed carbon content, ash, and calorific value, and reduced the volatile material content and hygroscopic equilibrium moisture of the biomasses. The volatile material content was lower and the fixed carbon higher in the coffee pruning waste, the ash content higher in the sugarcane bagasse, and the calorific value higher in the pine and eucalypt wood. The briquetting and the torrefaction processes increased the biomass bulk density, and the useful calorific value, respectively, and consequently the energy density of the briquettes produced with torrefied raw material under high pressure. The mechanical properties of the briquettes produced with all materials increased with the compaction pressure. Torrefaction and briquetting increased the energy potential of the biomasses evaluated to produce energy from clean technology.
Highlights
Biomass from urban green wastes and agroforestry industries, such as sugar and ethanol, grass, food, and timber, are sources of renewable and sustainable energy [1,2,3]
The calorific value of the wastes with different heat treatments was calculated, and overall, the torrefaction process decreased the content of volatile materials in the wastes (Table 1)
Torrefaction decreased the volatile materials of the bagasse sugarcane, coffee pruning, and pinus and eucalyptus sawdust wastes by 20.50, 16.06, 13.52, and 12.31%, respectively
Summary
Biomass from urban green wastes and agroforestry industries, such as sugar and ethanol, grass, food, and timber, are sources of renewable and sustainable energy [1,2,3]. The lignocellulosic wastes are used mainly for direct combustion, for heating and power generation in boilers [6]. The briquetting compacts the lignocellulosic biomass wastes reducing their irregular granulometry to geometric solids with a high density and burning potential [11,12,13]. The briquette can be used to generate heat or steam, reducing the use of natural gas, charcoal and coal, firewood, or other fuels in industrial processes [13,14]
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