Thermochemical behavior of agricultural and industrial sugarcane residues for bioenergy applications

Abstract

The Colombian sugarcane industry yields significant residues, categorized as agricultural and industrial. While bagasse, a widely studied industrial residue, is employed for energy recovery through combustion, agricultural residues are often left in fields. This study assesses the combustion behavior of these residues in typical collection scenarios. Additionally, it encompasses the characterization of residues from genetically modified sugarcane varieties in Colombia, potentially exhibiting distinct properties not previously documented. Non-isothermal thermogravimetrical analysis was employed to study the thermal behavior of sugarcane industrial residues (bagasse and pith) alongside agricultural residues from two different sugarcane varieties. This facilitated the determination of combustion reactivity through characteristic combustion process temperatures and technical parameters like ignition and combustion indexes. Proximate, elemental, and biochemical analyses revealed slight compositional differences. Agricultural residues demonstrated higher ash content (up to 34%) due to foreign matter adhering during harvesting, as well as soil and mud attachment during collection. Lignin content also varied, being lower for bagasse and pith, attributed to the juice extraction and milling processes that remove soluble lignin. Thermogravimetric analysis unveiled a two-stage burning process in all samples: devolatilization and char formation (~170°C), followed by char combustion (~310°C). Characteristic temperatures displayed subtle differences, with agricultural residues exhibiting lower temperatures and decomposition rates, resulting in reduced ignition and combustion indexes. This indicates heightened combustion reactivity in industrial residues, attributed to their elevated oxygen percentage, leading to more reactive functional groups and greater combustion stability compared to agricultural residues. This information is pertinent for optimizing sugarcane residues utilization in energy applications.

Hydrothermal Carbonization of Green Harvesting Residues (GHRs) from Sugar Cane: Effect of Temperature and Water/GHR Ratio on Mass and Energy Yield

“…This similarity suggests that GHR could be a viable substitute for bagasse currently used in cofiring with coal, without causing significant changes in the characteristics of the raw material. 52 Table 2 details the properties of the constituents of GHR, including buds, green leaves, and dry leaves, providing insights into their individual compositions. 54 While there are similarities in the constituents of GHR, differences are primarily noted in their ash content, which is significant from both energetic and technical perspectives.…”

“…This analysis demonstrates that the general composition of GHR is very close to that of bagasse, the industrial residue left after the extraction of juice from sugar cane, and pith, a derivative of bagasse. This similarity suggests that GHR could be a viable substitute for bagasse currently used in cofiring with coal, without causing significant changes in the characteristics of the raw material …”

“…This variability can affect the overall composition of the GHR depending on local cultivation and harvesting characteristics. These variations are influenced by factors such as the method of collection (mechanical or manual), the type of machinery used (whether it includes bud removal or not), the interval between sugar cane harvest and residue collection, and even the weather conditions during collection . Understanding these differences is vital for tailoring the HTC process to optimize the yield and quality of hydrochar, ensuring efficient and sustainable biomass utilization.…”

“…This method employs elemental analysis as the basis for calculating the content of lignin, cellulose, and hemicellulose. The polymer composition of GHR and hydrochars is then calculated as a linear combination of these theoretical mixtures, providing a detailed approximation of their molecular structure …”

“…Research on the thermal utilization of residues from genetically modified sugar cane is notably limited, with even fewer studies focusing on enhancing the energy characteristics of these residues through hydrothermal carbonization. − The ability to generalize findings is further constrained due to the genetic modifications tailored to adapt sugar cane to specific soil conditions and production objectives . In Colombia, sugar cane has undergone extensive genetic alterations, impacting the composition, structure, leaves, and stems of the plant .…”