Exotic Fruit Residue Hydrochars: Sustainable Materials for Circular Engineering Applications in Environmental Remediation, Electronics and Agriculture

The excessive use of non-renewable materials and products derived from fossil fuels has intensified the need to find alternative and sustainable routes to replace them with bioresources in recent decades. These bioresources are by-products or residues from second-generation biorefinery processes. Hydrochar has emerged as a promising solution due to its properties and applications. This carbonaceous material, generated from the hydrothermal carbonization (HTC) process, retains exceptional properties such as high carbon content, stability, capacity to absorb and eliminate contaminants, and high surface area. These properties make it a suitable candidate for various environmental and agricultural applications, contributing to the main objectives of circular and green engineering.

In Ecuador, the primary feedstock for hydrochar comes from diverse biomass waste materials, including sugarcane bagasse, oil palm fiber, peel and waste, as well as banana, plantain, rice, and fruit waste. This research focuses on potential hydrochars derived from various exotic fruit residues such as mango endocarps, moringa husks, palm residues, mangosteen, and blackberry bushes. The raw material undergoes preliminary analysis to define operating conditions for the hydrothermal process to produce hydrochar and HTC liquor.

The final product is subjected to different chemical analyses, including morphology characterization using BET and SEM to determine porosity and assess the hydrochar's capability to adsorb various molecular species. Additionally, the samples are analyzed using Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction to identify functional groups, structural changes, and crystalline compounds. Finally, a semiconductor device parameter analyzer measures voltage retention capacity at different frequencies.

Initial results indicate that the generated materials are suitable for insulation, dielectric applications, and potential agricultural purposes. Furthermore, the study highlights the influence of fruit type, hydrothermal carbonization conditions, and post-treatment processes on the electrical characteristics of hydrochars.

In conclusion, hydrochars from exotic agroindustrial residues show potential as an innovative and sustainable alternative for waste management practices, promoting circular engineering and bio-economy. This research contributes to the development of eco-friendly materials with diverse applications, addressing the growing need for sustainable solutions in various industries.