Thermochemical Conversion of Apple Pomace into Engineered Biochar: Production, Properties, and Technological Applications

Abstract

The engineering of carbonaceous materials from agri-food residues has become a promising strategy to advance sustainable materials, energy technologies, and circular waste management. Apple pomace, a high-volume byproduct of the juice industry, is an attractive feedstock for biochar because of its high carbohydrate content and abundance of phenolic compounds. In this way, this perspective provides a comprehensive engineering analysis of apple pomace-derived biochar, focusing on how feedstock characteristics, thermochemical conversion pathways, and reactor configurations govern the resulting structural, physicochemical, and functional properties. We synthesize recent advances in adsorption, catalysis, soil conditioning, energy storage, and electrochemical applications, emphasizing structure–property–performance relationships relevant to material design. Comparative analysis reveals that pyrolysis temperature is the primary driver of surface area, aromaticity, and functional group distribution, with high-temperature biochar favoring electrochemical and catalytic applications, while low-to-intermediate temperatures enhance adsorption and soil-related functionalities. Apple pomace–derived biochar exhibits competitive performance relative to other agri-food byproducts, particularly in adsorption capacity and electrochemical activity, due to its oxygen-rich surface chemistry and feedstock-specific mineral composition. Key limitations, including variable feedstock quality, limited recyclability assessments, incomplete technoeconomic evaluations, and the lack of standardized characterization protocols, are identified as constraints to scale-up and industrial deployment. Addressing these gaps is essential to position apple pomace biochar as an engineered material with the potential for integration into sustainable processes, low-carbon technologies, and circular bioeconomy frameworks.