Biochar catalysts from animal manure: Production and application

Biochar is a sustainable functional material rich in carbon, derived from renewable resources such as biowaste (e.g., animal manure). It has unique chemical structure, large surface area and porosity, and tailored surface functional groups via proper activation and/or functionalization, thereby having high potential as heterogeneous catalytic materials applied to different chemical processes. Therefore, using animal manure-derived biochar as catalytic materials could be key to sustainable agriculture and chemical industries. Recent recognition of animal manure-derived biochars as versatile media of catalytic applications has encouraged rudimentary studies on their catalytic capabilities; however, the use of animal manure-derived biochar as catalytic materials has not been systematically reviewed yet. This review gives an overview of recent achievements in producing biochar from animal manure and subsequent modification methods. The catalytic properties of the biochar with respect to its production/modification recipes are also discussed. Furthermore, the catalytic performances of animal manure-derived biochars for different catalytic applications, such as transesterification, hydrogen production, hydrolysis, C–C coupling reactions, and electrodes for oxygen reduction reaction, supercapacitor, and lithium-ion battery, are evaluated.