Varied Pyrolysis Behaviors of Typical Forestry, Kitchen, and Manure Wastes in CO₂

CO2 is a major product from pyrolysis of biomass, and it is also used for activation of biomass. The capability of CO2 for creating pores highly depends on the origin of feedstock. Herein, a potentially distinct response of varied feedstocks toward the CO2 atmosphere was investigated by pyrolysis of rice, spinach, pig manure, spirulina, or poplar sawdust in CO2 at 800 °C. The high ash content in pig manure and spinach promoted cracking/gasification, producing more gases while less bio-oil/biochar than counterparts. This also resulted in a low degree of aromatization as the O-containing species and aliphatic structures like −C– 6rch structures formed densified biochar of smooth surface but chemically inert to CO2 for generating pores. Aromatization of organics in spirulina did not proceed to a degree as high as that in rice or sawdust, retaining more oxygen. However, pore blocking from molten intermediates diminished the pores (104.4 m2 g–1). Sawdust-char showed the most developed porous structures (472.1 m2 g–1) with mainly micropores. Degradation of cellulose/hemicellulose and lignin together in sawdust created defective structure intermediates bearing phenolic −OH and carbonyls that were reactive with CO2 to generate more pores (472.1 m2 g–1).