Abstract:
To reveal the effects of different organic components of kitchen waste on the properties of their charring pyrolysis products, this study employed charring pyrolysis technology to partially carbonize the organic components of kitchen waste under moderate to low temperatures and oxygen-limited conditions, producing solid residues with micro-carbonized structures or carbon-coated layers. Compared with conventional pyrolysis (which involves complete carbonization) and hydrothermal carbonization (which requires high-pressure liquid-phase reactions), this technology offers significant advantages including mild reaction conditions and high nutrient retention rates. Five types of kitchen-waste raw materials, namely, unsorted, protein, starch, cellulose, and lignin categories, were selected and subjected to charring pyrolysis under the optimal conditions determined in the preliminary experiments and in an oxygen-deficient environment. The differences in the yields, physicochemical properties, and nutrient contents of the charring pyrolysis products of different components and their effects on the growth of cucumber seedlings were systematically analyzed. The results showed that there were significant differences in the properties of the charring pyrolysis products of different components of kitchen waste. The yield of starch products was the highest (83.89%); the electrical conductivity (290.1 μS/cm), total nitrogen, total potassium, and available nutrient contents of protein products were significantly higher than those of other component products; the cation exchange capacity of cellulose products was the highest (259.4 cmol/kg), and the total phosphorus content was high (38.01 g/kg); the moisture content of lignin products was the highest (3.3%). The total organic carbon content of unsorted products was the highest (632.5 g/kg), and the carbon-nitrogen ratio was moderate. All products were weakly alkaline (pH 7.50-8.36). The cucumber seed germination and seedling growth experiments showed that the unsorted products had the most pronounced promoting effect on plant height, leaf area, chlorophyll content, and biomass accumulation; the protein products inhibited seed germination due to excessive salt content. The study indicates that source classification can tailor the properties of charring pyrolysis products of kitchen waste, providing a basis for producing specialized organic fertilizers or soil conditioners.