Characterization And Identification Of Maturity Of Pig Manure Composting

Composting is a cheap, efficient and sustainable way for solid wastes utilization. Assessment of compost maturity is of utmost importance for achieving high quality compost to guarantee its marketability. However, traditional methods to assess compost maturity were time-consuming and high-costing. Therefore, excitation-emission matrix combined with fluorescence regional integration (EEM-FRI) method is developed as an easy-operated and fast method to assess compost maturity in this study.Composts with different ratios of pig manure, rice husk and straw were carried out in this study. Parameters of chemical, biological and spectrum of composts were characterized to reflect variations of organic matters during composting process, and the feasibility of EEM-FRI method to assess compost maturity were tested. The results were listed as follows.The highest quality composts came from the treatment with the highest carbon to nitrogen ratio (17.7) and the lowest water soluble carbon to water soluble nitrogen ratio (1.4), while the treatment with the lowest carbon to nitrogen ratio (13.9) and the highest water soluble carbon to water soluble nitrogen ratio (2.8) did not mature till the end of composting process.Multiple fluorescence labeling combined with confocal laser scanning microscopy (CLSM) and denaturing gradient gel electrophoresis (DGGE) were adopted to study the composition, architecture, and function of biofilms constituents at the microscale and change of bacteria, respectively. Bacteria with low G+C content played an important role in mesophilic and thermophilic phases. Most proteins were found in pig manure, whileα-polysaccharides existed in straw. Dead cells presented in the inner of straw, while cellulose and total cells existed in both pig manure and straw.Microorganisms in thermophilic phase mainly degraded cellulose andα-polysaccharides matters. Straw and pig manure were not completely degraded in thermophilic phase. Compared with thermophilic phase, the intensity of proteins,α-polysaccharides, cellulose and dead cells of cooling phase reduced while the number of microorganisms increased. The degree of aromaticity increased with composting process. More than ninety percent of carbon in water-soluble compounds was aliphatic carbon, and most of it was alkyl carbon and carbon in carbohydrates. Majority of aromatic carbon was olefinic carbon.Phenolic, alcoholic, amino acid, aliphilatic methylene, aromatic and olefinic, carboxyl, silicate, easy-degradable compounds and lignin, cellulose, hemi-cellulose were found in the whole composting process.Proteins were degraded in mesophilic and thermophilic phase, while cellulose and lignin were degraded in thermophilic and cooling phase.With the composting process, protein-like substances decreased while the concentration of fulvic-like and humic-like matters increased. EEM-FRI method was suitable to assess the maturity of pig manure compost.