Study Of The Spectral Characteristics In The Composting Process Of Livestock Manure

Aerobic composting is an effective way to solve the problem of organic waste pollution and realize its resource utilization.Maturity is an important index to test the quality of compost.Physical and chemical analysis and germination index are commonly used evaluation indexes of maturity,but there are some defects such as parameter instability and long period.As a fast analytical method,modern spectral analysis technology has been gradually applied to the detection of material change and maturity in composting process.In this study,the factory composting of chicken manure,pig manure and mushroom residue+chicken manure(mushroom residue,the same below)was used as the object,and the Fourier transform infrared spectrum was used Spectroscopy,FTIR,UV-vis and 3D-EEM were used to dynamically analyze the structural characteristics of different compost materials,and the spectral parameters and changing characteristics of three compost materials were discussed in combination with conventional physical and chemical analysis,so as to provide experimental support for rapid evaluation of the maturity quality of organic fertilizer.The main results are as follows:1.The temperature changes of the three materials are obvious in the whole composting process,and the duration of continuous high temperature stage(above 50℃)is more than 10 days.The moisture content of compost materials decreased generally,and decreased to slightly higher than 30%at the end of composting.The pH of the compost changed a lot,and reached a slight alkalinity at the end of composting.During the composting process,the DOC/TOC ratio of the materials also showed a significant downward trend.Chicken manure,pig manure and mushroom residue compost decreased by 51.85%,46.81%and 44.44%,respectively.The overall trend was consistent with the change of DOC concentration.2.FTIR spectrum showed that the three composts had basically the same structure in the whole composting process.After ripening,the aromatization degree and stability of compost materials were significantly improved,and polysaccharides and lipids were reduced.At the same time,with the development of composting,there are differences in the relative strength of some characteristic functional group absorption peaks.Among them,the content of phenols and carbohydrates in pig manure compost is higher than that in chicken manure compost and mushroom residue compost.3.The correlation analysis of UV parameters and DOC concentration of three compost materials shows that DOC concentration is closely related to three UV parameters of SUVA254,SUVA280 and A226-400 during the whole composting period.It shows that the integration of UV absorption spectrum of 226-400nm is significantly related to DOC content,and the change trend is consistent,which is the best absorption spectrum parameter to reflect the maturity of compost.The changes of UV spectrum parameters also showed that the aromaticity and stability of compost materials were improved at the end of composting.4.Three dimensional fluorescence spectrum analysis showed that two kinds of protein peaks and humic acid like peaks could be detected in the early stage of composting,but at the end of composting,the humic substance peak was strengthened;and the fluorescence intensity of fulvic acid like substance in mushroom residue compost was higher than that in chicken manure and pig manure compost,indicating that the content of fulvic acid like substance increased more;the two kinds of protein peaks in dom of chicken manure and mushroom residue still had certain fluorescence And the fluorescence intensity of protein like substance in chicken manure is higher than that in mushroom residue,while the fluorescence peak of tryptophan in pig manure is still existed.The results showed that after composting,the protein,fat and carbohydrate in the raw materials were decomposed,and some of them were synthesized into high molecular weight humic acid like fluorescent substances.The results are consistent with those of FTIR and UV.5.The results of three spectra and semi quantitative analysis showed that the aromaticity and stability of compost increased significantly,and the content of polysaccharides and fatty compounds decreased.It is still limited to judge the maturity of compost only by the spectral change of compost materials,so it is difficult to get a clear quantitative index.However,from 45d to the end of composting,the difference of spectral characteristics of compost materials decreased and tended to be stable,which was consistent with the change trend of compost temperature,DOC concentration and other maturity indicators.It can be used as an auxiliary judgment indicator of compost maturity.Of course,this is related to the limited time and the limited amount of data obtained in this paper.It is necessary to carry out quantitative analysis on the material structure and composition of compost and combine with the deeper mining research of other analysis methods to more comprehensively,comprehensively and accurately represent the maturity of compost.