Evaluation of lignocelullose compost stability and maturity using spectroscopic (FTIR) and thermal (TGA/TDA) analysis

The follow-up of different physico-chemical parameters (TOC, TKN, C/N) over 14 months showed more rapid composting and greater maturation for the DPGC compost (containing a mixture of date palm waste with couch-grass clippings waste) than for the DPW compost (containing date palm waste alone). Simultaneous mineralization and nitrification phenomena were recorded throughout both composting, this indicate a gradual degradation of date palm waste. The final values of N-NH4+ in both composting showed that maturity was not achieved yet. FTIR analysis showed that both composts were rich in aromatic, phenolic, aliphatic and polysaccharidic structures. The characteristic ratios of IR bands (RIR) showed aromatization of the organic matter in the two composts, higher in the DPGC compost parallel with an advanced maturation. The TGA/DTA analysis showed that the OM transformations were less extensive in DPW compost. The values of the RTGA ratios gave the same end value for both composts, indicating that this index does not correctly assess biological stability. The variations recorded in mass losses associated to exothermal peaks showed that the transformations of OM did not lead to aromatization but rather to functionalization of the OM.