title: Influence of the composition of the initial mixtures on the chemical composition, physicochemical properties and humic-like substances content of composts.
abstract: The influence of the proportion of C- and N-rich raw materials (initial C/N ratio) and bulking agent on the chemical functional groups composition, humic-like substances (HS-like) content and physicochemical properties of composts was assessed. To achieve these goals, seven initial mixtures (BA1-6 and C1) of dog food (N-rich raw material) were composted with wheat flour (C-rich raw material). Composts were analyzed in terms of chemical functional groups, physicochemical, maturity and stability parameters. The C-rich raw material favored the formation of oxidized organic matter (OM) during the composting process, as suggested by the variation of the ratios of the peaks intensity of FT-IR spectra, corresponding to a decrease of the polysaccharides and an increase of aromatic and carboxyl-containing compounds. However, although with high proportion of C-rich raw material, mixtures with low initial C/N seems to have favored the accumulation of partially oxidized OM, which may have contributed to high electrical conductivity values in the final composts. Therefore, although favoring the partial transformation of OM into stabilized HS-like, initial mixtures with high proportion of C-rich raw material but with low initial C/N led to unstable composts. On the other hand, as long as a high percentage of bulking agent was used to promote the structure of biomass and consequently improve of the aeration conditions, low initial C/N was not a limiting factor of OM oxidation into extractable stabilized humic-like acids.
authors.affiliation: Departamento de Ambiente, Escola Superior de Tecnologia e Gestão de Viseu, Campus Politécnico de Repeses, 3504-510 Viseu, Portugal; LEPAE-Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, 4200-465 Porto, Portugal; Instituto Superior de Agronomia, UIQA, ULisbon, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
authors.forename: Maria Elisabete F
authors.initials: ME
authors.lastname: Silva
authors.forename: Luís Teixeira
authors.initials: LT
authors.lastname: de Lemos
authors.forename: Olga C
authors.initials: OC
authors.lastname: Nunes
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: Cunha-Queda
mesh_terms: D000821:Animal Feed; D002244:Carbon; D045424:Complex Mixtures; D006812:Humic Substances / Q000032:analysis*; D009584:Nitrogen; D010084:Oxidation-Reduction; D012037:Refuse Disposal; D012987:Soil / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014908:Triticum
chemical_list: D045424:Complex Mixtures; D006812:Humic Substances; D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: Bulking agent; Humic-like substances; Initial C/N ratio; Maturity; Raw materials; Stability