Optimization of the humification process during composting and recovery evaluat...

• Author(s): Silva, Maria Elisabete Ferreira
• Date: 2013
• Persistent ID: http://hdl.handle.net/10400.5/6971
• Origin: Repositório da UTL
• Subject(s): bioavailability; compost; heavy metals; humic-like substances; recovery
• Document Type: Doctoral Thesis
• Language: English
• Advisor(s): Queda, Ana Cristina Ferreira da Cunha; Nunes, Olga Cristina Pastor; Lemos, Luis Eugénio Pinto Teixeira

Description

Doutoramento em Engenharia do Ambiente - Instituto Superior de Agronomia This work aimed to contribute to the knowledge about the formation of humic-like substances (HS-like) during composting and to assess the recovery of these substances from commercial compost with low quality. Several mixtures with raw materials of known composition (wheat flour, dog food) were composted. First, it was studied the influence of mild solvents, sodium and potassium pyrophosphate, in the yield and characteristics of extracted HS-like, as well as in the coextraction of heavy metals from compost. Secondly, it was assessed the influence of raw materials, presence of bulking agent and initial C/N ratio on the humification during composting. Third, commercial composts were used as HS-like source. In all phases, composts and HS-like were characterized using the conventional physical, chemical, stability and maturity parameters. The fractionation of heavy metals was also determined. Results showed that potassium pyrophosphate can be used advantageously for the HS-like extraction. During composting the HS-like content were influenced by presence of carbon rich raw materials and the initial C/N ratio, being their production independently of the composts quality. The HS-like produced from commercial composts showed low level of co-extracted heavy metals, however, the presence of Cu, Cr and Pb can influence negatively their composition.