title: Advantages and risks of using steel slag in preparing composts from raw organic waste.
abstract: It had been reported that iron and manganese oxides in steel slag enhanced the production of humic acid (HA) from low-molecular-weight compounds, such as phenolic acids, amino acids, and saccharides. In the present study, this function of steel slag was applied to the composting of raw organic wastes (ROWs). The degree of humification of HAs is an important factor in evaluating compost quality. Thus, HAs were extracted from the prepared composts and the humification parameters were determined, in terms of elemental compositions, acidic functional group contents, molecular weights, spectroscopic parameters from UV-vis absorption and13C NMR spectra. The timing for adding steel slag affected the degree of humification of HAs in the composts. The weight average molecular weight of a HA when slag was added initially (29 kDa) was significantly higher than when slag was added after elevating the temperature of the compost pile (17-18 kDa). These results show that ROWs are decomposed to low-molecular-weight compounds after the pile temperature is elevated and the presence of slag enhances the polycondensation of these compounds to produce HAs with a higher degree of humification. Because the slag used in the present study contained several-tens ng g-1to several μg g-1of toxic elements (B, Cu, Cr, and Zn), leaching tests for these elements from the prepared composts were carried out. Levels for leaching boron from composts prepared by adding slag (0.2-0.4 mg L-1) were obviously higher than the corresponding levels without slag (0.05 mg L-1).
authors.affiliation: a Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Faculty of Engineering , Hokkaido University , Sapporo , Japan.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Tu
authors.affiliation: a Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Faculty of Engineering , Hokkaido University , Sapporo , Japan.
authors.forename: Apichaya
authors.initials: A
authors.lastname: Aneksampant
authors.affiliation: a Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Faculty of Engineering , Hokkaido University , Sapporo , Japan.
authors.forename: Shizusa
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: a Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Faculty of Engineering , Hokkaido University , Sapporo , Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tanaka
authors.affiliation: a Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Faculty of Engineering , Hokkaido University , Sapporo , Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Nishimoto
authors.affiliation: a Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Faculty of Engineering , Hokkaido University , Sapporo , Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D006812:Humic Substances / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000032:analysis; D008970:Molecular Weight; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013056:Spectrophotometry, Ultraviolet; D013232:Steel; D013696:Temperature; D018505:Waste Management / Q000379:methods; D014866:Waste Products
chemical_list: D006812:Humic Substances; D008670:Metals; D012987:Soil; D014866:Waste Products; D013232:Steel
keywords: Boron leaching; composting; degree of humification; humic acid; steel slag