title: The effect of airflow rates and aeration mode on the respiration activity of four organic wastes: Implications on the composting process.
abstract: The aim of this study was to assess the effect of the airflow and of the aeration mode on the composting process of non-urban organic wastes that are found in large quantities worldwide, namely: (i) a fresh, non-digested, sewage sludge (FSS), (ii) an anaerobically digested sewage sludge (ADSS), (iii) cow manure (CM) and (iv) pig sludge (PS). This assessment was done using respirometric indices. Two aeration modes were tested, namely: (a) a constant air flowrate set at three different initial fixed airflow rates, and (b) an oxygen uptake rate (OUR)-controlled airflow rate. The four wastes displayed the same behaviour namely a limited biological activity at low aeration, while, beyond a threshold value, the increase of the airflow did not significantly increase the dynamic respiration indices (DRI1 max, DRI24 maxand AT4). The threshold airflow rate varied among wastes and ranged from 42NL air kg-1DMh-1for CM and from 67 to 77NL air kg-1DMh-1for FSS, ADSS and PS. Comparing the two aeration modes tested (constant air flow, OUR controlled air flow), no statistically significant differences were calculated between the respiration activity indices obtained at those two aeration modes. The results can be considered representative for urban and non-urban organic wastes and establish a general procedure to measure the respiration activity without limitations by airflow. This will permit other researchers to provide consistent results during the measurement of the respiration activity. Results indicate that high airflows are not required to establish the maximum respiration activity. This can result in energy savings and the prevention of off-gas treatment problems due to the excessive aeration rate in full scale composting plants.
authors.affiliation: Composting Research Group (GICOM), Dept. of Chemical Biological and Environmental Engineering, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Mejias
authors.affiliation: Composting Research Group (GICOM), Dept. of Chemical Biological and Environmental Engineering, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain; Department of Environmental Engineering, Democritus University of Thrace, Xanthi, Greece. Electronic address: dkomilis@env.duth.gr.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Komilis
authors.affiliation: Composting Research Group (GICOM), Dept. of Chemical Biological and Environmental Engineering, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Gea
authors.affiliation: Composting Research Group (GICOM), Dept. of Chemical Biological and Environmental Engineering, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Sánchez
mesh_terms: D000818:Animals; D002417:Cattle; D000076282:Composting; D005260:Female; D008372:Manure; D010100:Oxygen; D012722:Sewage; D012987:Soil; D013552:Swine
chemical_list: D008372:Manure; D012722:Sewage; D012987:Soil; D010100:Oxygen
keywords: Airflow; Biological activity; Composting; Dynamic respirometric index; Oxygen uptake rate