title: Storage management influences greenhouse gas emissions from biosolids.
abstract: Biosolids produced by wastewater treatment plants are often stored in stockpiles and can be a significant source of greenhouse gases (GHG). Growing trees in shallow stockpiled biosolids may remove nutrients, keep the biosolids drier and offset GHG emissions through C sequestration. We directly measured methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) flux from a large biosolid stockpile and two shallow stockpiles, one planted with Salix reichardtii (willow) trees, from December 2009 to January 2011. All stockpiles emitted large annual amounts of GHG ranging from 38 kg CO2-e Mg(-1) dry biosolid for the large stockpile, to 65 kg CO2-e Mg(-1) for the unplanted shallow stockpile, probably due to the greater surface area to volume ratio. GHG emissions were dominated by N2O and CO2 whilst CH4 emissions were negligible (<2%) from the large stockpile and the shallow stockpiles were actually a CH4 sink. Annual willow tree growth was 12 Mg dry biomass ha(-1), but this only offset 8% of the GHG emissions from the shallow planted stockpile. Our data highlight that biosolid stockpiles are significant sources for GHG emissions but alternate management options such as shallow stockpiles or planting for biomass production will not lead to GHG emission reductions.
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia.
authors.forename: Ramaprasad
authors.initials: R
authors.lastname: Majumder
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Livesley
authors.affiliation: Technology and Marine Research, Melbourne Water, 990 Latrobe Street, Docklands, VIC 3008, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Gregory
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia; Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria. Electronic address: sarndt@unimelb.edu.au.
authors.forename: Stefan K
authors.initials: SK
authors.lastname: Arndt
mesh_terms: D018533:Biomass; D002245:Carbon Dioxide / Q000737:chemistry*; D005740:Gases / Q000032:analysis; D017752:Greenhouse Effect; D008697:Methane / Q000737:chemistry*; D009609:Nitrous Oxide / Q000032:analysis; D062611:Solid Waste; D013997:Time Factors; D062065:Wastewater / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide; D005740:Gases; D008697:Methane; D009609:Nitrous Oxide; D062611:Solid Waste; D062065:Wastewater
keywords: Biomass; Carbon offset; Methane; Nitrous oxide; Respiration; Sequestration; Sewage sludge