Tuesday, February 6, 2007

Biosolids: CO2 Source or Sink?

Guanglong Tian, Chicago Metrop. Water Reclamation, MWRDGC, 6001 W Pershing Rd R & D Dept., Cicero, IL 60804-4112, Thomas Granato, Metrop. Sanitary Dist. Chicago, Metrop. Wtr. Reclm. Dist.Chicg, 6001 W Pershing Rd.R & D Lab, Cicero, IL 60804, and Albert Cox, MWRDGC, R & D Complex, 6001 W. Pershing Rd., 6001 W. Pershing Rd., Cicero, IL 60804, United States of America.

Mitigating the increase in atmospheric carbon dioxide concentration has been the focus of international efforts. If biosolids are disposed of in landfills or by incineration, most of the biosolids-C will be released to the atmosphere. However, the biosolids-C might be sequestrated in soil as soil organic matter if land-applied, and the subsequent improvement in soil fertility increases the biomass production, leading to the sequestration of atmospheric CO2 in soil. Investigations on the impact of application of biosolids for land reclamation on C sequestration in soil were conducted at Fulton County, Illinois where over 40 fields of strip-mined and non-mined land, sized from 3.6 to 66 ha, received biosolids at a cumulative loading rate from 455 to 1816 dry Mg ha-1 for 5 – 23 years in rotation from 1972 to 2004. The soil C sequestration ranged from 10 to 200 Mg C ha-1 in the biosolids-amended fields. The mean soil C sequestration in fields, where biosolids applied at a mean cumulative rate of 1100 Mg ha-1 and ceased for only 2 years, was as high as 120 Mg C ha-1 as compared to as low as 20 Mg C ha-1 in control, demonstrating a high potential of soil C sequestration in the biosolids land application. The total soil C sequestration was 100 Gg C for the entire 1120 ha biosolids amended-watershed. Based on the estimates from fields where biosolids application has ceased at various years it still takes at least 50 years to lose the sequestrated C if no further biosolids are applied.