Part 2: Case Study of Energy Use and GHG Emissions from Land Application Program at Columbus Ohio

As part of the larger solids master planning effort for the City of Columbus1 Ohio (Columbus), comparing various end use options (composting, incineration, and landfilling), land application was evaluated as one of the potential end use options. Overall viability, costs, energy impact, and greenhouse gas (GHG) emissions were all considered. This paper explores the methods utilized and the results for determining 1) energy use and 2) GHG emissions that results from requisite activities involved in the land application of biosolids. The energy use section includes energy additions, fertilizer energy substitutions, and total energy for the land application program. The GHG section provides estimates of GHG emissions for all practices associated with land application and was divided into a discussion of emissions from the burning of fossil fuels, emissions avoided through fertilizer substitution, carbon stored in the soil through carbon sequestration, biogenic release of GHGs, and overall (net) GHG estimates for land application. This abstract describes the second part of a two-part presentation and paper regarding land application of biosolids as an option for Columbus2.Recent focus on GHG emissions from all human activities has intensified. Wastewater treatment and solids management activities are no exception. Most solids master planning studies now include a GHG evaluation component. For Columbus, exploring solids management options using a triple bottom line (TBL) approach was essential; measuring against economical, ecological, and social values. An expansion of the TBL approach was used in this case that included a fourth category; technical feasibility.Energy use in land application of biosolids compares favorably to other biosolids handling options. Recent papers show that net energy use in the handling and processing of biosolids is estimated to be lower for land application of anaerobically digested biosolids than for other biosolids handling and treatment options, while the highest energy use and cost, both environmental and economic, is associated with incineration (Murray et al., 2008). The same author also indicates that other handling options, such as heat drying and composting followed by land application also have a higher energy use than land application alone (Murray et al., 2008). Net energy use in land application of biosolids includes additions such as transportation, handling, land application, and incorporation; and credits such as fertilizer substitution and carbon sequestration. The energy section of the study examined current literature on the energy use associated with land application, provided an approach to estimating net energy use, and applied that approach specifically to biosolids handling and treatment scenarios for Columbus.The section on GHG emissions examined current literature on the net GHG emissions resulting from biosolids land application practices and applies the findings of GHG assessment literature to the practices of Columbus land application program. Sources of emissions include fossil fuels burned in the handling and transportation of biosolids, emissions created in the generation of electricity, biogenic emissions from biosolids (including CO2, N2O, NO2, CH4, and CO), emissions avoided through fertilizer substitution, and carbon sequestration in soils due to biosolids application.One of the interesting findings from this case study showed that the GHG emissions from transportation of biosolids were relatively small compared to other end-use activities. Also, GHG emissions avoided by substituting biosolids for fertilizer were significant. Additional findings will be reported in this paper.