Biosolids management with net-zero CO₂ emissions: a techno-ecological synergy design

Abstract

Management of biosolids from industrial and municipal wastewater facilities presents multifaceted issues ranging from greenhouse gas emissions, high odor and high treatment costs. Until now, most studies that have focused on identifying the best treatment pathway are based on optimization of technological alternatives and life cycle analysis studies. Such studies aim toward sustainability but ignore the capacity of local ecological systems to provide ecosystem services, thus leading to design solutions that may be sub-optimal due to shifting of impacts outside the boundary, resulting in degradation. This work uses a techno-ecological synergy design methodology to identify optimal strategies for biosolids treatment and disposal, by balancing the supply and demand for carbon sequestration ecosystem service. Both the technological systems that create the ecosystem service demand and ecological systems that supply those services are included within one design framework. Technological alternatives for biosolids management in Central Ohio considered in this work are land filling, land application, incineration and composting. Approaches for supplying the carbon sequestration capacity include forestation, extension of timber cycles and geological sequestration. An additional case where biomass utilization from extension of timber cycle to produce renewable energy is also explored. Results from this study demonstrate that including carbon sequestration ecosystem service explicitly in the design problem leads to solutions where the ecosystem service demand and supply can be balanced, while also being cost-effective. Thus by including ecological systems in the design boundary, the optimal solution space expands to reveal novel solutions that cannot be found by the conventional techno-centric approach.