A. Abuşoğlu, E. Özahi, A. Tozlu
3rd International Conference on Engineering and Natural Sciences (ICENS 2017), ISBN: 978-605-83575-4-9, Budapest, Hungary, May 3-7
Publication year: 2017

In this study, two interconnected systems using biogas and stabilized sewage sludge, which are
important by-products of an actual municipal wastewater treatment system, are compared in terms
of environmental impacts. In the first system, biogas produced from sewage sludge by anaerobic
digestion is burned in an internal combustion gas engine driven cogeneration system to generate
electricity. In the second system, the stabilized sludge taken from wastewater treatment plant is
burned in a fluidized bed combustion system for elimination purposes. In this context, sludge
stabilization and its disposal are the most complicated environmental problems faced by researchers
and managements working in this area. The utilization of novel solutions or different application
methodologies are brought to agenda for the management and beneficial use of sewage sludge.
The environmental impact assessment is performed using the life cycle analysis (LCA) method. Life
cycle analysis is a novel approach which comprehensively evaluates the potential impacts of a
production or a process that causes environmental effects and compares these effects with other
similar productions or processes. The environmental impact assessments of interconnected systems
presented in this study are calculated and compared in three main impact categories: Climate
change, acidification and eutrophication. According to the results obtained; (i) the impact value of
climate change category per unit time for the biogas engine driven cogeneration system is 0.324 kg
CO2-equivalent while it is 0.247 kg CO2-equivalent for the fluidized bed sewage sludge combustion
system, (ii) the impact value of acidification category per unit time is found to be 0.000491 kg SO2 –
equivalent for cogeneration system and 0.000228 kg SO2 -equivalent for fluidized bed combustion
system, (iii) the impact values of eutrophication category per unit time for cogeneration and
fluidized bed combustion systems are calculated to be 0.000124 kg NOx -equivalent and 0.0000436
kg NOx -equivalent, respectively.

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