Abstract
Today it is obvious that the existing linear model of the economy does not correlate with the principles of sustainable development. The circular economy model can replace the current linear economy whilst addressing the issues of environmental deterioration, social equity and long-term economic growth. In the context of effectively implementing circular economy objectives, particular importance should be attributed to wastewater treatment sludge management, due to the possibility of recovering valuable raw materials and using its energy potential. Anaerobic digestion is one of the methods of recovering energy from sewage sludge. The main goal of this study is to make a preliminary evaluation of possible sewage sludge biogas and biomethane solutions using a computation model called MCBioCH4 and compare its results with laboratory tests of sewage sludge fermentation from the northern wastewater treatment plant (WWTP) of Ekaterinburg (Russian Federation). Laboratory experiments were conducted to determine the volume and qualitative composition of biogas produced throughout anaerobic fermentation of raw materials coming from the WWTP. The specific productivity of samples ranged between 308.46 Nm3/tvs and 583.08 Nm3/tvs depending if mesophilic or thermophilic conditions were analyzed, or if the experiment was conducted with or without sludge pre-treatment. Output values from the laboratory were used as input for MCBioCH4 to calculate the flow of biogas or biomethane produced. For the case study of Ekaterinburg two possible energy conversion options were selected: B-H (biogas combustion with cogeneration of electrical and thermal energy) and M-T (biomethane to be used in transports). The results of the energy module showed a net energy content of the biogas between 6575 MWh/year and 7200 MWh/year. Both options yielded a favorable greenhouse gas (GHG) balance, meaning that avoided emissions are higher than produced emissions. The results discussion also showed that, in this case, the B-H option is preferable to the M-T option. The implementation of the biogas/biomethane energy conversion system in Ekaterinburg WWTP necessitates further investigations to clarify the remaining technical and economic aspects
Highlights
Nowadays the environmental situation is keenly exacerbated, due to the increased anthropogenic load exceeding the ability of the biosphere to support the process of self-regeneration
In the last few decades the circular economy has increasingly been advertised as an economic model that can replace the current “linear” economy whilst addressing the issues of environmental deterioration, social equity and long-term economic growth with the explicit suggestion that it can serve as a tool for sustainable development [3]
It was shown that carbon dioxide emissions could be considered an indicator of the environmental impact of organic fuels combustion, since they correlate with toxic emissions during the utilization of various types of organic fuels and indirectly characterize the dynamics of the pollutant load [55,56,57]
Summary
Nowadays the environmental situation is keenly exacerbated, due to the increased anthropogenic load exceeding the ability of the biosphere to support the process of self-regeneration. Resources 2019, 8, 91 is a consequence of the practice of human consumer’s behavior towards the natural environment. Throughout their evolution and diversification, industrial economies have hardly moved beyond one fundamental characteristic established in the early days of industrialization: A linear model of resource consumption that follows a take–make–dispose pattern [1]. Circular economy is an environmental issue, it affects the way we produce, work, buy and live [5]
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