Abstract
Abstract. The combination of anaerobic digestion and pyrolysis technologies could be a novel energy-biochar production system to maximize energy and nutrient recovery from pulp and paper mill sludge. Herein, the life-cycle energy production and emissions reduction of sludge treatment from a typical pulp and paper mill were investigated, in which alternative uses of biogas for industrial or household application, in different regions of the world, were assessed. The three scenarios considered for different end-uses of biogas are: (A) biogas for vehicle fuel in the transportation sector in Sweden, (B) biogas for heat and electricity in the power sector in Brazil, and (C) biogas for cooking in households in China. The results of Environmental Life-Cycle Assessment (E-LCA) show that for all these three scenarios, the use of biogas and pyrolysis gas contributes most to emissions mitigation, while the dewatering and drying processes carried out on the sludge, contribute the most to the environmental emissions. Addition of biochar to the soil, contributes significantly to a reduction in global warming by sequestering carbon in the soil. Compared to scenarios B and C, Scenario A, in which biogas substitutes gasoline in transportation, and heat from combusted pyrolysis gases is used for district heating in Sweden, demonstrates the highest environmental performance for all the evaluated impact categories.
Highlights
Wastewater – municipal, industrial and agricultural – holds within itself a wide variety of organic and inorganic constituents, which can be looked upon as resources
Environmental Life-Cycle Assessment (E-LCA) has been previously applied to anaerobic digestion (AD) of wastewater sludge by researchers (Chen and Chen, 2013; Suh and Rousseaux, 2002) and the results show that the AD reduced significantly the environmental costs of sludge disposal compared with the traditional practice of landfill
The environmental impacts associated with the setting-up and maintenance of the infrastructure were not included on the premise that these are amortized over a reasonably long useful lifetime
Summary
Wastewater – municipal, industrial and agricultural – holds within itself a wide variety of organic and inorganic constituents, which can be looked upon as resources. The resources from wastewater can be recovered and recirculated to the anthroposphere, in a circular economy, which many countries in the world are striving to move towards. The motivations behind attempting to close the loop are manifold – economic and environmental, geopolitical and social. Recovery and recycling of resources from wastewater will aid in the conservation of virgin resources – both biotic and abiotic, and of the quality of sinks into which the anthroposphere disposes its wastes (Venkatesh, 2018). Environmental impacts associated with the production of goods which are replaced thereby, are avoided
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