sustainability
Article Energy Recovery from Waste Paper and Deinking Sludge to Support the Demand of the Paper Industry: A Numerical Analysis
Simona Di Fraia and M. Rakib Uddin *
Department of Engineering, University of Naples “Parthenope”, 80143 Napoli, Italy; simona.difraia@uniparthenope.it * Correspondence: mohammadrakib.uddin001@studenti.uniparthenope.it
Abstract: The recovery of fibres from waste paper (WP) and deinking sludge (DIS) reduces the stress on nature compared to the collection of virgin pulp for paper production. Moreover, if not recycled, WP and DIS are mainly landfilled and incinerated, being thus responsible for the release of greenhouse gases (GHGs) into the atmosphere. In this context, energy recovery from WP and DIS would contribute to increasing energy independence and improving waste management in the pulp industry. From a broader perspective, it would increase renewable energy generation, supporting the paper industry in reducing fossil fuel consumption and GHGs emissions, in line with the goals of the European Union (EU) Green Deal 2021. For these reasons, in the present study, the combined heat and power generation potentiality of WP–DIS blends through gasification in combination with an internal combustion engine is numerically assessed for the first time. The air gasification process is simulated by applying a restricted chemical equilibrium approach to identify the optimum operating temperature (850 ◦ C) and equivalence ratio (0.2). Electrical and thermal energy generation potentiality, considering WP and DIS production in the EU in 2019, is estimated to be in the ranges of 32,950–35,700 GWh and 52,190–56,100 GWh, respectively. Thus, it can support between 25 and 28% of the electrical and 44–48% of the thermal energy demand of the paper manufacturing sector, reducing the CO 2 emission in the range of 24.8–28.9 Gt.
Citation: Di Fraia, S.; Uddin, M.R. Energy Recovery from Waste Paper and Deinking Sludge to Support the Demand of the Paper Industry: A Numerical Analysis. Sustainability 2022 , 14 , 4669. https://doi.org/ 10.3390/su14084669
Keywords: waste paper; deinking sludge; pellet; gasification; restricted chemical equilibrium model; syngas; sensitivity analysis; optimization; combined heat and power
1. Introduction The pulp and paper industry presents a significant energy demand, mainly satisfied by fossil fuels [1,2], which cause high greenhouse gases (GHGs) and pollutant emissions [3]. Moreover, the pulp and paper industry generates a considerable quantity of waste as a small fraction of starting biomass is transformed into the final products of paper [1]. Thus, this sector could increase renewable energy production by recovering its waste, contributing to the sustainable energy transition. Another way to increase the eco-efficiency of this sector is recycling used paper to extract the pulp. Indeed, such a practice is glob- ally increasing to reduce the stress on nature to collect virgin pulp from trees and the environmental pollution caused by landfilling or incinerating the used paper [4–6]. It is estimated that pulp collection from recycled used paper could save on average 8.2 million trees annually [7]. Cellulosic fibre length, as well as strength, decreases during the col- lection of pulp, requiring its blending with virgin fibres for paper production. However, used paper can be recycled three to eight times to collect cellulosic fibres, then the used paper has to be discarded as solid waste [8,9]. Based on the data presented in the CEPI-2020 (Confederation of European Paper Industries) report, in 2019, world average used paper recycling was 58.6% with the highest rate in the European Union (EU) (72.5%), followed by North America (65.7%), Asia (53.9%), Latin America (47.2%), and Africa (35.2%) [4]. During the recycling of used paper to collect the pulp, waste paper (WP) and deinking sludge (DIS) are generated as waste products. WP consists of fibre lumps, staples, sand,
Academic Editor: Agostina Chiavola
Received: 18 March 2022 Accepted: 12 April 2022 Published: 13 April 2022
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Sustainability 2022 , 14 , 4669. https://doi.org/10.3390/su14084669
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