Energies 2021 , 14 , 1161
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While pulp and paper is an energy-intensive sector and consumes a lot of energy in Austria, it is one of the least CO 2 -intensive industrial sectors. Greenhouse gas emissions in P&P can be attributed to direct and indirect emissions. Direct emissions are emissions from the burning of fuels on-site (fossil fuels and biofuels) and non-energy related sources such as carbon dioxide emissions as a by-product of the chemical reaction in the lime kiln. The in-direct emission comes from the external power supply that has been purchased for the plant [15,17]. For calculating the total CO 2 emissions from the P&P sector, only fossil fuel emissions are taken into account. The biofuel emissions are classified as carbon-neutral, according to the GHG Protocol of the Intergovernmental Panel on Climate Change (IPCC) [35]. The carbon neutrality of bioenergy does not mean that emissions from bioenergy are not considered. Instead, they are assigned to the forest and land-use sector [36]. Hence, the main reason for the difference in carbon dioxide intensity between paper manufacturing and other industrial sectors is the extensive use of biofuel as an energy source [15]. In 2017 the total emission of the Austrian P&P sector was 1811 kilotons (kt) [8], which was 90% direct and 10% indirect emissions, corresponding to 7% of total industrial emissions. As illustrated in Figure 5, P&P showed a general decreasing trend in direct fossilCO 2 emissions from 2157 kt (0.54 kt CO 2 per kt paper) in 2000, to 1639 kt (0.37 kt CO 2 per kt paper) in 2017 [8,9]. This was mainly due to the increased use of biofuel instead of fossil fuels as an energy source. (Figure 4).
Figure5. Historical trend of CO 2 emission in the P&P industry in Austria 2000–2017 [9,30,32–34]. 3. Modeling Approach To assess the potential of technology-based energy efficiency improvement and CO 2 mitigation measures on the P&P processes, we developed an analytical model based on a linear bottom-up approach. By calculating the energy consumption of each step of the production process, the fuel consumption and CO 2 emissions can be estimated. This approach makes it possible to calculate the impact that selected measures in a specific process would have on the energy consumption and CO 2 emissions of the entire production process. The first application of the model is the calculation of annual emissions and energy con- sumption of each paper product individually (printing and writing paper, tissue, newsprint, and packing paper), considering different production conditions such as integrated (int) or non-integrated (n.int) production, type of pulp used, and RCF content, to obtain the specific
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