Energies 2023 , 16 , 746
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balance for a typical kraft pulp mill was constructed to illustrate the potential of a pulp mill as a producer of bio-based side streams, renewable electricity, and CO 2 . The mill balance was based on a mill model used in previous studies [27,28]. Based on the collected data, the potential, the effects of new processes on the mills, and the magnitudes of possible CO 2 savings were estimated. 2.3. Distribution and Progress of the CO 2 Emissions in the Global Pulp and Paper Industry The European PPI covers only approximately one-fourth of the global pulp and paper production, and therefore, it is important to briefly widen the perspective of this study to other PPI countries. A geographical distribution of fossil and biogenic CO 2 emissions originating from global pulp and paper production was evaluated to understand the role of different regions in CO 2 emissions generation. The expected progress is discussed by comparing the development of the PPI in the OECD countries and developing countries. CO 2 emissions were estimated for all continents that produce pulp and paper (Europe, North America, South America, Australia, Asia, and Africa). In this study, the continents were compared, but it should be noted that there were differences also within the countries located on the same continent. Data on CO 2 emissions were collected, but to the authors’ knowledge, no comprehensive statistics on regional emissions or fuel use of the PPI exist, and especially biogenic CO 2 emissions are poorly reported. Thus, when the emission data were not available, the CO 2 emissions were estimated by the authors. Due to variation in data availability, two main approaches were used for estimating theCO 2 emissions of the regions. In the first approach, the emissions were calculated by multiplying fuel use by CO 2 emission intensity of the fuel (Equation (1)).
n ∑ i = 1
CO 2 emission 1 =
(1)
F i I i
where F i stands for fuel consumption by fuel type (GJ), and I i is theCO 2 emission intensity of a certain fuel (kgCO 2 /GJ). The second approach utilized production volumes of the regions and specific CO 2 emissions of products (Equation (2)).
n ∑ i = 1
CO 2 emission 2 =
(2)
P i i i
where P i stands for production volume (tons), and i i is the specific fossil CO 2 emissions of the product (kgCO 2 /ton). CO 2 emission intensities were adopted from a comprehensive fuel properties database provided by the Statistic Finland [29]. Production volumes were collected from FAO [24], and reports on energy use and emissions [18,30–33] were utilized. Data on the use of biofu- els were poorly available, and thus, assumptions were needed to calculate the consumption of biofuels to be able to estimate the emissions. Moreover, the calcination process in kraft pulp mills generates biogenic CO 2 emissions. Due to the lack of data, the biogenic CO 2 emissions from calcination were calculated using production volumes and an average value for the emissions. The following assumptions were used: • Pulp production generates approximately 19 GJ/ADt of black liquor and 0.7–3 GJ/ADt of wood residues, which are typically combusted to energy [34]. • The calcination process in chemical pulp mills produces about 196 kgCO 2 /ADt of biogenic CO 2 [35]. The total fuel use provided by the International Energy Agency (IEA) [1] was utilized to estimate global fossil and biogenic CO 2 emissions of the PPI. The overall emissions were used to evaluate the validity of the regional values.
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