Energies 2023 , 16 , 746
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for example, the use of deep eutectic solvent may reduce the primary energy demand of pulping by 40% [44]. However, the adoption of new technologies that significantly change the pulping or paper-making processes may be difficult and slow due to concerns about the effects on the operation.
Table4. An example of development of specific energy consumptions. Estimates were created for the Finnish pulp and paper industry based on Carlson and Heikkinen, and Pöyry [45,46].
Paper and Paperboard
Type of Energy Year
Chemical Pulp Mechanical Pulp
1970 1995 2015 2035 1970 1995 2015 2035
14.2 12.4 11.1 717 682 671 536 9.0
0.1
6.7 6.0 4.6 4.2 746 711 606 557
− 1.5 − 1.6 − 2.3 1630 2320 2361 2164
Heat (GJ/t)
Electricity (kWh/t)
A proposed revision of the EED calls for increasing the annual energy savings require- ment for 2024–2030 from 0.8% to 1.5% [6]. As a large energy user, the PPI must significantly contribute to the energy savings. The authors’ previous study shows that the Finnish and Swedish PPIs managed to substantially improve their energy efficiency between 2002 and 2017 [21], but the improvement pace did not meet the requirements of the EED. Thus, the improvement pace must be accelerated, and the need applies most probably also to other PPI countries. The EEI can lead to notable savings in energy costs in energy-intensive indus- tries, and therefore, it has been discussed if there is a real need to support the industrial EEI by policy incentives or if market forces can drive the change toward energy savings [47]. However, barriers to EEI, such as technical risks or a lack of access to capital, are hindering even the adoption of cost-effective measures [48]. Thus, political stimulation is needed for overcoming the barriers. 3.3. Fuel Switching and Electrification In the PPI, fossil fuels are used in steam production and pulping (lime kilns) and papermaking (dryers) processes. All fossil fuels are technically possible to replace with biofuels or electricity [49], but the likelihood to reach net-zero emissions depends on the mill type. Modern chemical pulp mills can already achieve fossil carbon-free operation [50], and consequently, it is realistic to expect that new-build mills do not need fossil fuels during normal operation. Decarbonization of stand-alone paper mills is more challenging because the energy production relies on fossil fuels instead of biomass, which is a dominating fuel in the pulp mills. Currently, electricity and steam are produced in boilers that combust mainly natural gas, but also some amounts of coal-fired boilers are used. The pulp and paper-making processes are technically possible to decarbonize. Electricity- based paper dryers are already used in some mills, and further electrification of the dryers could reduce annual emissions by 1–2 MtCO 2 in Europe [51]. Some mills have also stated an aim to combust hydrogen in dryers [52]. Recent studies suggest that also lime kilns can be electrified using electric gas-plasma technology in the future [53], which may be an interesting opportunity especially for mills that have no excess biomass. In addition, indirect electrification, i.e., the use of renewable hydrogen or hydrocarbon, is a possible but currently costly and rather inefficient opportunity to decarbonize the lime kilns. So far, the use of biofuels has been a leading solution as many pulp mills have bio-based residues that can be combusted in lime kilns. Production of pulp consumes approximately 250 kg/ADt of lime (CaO) [35], and the production of lime requires 6–10 GJ/kg CaO of heat [54]. The European PPI produces annually 32 Mt of kraft pulp, and mills combust mainly natural gas in the lime kilns, which
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