Energies 2021 , 14 , 1161
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For future prospection, the total electricity purchased from the grid each year ( E grid , y ) was then estimated based on g y (Equation (16)). E purchased , y = g y · E y (16) 3.3. Mathematical Formulation: CO 2 Emission TheCO 2 emissions due to the consumption of fossil fuels ( CO 2 direct , t) is calculated as the summation of the amount of fossil fuels consumed ( F i , t) multiplied by the emission fac- tor of each fossil fuel ( ef i , t CO 2 /t fuel ), reported to Austria’s National Inventory Report [38] (Equation (17)). CO 2 direct = ∑ i F i · ef i (17) The CO 2 emitted due to the consumption of grid electricity ( CO 2 indirect , t) is cal- culated as the product of the grid electricity consumed ( E purchased , kWh) multiplied by the respective emission factor for the paper industry ( ef grid , t CO 2 /kWh). To calculate ef grid (Equation (19)), the total emissions from energy production of the electricity grid ( CO 2 grid , y , t) is estimated as the summation of the product of the consumption of each fuel used to power the grid ( F grid , i , y , t) [39] and the respective emission factors (Equation (18)). The grid emission factor is then calculated as the division between CO 2 grid , y and the total grid electricity in year y ( E grid , y ). The value used in this section corresponds to the most recent data available. CO 2 grid , y = ∑ i F grid , i · ef grid (18)
CO 2 grid E grid
(19)
ef grid =
TheCO 2 emission due to the purchase of grid electricity is then calculated (Equation (20)). CO 2 indirect = E purchased · ef grid (20) The mentioned equations in Sections 3.1–3.3 are also used for each selected technology, and will analyze the decarbonization scenario. 4. Decarbonization Technology Selection Based on the literature, there are already a number of opportunities for reducing energy consumption and greenhouse gas emissions in the pulp and paper industry, and others will be available in the future. In general, upgrading existing mills with energy- efficient technologies, such as switching fuel from fossil fuels to on-site produced biofuels (bark and black liquor) in combination with CHP, improving the energy management system, increasing the use of waste paper and paper recycling, and implementation of innovative technologies are the key options identified to reduce CO 2 emissions and energy consumption in the P&P sector [10,16,40]. In this work, a list of best available technologies (BAT) and emerging innovative tech- nologies (IT) has been compiled based on a comprehensive literature review in Tables 8 and 9. These technologies are applicable at different stages of the pulping and papermaking pro- cess. For each technology, the energy-savings (heat or electricity) and the CO 2 reduction potential in the associated process are considered, and to find out how mature the technol- ogy is, the technology readiness level (TRL) is monitored.
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