Energies 2019 , 12 , 247
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Figure1. Trend in the relationship between the amount of data and the precision of identification for improvements according to literature (e.g., [28,51]).
Additionally, due to the uncertainties that can originate from the usage of different PEFs, more uncertainties when benchmarking at international level come from data on a highly aggregated level, such as when applying the total annual energy used without further explanations and specifications (see e.g., Table 1). For example, SEC can be higher or lower for an entire PPI depending on the dominant type of the mill, i.e., pulp mills, paper mills, integrated pulp and paper mills, etc. The types of products that the various mills produce can also affect SEC. The decision on whether to use only direct process data or to include other data, e.g., energy used for waste water treatment, support processes, etc., also influences SEC. Examples of SEC are presented in Table 4.
Table 4. Examples of SEC for the pulp and paper industry (PPI). “n.s.” means that the PEF was not specified in the references and was therefore recalculated as presented in Section 3.
Total Energy (GWh/kt)
Energy Used by
PEF
Region
Reference
Year
Source for SEC
PPI PPI
16.70
n.s. n.s. n.s. n.s. n.s.
India USA India India
[53] [54] [53] [53]
1987 1994 2002 2009 2016
From literature From literature From literature From literature From literature Calculated from official data
PPI (processes)
9.33
PPI PPI PPI
14.20 11.10
Best available technologies (BAT)
6.40
[53]
average 2006–2016
PPI (average)
3.86
~1.7
Sweden
[6]
Pulpmills Pulpmill
average 2006–2015
Calculated from official data
4.23
~1.7
Sweden
[6]
Paper mills Paper industry
6.23
n.s.
USA
[46]
1981
From literature
Organization for Economic Co-operation and Development (OECD)
[55]
2001
From literature
Papermill
3.90
2.50
average 2006–2016
Calculated from official data
Papermill (Average)
4.39
~1.7
Sweden
[6]
Integrated mills Integrated mills
average 2006–2017
Calculated from official data
2.95
~1.7
Sweden
[6]
When comparing the results from other studies, it is not always clear what a certain SEC covers de facto depending on the choice of wording. For example, “pulping” is used to describe the process used “to free fibres in wood from lignin that binds these fibres together, and then to suspend the fibres in water into a slurry suitable for paper making” ([56], p. 14). For example, the SEC of “pulping chemical” is 1.48 GWh/kt in [54] and probably refers only to the pulping process according to the definition above
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