Environmental issues like global warming, waste management, paper production and consumption are an area of debate and interest to many. Highlighting the environmental impact of printing is one of the ways to influence user behavior.
SavaPage uses the number of printed Sheet Units to calculate three impact metrics: trees and energy consumption, and carbon production.
The default values SavaPage uses for environmental metrics can be the subject of debate. Of course you are free to set the metric to any value that works for you. Please inform us about facts and findings you feel confident about.
A Sheet Unit (SU) is the size equivalent of an A4 sheet. So,
A4 == 1.00 SU A3 == 2.00 SU A2 == 4.00 SU A1 == 8.00 SU
A5 == 0.50 SU A6 == 0.25 SU A7 == 0.12 SU A8 == 0.06 SU
Note that SU precision is 2 decimals. As environmental impact is concerned, A4 and US Letter sheets are handled as equivalent, so ...
US Letter == 1.00 SU
SavaPage uses the media size chosen by the user to calculate the printed Sheet Units of a Proxy Printer print job. Some print examples:
6 pages double-sided on A4 :
6 pages double-sided on A3 :
6 pages 2-up on A4 :
6 pages 2-up double-sided on A4 :
SavaPage is not able to anticipate printer intelligence, for instance, when a printer uses different trays (with different media sizes) for different page sizes within the job document.
This metric is the percentage of a tree used to produce the paper of the
printed Sheet Units. The metric is adopted from
Conservatree.org and is as follows:
A prototypical tree is 40 feet tall and 6-8 inches in diameter.
One tree makes 16.67 reams of copy paper or 8,333.3 SU.
83333 is set as default for the configuration key:
This metric is the energy used to produce the paper of the printed Sheet
Units. The metric is adopted from
Paperonline.org and is as follows:
Around 500 kWh of energy are required in Europe to make 200 kg of paper.
So one A4 or Letter sheet of office paper costs 12.5Wh to manufacture .
12.5 is set as default for the configuration key:
This metric is the amount of CO2 released for producing
the paper of the printed Sheet Units. The metric is adopted from the
Swiss Federal Institute of Technology Zurich and is as follows:
One A4 or Letter sheet costs 5.1g of CO2 to production.
5.1 is set as default for the configuration key:
This metric takes into account the CO2 produced as a byproduct of paper production only. It does not take into account the CO2 related to the production and operation of the printer and the ink or toner cartridges. Defining broader system boundaries and tracking down all parameters involved requires a major effort, and is beyond the scope of this manual. Of course you are free to set the parameter value for this metric to any value that works for you.
 A sheet of 5g requires (5/200.000) * 500 = 0.0125 kWh = 12.5 Wh.