Maybe it's not the direct answer to your question, but we used the CO2-index as the standard and compared environmental impacts of other pollutants for at least 3 environmental impact methods. That was in 1994. I am sure someone has done the updated work.

"Life cycle assessment. A comparison of three methods for impact analysis and evaluation. H BAUMANN, T RYDBERG. Journal of Cleaner Production - J CLEAN PROD 01/1994; 2(1):13-20. DOI:10.1016/0959-6526(94)90020-5. ABSTRACT For the evaluation of data resulting from the inventory stage of a life cycle assessment, two sets of environmental indices based on Swedish data have been calculated according to the 'ecological scarcity method' and the 'environmental theme method'. These are compared with indices from the method for 'environmental priority strategies in product design'. The relative importance of CO2, SO2 and NOx in the three evaluation methods, expressed as index ratios CO2:SO2: NOx, was calculated to be 1:200:250, 1:220:350 and 1:150:6100, respectively."

You can look further into various Life Cycle Impact Assessment methods to get other evaluations.

Maybe it's not the direct answer to your question, but we used the CO2-index as the standard and compared environmental impacts of other pollutants for at least 3 environmental impact methods. That was in 1994. I am sure someone has done the updated work.

"Life cycle assessment. A comparison of three methods for impact analysis and evaluation. H BAUMANN, T RYDBERG. Journal of Cleaner Production - J CLEAN PROD 01/1994; 2(1):13-20. DOI:10.1016/0959-6526(94)90020-5. ABSTRACT For the evaluation of data resulting from the inventory stage of a life cycle assessment, two sets of environmental indices based on Swedish data have been calculated according to the 'ecological scarcity method' and the 'environmental theme method'. These are compared with indices from the method for 'environmental priority strategies in product design'. The relative importance of CO2, SO2 and NOx in the three evaluation methods, expressed as index ratios CO2:SO2: NOx, was calculated to be 1:200:250, 1:220:350 and 1:150:6100, respectively."

You can look further into various Life Cycle Impact Assessment methods to get other evaluations.

The global warming potential of CO2 is 1.0 (in the appropriate units) and the global warming potential of water vapor (H2O) is:

(low end) = 0.1 x GWP of CO2

(high end) = 0.23 X GWP of CO2

The global warming potential of C6H6 is 1500. Page 11 of the enclosed presentation will provide some very good data for you to use to compare the GWP of different gasses.

http://www.greenchemistrynetwork.org/pdf/AdisaAzapagicManchester.pdf

This document should help you as well.

Thanks a million for your answers.

I just want to know if for example one product release 1 kg CO2e during its production phase, how bad it will be when compared with another product which release 0.25 kg CO2e during this phase? What will be the ratio?

Basically, you are asking an LCA question.

You need to consider whether the two products are functionally equal.

Also, the unit given 1kgCO2 — what is its reference? 1kgCO2/kg productA or what? What is the weight and material of product A and product B respectively?

I recommend you to get in contact with Ali Daneshi, PhD student at Tarbiat Modares research university in Tehran. He is a PhD student of LCA, he can assist you in these matters.

Thanks a lot for your helpful tips.

Yes, they are functionally equal. I just compare 1 meter of PVC pipe with 1 meter of HDPE pipe. They also have the same size.

You will find 'cradle-to-gate' date (i.e. from raw material to the produced material) in this free and open LCA database: http://lifecyclecenter.se/tools-data/cpm-lca-database/

Search for PVC and HDPE respectively (under 'Exact substance name =' - it is quite far down in the form) and you will find the emission profiles for respective material.

You can also check the Association of Plastics Manufacturer's site — they have quite a lot on the LCA of plastics: http://www.plasticseurope.org/plasticssustainability/eco-profiles.aspx