The carbon dioxide paradox

January 2010

The ISO 14001 standard implementation makes every company to look after, among all the products it uses, those which are volatile organic compounds (VOC), in order to lower their emission.

As for PT and MT one of the main concerns is liquefied petroleum gas (LPG) used as propellent in spray cans: obviously it is a VOC.

A spray can using LPG as propellent generally contains 66 to 98% weight/weight of VOC though some suppliers display much lower figures in their Material Safety Data Sheets (MSDS), something as 20 to 30%!

Spray cans are the source of about 3% of the VOC emissions.

One way to lower VOC content comes by using compressed gases such as CO2 (carbon dioxide) in lieu of LPG.

But CO2 was far from a total appraisal due to too a high pressure as well as the fact that, if the spray can is not used upright 100% of the time, there is a loss of gas making it impossible to use all the product in the can. Furthermore the spraying parameters for products heavy in solids (paint, hair spray, NAWD for PT, white contrast paint for MT, etc.) lead to a very low quality of the layer.

And yet CO2 has two advantages: non-flammable and above all it allows for putting a lot more of product in the spray can.

These advantages being counterbalanced by disadvantages some PT/MT manufacturers went back to using LPG. But now a swing of pendulum seems to favour again CO2 just to lower VOC emissions!

One must realize that in the PT/MT world as in history, what is fashionable may swing back.

Let us ask a simple question: how much of propellent in a spray can?

As a general matter of fact compressed gases are 3 to 7% of the entire weight. LPG may be in the range 30 to 60%.

Let us imagine that, so as to comply with the ISO 14001 standard all the spray cans are propelled by CO2. About 12 billion spray cans are manufactured every year in the world, and take for granted an average content of 10 grams (ca 0.35 oz) CO2 per can.

This comes to 120,000 metric tons of CO2 per year.

Just for comparison let us calculate how many cars emitting 120 grams (ca 4.23 oz) CO2 per km, running for 20,000 km (ca 12,430 miles) a year would emit the same mass.

In fact this is the amount of 50,000 cars!

Are we on the way to put in place a tax on the spray cans emitting CO2, as is done for cars in Europe?

Here is the real paradox. On one hand the VOC emission is lowered; on the other hand the CO2 emission is increased. Real paradox? Or only apparent paradox? The carbon dioxide used in spray cans comes either from air or more commonly from industrial processes: the CO2 used as propellent in fact is CO2 which does not go to the atmosphere-- well ... not now!

Nevertheless could we imagine an "Extremist greener than greener" Non Governmental Organisation (NGO) asking Parliaments for a "carbon-tax" on CO2-propelled spray cans?

No, this will never occur!