Taking very rough figures from Chapter 12 of Jamie Goode’s “Authentic Wine”, a wine bottle cork has a carbon footprint of 0.01 kg CO2 while a screwcap has 0.04 kg. They are not large contributors to the Earth’s total production of greenhouse gases, but there is a large percentage difference, and every little helps. So we should be choosing natural corks for the sake of the planet, right?
Well, not so fast. The total CO2 emissions for getting a bottle of wine to the consumer is more of the magnitude of 1.5 kg. So the percentage difference due to closure choice on the total bottle footprint is actually of the order of 2%. In itself, that does not change the carbon footprint argument for chosing natural cork over screwcap, because a saving is still a saving.
However, if you open another bottle when you find one that is faulty due to a dodgy cork, that changes the balance quite significantly. Using the numbers presented above, if a cork fault causes you to open another bottle at a rate of about 2%, the carbon footprint advantage of natural cork disappears.
You can juggle with the numbers as you wish. I doubt most people would discard 2% of bottles, but if you are reading this blog I suspect you are more likely than most to discard faulty wine. And you might also be drinking wine with a total carbon footprint considerably more than 1.5 kg – it depends a lot on how it is transported.
Irrespective of the precise numbers, the number of discarded bottles is something you should take into consideration if you are concerned about your carbon footprint enough to worry about the difference between natural corks and screwcaps.