Would you woo your valentine with a plastic bottle of wine?

Adnams Brewery recently added some South African wines to their list that come in bottles made from PET, the same plastic as fizzy drinks bottles. This saves energy and carbon emissions both from making the bottle and in transport (because the PET bottles are lighter). If your partner is environmentally conscious would they appreciate these savings?  How much difference does the plastic bottle actually make? Adnams doesn't say how much so I have done some calculations. Also there are other options such as bag in a box or using thinner glass bottles.
The Adnams wine comes from S. Africa so this is what I have based my calculations on, comparing

• an ordinary 500g glass bottle with about 80% recycled content
• a thinner 365g glass bottle (much lighter than this and there will be too many breakages)
• a 54g PET bottle with 50% recycled content

The chart below shows the results. The thinner glass bottle saves a bit on carbon emissions but the PET bottle saves more: 44% of the emissions from bottle manufacture and transport. However the savings are only 25% when you take into account growing the grapes and producing the wine.

Carbon emissions from production and transport of wine from. S Africa. See yellow box for assumptions.

Assumptions behind the chart:

Phase	Emissions	Data source
Wine production	385g	How Bad are Bananas[1]
Bottle manufacture	various	WRAP [2]
Shipping	11,000 km at 13 gCO2/tonne-km (General cargo)	DEFRA emissions factors[3]
Road transport	400km at 250 gCO2/tonne-km ((rigid HGV)	DEFRA emissions factors[3]

For wine from Australia the shipping component is much larger and the savings from the lighter bottles are more important.

You can also get wine in boxes, made of cardboard with a plastic bladder lining. These typically contain three litres, equivalent to four bottles which may or may not be a good thing depending on your plans for the evening. Of course you don't have to drink it all at once. One of the advantages of a box is that it keeps better after opening than a bottle. This is because the bladder folds up as you pour the wine out and does not leave any air spaces.

The plastic bladder may not be recyclable. Alternatively you can sometimes get wine in tetra-paks or smaller - Waitrose has some bottle size tetra-paks of Fairtrade wine - and these can be recycled. A tetra-pak has about half the emissions of an equivalent sized PET bottle [4] so that saves quite a bit more.

PET bottles do not contain plasticiser and there is little danger of flavour changes due to leaking of anything into the wine [5]. However, plastic is not as impermeable to air as glass and the wine will oxygenate over time so you would not want to keep the wine in a plastic container of any sort for more than a year or so. The tetra-paks have a shelf life of 18 months. This means plastic packaging is not suitable for wines to be matured in your cellar and perhaps this is what gives the impression that wine in plastic bottles is 'cheap'. If you don't want to let on where your wine came from you could pour it into a glass carafe for serving.

Finally, there is the rest of the meal to consider. A 100g serving of chicken adds another 600g or so of CO2e, of steak would be another 1800g CO2e: nearly twice as much as one bottle of S. African wine.  Personally I would go for something like a South African vegetable curry - appropriate with the S. African wine, and with a little bit of spice.

[0] Plastic Wine bottles - what's your view (2014) Adnams Brewery
[1] How Bad are Bananas by Mike Berners-Lee Profile Books Ltd 2010
[2] Carbon  Impact of Bottling Australian Wine in the UK - PET and Glass Bottles  (2008) WRAP
[3] Guidelines to Defra /DECC GHG Conversion Factors for Company Reporting (2012) DEFRA
[4] Tetra Pak v plastic water bottles - which is best for the environment? (2011) Guardian
[5] Plastic bottles for wine - is there a leaching problem www.habitat21.co.uk