It’s not as simple as that… 

Sustainability.  How many times do you hear this word thrown around? Nothing is completely sustainable, it is a destination that is only approached. But almost any aspect of this subject is fraught with problems and the deeper you delve, the trickier it gets.  

I was on a big zoom meeting today that was discussing an important initiative in the UK to introduce restrictions on wine producers whose bottles are too heavy. Heavy glass is bad; that is a simple and true statement when it comes to wine bottles, but as more and more questions were being asked I found myself having to type replies starting with ‘It’s not that simple…’ So, lets unpick the layers of this example because they are a good example of how tricky it all gets. 

First, this is important. Glass is one of the biggest carbon costs, sometimes THE biggest, any winery has.

Lighter is better, but we have to consider what the bottle is made of as well. Recycled glass uses much less energy to melt than the energy to make new glass, which also is using materials which are running out and have environmental problems of their own. In carbon terms a bottle made from 80% recycled glass (which is a good, but achievable figure) roughly halves the carbon cost of making the bottle compared to one made from new glass. 

The fuel used to power the glass furnace is where the carbon cost mainly comes from, so being able to use zero carbon fuel would be ideal. But once a glass furnace is built and started it can never be allowed to cool: to do so would destroy it! So changing the fuel used to power a furnace without it cooling is a major technical challenge. I know of people researching this right now, but the most likely solution is to change the fuel when an old furnace is decommissioned and replaced, a once in about 15 year occurrence. Electric furnaces have a number of challenges, so it may be that a hybrid electric / gas furnace might be the best solution. Using renewable gas such as bio-methane may be a close to ideal solution, if a source can be identified. Hydrogen technologies are likely to be quite a long way away.

Then there is where the bottle is made. It is best if it is as close as possible to the bottling location. A surprisingly high percentage of bottles, even in New Zealand, come from China, so making a bottle of wine in New Zealand using a Chinese bottle sent to the winery, then exporting it back to Hong Kong (or anywhere else) is not a good thing! But not many people have a bottle manufacturer just up the road. Ours is in Auckland, the only bottle manufacturer in NZ, so the bottles have to come from there. We can cut transportation carbon by getting them sent to a (relatively) local port: Christchurch or Dunedin, by boat, which we do. 

They are very light in weight, 417 grams, so well under the optimal weight chosen by the UK initiative I mentioned (they are targeting 420g by 2026) and we’ve been using them for 9 years now with no problems. We may be able to go lighter still, and are in discussions on this (our manufacturer makes a slightly lighter one in Melbourne, but not in Auckland, but they might be persuaded to try it locally). But 417g gets us down close to the bone already.  They are also typically about 67% recycled, which is a very good figure.

Many have asked us about re-usable bottles. This is good in principle, but almost impossible to work for a winery like ours. A reusable bottle will need to be heavier to be robust enough for many cycles of use, but a large percentage of our wine is cellared by customers for years, so we’d be taking these valuable and heavier bottles and locking them out of use. Reuse is good for milk, which was once the way everywhere, and might work for wines where they are drunk within a few weeks of purchase, then returned properly to be reused. A big supermarket may be able to make such a system work with their own label wines, as they could control the whole cycle, and communicate with the users, but the failure rate in most other cases, would be greater than the potential energy savings. 

So we start with a simple question, is a lighter bottle better? That is where the sustainability maze takes us. (Actually this is just part of the maze, we haven’t even looked at alternative materials).  Almost any sustainability question has a similar complexity behind it. There is one thing you can be sure of: anybody who throws this word around casually is not to be trusted. Any claim needs to be quantified, with proper analysis of the detail. Anything less is just… well just not sustainable.