Cans or glass: which emits less CO₂?
Two formats, two atmospheres and one simple question: which is the best choice for the climate?
At Smile, we do both: cans and glass bottles. And like many, we long assumed that glass was automatically more environmentally friendly, more recyclable, more natural, etc.
Except that when we calculated our carbon footprint in 2024, we realized that our biggest source of emissions was our packaging, specifically our glass bottles. Not because glass is bad, but because in our current operations, it is single-use. That's why we decided to develop the can.
Deposit: when glass really makes a difference
There is one crucial point that is often overlooked: glass is only the best choice when the bottle is reused several times through a deposit system. This avoids having to manufacture a new bottle for each purchase.
And there is a simple rule of thumb that often applies: after four uses, returnable glass generally becomes more advantageous than single-use glass. (1) This gain depends on various factors: a good return rate, reasonable distances (collection/washing/recirculation), optimized washing, and bottles that are not too heavy. (2)
However, at our current scale, our bottles are non-returnable. We would obviously like to set up a deposit loop, but this requires volume, a return network, storage, washing, etc., and we are still too small to do this (we are trusting you to make it happen!).
So the real comparison for Smile is mainly: cans vs single-use glass.
The weight of glass (really) counts in CO₂ emissions
In most life cycle assessments (LCAs), it is the weight of the packaging that has a significant impact on the final result, particularly due to transport. (3) And here, with our Smile measurements, it is very clear:
- A single-use glass bottle (330 ml) weighs 158 g (empty)
- A can (330 ml) weighs 10.5 g (empty)
Simple calculation: for the same product, you transport 158 − 10.5 = 147.5 g more material per unit when you choose glass over cans.
For 1,000 units, that's 147.5 kg of extra weight to move. And this impact is even greater when you have to deliver fresh goods, make small deliveries and make multiple stops in the city. (3)
Single-use: why does the can often have the advantage?
When comparing packaging from a ‘single-use + recycling’ perspective, the conclusion is often the same: non-returnable glass is among the highest emitters. (4) The Carbon Trust report also shows that ‘one-way glass’ has one of the highest carbon footprints (5).
Why? Firstly, because recycling does not change the weight (transport remains heavy). Secondly, because glass is a very energy-intensive industry: remelting glass requires furnaces at 1,500°C. (6) In single-use applications, this energy must be put back into the machine for each new bottle produced.
At Smile: why we offer both formats
At Smile, we keep both cans and glass bottles because, quite simply, uses and preferences vary.
- The can (25cl) is our most CO₂-friendly single-use option and the most practical for everyday use (transport, refrigeration, events, hospitality, fridges). It's also perfect for on the go: easy to carry, sturdy, etc.
- We also keep the glass bottle (33cl) for a very ‘Smile’ reason: transparency. We are proud of our product and we like it to be seen: the color, the life of kombucha, etc. And then, for some cafés and points of sale, the bottle has a more ‘table’ and aesthetic aspect. And as our bottles are always kept cool, the fact that they are transparent is not a concern from a UV point of view.
And we prefer to be transparent all the way: our bottles are not returnable at present. So in our case, glass remains mainly single-use, and it is not the most low-carbon option. This is exactly why the can has become so important to us: it is currently the best compromise between CO₂ impact, practicality and accessibility.
Disclaimer:
This article is based on life cycle assessment data and published carbon footprint studies. The numbers are real, the conclusions are ours. Carbon accounting is a complex science and results vary depending on methodology, geography and scale. We did our best to be accurate and honest. If you spot an error, we genuinely want to know.
Sources:
(1) ADEME – Observatoire du réemploi et de la réutilisation. (s. d.). Le réemploi des emballages (repère : “dès 4 utilisations…”).
https://observatoire-reemploi-reutilisation.ademe.fr/emballages
(2) ADEME. (2023, 29 juin). Évaluation environnementale de la consigne pour le réemploi des emballages en verre en France (Volet A / Volet B + compléments). Librairie ADEME.
(3) Pasqualino, J., Meneses, M., & Castells, F. (2011). The carbon footprint and energy consumption of beverage packaging selection and disposal. Journal of Food Engineering, 103(4), 357–365.
https://www.sciencedirect.com/science/article/abs/pii/S026087741000542X
(4) Barrow, M., Pernstich, P., & Cumberlege, T. (2021). Carbon footprint of soft drinks packaging: A comparative analysis. The Carbon Trust.
(5) International Aluminium Institute. (2024). Comparing the carbon footprints of beverage containers (factsheet).
(6) ScienceDirect Topics. (s. d.). Glass melting (température de fusion typique ~1500°C).
https://www.sciencedirect.com/topics/materials-science/glass-melting
