How much CO₂ does your brewery actually produce? A guide for mid-sized brewers

If you've ever stood next to a fermentation tank during active fermentation, you've felt it — that subtle, prickly sting at the back of the throat that means CO₂ is in the air around you. What you might not have asked is how much of it is coming out per hour. For a mid-sized brewery the answer is hundreds of tonnes a year. Most of it is vented to atmosphere.

Fermentation CO₂ is one of the biggest waste streams on a typical brewery site by volume. It's also one of the few that's commercially valuable, food-grade with minimal treatment, and almost entirely thrown away. Understanding the numbers is the first step in deciding whether to do something about it.

The basic chemistry, in one paragraph

Alcoholic fermentation is a fixed-ratio reaction. For every kilogram of pure ethanol produced, the yeast emits roughly 0.957 kg of CO₂ — almost exactly one to one by mass. That ratio doesn't change much across beer, wine, cider or spirits wash. It does mean the maths is straightforward: if you know your production volume and ABV, you know your CO₂ output.

A worked example: 100,000 hl beer at 5.3% ABV

Let's take a mid-sized UK brewery producing 100,000 hectolitres of 5.3% ABV beer per year — multi-tank, continuous operation, the kind of scale where in-house capture becomes economic on cost savings alone.

• Total volume: 10,000,000 litres (100,000 hl × 100 L)
• Pure alcohol volume: 530,000 L (10,000,000 × 5.3%)
• Alcohol mass: ~418,000 kg (using ethanol density of 0.789 kg/L)
• CO₂ produced annually: ~400 tonnes (418,000 × 0.957, alcohol to CO2 molar conversion)
• Average CO₂ production rate, year-round across all active tanks: ~46 kg/hr

Four hundred tonnes a year. Almost food-grade out of the tank. Routinely vented.

What about smaller breweries, wineries, and distilleries?

The same logic applies, but the volumes scale. A small 1,000 hl craft brewery produces around 4-5 tonnes per year. A 10,000 hl brewery sits around 40-50 tonnes. A 100,000 hl mid-sized brewery hits 400+ tonnes.

A mid-sized English winery producing 1,000,000 bottles of 12% ABV wine emits around 100 tonnes of CO₂ across harvest — but it's concentrated into a few weeks rather than spread across the year. A small gin distillery using 200,000 L of wash per year emits around 16 tonnes. A mid-sized industrial fermentation operation can easily exceed 1,000 tonnes annually.

The trick is that for breweries, the fermentation cycle is year-round and continuous. For wineries, it's seasonal and concentrated into harvest. For distilleries, it's continuous but the CO₂ is produced before distillation, before the spirit is made — which means many distillers don't even realise it's there.

Why this matters commercially

At 2025-26 UK prices, 400 tonnes of food-grade bulk CO₂ costs somewhere between £120,000 and £240,000 a year — bought back from a supplier whilst you've already produced it on-site, under restrictive long-term contracts which sometimes don’t even guarantee supply, due to geopolitical issues and global supply chain disruption risks. That's a six-figure annual cost against a gas you're literally venting to the atmosphere.

The same 400 tonnes, captured and certified through the EU's CRCF biogenic removal pathway as permanent sequestration, is worth roughly £350 per tonne at current voluntary market pricing — around £140,000 of additional annual revenue. Note that this credit revenue depends on the UK and EU permanent storage infrastructure being operational at scale; that buildout is underway and broadly expected to be commercially mature by around 2030.

Whichever way you look at it, the gas has materially more value sitting in a storage tank on your site than vented to the sky.

Try it on your own numbers

We built a CO₂ production calculator so you can plug in your annual production and ABV and see your number in under a minute. It's the same calculation I just walked through, with no email required.

If your number surprises you — or if it confirms what you already suspected — and you'd like to talk through what on-site capture would look like at your site, get in touch.