Coffee Troupe

Roasted by Rich Helms

Surprise Roasted Coffee Bean Degassing Discovery

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Posted by Rich on December 10, 2011 at 2:32 pm

Degas 3 Setup

The degassing experiment three was drawing to a close. To recap 100 grams of dark roasted beans were put in one flask, 100 grams of the same beans but ground were put in the other flask. After 24 hours 294 mls of CO2 were released from the ground coffee. Even after 3 days the ground coffee maxed out at 300 mls supporting the literature (1) that ground coffee degasses in 12-24 hours depending on grind.

The whole beans were a different story. The 130 ml of day one grew to 290 mls in nine days. The literature said about 7 days for most degassing. I was getting ready to clean up the experiment when I had an idea. Just for “shits and giggles” why not grind the nine day old beans. They had stopped releasing CO2 but was there any inside that grinding would release? Using the same grinder settings as previous experiments I ground the 100 grams and quickly returned to the flask and stoppered. I was surprised to see gas released with a similar curve to freshly roasted coffee.

In one day 112 mls of CO2 were released. Like fresh roast beans almost all of the release was in the first 24 hours. While only 38% of what a fresh roast grind release, the total release was 406 mls versus 296 for fresh ground.

Grind Nine Day Old Beans

I have not found any literature on CO2 degassing in older coffee. I am going to continue other degassing experiments to open up the parameters of cause/effect.

My color spectrometer has not arrived yet. Really looking forward to experimenting with it.


  1. Development of an apparatus for measuring the degassing behavior of coffee with the option to examine the influence of protective gases for aroma preservation : KOZIOROWSKI, Thomas; BAUMEISTER, Heinrich; JANSEN, Gerhard; BONGERS, Sandra; PROBAT-WERKE, Emmerich, Germany – Probat
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  • On May 7, 2013 at 12:20 am Robert Suntay said

    Thank you for the info. Also looking forward to your next experiments.

  • On November 6, 2013 at 3:54 am Amelia said

    Thank you for the info! The first time I’ve heard of degassing coffee was in a meeting a couple of weeks ago. We were preparing french presses of course ground coffee and learned a new method. Have you experimented with hot water? Actually preparing the coffee to see what kind of co2 levels are then released? I would love to know! Thanks!

    • On November 6, 2013 at 12:41 pm RichHelms said


      When I measure CO2 escaping from coffee it is the only gas being released. When coffee is added to hot water, the water is also releasing steam. I will have to think on that one. An interesting problem. I have not seen any experiments that look at CO2 release during brewing. Thanks

  • On April 9, 2014 at 11:11 am Leandro Soares de Oliveira said

    Dear Rich Helms, I read your comments and evaluations about the degassing of coffee. I have been working with coffee for quite sometime and have a few comments on your experiments. When you grind the coffee, there will be a major loss of CO2 during this process, for the macrostructure of the bean is being broken (the whole bean holds CO2 up to an internal pressure of 6 atm after roasting) . Thus, this partially explains the differences between the volumes of CO2 when degassing the ground and whole beans. Thus, a solution to that problem would be grinding the coffee together with dry ice (which is basically solid CO2) in a way that the temperature would drop in such a way not to allow the escape of the CO2 during grinding. The grinding would release the CO2 from the dry ice and keep the CO2 of the bean in the bean. Ideally, liquid nitrogen should be used to guarantee no release of CO2 during grinding. Also, the amount of CO2 in a bean will vary with the degree of roast and this should be considered when comparing different tryouts with different roast batches.
    Anyway, qualitatively, your experiments are simple but effective.
    Leandro Oliveira

    • On April 9, 2014 at 11:26 am RichHelms said


      I am aware of the loss of CO2 during grinding. I have been working on a new experiment to measure the CO2 loss during grinding. This has turned out to be a far more complicated measurement.

      In this case I had assumed that the whole beans once degassed were done. What I realized in this experiment was that much CO2 was still trapped in the beans and that grinding would release it and permit more to escape from the ground coffee.

      • On April 7, 2016 at 7:54 pm Ryan Lenz said

        Loving this site and this experiment–good on you.

        What about a relatively simple solution–simply sealing your grinder (perhaps a blender?) and collecting the gas directly out of it? A rough version would just be a tube glued into the lid of the a blender. You’d probably have to sacrifice the blender as you’d need to seal it off completely, but blenders can be had cheap enough….

        • On April 7, 2016 at 8:08 pm Rich Helms said

          Grinders are not closed systems. I had thought about a blade grinder which would be easiest to seal the top but the shaft for the blade is not sealed. It is a thought though. I may examine my blade grinder more

  • On June 1, 2014 at 7:01 pm Germain Nolet said

    Hi RichHelms,

    Your experiment on degassing was pretty interesting to read!

    I also suggest that you check the Carbon monoxide generation during the process!

    Keep up your good work.