Quinta do Portal – Reuse of carbon dioxide from fermentation




During the winemaking process we have the need to use CO2, mainly in the pre and post fermentative phases. When we sometimes have a wine in need of protection, we have another wine next to it that spills tons of CO2 into the atmosphere. The feeling of inability to move a little carbon from one vat to the other with our hands, combined with the ease of using carbon trapped in a pressure bottle, often leads us to choose the most comfortable solution. Unless you are present and feel that you should not interfere too much with something external and strange. And in doing so, try to use what you have around! The first thing you should feel is to use your hands to solve the problem.  If you don’t feel that your hands are the most efficient solution in the literal sense… we have to move to the metaphorical sense.

PROJECT STARTING DATE: 2006 harvest seasonENDING DATEon going


Our goal is to recover an element in its pure state that is wasted and make it useful and necessary in the process.




It is a philosophy that we are learning and giving more and more importance. The solution is sometimes under our noses, we have to pay attention and look. Another maxim is to look for the solution in the surroundings, this also includes resorting to partners, or solutions that are closer to us. Give preference to proximity!


Analysis of carbon dioxide supply vats:

Any vat in fermentation can be a supplier, but given the possibility of choosing, we will leave aside those that may have some oxygen difficulty. Those are the ones macerating with solids, usually with higher temperatures, because we have to close the vat!

It is preferable to choose a tank that will be fermented at a lower temperature (14-17ºC) and that is healthy at the time. And this is easy to check. They are the ones that are aromatically clean and with fresh aroma, if we are speaking of of whites and rosés’ fermentations that are in full fermentation process. Once chosen we have the solution for one week, since it is a slow fermentation.

Analysis of carbon dioxide receptor vats:

Let’s eliminate the ones where we want to use a particular commercial yeast. As we are increasingly moving away from this solution, it is easy for us.

We will select the ones that need some protection until it can supply its own CO2. An excellent example is the case of fermentations in open tanks. The same area of ​​contact between the solids and the liquid good for the extraction is the same area that the solids have with the outside of the fermentation. This is the case of Port and Douro reds fermentations in open vats such as the case of Lagares.

We will select those that after fermentation need to be in contact with the fermenting solids for a longer time and need protection as they are no longer able to produce enough CO2. It is the example of Douro reds fermentations in open tanks.

We can select red or white closed vats in the pre fermentative stage. And instead of accepting a stealth contamination from the cellar, we can make a contamination by yeast we know is working in a healthy way.

In this case, we do not need to use it in the post-fermentation phase, as it can produce enough CO2 for that phase, as long as … the vat is closed in time!


So what is the procedure after selecting the supply and receiver vat?

All closed vats have a lid! Just put an outlet on the lid where we can then connect a flexible hose. Closing the fermenting vat does not cause any problem as long as it is done consciously. Nobody can imprison a fermentation! The consequence of such attempt is the creation of an authentic bomb. We have to assure that the outlet is free of any tap to prevent anyone from inadvertently closing it!

After closing and if the tank has a measuring scale, we will have to close the tap that allows measuring the volume of the tank. The pressure inside the vat is sufficient to raise the must on the scale and pour it over the top of the vat.

Then it is only necessary to, from time to time to taste the wine, and when detected any flavors, interrupt the process and supply oxygen to that vat.

Like this it’s easy to send the carbon to the receiving tank afterwards. In the case of an open vat, simply place the tube at its center on top of the solids. In the case of a closed vat and without maceration, just place the tube on top of the vat, which, being the CO2 heaviest than O2, soon takes its place at the top of the must.


Fermentative safety is guaranteed as long as we are aware of the risks. The cost gains … we didn’t compare because we started using something that, since it is free, we use it indiscriminately. We use it even in situations that normally wouldn’t use CO2!


This is a project that requires internal company sponsorship and support.  Consistent attention is critical for our hives, and we need to ensure we have appropriately educated employees to continue to maintain these critical hives.


we cannot imagine connecting a fermentation vat to a gas network in the cellar, due to the risks of its inadvertent use.

But it would be interesting to be able to filter this air and thus be able to use it in more areas, namely in the pressing zone!


Replicating this method is as you can see, very simple … just get your hands on it! And have common sense.

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