CO2 capture during fermentation

As our wine was bubbling away, the COP 26 conference was getting underway and climate change was being discussed everywhere. Alex and I had just been talking about the potential benefits of regenerative agriculture and joking about selling carbon credits, when he said, "Of course, the process of making wine is not carbon neutral." 

Hmmm, I thought. Right. Fermentation gives off CO2 but how much? Certainly, 4 demijohns aren't going to break the bank and we can absorb the CO2 created with the sequestration of carbon on our land. We'll plant another tree or ten. 

And then I saw an article today that one winery has started capturing and storing the carbon from fermentation tanks. God, are we on the cusp of something pretty amazing! The technology exists and is being applied to brewing beer, where the carbon can just be put back into the liquid for carbonation. So it can be adapted to winemaking as well. And now it has been.

The Trefethen Family Vineyard has adopted carbon capture technology and is conducting an experiment to see how it works in winemaking. Earthly Labs' "CiCi" is a carbon capture system designed specifically for brewing. It captures CO2 from fermentation, transforms it into a liquid, purifies it and stores it for reuse. This is the first winery using this system. Other wineries use other systems. 

Although winemaking doesn't involve huge volumes of CO2, the pollutant-free CO2 that is produced forms in a way that makes capture pretty easy. Apparently, every year, someone in a winery dies of asphyxiation so there are safety reasons for removing the CO2 as well. Capturing, removing and storing or selling the CO2 could turn winemaking into a negative emissions industry. 

So many people are experimenting with sustainability issues, that a nonprofit called Port Protocol has been formed to keep track of initiatives. Visit the Porto Protocol website for practical content on all subjects related to climate solutions and sustainability in viticulture and vinification. 

Smart Viticulture is a very interesting consulting firm that is a member of the Porto Protocol. 

Correcting the sugar content

Looks like we messed up. 

Our red must has tested at just over 1.008 on the hydrometer and 5 on the Brix scale. That won't get us to the right alcohol content - too low. We should have added sugar to the must at the first stage but we didn't.

When making wine, the Start Gravity should be 1.070 (normal finished ABV will be 10.5%) to 1.090 (normal finished ABV will be 13%). Finish Gravity should be 0.990 (for dry wines) to 1.005 (for sweet wines).

Alex made a simple sugar syrup dissolving sugar in boiled water. We have to wait for it to cool to room temperature. 

Now we have to figure out how much syrup to add. Because I had to dilute the sugar solution by half to get the hydrometer to read the SG, the specific gravity of the syrup is 1.110 x 2  or 1.220. 

So to increase the SG to where the potential alcohol would be sufficient, we'd have to add 40 oz sugar per gallon or 2.5 lbs per gallon. That would be 1 l of water or 1.5 l of syrup. (Alex did the maths.)

Just as a note to self:  3 kg water plus 3 kg sugar = 1 demijohn.

So we expanded our two demijohns to three with the sugar syrup and must (stirred to keep the yeast equal) divided equally among the three. I tested the SG of the resulting must and it read SG 1.070. That should get us to over 9% ABV. 

Curiously, I just measured the SG of the Solaris must, and it, too, reads 1.008. Not surprising as it started out at the exact same SG as the Rondo must. So we'll have to repeat the procedure for the white. 

So we have 1.5 l of Solaris must, measured by weight. So if we need 40 oz sugar per 3.78 l above, we need:

40/3.78 = x/1.5 = 15.9 or 16 oz of sugar. We added 16 oz of sugar dissolved in 16 oz of water to the 1.5 l of must and essentially doubled the volume. The SG read 1.082, a little higher than the red but perfectly fine. 

Let's hope we have restarted the fermentation. At least we now have 1/3 more wine to bottle. 

Here are 10 more things that can go wrong in fermentation. 

https://www.brewersfriend.com/abv-calculator/ 

The second stage

We racked the wine into the demijohn and corked it with the oyster farm cork with fermentation airlock. It smelled very good and Alex said he tasted it yesterday and it was good. But the specific gravity was 1.02 so we have a little ways to go to get to 0.99. It might be just a little cool in the pantry area. It will remain there for about two weeks before stabilizing. 

There is not much more to this stage so we'll just wait and hope it continues to ferment a little more. Meanwhile, the remaining grapes, those that were way behind ripening, are not ready to pick and eat. 

Making the wine

Lovely morning but heavy rain due all afternoon

I've been reading up about how to make wine at home. Unfortunately, none of the descriptions covers our situation so we have had to punt. We mashed the grapes by hand and with a sterilized wooden meat tenderizer. That worked reasonably well. For ten days, the grapes have fermented. Alex stirred daily and the bubbling going through the fermentation airlock was at times scary and loud but very satisfying. 

I bought yeast and Campden tablets. But how to extract the liquid from the vat after the first fermentation? Alex decided my muslin bag for making apple jelly was just the thing. Well in no book have I seen this, but it's worth a try. We found a nice demijohn at Ross House and cleaned it up. It looked like it hadn't been used in 30 years. Full of dead bugs and spiders. But it cleaned up beautifully and I sterilized it with the stuff that came with the winemaking kit. 

Alex found some predrilled stoppers from his old oyster growing days and they happened to fit the demijohn and the airlocks perfectly. Stage 2 would be completed without additional expenditure. And as the final steps of stabilising the wine won't be necessary -- we're going to have maybe 2 bottles if we're lucky -- we should be bottling on about a week. I'll report the specific gravity in the next post after we've measured it. 

BTW, YouTube has loads of useful how-to videos:  https://youtu.be/n7tauROWh0Y  

So what's next in making our wine

Hydrometer suspended in grape juice

The wine must has to ferment for about 2 weeks in the first stage. When fermentation stops, you have to test the specific gravity. When making wine, the Start Gravity should be 1.070 (normal finished ABV will be 10.5%) to 1.090 (normal finished ABV will be 13%). Finish Gravity should be 0.990 (for dry wines) to 1.005 (for sweet wines). 

I've seen many recommend that wine should be fermented down to dryness. If you like a sweeter wine, you can then add sugar or grape juice at the end to reach your preferred sweetness. It is a dangerous business stopping the fermentation early. 

So the hydrometer is probably the most essential piece of equipment to make wine with success. I've ordered a spare as I can imagine that it's pretty easy to break. I've also read about how to read the hydrometer properly. You have to make sure your hydrometer is floating freely and not stuck against the cylinder. You read at the bottom of the meniscus not the top (I remember that from chem class). It measures the Specific Gravity (SG) of the liquid being fermented. This will then in turn give you a guide to the Alcohol by Volume (ABV) you will be able to produce. The hydrometer is used throughout the fermentation to ensure sugar is being converted into alcohol. As more sugar is converted to alcohol, the SG will fall.

The Alcohol by Volume (ABV) is calculated by subtracting the start gravity from the finish gravity and dividing this figure by 7.362. For example, the starting point for our wine is 1.100 and if this ferments down to 0.990, the drop will be 110 points. This divided by 7.362 is 14.94% ABV. That should kick a punch. 

You have to make certain the fermentation is complete and stopped at the right time. Sometimes fermentation slows down or stops too early. A stuck fermentation is one that falls short of reaching the expected final gravity, and as with many things brewing, the term is relative. A wine that stops at 1.000 probably suffers more from poor instrument calibration than it does from stuck yeast. A 1.100 wine that stops at 1.045, though, still has a way to go and needs some help.

There are tricks that one can use to restart the fermentation process. One is temperature. If the hydrometer is placed in water at 20°C, it will read 1.000.  Most people only use the hydrometer as a guide but if you want to be really accurate then this should be done with a liquid temperature of 20°C. If the liquid is 5°C higher then add 0.001 and similarly if its 5°C lower then delete 0.001.

Warming up the must is probably the most reliable way to restart a stalled fermentation. Some yeast strains are more temperature-sensitive than others and may require some warmth to complete the job. Some strain are famous for refusing to budge until they are warmed as high as 95°F (35°C). Some British yeasts are stubbornly flocculent; it’s worth giving the must a good swirl a couple of times a day just to keep the yeast cells in suspension until they’re done.

Licenses & fees

We're not ready to make wines yet, but the time may come this year when we may actually have a crop of grapes to try fermentation. We decided that if we didn't succeed in making wine, we'd go the distillation route to an eau de vie or vodka. So I have begun my research into what it would take.

It is illegal to distill for home use in Ireland. It is illegal to distill without a licence regardless of whether you intend to sell it or not. Plain and simple. In several other countries you apparently can but not in Ireland. Unless you use brewing vodka kits, with no distillation. There are robust yeasts that can get quite high alcohol concentration without distillation. These are just neutral wines which are treated with carbon to reduce smell and taste. Alcohol can be tax relieved in the case of wine, beer or other fermented beverage produced at home for personal use and not for sale, but it must be authorized by Revenue.