I love watching my kombucha as it brews, and watching the pellicle thicken. I wanted to test the hypothesis that the microbial community inside the brew is able to utilise carbon dioxide. I kept on noticing that the cellulose pellicle would continue to thicken even months after initially setting up a fresh brew. Surely the sugar has been used up already? Of course there are other competing hypotheses, but there are relatively simple ways to monitor CO2 using arduino-compatible sensors, so I thought it would be fun to find out. And wouldn't it be cool to be able to make kombucha leather out of thin air?!
This project uses MQ135, DS18B20 and PH4502 sensors to monitor CO2, temperature and pH respectively.
I love how it looks! From the image in the description, among my other ongoing brews the monitored one looks like some kind of Frankenstein's monster.
Everything makes sense when initially set up, however the pH probe drifts very quickly. It matches what a piece of pH paper indicates immediately after it is immersed, but within a few minutes it drifts to read around pH ~1.5. If I recalibrate it, it displays an accurate measurement again but drifts just like before. Unsure if this sensor is appropriate for continuous or long term use.
On the CO2 front, in the mornings the CO2 is very high (thousands of ppm), but in the evening its more normal (400 - 500 ppm). The evening readings appear to be gradually declining. I think it is not perfectly airtight, and the changes in temp with my radiator (behind where my kombuchas are brewed) causes changes in movement of different gases throughout the day.
Will continue to monitor thru this brew but I think it needs a different or better way to measure pH.