What I want to do
I wanted to build out an air remediation plant for my home by following the activity instructions pretty closely for my first attempt.
My attempt and results
Build date: August 13th, 2016
- One snake plant (Sansevieria trifasciata) $20
- 42L Large bag of Growstone $28
- 624g Marineland activated carbon $13
- 1 Whisper 10 $7
- 1 Hose & Diffuser $4-6?
- Planter $10
This build was more expensive than it had to be. I think I overspent on the plant and alternatively I could have gone with a smaller one or been really patient and used cuttings. The pot was an aesthetic choice, but plastic still. I could have shaved a bit off there. The growstone was more intentionally overbought because I wanted to use it again. I didn't use very much of it for this build. The carbon was about half used.
Here you can see the hose interface I chose. I put the valve near the base and epoxied into a hole I drilled into the pot. I felt like that might be more reliable than trying to seal a flexible hose. The epoxy was probably not an ideal plastic bond.
I presoaked the growstone and carbon. They were difficult to mix because of the porisity of the growstone, and density of the carbon. I was worried the carbon would all go to the bottom, so as I scooped the stone in I alternated to try to get a good mixture.
I'm not very good with plants yet, after I got done I thought I probably killed it by exposing too much of the plant. (which is why I decided to tear it down tonight)
I used a timer to adjust the air, I wanted to be able to give it a few weeks with only half hour, and then stagger the increase in airflow.
I drilled a hole in it to keep the water from going over where I thought the air intake diffuser was situated about halfway up the planter. This was poorly thought out on my part because 1) I didn't know exactly where the intake was and 2) I don't know when I'm about to overfill, and usually it goes everywhere
Teardown After 7 Weeks Oct 7th
I decided to tear the plant all the way down to be able to look for root growth and weigh different parts of the planter (carbon vs growstone vs plant vs unabsorbed water). For airflow it has been 1 week of no airflow, then 3 weeks w/ 1 period (24h apart), and finally 3 weeks w/ 2 periods (12h apart). A period on the timer is 30 minutes.
I wanted to also see if I had killed the plant and it was just lying to me by being so pretty on top.
Some interesting things.
Here is the difference between a two growstones in close proximity to the root (pictured at bottom) and on top of the planter (top). The stones near the roots and carbon were quite moist, even though it was well above the waterline defined by the hole in the bucket.
The carbon didn't all wash down even through weeks of intermittent watering. Also I saw what I was hoping to see: root growth right through one of the carbon veins.
After I saw that I lost the heart to tear it all the way down to get the component weights and see how much carbon sits at the bottom in the water. I saw a lot of active root growth and shoots coming up too, so I think maybe the plant will make it.
Questions and next steps
What if we used a flour or starch based glue to attach carbon nodules directly to roots? Would that VOC sink being so close be beneficial to the plant & bacterial colonies?
How much carbon is enough? How do we optimize the location? (not too high or it misses the roots, not too low or it is below the airflow area/submerged)
How much is moving air through activated carbon cheating re: formaldehyde remediation? AKA how can we know how effective the plant is if the activated carbon is so effective at removing VOC's in the short term? I believe the plant is ultimately involved, but after reading through all the peer reviewed articles I can find, I don't see any direct test of plant-managed bacteria colonies removing stored VOC's from activated carbon. The closest test involved plants that were tested over a 6 month period and got better (presumably more and more specialized bacteria) at eating formaldehyde. I'd like to try to come up with a test for this. I'm working on an experiment design with my brother who is a chemist familiar with VOC test techniques.
When do I add liquid plant food? :-)
Next step for the plant tests for me is:
- Try to miniaturize some of the parts, re: replacing the pump with a 5v fan that can be run w/ all of those USB dc converters for old cell phones we all have lying around.
- Find an affordable self-watering planter with a water indicator
- Try a couple of different plants (small bella palm and small spider plant are next).
- Try to propose a combination of the first two bullets for a kickstarter perhaps.
Why I'm interested
I like clean air. I have a bathroom with some exposed particle board. I think it stinks. I'd like to see people live with more plants.
One of the things the author of the original studies funded by NASA found was that homes with plants had higher humidity, which is normally associated with mold growth but tropical plants give off anti mold VOCs of their own as a defense mechanism.
These kind of home human-plant symbiosis findings amaze me.