Algae Bioreactor

With my failed algae containers from my previous post, I needed a more permanent place for my algae culture.  I decided two liter bottle sitting in the recycling would be perfect for this purpose!  While the algae probably would have been fine if I just poured it into the bottle with more water, I wanted a more permanent installation since I had already gone through the trouble of growing the stuff and it might be a while before I think of a new use for it.  As I mentioned previously, the problem with large containers of algae is that the CO2 that the algae feeds off of needs to be dissolved in the water somehow, and the smaller the surface area of the water, the less CO2 there would be.  With that in mind, I ended up buying an aquarium pump, tubingairstones, and more algae food.2015-07-07 19.32.41

The first step for setting up the reactor was cutting a hole in the soda cap to pass the air tubing through, in addition to two smaller holes to let the stale air escape.2015-07-07 19.35.36

Next was setting up the pump, tubing and attaching the airstone after running the tubing through the cap
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I tried to measure out enough tubing beneath the cap so that the airstone was resting on the bottom of the bottle.  Over time the algae sinks in a static solution so having the airstone at the bottom creates enough turbulence to prevent the algae from settling to the bottom of the container.  The more spread out the algae is in the water, the more uniform the green color will be.
2015-07-07 19.38.51And the final setup!  Everything ran fine so the only thing left to do was wait for the algae to replicate enough to take advantage of the space in the new container.

2015-07-17 19.58.28And here’s the setup about a week later.  This algae grows fast!

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Carbon Sequestering Sculptures

I recently realized that I wasn’t taking full advantage of how the Maker community has expanded over the past few years and the fact that there are tons of DIY contests running all the time.  After browsing around a bit, I decided that I wanted to try to enter the Instructables 3D Printing Contest.

I wanted to create an entry that was simple, didn’t require any custom parts/electronics aside from the 3D printed pieces, and was a little outside my current knowledge base.  With those criteria in mind I decided try to combine my interests in 3D printing, environmentalism, and carbon sequestration technologies.  Since ugliness is an argument often used against wind turbines and other green tech, I wanted to try and create something both pleasant to look at and beneficial to the environment.  I ended up trying to design a sculpture that also sequestered atmospheric carbon (CO2) using cyanobacteria.

Since I already had some transparent PLA filament lying around, I designed a simple, hollow sculpture with thin walls (~.5mm) to maintain a high transparency in order to let the rich green color of the algae show through and provide the algae with enough sunlight to live off of.

twist
An OpenSCAD rendering of a simple hollow sculpture.

Since the algae feed off CO2 from the air, the container couldn’t be too deep or too narrow, otherwise the algae at the bottom wouldn’t receive enough air and would die off.  This could be solved by buying an aquarium air bubbler, but I wanted to keep the project as simple as possible.

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For the algae, I decided to use Spirulina because I found a handy growing kit for it.  The kit arrived in the mail, I followed the instructions, and soon I had my very own algae cluster growing!

Printed simple sculpture
Printed simple sculpture

With the algae ready for transplantation I printed out my sculpture/container design.  Once the sculpture was printed, however, I started running into problems.  It seems that when the walls of the container are thin enough to remain mostly transparent, they’re also too thin to be waterproof!  After filling up the container (luckily I tested it with tap water first), little droplets immediately started seeping through the gaps between the print layers.

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In an attempt to compensate for this, I tried using a transparent coating to seal up the holes but maintain transparency, but as is visible in the above photo, with the 3-5 coats necessary to prevent leaking, the sculpture was more opaque than I would have liked.

So while the project ultimately didn’t pan out, I learned some useful things about 3D printing:

  • PLA is difficult, if not impossible, to waterproof
  • Transparent filament isn’t actually that transparent using FDM printers, though it would be good for light diffusion

And I got to go a little more outside my comfort zone and learn some things about algae and biological processes.