Creating a solar-powered, no running cost, algae bioreactor.
Step 1: Finished bioreactor
I apologize for not getting any pictures during construction of my solar-powered algae bioreactor, but I only decided to make an instructable out of it after the fact. There are many diy's about making biodiesel out of oil, and algae has been discussed far and wide as a great source of vegetable oil for conversion. However, I've only seen a few homebrew solutions for actually GROWING the algae. There's a great one here on instructables, but it uses CO2 bottles to provide the algae with the carbon dioxide which they need to grow. As a proof of concept that's fine, but I don't think it makes any sense in the long run -- bottled CO2 is probably more expensive both cash-wise and environmentally than the algae grown from it. There's CO2 available in the air, but only a flat, shallow pool of water has adequate surface area to absorb enough CO2 for algae growth. Here's my solution: a solar-powered small aquarium air pump, which aerates the water inside a five-gallon water bottle. Notice that the water is cloudy after only a couple of days; that's the algae starting to grow. If you look closely you can clearly see the air bubbles which prove that the air pump is still running; the sun has set on the system in this early-evening shot, but the rechargeable batteries are keeping the pump running.