An Algae Bioreactor From Recycled Water Bottles

In this instructable, we describe how to build a photo-bioreactor that uses algae to convert carbon dioxide and sunlight into energy. The energy that is produced is in the form of algae biomass. The photo-bioreactor is built from plastic recycled water bottles. By designing the apparatus to be compartmentalized, we are able to do many experiments in parallel.

Michael Fischer
mfischer @t stanford.edu

By using algae as a biofuel, we can increase the world's supply of oil while at the same time we decrease the amount of atmospheric carbon dioxide used during its production. The resulting product is a sustainable biofuel whose carbon footprint is neutral inasmuch as the CO2 produced on consumption is essentially balanced by the CO2 used in its production. In this instructable, we first make the carbon dioxide delivery system, then mount the water bottles on a rack, and then inoculate the bottles with algae. After letting the algae grow for a week, we extract the biomass.

Step 1: Make Carbon Dioxide Delivery System

To make the carbon dioxide delivery system, connect an eight port sprinkler system manifold to a one inch long PVC pipe. To get good seals, use Teflon tape to tape the threads before attaching the pieces together. Next, attach the one inch pipe to a T-connector. Block off one end of the T-connector and attach the other end to a foot long PVC pipe.

Step 2: Attach Tubing to Manifold

For each manifold, cut eight-pieces of flexible tubing and connect each piece to a port of the manifold. The manifold that I am using has a dial on each port to control the rate of flow. Make sure all the ports that you use are open and allow approximately the same amount of carbon dioxide to flow through the port.

Step 3: Mount Carbon Dioxide System

Mount the air system to a metal rack using zip ties. Attach the air system to a tank of carbon dioxide.

Step 4: Mount Water Bottles

Hot glue the water bottles to the metal rack.

Step 5: Make Algae Media

We next make the medium to grow the algae. Although there are many possible mediums, a standard garden store fertilizer contains all the nitrogen and nutrients that the algae need.

Step 6: Media Inoculation

A good source of algae is pond algae, if available. If not, there are a large number of online vendors that sell batches of algae. To inoculate the culture, measure out a fixed amount of algae and add it to the growth medium.

Step 7: Growth and Harvesting

After several days of sunlight and CO2 exposure, the algae are much denser. A French press is then used to extract the algae from the solution. The biomass of the dried algae can then be used as a fuel. As a by-product of this process, a large amount of atmospheric CO2 is sequestered.

By: Michael Fischer, Stanford University, mfischer @t stanford.edu