DIY Algae Bioreactor from Recycled Water Bottles

Lessen your carbon footprint by building this DIY algae bioreactor capable of producing its own biofuel.

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by Flickr/deckerme

Do It Yourself Projects to Get You Off the Grid (Skyhorse Publishing, 2018) is illustrated with dozens of full-color photographs per project accompanying easy-to-follow instructions. This Instructables collection utilizes the best that the online community has to offer, turning a far-reaching group of people into a mammoth database churning out ideas to make life better, easier, and, in this case, greener, as this volume exemplifies. Twenty Instructables illustrate just how simple it can be to make your own backyard chicken coop, or turn a wine barrel into a rainwater collector.

You can purchase this book from the Mother Earth News store: Do It Yourself Projects to Get You Off the Grid.


plastic water bottles lined up on metal shelves with tubes leading to them filled with green liquid

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. 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

1. To make the carbon dioxide delivery system, connect an eight-port sprinkler system manifold to a 1″ long PVC pipe.

white pvc T joint, a piece of black pvc pipe, a roll of tape on a red plastic holder, two small plastic round pieces, and a round black device with green ports on four sides

2. To get good seals, use Teflon tape to tape the threads before attaching the pieces together.

3. Next, attach the 1″ pipe to a T-connector. Block off one end of the T-connector and attach the other end to 1′ long PVC pipe.

white t-connector with the left side blocked off, the right side connected to a black pipe, and the top connected to the mainfold

Step 2: Attach Tubing to Manifold

1. 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.

t-connector and manifold connected to clear plastic tubing laid out

2. 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

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

two manifolds with tubing coming out of them attached to pipe zip tied to a metal rack

Step 4: Mount Water Bottles

1. Hot glue the water bottles to the metal rack.

person holding a water bottle angled and a red glue gun underneath putting hot glue on a bar of a metal rack
plastic bottles lined up along a metal rack

Step 5: Make Algae Media

1. 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.

person holding a pink spoon topping it in to a gallon jug of water

Step 6: Media Inoculation

1. 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.

2. To inoculate the culture, measure out a fixed amount of algae and add it to the growth medium.

plastic bottles lined up on a metal rack with one on the far right having green liquid and the rest having clear water inside
line of plastic water bottles on metal rack with a funnel in one
person holding a plastic tube to a small glass dish of dark green liquid with liquid filling the tube
three rows of plastic water bottles filled with green liquid with tubes coming out of all of them leading to manifolds

Step 7: Growth and Harvesting

1. After several days of sunlight and CO2 exposure, the algae are much denser.

2. A French press is then used to extract the algae from the solution.

french press with glass pouring spout and black handles sitting on a tile counter

3. The biomass of the dried algae can then be used as a fuel.

inside of a french press compressor with the underside covered in dark green algae being held over a sink

4. As a by-product of this process, a large amount of atmospheric CO2 is sequestered.

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From Do It Yourself Projects to Get You Off the Grid by Instructables.com (Skyhorse Publishing, 2018) Copyright Skyhorse Publishing. All rights reserved. Used by permission of Skyhorse Publishing.

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DIY Projects Off the Grid

In this inspiring book, readers can enjoy a focused series of projects designed to get you thinking creatively about going green. Do-It-Yourself Projects to Get You Off the Grid illustrates just how simple it can be to make your own backyard chicken coop, or turn a wine barrel into a rainwater collector. Including dozens of full-color photographs per project accompanying easy-to-follow instructions, this collection utilizes the best that the online community has to offer, turning a far-reaching group of people into a mammoth database churning out ideas to make life better, easier, and, in this case, greener, as this volume exemplifies. Order from the Mother Earth News Store or by calling 800-234-3368.