In this instructable we will go over how to construct an at-home version of a photo-bioreactor which will use solar energy and artificial lighting with carbon dioxide to produce algae biomass.
The aim of this project is to create an model which harbors an ecosystem fit to help us escape a fossil fuel economy. We are in an era that is experiencing a shift from humanity trying to dominate nature, to then trying to preserve parts of nature and now trying to reach a reconciliation with nature. This is the algae experiment; an idea that is trying to move away from a linear wasteful and polluting way of using resources to a closed loop system where all resources are kept in a closed loop cycle.
Check it out working.
Follow the possibilities of harvesting algae for fuel & see the difficulties met along this journey on-line at
a published paper on the subject can be found on
For more info or to get in touch you can reach me at
Step 1: Shape, Size & Materiality
The over all shape of the photo bioreactor is inspired from a previous project I had been working on where it follows a mean summer solar path of the UK. It is meant to be both an educational model but also embody certain architectural elements within allowing it to possibly be viewed as an informational pavilion.
Step 2: The Ribs
I considered using two materials for the support system.
I tried clear acrylic so as not detract from the function, which would be the algae tubes containing the algae. However. having to deal with all the transparencies of the materials made the model seem very confusing.
I needed each rib to consist of two pieces of wood in order to provide a stable ‘leg’ for each segment whilst I would be putting the model together but also to be able to withstand any rocking from pressure the model would experience during the cultivation hours. I ordered 50 M4 grub screws with a cup point and 150 M4 hexagon nuts and got started on the ribs. (M4 denotes the diameter of the screw; 4mm) I spaced the ribs apart 20mm which allowed them to be able to free stand. Together all 5 sets made a very sturdy model base.
Step 3: The Tubes
I wanted to use a closed loop system where the algae would travel constantly and safely without getting contaminated, so using clear acrylic tubes was the best option.
I initially wanted to use 15mm outer diameter tubes with an inner diameter of 12mm in order to carry the water required to grow the algae, as well as to match the pump power (4000 Liters per hour) that I had obtained for a previous model. However I quickly realized that at every return point of each tube there was no silicone or plastic based hose that was flexible enough to bend around to each connection point.
This wasn’t all disappointing as it meant that I could downsize to 12mm outer diameter tubes with an inner diameter of 8mm and save on cost at the same time. Unfortunately even though I moved down to that size, finding a hose which would fit on the outside of the 12mm seemed impossible.
That is when I decided to try to enter the 8mm inner area of the tube; something considered very unconventional and ‘inconvenient’ but to me this was the only option as far as flexibility was concerned with the materials available to me. I found a 8mm outer diameter silicone tube and it fit perfectly inside.
Step 4: How It Came Together
The trouble now was to sort out the frequency and amount of tubes per rib. I needed enough to cover as much of the surface as possible in order for the algae to capture as much light as possible. I therefore ordered 20 x 1m length 12mm outer diameter tubes. This allowed me enough spacing to double up in the future on the inside if I could raise more money to have a second set under the first set of ribs.
Although at first one pair of tubes seemed easy to connect to each other with the 8mm silicone hose, repeating the process 40 times with such a small radius and a tendency to buckle in and fold on itself seemed impractical. I therefore had to come up with a different system of transporting the algae from one tube to the next. This meant either re-designing the ribs to a much larger scale which would set each tube further apart or changing the tube to an even smaller size which would allow me to purchase an even thinner hose with more flexibility to achieve that goal.
I decided not to go with either, instead I changed the pattern of transport; rather than consecutively going from tube to tube, I would skip 3 tubes on one end and 2 on the other, 3 on one, 2 on the other and so on and so forth. This allowed me to stick with the same design & tubes which were already put together and get a much larger radius which would ensure that the hoses would not pop out of place because of the pressure or their internal positioning in the acrylic tubes
Step 5: The Plinth/base
With the ‘above ground’ part of the model completed, it was now time for the plinth to be constructed which would house all the mechanisms that would operate the model ‘below ground’. The plinth required to place the model on a height which would be comfortable to be viewed by an audience of both children & the elderly but at the same time not be overstated and detract from the model itself.
I decided to make it 1m tall and allow 15cm for each side of the 1m tubes to have space for the turnaround of the hoses. The final dimensions of the plinth were 1m tall, 1,3m long by 0.3m wide.
As this was going to be both an exhibition piece and a University project I felt that there was a strong educational aspect to it. I wanted to somehow be able to tell the story of the algae with this model. I decided to make viewing holes on the rear side which would show the process much like the doughnut company Krispy Kreme has certain stores where the customers can see the production line of how the doughnuts are made from the dough to the glazing.
On these holes I would label what each component would do. Bio-reactor, CO2 pump, air intake, light source. Once deciding on the location of these objects, I decided that rather than having separate holes with separate names, it would be better to have one panel which would be seen as one object containing all the information one needs to know which would be far less distracting.
This turned out to be a really good choice after all and the laser cutting machine did an excellent job. Etching turned out to be much harder than I thought as every letter had to be converted to an object which meant that there was a much higher chance for an error to occur. Each letter had to be checked and cleared of any unwanted lines as well as check for disconnections in the comprising lines.
Step 6: Colour
After that the plinth was ready for painting, a clean white look turned out to be the right choice and a color scheme of white, natural ply & clear proved successful. In hindsight I should have used far less paint quantity on the water tank door as the 3mm ply could not handle the paint and warped. It is purely an aesthetic problem, one that can be addressed after the exhibition is over.
Step 7: Sealing the Bio-reactor
With the plinth drying it was now time to seal the tubes and the hoses shut to make a closed loop bio-reactor. I used the super-instant glue rather than silicone because of its ‘instant factor’ and the fact that the hose & tube were such a tight fit that silicone would only create clumps inside the tube and probably cause more problems than it was worth.
When trying to fit each hose in the tubes it was extremely hard to get each one in at first. To solve the problem I countersunk all the tubes in order to get a ‘start’ in each hose so that it could slide in with ease. This was an excellent solution as later I poured glue on the countersunk tube with the hose in place which created a lake which would seal shut. Result: not a single connection out of the 40 connections leaked.
Because the tube was a very small space with a limited air supply, the instant glue would not dry instantly, this created a small puddle inside each connection. I therefore had to try various positions every 5~7 minutes to ensure that each connection would seal on all 360o.
Step 8: Hose Fitting
A minor adjustment had to be made to the pumping mechanism. Due to the fact that the 4000 Liters per hour was significantly more powerful than the 15 Liter water tank I was intending to use I had to make an outlet where the pumps power would effectively be cut in half in order to take the stress off all the plumbing connections so they would not suddenly blow apart from the pressure.
The adjustable handle also meant that I could regulate the speed at which the algae would travel round the model and effectively either accelerate or decelerate the growth when needed.
Whilst I would be transporting the model, I would like to have the ability to separate the bio-reactor from the plynth. I used some heavy duty clip-on clip-off fittings which allowed me to completely disconnect the bio-reactor without compromising any connection points.
Step 9: Test Runs
After letting the glue settle for 40 hours, the first test run with still water was extremely successful. The air bubbles traveled at a steady pace throughout the model and all the connections held up perfectly. This run lasted for 4 hours. I then proceeded to add algae incrementally over the next week.
Step 10: Growing the Initial Algae Culture Pt I
During the building period, I had started to grow algae using the simple method of a water bottle, algae food & the sun. This proved successful in the UK but even more successful in Greece where the sun lasted for longer during the day. I started with a culture sent to me by the Algae Depot of 50ml and after a few days I reached 3 x 100ml travel bottles.
I then proceeded to continue to grow that culture until I eventually reached the required 5.5 Liters after approximately 2 weeks. The algae was growing exponentially quicker due to the limited bottle room I would provide along with excellent sun exposure and feeding regime.
Step 11: Growing the Initial Algae Culture Pt II
Step 12: Test Runs
I let the algae run in the bio-reactor for 10 days and achieved excellent results.
Perhaps it was the location of the model posistioned against a window which received very good sunlight both artificial and genuine but it had grown at a steady pace becoming greener every day.
Step 13: Outcome
Being an ongoing project I do not have the algae biomass output of this experiment yet.
I will keep you posted through my tumblr blog
where any publications results and other events that will be organised shall be posted.
Thank you for looking through this instructable and please contact me if you need any further info.