I was clearing out at the weekend and eventually ended up at my pile of empty water bottles. I dont know why I saved them but after looking around online (more specifically searching for stuff to do with plastic bottles on instructables), I realised I could create a small scale automated algae farm to power a generator or use as bio-diesel (either of which saves me money).
So here I am with my new (WIP) instructable on creating a bio reactor.
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Steps 2,3 and 4 will all have their own instructables with materials and so on, however I will give approximate costs of each project here. Each stage will also feature its finished state here.
Because of this, I welcome you to offer constructive criticism in my development plans on this page.
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Step 1: Design
My first step was to design.
The majority of bottles I have around are 5 litre bottles, so started with them.
After some mental development, I came to the conclusion the nozzle of the bottles would face downwards and be connected to a system that will empty the bottle at intervals (so, automatically) which will later be determined by growth rates. I am aware this will not drain all algae, some will be stuck to walls, however this will be useful because the next batch wont need a new introduction of algae.
## Up until now, most systems I have seen have had manual contents release systems ##
Measuring the cap gave me a 2" diameter to work with. Originally I thought I would use the cap as the exit point for the algae but as I brainstormed, I realised I could do better.
Using a length of pipe, perhaps 7cm or 3", with a diameter of 2", I can create an exhaust system. I can also have a CO2 injection node (one way valve, pointed downwards) which would increase growth rate. The exhaust will need to use some kind of valve as a release mechanism. ((NEEDS WORK))
The base of the bottle will be cut off. Above this, I can have piping that delivers (using a pumped delivery system) fresh growth medium when the contents has been drained and it will also allow the oxygen to release (a sealed system would build pressure and would do nothing to help growth)
The exhaust system will eventually form a cone (If I cant get plastic to form this, a funnel with a diameter >2" would work if hot glued to the bottom of the exhaust) which leads into piping. Right now, I am unsure on material ?: but think I may use latex tubing with approx 1/2" diameter however would be happy to go for a plastic based solution realistically - whatever turns out cheapest. It does however need to be flexible while this is experimental.
This eventually leads to the processing unit. Im still unsure on whether growth medium can be recovered.
Concept 1: I use a press to seperate algal sediment. This will give me algae which could be dried for resale or burned as a fuel source. The liquid left requires more thought still. From what Ive read, algal oil will make up to 50% of the liquid, which should theoretically leave >50% growth medium.
Concept 1-1: Creating a centrifuge could resolve this - allowing me to seperate the media for re-use and go on to process the oil as biodiesel. Would need me to make a centrifuge however.
Concept 1-2: Distillation is an option, however could actually seperate the growth media particulates - the water may evaporate but not the nutrients with it - making it useless to recycle and the nutrients would end up wasted during biodiesel filtration.
Concept 1-3: Leaving the liquid to seperate into oil and media - normally oil will float on water because it is less dense, but would the media be denser? Will the nutrients form their own layers?
To develop more on my plans for the algal product, it will be:
Concept 1-0-1: moved to a point where it can be collected
Concept 1-2-1: moved into a chamber where it can be burn to power the distillation. Fumes would be purely CO2 so can be stored for release in the colonies. Ash can be used as fertiliser.
Growth media will be stored on it's own in something large enough to store a full cycle's worth of media for the bottles. It will be hooked up to a pump (?: perhaps a centrifugal pump, or pressure based) to deliver it to bottles that have emptied.
In the event I can recycle media in Concept 1, media will be pumped back into this unit.
If a 50% recycle rate of media can be achieved, media cycles will last almost twice as long.
Step 2: Prototype
My next step was to create a prototype, 1 bottle system to test exhaust design, media solution against growth and C02 against growth.
Step 3: Pilot
With a prototype in mind, in this step I intend to create a 5 bottle array that will test automation and integrity.
The first step is to build the rack.
I have in mind a design that uses old tent/awning poles which I can will try to scavenge. I will build a one-shelf design with racks designed to hold the 5L water bottles.
Step 4: Mass Production
I hope to eventually create a large array (~40 - that's 4 shelves of 10 or could possibly create 2 lots of 2 shelves of 10 with a gap in between - although it all depends on aesthetics) that I can set up in a sun facing direction in my garden.
Along with this, I will experiment with various techniques to enhance production. Genetically modified algae for example, or a controlled light experiment.
Depending on production rates, this size may well become profitable, only time will tell.