Using bacteria to generate PHAs is not a new idea! It has been around for since 1980, but until recently it was too expensive to implement due to the recovery and purification phases.
These phases traditionally involved a lot of toxic solvents, and a lot of water. Recently, researchers have looked at using enzymes (such as papain [from pineapples]) to break the bacterial cell walls, and recover the PHA granules - hence getting around the usage of toxic solvents.
More recently (in the last 5-10 years), researchers have kinda randomly stumbled upon the idea of using animals to extract the PHA from the bacterial cells. The idea being that animals eat the bacterial cells, they only digest the non-PHA parts of the cell, and they poop out the PHA! Then the pooped out PHA can be purified using minimal amount of solvents, even just plain water! And we thus have PHAs that can be used for making things! I'm still not sure if this new approach will scale to industrial-level generation of PHAs, but perhaps it would work at an at-home scale! Hence my concept of the plastic-producing personal bioreactor!
https://hackaday.io/project/164603-plastic-producing-personal-bioreactor/log/161126-extracting-and-purifying-phas-using-mealworms for more in-depth prelim research I have done!
NB. I'm still not sure how good PHAs are as 3d-printing filaments. There are a couple on the market, and some PLA/PHA blends too. Obviously it depends on what you are planning to make! That's what I am investigating at the moment.
DESIGN OF THE PLASTIC-PRODUCING PERSONAL BIOREACTOR SYSTEM
So, it really has 3x subsystems! I've only just started looking at the design. But there will be a couple of manual steps, I am sure. It's not going to be a very low-cost thing. I envisage cost would be at least $1000/900€, and it will require some manual input (sorta like growing a plant + feeding your pet daily) .
- Bacterial growing system
So at the moment, it seems we would need several glass chambers. One to start off the bacteria. One to grow the bacteria, and then switch-up its growth medium to induce generation of PHA. One in which to centrifuge the bacteria, so we can collect their cells. We can have gravity flow between the chambers, which [the flow] would be allowed at certain times.
- Mealworm farm
And then we need a small mealworm farm. That's just a tray full of mealworms, with a sieve, and tray underneath to collect their poop. Most likely, the collected bacterial cells would have to be fed to the mealworms manually each day.
- Purification system
So again, most likely manually, the poops would have to be collected from the mealworm farm, and introduced the the purification system. More glass chambers (perhaps 2?)
I do think this is viable. Albeit it may be more expensive than I envisaged! I will appreciate any input on this!