1Building the Hearth
The words 'heart' and 'hearth' share the same root. The hearth is the heart of the Metabolizer. It's primary sub-systems are a reactor, a reaction vessel, a distillation tower, and a support structure.
The Support Structure:
The support structure I used is a 7' tall "lava" style patio heater. Patio heaters with glass tubes like these break fairly often, and people often don't want to fix them, and so they are easy to find used for cheap or free. I got mine at a goodwill outlet for $15. You don't need to use a patio heater like this, but you do need something sturdy to hold the distillation column in place securely, and this works kinda perfectly. All you have to do is remove the propane regulator, catalytic burner assembly.
The Distillation Column:
The purpose of the distillation column is to cool and refine the hot gasses as they escape from inside of the keg and it heats up. The distillation tower needs to make a secure, but pressure-releasable seal to the top of the keg, and it needs to cool the gas flowing through it.
There are lots of ways to do that- copper tubing, CSST gas tubing, but I ended up using Tri-Clamp fittings because they are easily available (they are commonly used for homebrewing) and because they are highly modular and easy to reconfigure and prototype with. It's like playing with legos.
I used both TC2" and TC1.5" fittings in my build, but in retrospect, I wish I'd just gone TC1.5" for the whole tower. The 1.5" parts are cheaper, and you can fit more distillation stages in the same space. TC 1.5" ferrules also make a perfect seal with the neck of a Sanke keg, so it just makes sense to make the whole tower 1.5" fittings.
I have some alternative AliExpress links in the "Hearth" tab of the BOM spreadsheet in the Files Section. You could fit in 4 condenser cups instead of the 2 I have now, which would mean more control over the fractional distillation process, and potentially the ability to select for higher-grade fuels. More testing is needed here.
When I fire a keg, I pack a bit of wet sand around the neck of the keg and the tower base, and between that and the weight of the tower resting on the keg, that makes it gas tight. When I'm done firing and want to unload a keg, I can pull down on the pulley line, and it lifts the column up and off the keg, and can be locked in that position, so that you can easily unload the spent keg and load a new one.
I am using 1/6th Barrel Style Sanke Kegs as "fuel cartridges". These can be bought new for around $100, but are also commonly available used/free. Check craigslist. I got like 4 just by asking my friends on facebook. The more you have, the better. You can fill them up with shredded burnable fuel material, dry them, fire them, cool them down, clean them out, and then refill them...
The Keg simply acts as a relatively high-temperature resistant reaction vessel, that can contain the hot biomass without letting any air in. I'm using them because they're widely available, and can handle temperatures higher than biomass needs to be to pyrolize.
Is actually just a nearly-unmodified Char-Broil Turkey fryer. They cost $100 or so new, but can often be found used. I got mine for $5. It works well because it keeps the heat contained and directed without adding much weight, it allows you to heat kegs with an outter ring of charcoal, and it also has a built in propane gas burner, which can can be used to start charcoal with propane, or to feed syngas back into the reaction chamber once the reaction is going. In bio-char making, this is called "retorting"- and if you don't want to store the gas, you can simply retort it and make biochar from woodchips.
You don't need to use a turkey fryer for this, but I had one and it works fairly well. Primary desing concerns are that you need to keep the reactor hot, you need to be able to set the keg securely in the center, and you need to be able to apply heat effectively from the bottom. I could imagine lots of other ways to do this, so maybe just use what you have! I was also experimenting with using a full-size keg as a reactor, which might work but needs more experimenting.
I used standard 1/2" appliance hoses for the water lines, and 1/4" compression fittings and copper tubing for the distillation cup lines. If you don't want to deal with capturing and storing liquid hydrocarbons, you can simply not use the distillation cups, or cap them, and that will cause the tars to flow back into the reactor and break apart into smaller molecules. The way you do the connectors will depend on what kind of TC fittings you get. I used brass tees with 1/2" copper adapters in order to spiral the tubing around the center column.
2Building the Printer
The best instructions for building the MPCNC are available at V1Engineering.com. I will not try to improve on their documentation, because I can't. I will make the following notes about what we learned during our build, though.
1. We printed the 1"/25.4mm version of the MPCNC parts, which lets you use exactly 1" OD tubing. If you want to use conduit, you have to make sure you print the right size parts. 3/4" EMT conduit is something like .94" OD, and so we had to use 1" aluminum tubing instead, which increased the cost a little.
2. Wire the steppers in parallel! I bought the parallel wiring kit from V1 engineering, and got their nicest control board. It helped a lot!
Find the BOM in the Components Section, and the exploded annotated assembly model in the Files section. This design works but could be drastically improved. The goal was to do large-format 3D printing directly from recycled flakes, skipping the filament step. We've proven thats possible with this simple extruder, but lots of upgrades could be made to reduce weight, increase stiffness, and ease-of-mounting.
The extruder is designed to receive plastic flakes through a hopper connected to a cyclonic filter and vacuum system, that sucks plastic flakes up from a bucket, and drops them into the feed hose. It can also note enough material for small shapes, without refilling.
3Building the Shredder
The shredder I'm using is a "Precious Plastic" open-source shredder. The shredder box cost me about $400 to get the parts cut, and a few days to assemble. The electric motor and gear reducer was the hardest part to source, and cost me another $300. You don't have to use a PP shredder, but they're the best open source option I know of. An industrial shredder might work a bit better if you can find one, but the scale of the PP design is ideal for backyard processing. Wood chippers don't really work well enough for our purposes, as they are designed for wood and tend to try to "whack" things apart, which doesn't work well for plastics. Industrial paper shredders are and option, but their motors are often under powered and must be modified. Don't even try using a cheap paper shredder.
Find full plans at PreciousPlastic.com, or in the files section. I highly recommend reading the Precious Plastic forums before building- you'll find a lot of improvements and hacks there.
I am currently using a Harbor Freight Predator 2000 inverter generator. I took off the side panel, unscrewed the air filter housing, and cut a piece of plastic to fit over it with a hole for the gas delivery tube. The system I use in the video is complicated, but ultimately I just used a little ball valve to get the air fuel mixture right. It produces clean AC power from trash-gas, but how much? More testing needs to be done!
5Building the Gasometer
The gasometer works by letting gas fill a closed barrel that is submerged in water. As the gas enters the through the top, it pushes the floating barrel out of the water. In order to increase stability, I added 2 bulkead fittings and was able to get 2 PVC pipes to sleeve into one another- 1.5" and 2"- so that the barrel doesn't tip as it fills. This has the added benefit of creating a through hole through the whole assembly, so a pole or conduit pipe can be placed through the center and held upright be the weight of the water- a handy feature for building deployable structures. Check out the design SKP in the file section to see the assembly details.
6Building the Turbine
The Turbine I'm using ends up being light, cheap and effective. Get yourself a coro-claw, (see Components) and rip 12 or 24 (depending on how many blades you want) 6-8' coroplast strips, along the flutes. Measure so that each blade is 10 full coroplast flutes long. On the 11th, cut. Then take these strips and pull them through the laser cut bottom. You can affix them to the top by scoring a 1" tab on the end, feeding the blade through the top slot, and then folding the tab over and pinning it with a box rivet.
Next steps are to add power generation to the tubine, and see if can generate appreciable power from it.
7Building the Network
In the Files section you'll find a set of instructions for how to set up NodeMCU or similar IoT controller board to work as a remote sensor for the Metabolizer using the Blynk app. We are just beginning to scratch the surface of IoT, but in the future I would like all of the performance data of the Metabolizer recorded by sensors in real time, so that we can compare our results in a meaningful way, and share successful "recipes".