The goal of the Metabolizer project is to develop an opensource, rapidly-deployable emergency infrastructure system that can meet as many human needs as possible by breaking down trash and locally-available biomass at an individual or community scale. Scroll down for specs and build info.

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For build info and specs on the Trash Printer, our opensource recycled plastic 3D printer, please visit

For The Magic Tool Bus, our sustainably converted Trimet shuttle bus that is a traveling maker space and offgrid living space we hold workshops and demos out of, please visit and follow us on Instagram.

And finally, we are deeply inspired by the Precious Plastic Movement and highly suggest checking them out for context and motivation. We are not alone in this regenerative effort, and neither are you.


Estimated Cost to Build: $3000-$5000

Tools Required: Power tools, laser cutter or 3D printer

Inputs: Any reasonably dry biomass; Charcoal; Waste Plastic

Outputs: 1500W 120V 60hz Electricity; Hot Water; Charcoal; Syngas; 3D printed plastic objects

The Gasometer

The Syngas is stored in a simple, low-pressure container called a Gasometer. Gasometers have been used since the industrial revolution, and were orginally used to store and deliver coal gas. The gasometer cools the gas and stores it for later on-demand use.

The Hearth

The Hearth uses charcoal to thermally decompose biomass inside a stainless steel keg. This produces a thick smoke that passes through a distillation tower, which condenses out the heavier hydrocarbons (tars) and produces a clean-burning gas called Syngas.

The Generator

The Syngas produced by the Hearth is clean enough to power nearly any standard internal combustion engine, with minimal modification. The current prototype uses a Harbor Freight “Predator” generator for it’s low-cost and quiet operation.

The 3D Printer

The 3D printer is an open-source, low-cost, mostly-3D printable “MPCNC” gantry that allows a computer to control a specially-designed low-cost plastic extruder that enables large-format printing of plastic objects directly from the recycled plastic flakes that are produced by the shredder, without the need to convert it into filament first.

The Shredder

The Metabolizer utilizes the open-source “Precious Plastic” shredder to break wastes apart into small, easy-to-process bits, the same way your teeth break down food for easy digestion. The shredder can break down plastics for recycling, as well as burnable biomass, such as packaging, cardboard, junk mail, food scraps, and yard waste.


Like the organs in your body, the metabolizer is a complex system made up of several physically-distinct-yet-interdependent systems, each performing a unique set of metabolic functions that enables the whole system to keep operating. Like your teeth, the shredder mechanically decomposes wastes into small bits. Like your stomach, the hearth uses energy to chemically decompose the shredded biomass, releasing a surplus of energy and producing a hydrocarbon fuel. Like the mitochondria inside of your cells, the generator converts those simple hydrocarbons into electricity- a refined and flexible energy source similar to ATP in the body.

Chemically speaking, the metabolizer performs the same basic metabolic ecosystem service that fungi do- it breaks down complex biomass by reacting it with oxygen from the air, to produce Charcoal (C), Carbon Dioxide (CO2), Water Vapor (H2O), and Energy(!!!)


The Metabolizer is designed to be easy to build out of easy to find parts. It requires no welding or specialized skills to build, and nearly all of the parts can be purchased through Amazon Prime. However, many of them can also be found locally for cheap or free.

The links on this site are “affiliate links” and if you buy any of this stuff after clicking these links- I get a surprizingly not-zero amount of money from Amazon. That helps me do this work and keep it open-source. However, these links are provided primarily as a reference- many of these items can be found used for cheap or free, and sourcing used parts locally will save you a ton of money, and it will save the world a lot of resources- so please check craigslist before you buy a new patio heater on Amazon, for example. BUT, if you do buy a new patio heater on Amazon, I’ll get like $15 for it if you follow the link, and that would be neat.

Just be sure to feed all the packaging to your metabolizer when you’re done.

(2) 1″ diameter 300W Heater Bands

Sourcing Notes

These are the ones I used, Amazon seems to be out of stock. You can also take the band-heater element out of most “crockpot” style warmers, and wrap it around the barrel. The PID will take care of the rest.

Est. Cost New


(1) Char-Broil Propane Turkey Fryer

Sourcing Notes

Found mine for $10 at Goodwill. The fryer adds structure to hold the charcoal, keeps heat focused on the keg, while also giving you decent low-temp control. Comes set up with a propane burner that can be used to retort the syngas for making biochar.

Est. Cost New


(1) 4:1 Planetary Geared NEMA24 Stepper Motor

Sourcing Notes

This is the most expensive part of the extruder, but it’s the best way I’ve found to get sufficient torque for extrusion AND precise computer control. Open to suggestions and improvements, but this works.

Est. Cost New



The current prototype is just that- a basic but functional proof-of-concept. It is not a finished product, but it has been designed to be as easy for others to build as possible- so that if you want to, you can build your own, wherever you are, using parts that are easy to find. The build documentation offered here is offered freely, in hopes that others will use it to build their own versions, and share what they learn in the process, so that together we can systematically increase the performance of biomass-to-energy systems like these, while lowering the barriers to entry.