Thermophilic Composting: The ecological “Mr. Fusion”

The temperature of compost made from humanure and food scraps collected from the 2014 SOS conference on the 14th July 2014. The compost pile was located in Canberra in the middle of winter. The scale on the thermometer is in Fahrenheit and reads 162°F, or approximately 72°C. Photo by Jono Crane.

The temperature of compost made from humanure and food scraps collected from the 2014 SOS conference on the 14th July 2014. The compost pile was located in Canberra in the middle of winter. The scale on the thermometer is in Fahrenheit and reads 162°F, or approximately 72°C. Photo by Jono Crane.

 

Do you remember the final scene in ‘Back to the Future’ where Doc returns to Marty McFly’s sleepy suburban house his DeLorean time machine? This time, Doc arrives from the future; instead of waiting for a lightning strike or acquiring weapons-grade plutonium to generate the 1.21 gigawatts of power required to time travel, he takes a banana peel and a can of beer from the garbage. Dropping the banana peel, pouring the left-over beer and finally throwing the can itself into the small “Mr. Fusion” device mounted on the back of the time machine is all that is required to power Doc’s DeLorean.

In the film, the intrepid time travelers flew back to the year 2015, where the Mr. Fusion technology apparently came from. Well, it is now 2016 and you might feel a bit disappointed that you can’t buy your own Mr. Fusion from Aldi or JB Hi-Fi. Don’t despair—a similarly miraculous technology is within everybody’s reach. It is called thermophilic composting.

 

Thermophilic composting is the process of using thermophilic (heat-loving) bacteria to transform food scraps and other organic “waste” into sanitised plant fertilizer, or compost. The Mr. Fusion part is you can use literally any organic matter (e.g. banana peels and left-over beer) to produce energy (in the form of heat) and rich plant fertiliser that you can use to grow food.

Ok, so you cannot chuck in the empty beer can, but there is a consolation: the organic matter you use can be anything that has recently been living. This opens up some amazing recycling possibilities. For instance, the roadkill on Canberra’s freeways: instead of leaving them fester, attracting disease or scavengers that could cause further road hazards, compost can use them to heat a home or grow salad greens.

Thermophilic composting can transform chicken, sheep and horse manure into energy and compost, but why stop there? Our own human waste—human manure, or “humanure”—can be rendered safe to use on food-producing plants via this miraculous process. We can even generate hot water for washing our hands afterward.

 

How much does one of these Mr. Fusion/Mr. Compost contraptions cost? The great news is if you are reading this issue of Woroni, you almost certainly can afford one! Thermophilic composting only requires four ingredients, most of which are probably around your home. The magic four ingredients are carbon, nitrogen, oxygen and water.

Carbon is anything that was recently living and is ‘brown’ and ‘dry’: sawdust, autumn leaves, newspaper (yes, you can compost this issue of Woroni when you’re done reading it).

Nitrogen is anything that was recently living and is ‘green’ and ‘wet’: green leaves and grass clippings, vegetable scraps, roadkill, dog poo, and so on.

Oxygen is the stuff you’re breathing and water falls from the sky.

So if you have this issue of Woroni, a salad sandwich, you are sitting outside and it is raining, you have all four ingredients and are ready to start!

As Doc demonstrated with his nonchalant refueling of the DeLorean, you do not have to be a rocket scientist to make this work. You need about 30 bits of carbon for every one bit of nitrogen. For instance, if you have a lot of salad sandwiches that need composting (the nitrogen), you should add plenty of copies of Woroni (the carbon) to get the magic 30:1 ratio. Mix your carbon and your nitrogen together in a pile. Shred the copies of Woroni as you mix to leave plenty of air pockets (oxygen) and then wait for it to rain (water).

 

The compost produced in the photo above followed exactly the same process. We started with the vegetable and meat scraps from the 2014 Students of Sustainability conference. These were combined with what we collected from the four compost toilets installed at the Aboriginal Tent Embassy where the 300 conference participants were camping. Within one week, the compost’s core temperature had reached 72°C; this, even with the frosty outdoor temperatures of a typical Canberra winter — that’s some hot shit!

72°C is on the high end of the scale and might not be achievable in less than ideal conditions; however, it is totally within even an amateur composters ability to achieve sustained temperatures of 55°C and above. One hour of exposure to these temperatures will kill all human-harmful pathogens, viruses and bacteria. (If you want to learn more, and perhaps get your hands dirty, check out Joe Jenkins’ fabulous “Humanure Handbook.” It is available online as a free PDF.)

So in 2016 what’s better than a Mr. Fusion you can buy from JB Hi-Fi? An open source Mr. Compost!

Only question remains: if Doc turns up on your street in his DeLorean, when he gets out of the time machine and looks around will he say “Great Scott!!” or “Great Rot!!”