Your own, personal biodigester

Written by tim


The Park Spark Project, brainchild of conceptual artist Matthew Mazzotta and supported by MIT and the City of Cambridge, has created a piece that combines a small methane digester at a dog park with an “eternal flame” lit from the gas coming off decomposing dog poop.

I am completely on board with the concept: dog waste, picked up with biodegradable bags and deposited into the digester, decomposes over time. The anaerobic conditions inside the digester create methane gas, which is then piped to an adjacent, old-fashioned gas lamp. The lamp supposedly burns continuously, forever showcasing the link between waste and energy. Waste turned to energy – just from walking your dog!

The implications of this project are important: small-scale digestion can work for a relatively small group of people. Dogs certainly create a fair amount of waste in the aggregate (I’ve seen an estimate that pet waste is 4% all landfill material, though that seems high to me), but dogs and their owners are scattered throughout the country, and their density diffuse even on the scale of one city or town. Doggie doo-doo is also one of those waste streams that floats just below the standard of “deserving lots of conscientious thought.”

So more power from poop, I say! The more conventional “waste” streams are turned into power, energy, or something else useful and pleasant, the better off we’ll all be.

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  1. Jeff B

    So how about taking this one step further and use it for disposable diapers?

  2. John Ritter

    How about doing this on a large scale and running an internal combustion engine on the methane? (Or a steam engine, which might be more tolerant of the moisture in the methane.)
    Turn a generator with the above engine. Then charge batteries used for electric bicycles and electric transportation of other sorts.
    Do these things that impinge on corporate profits. They won’t be hurt by the slight impingement, they will benefit by the fuel costs that we retain to spend on their other products!

  3. lisa

    wow! when can we get them for home use (cat litter, chicken coops, whatever… why not septic tanks?)

  4. Tim

    There are some links through the Park Spark Project’s website to some creative folks doing small-scale digesters for home use, check them out if you’re interested in building your own! One guy has a very simple system for his food and table scraps that is essentially a PVC tube with a nozzle at the top to burn off the methane.
    As for large scale digesters, many (if not most) municipalities use large digesters to clean and purify wastewater. The process creates some gas, but mostly the bacterial ponds’ primary purpose, I believe, is to reduce contaminants, heavy metals, and other pollutants before the wastewater is released to surface waters or the ocean. Some municipal wastewater digesters collect and burn off methane. TerraPass has even explored carbon credits from these systems, but they often run into additionality (because many treatment plants are required to install gas systems) and volume (they don’t create as much gas as you’d hope) problems which make them difficult projects from the carbon perspective.

  5. eric

    Lisa, great idea using a septic tank to generate Methane gas; I have been playing with that idea for a while. It will be the ultimate in recycling!