It’s a Gas, Gas, Gas!

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The romantic era poet George Byron wrote “The dust we tread upon was once alive.” Such contemplative reflection, over the interaction humans have with the environment, continues today in the evolving intellectual disciplines of science, philosophy, and religion.

Those that would have us believe that liquid is gas and that solar energy is “alternative” have long been packaging ideas for those they assume lack critical thinking skills. All of the physical energy that we can leverage while on earth traces its roots to that blazing orb at the center of our solar system. While the taming of fire is considered one of the cornerstones of civilization, any use of it today is seen, by some, as clear evidence we be bad!

While composting is considered an environmentally responsible thing to do, the methane rising from your open air compost heap has a “100-year global warming potential 25 times that of CO2,” and, “measured over a 20-year period, methane is 84 times more potent as a greenhouse gas than CO2 according to the United Nations Economic Commission for Europe. Methane that is released directly into the atmosphere is harmful to the environment, for it quickly rises to the top where it remains for about 8 years until it is reduced, through oxidation into carbon dioxide and water.

As the main component in natural gas, that methane produced from non-fossil sources such as green waste can, when burned under the right circumstances, reduce such harmful environmental impacts. The advantages of using methane to produce heat at ground level has environmental benefits as compared to letting it absorb infrared radiation from the sun at high altitude. Whether you are trapping methane from the compost to run an internal combustion engine, burning it to send supplemental heat to your home or greenhouse, or simply accenting your backyard with continuously burning tiki torches, you are helping to mitigate further damage to our shared air envelope.

Methane is lighter than air, so redirecting the gas can be as simple as laying a perforated pipe on top of the compost pile with a tarp above that. There is usually no need to worry about gas escaping from beneath the lower edges of the tarp as long as the gas is being pulled from the top of the mound fast enough. Pulling it too fast has little benefit as methane is not usually stored in tanks. This is because the symmetry of its molecule makes it hard to liquify. One could, theoretically, store methane in a tank in a gaseous state. In such a case it would then have such low density it’s unlikely you could, in all practicality, store a usable amount.

There is, however, an advanced science related to composting that fulfills the entire wish list as it relates to biogas production, storage and use. It also introduces greater efficiencies with respect to the traditional use of compost dating back to at least the times of ancient Rome, and as it was practiced by George Washington. While the soil amendment benefits are well understood, optimizing the process through what is now termed anaerobic digestion has become an exciting field of study for hobbyists and other problem solvers.

At the head end of a digester is some combination of kitchen disposals, leaf shredders, mulching mowers, and wood chippers,. These grinders effectively chew the food that is then dropped into the artificial stomach where digestion is aided by means of the probiotics that support the composting equivalent of gut flora. The microbes contained in what gardeners think of as compost activators will do the real work of generating a valuable gas while also producing the finest of soils.

The entire biological waste stream can be processed through anaerobic digesters, although human waste is usually dealt with separately to provide an extra layer of protection against the spread of human pathogens. The digesters themselves can, for the most part, operate passively depending largely upon the activities of a variety of microbes. The process can be enhanced with some combination of stirrers, turners, and blowers. Effective storage of biogas can be achieved through the use of balloons within, or a floating rooftop upon, the digestion chamber. Such expanding storage systems can also serve to pressurize the gas line as it feeds cooking, heating, and electrical generation systems.

As with any composting effort, having a variety of materials in the mix will insure success with the fermentation process while yielding the highest quality gas and soil. The process can be optimized through any combination of wet or dry, batch or continuous, thermophilic or mesophilic, and one stage or multi-stage systems. 

Whatever you decide about how you design your system, success ultimately depends upon keeping your cute little pet microbes happy. The good news is that, whether you decide to feed them from a long neglected pile of munchies from your lawnmower or by means of the advanced cooking methods we’ve described, we can assure you, they’re not picky eaters.

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