Agriculture Reference
In-Depth Information
So traditional (aerated) composting isn't as much of a free lunch as some would have you be-
lieve. When you compost organic matter aerobically using traditional methods, you will generate a
highlevel ofgreenhouses gasseslikemethane andnitrousoxide,inaddition toalotofCO
2
.Thatis
why the compost pile gets measurably smaller — a lot of the carbon is volatized off into the atmo-
sphereastheorganicmatterbreaksdown.Foraneco-consciousperson,thatisn'tgood.ItisMUCH
better to have that carbon tied up in the soil matrix than it is to have it in the atmosphere.
Even under the best aerobic composting conditions, greenhouse gasses are emitted. But in real-
itymostpeopledon'tmaintainperfectaerobiccompostpiles;theyletthemgoanaerobic,andthatis
a cause for concern. How many people start actively aerating a compost pile but then give up over
time, leaving it untouched and anaerobic? A lot. When organic material composts anaerobically,
nitrous oxide, ammonia, and hydrogen sulfide are produced. That is why anaerobic compost piles
stink; the smell is a combination of these gasses. The ammonia not only smells but also leaches
out of the pile into the ground, where it can potentially contaminate ground water. This also takes
the nitrogen out of the compost, which is not what you want — you want nitrogen in your com-
post, where it will ultimately feed your plants. Methane is also produced in the pile when methane-
producing microbes take over. These microbes prefer anaerobic conditions at a neutral pH; under
those conditions, they can dominate the pile and multiply rapidly, producing a lot of methane. This
is how they produce methane in bio-digesters, where it is harvested and used for fuel in industrial
situations. Theaverage homecomposter isn'tharvesting themethane sothegasgoesintotheatmo-
sphere. All of this GHG production can be avoided by fermenting food waste using bokashi instead
of breaking it down in an oxidative process.
When you compost with bokashi, you are fermenting organic waste anaerobically at a low pH
so greenhouse gas production is drastically reduced. Methane-producing microbes can't survive at
a low pH, so very little methane gas is produced. But what about the other microbes involved —
don't they generate gasses? Lactic acid bacteria are one of the primary constituents of the group of
microorganisms used in bokashi bran to ferment food waste, and lactic acid fermentation is a pro-
cess that does not generate any gasses. In a study, Dr. Lawrence Green found that:
Organic waste processed by bokashi fermentation produces no measurable gas during the
7-day fermentation process and when then mixed with soil it is further degraded without
evidence of any gasses being liberated. Based on these findings it appears that bokashi fer-
mentation does not produce measurable gas emissions in its conversion of organic waste
into a nutrient-rich end product that can be used to support plants and crops.
— Green, “A Pilot Study Comparing Gaseous Emissions”
Unscientific visual observation shows that no excess gas is produced when you compost using
bokashi in an anaerobic container; the container doesn't swell, and there is no audible
poof
when it
is opened after a two-week fermentation. This is clearly an area where more research is needed, but
based on the science of the processes involved and the information available today, it seems that
few if any greenhouse gasses are produced during the bokashi fermentation process.
No loss of nutrients — everything ends up where you want it, in the soil
