Dear Science,
I’ve always been the conscientious kind of consumer who separates
her trash and recyclables. Recently, I have also started making sure I
buy only biodegradable things: cardboard containers, the corn-based
plastic alternatives, paper instead of plastic if I can help it. Well,
you get the picture. These days, most of my trash is as biodegradable
as I can make it. Here’s a logical problem, though: If I put all
this wonderful biodegradable trash in a trash bag, isn’t it just going
to stay in the landfill forever, trapped inside a plastic bag, with
nowhere to biodegrade? Should I try to bury it someplace,
instead?
Thanks,
Trashed
Your suspicion is mostly correct. Entombed deeply in a landfill,
your biodegradable trash is forced to degrade without oxygen, creating
copious amounts of methane gas. Methane is a potent greenhouse gas, far
worse than carbon dioxide. If you’re sending something to a
landfill, it’s better for the planet if it never degrades.
A landfill is intended to be a place without time, where trash is
meant to stay isolated from the surrounding air, water, and
soil—somewhat like the Republican plan for America, through
immigration reform (a completely sealed USA). Degrading isn’t in the
plan; it happens anyway, just in a different way.
I now need your close attention. Put your biodegradable cardboard
container on your lawn and it will eventually get wet. Microbes will
start to eat it. Inside each microbe cell, the carbon and hydrogen
chains of the cardboard are steadily stripped down to more and more
basic carbon molecules as the cell busily collects energetic electrons
released during this metabolic degradation. These electrons are shoved
into the mitochondrion of the cell, where most of the energy is
captured and used as fuel for the cell. Eventually the cell must do
something with these electrons. Free electrons are the
nuclear waste of a cell, the nasty by-product of a very efficient
energy source. Left to roam about, the electrons are likely to
shred up something important. Almost all cells eventually dump these
waste electrons onto a passing oxygen molecule, creating carbon
dioxide. (Plants, during photosynthesis, do the opposite: They store
energy by stealing electrons from carbon dioxide to build up carbon and
hydrogen chains, releasing oxygen as a waste product.)
Your same biodegradable container interred in a landfill will
inevitably get wet. Microbes will attempt to break down the hydrocarbon
molecules, like they would on your lawn, but no longer have oxygen.
Instead of the more efficient, free-electron-generating but
oxygen-requiring metabolism, these microbes must stop somewhere before
carbon dioxide. Generally this is at methane, a carbon and four
hydrogen atoms. The methane bubbles out of the landfill and contributes
to climate change.
Where should your biodegradable waste go? Ideally into a
compost pile, where plenty of oxygen encourages healthy degradation. If
you live in Seattle, put it in your yard-waste container and the city
will do this for you.
Oxidatively phosphorylatingly yours,
Science
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dearscience@thestranger.com
