Embodied energy is pretty easy to understand,
which is why I personally use it as the reference
number. As you can imagine, embodied carbon
could vary greatly depending on the energy
source that was used to produce the material. If
we were making all of these materials with zero
carbon electricity, most would have near-zero
embodied carbon.
But this assumes the material is only used
once. In reality, to compare all these things we
need to recognize that the energy or carbon
impact of an object is determined by the equation:
Energy utility of a thing =
Weight of thing
×
embodied energy
Lifetime or number of uses
This equation tells you some really important
things. You can lower the weight of a thing —the
strategy used by many companies to say, shave
a few grams of plastic off your toothbrush —but
the weight savings are generally really small
(though often much hyped) and often designers
use exotic materials like carbon fiber composites
to achieve those weight savings, at the expense
of the embodied energy actually going up! The
other strategy lots of “green” companies use
is material substitution — like all the “green”
products made of bamboo. People associate
bamboo with “green” but it isn’t always so.
Oddly, it’s that number underneath — the
denominator — that makes the big, big
difference: the number of uses, or the lifetime. If
your bamboo toothbrush is only ever used once,
it’s an awful idea. If you use your carbon fiber
bicycle for 15 years and 60,000 miles, it was an
excellent choice. I’ve always thought about
this as a giant opportunity. Think about
how to make heirlooms: great
products that people use for a long
time, and amortize their embodied
energy over a much longer period.
(See Make: Volume 10, “Makers vs.
Shakers.”)
Vehicles are one category where
technocrats obsess about embodied
energy, and for good reason.
Approximately half the
carbon emissions of
a typical car are in
the production stage,
before it ever drives a mile. One thing that excites
me about electric cars is that they’re so simple
they should last much longer.
Industrial energy use, and material resource
use, is such an important topic that the DOE
publishes fantastic studies on just how good
could we get at producing various industrial
materials. These are known as Energy
Bandwidth Studies
1
. They’re worth looking at,
to see the big energy consumers and carbon
emitters, and to find out where inventors and
engineers can make the greatest impact to fix
our planet. Let’s look at a few:
Steel
The carbon emissions of steel are a result of the
energy used in heating the steel and processing
it, and of the coal used in the process of making
the raw iron in the first place. All steels have
significant quantities of carbon in them: “low–
carbon steels” are ductile and pretty strong,
“high–carbon steels” are more brittle but super
strong. Today 69% of steel is recycled in the U.S.
FIX IT: Today the heat for the steelmaking
process in most places comes from natural gas,
but there’s no reason it can’t come from clean
electricity. And there are companies all over the
world working on ways to add the carbon content
without having to add it as coal in the blast
furnace. A Rearden Metal-sized fortune
2
will go
to whoever succeeds.
Concrete
I’ve always been astounded with the statistics
on concrete. In the U.S. we produce almost 2
tons per person per year! The stuff is now
everywhere. Joni Mitchell was
bang on target when she sang of
paving over paradise. It’s estimated
that 8% of global emissions come
from cement alone. Half of those
emissions are from the energy
required, the other half are emitted
in the creation of the clinker —the
lime-based binder that holds it all
together.
FIX IT: Limestone (CaCO
3
) is heated
to become lime (CaO) which leaves a
CO
2
leftover. But it doesn’t have to be
FIX OUR PLANET: Decarbonize Our Stu
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