Stand With the Children — This essay concludes our series on how makers can decarbonize our world. Read the whole series and find hands-on projects to make a difference at Adapted from Rewiring America: A Handbook for the Climate Fight, Also coming in 2021: an expansion of these ideas in Electrify! (MIT Press).

Solving climate change isn’t much good if we suffocate our oceans with plastics, kill our bees with pesticides, and pollute our waterways with excess fertilizers and toxins. Yes, we can decarbonize our energy supply with existing technology, but we’ve got to fix our industrial ecosystem too. Industry is where our climate change challenges collide with all our other environmental problems. The upside: There are huge opportunities for double wins — where we fix not only climate but also the other ills of the way we make the things in our lives.

Makers and engineers, the world needs you to fix manufacturing — to innovate and invent new, low-carbon methods and materials. And quick.

Our #1 Energy User

Our industrial economy is actually America’s largest consumer of energy (≈32%) and a huge emitter of CO₂ and other climate warming gases. We can see the energy flow breakdowns in Figure A. The industrial sector, as defined by the U.S. agencies who measure our energy uses and carbon emissions, includes mining, construction, agriculture, and the biggest component, manufacturing.

Figure A: U.S. energy flows through the industrial sector — Quadrillions of BTUs (quads) per year

This Sankey diagram, which is largely built on the semi-annual Manufacturing and Energy Consumption Survey (MECS), tells us quite a lot. You can dive deep down this rabbit hole. One thing that sticks out is just how much of our industrial sector is involved in finding, mining, and refining fossil fuels. Nearly 2 quads (quadrillion BTUs) are used in natural gas and oil exploration. Around 3 quads are used in refining crude oil into gasoline. All told, something like 6 quads of the industrial sector’s 32 total quads would disappear in a renewables-powered world! About 1 of those fossil quads is used just for making fertilizer. Fertilizer is good, and we need it, but we don’t use it very efficiently and could use much less while maintaining a healthier and better food system.

While we can easily understand why our cars and homes produce CO₂ emissions from the giant amounts of fossil fuels we feed them, there’s a lot more to understanding how the things that we purchase as “goods” contribute to emissions.

First, let’s look at the flow of materials through the economy; it’s an excellent complement to understanding the flow of energy. Figure B shows just how much stuff we move around. The 6,544 million metric tons of stuff we take from the natural world each year (in the U.S.) amounts to 20 metric tons per person!

Figure B: U.S. flows of materials through the economy — Millions of metric tons per year

(Funnily enough, this is without even counting CO₂. When we burn those 1,936 million metric tons of fossil fuels, they mix with oxygen to create CO₂ — around 6,700 million metric tons of the gaseous stuff, more than everything else we push around combined! Contemplate that before you get too enamored with the propaganda around carbon sequestration — you’d have to bury more CO₂, every year, than all the other stuff we dig out of the ground and take from forest and field. That’s going to be one hell of an environmentally destructive process.)

On the bright side, looking at these giant material flows gives us the opportunity to contemplate a more sane version of carbon sequestration. Looking at those flows, especially the bigger ones, ask yourself: “Can I conceivably bury or sequester carbon in that flow?” Makers, if you can figure out how to answer yes, you’ll make an enormous contribution to addressing climate change.

If we are to sequester carbon, it most likely will be by utilizing the large material flows we already engage in. Stash it in the soil and rock we move, or in forestry and wood products, or in concrete and drywall. It may not be as glamorous as carbon “air capture” but it’s more likely and more reasonable. It is realistically slower than the pathways that’ve been modelled into UN IPCC emission reduction scenarios. That means you’ll need to figure it out quick and get going.

So what I’m trying to do in this article is really two things. I’d like to show you the efficiency wins and technology transformations that can sharply reduce industrial energy flows, but I also want you to keep an eye open for opportunities to sequester CO₂ in the materials of our existence.

Embodied Energy: Thinking About the Energy in Stuff

Table C

Engineers think about the energy or carbon footprint of a product in terms of its embodied energy or its embodied carbon (see Table C).

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:

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 Studies¹. 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:


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 fortune² will go to whoever succeeds.


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 (CaCO₃) is heated to become lime (CaO) which leaves a CO₂ leftover. But it doesn’t have to be this way. We should be able to make cement that absorbs CO₂ through its lifetime. And we certainly should be able to build with less concrete. Covering ground with concrete has negative effects on drainage, soils, and more. I’m sure we can do better.


Most aluminum is already made with electricity, so once again, in theory we can make it without carbon emissions, but the energy input is not the only source of carbon. In the arc furnaces that we smelt aluminum in today the electrodes are carbon. This is the source of much of their carbon emissions. Today 69% of aluminum is recycled in the U.S.

Fix it: Apple recently worked with Alcoa and Rio Tinto to create the first batch of carbon–free aluminum. I’ve personally always found aluminum to be a wonder material, so I’m glad we are on a good track for carbon-free Al.


In concept, paper can be a zero net carbon product. About 63% of paper and paperboard are recycled in the U.S.

Fix it: The huge amount of energy used in the paper and pulp industry (more than 2 quads!) is mostly used in separating the cellulose fibers from the lignin glue that holds trees together. We can invent something better.


Wood is good. I like to think it’s the second best method for carbon sequestration, after books!

Fix it: We need to do much better forestry management, but people are already building wooden multi-story housing and wood is really a perfect sustainable building material. I once planted 30,000 trees. They all grew up. They could have been my entire lifetime’s supply of construction materials. And then some.


Glass can be recycled basically infinitely, but it does use a lot of energy to produce it (principally because the melting point of glasses is so high). Today 34% of glass is recycled in the U.S.

Fix it: We are getting good at making stronger, thinner, tougher, glasses, but maybe all we really need is a cultural shift back towards reusable glass packaging. It’s cleaner and chemically much safer than storing your food in plastic.


Plastics on their own, unless we change things quickly, emit 10%–13% of our remaining carbon budget³. This isn’t as obvious as you think. Plastic molecules have big long carbon backbones and last forever, so you’d think we could sequester carbon in them. (Drill for oil to mold giant plastic dinosaurs that we could re-bury to sequester carbon! Kidding.⁴) What actually happens is that in the creation of olefins — the precursor to most plastics — there are large amounts of nitrous oxide emissions, and they are even worse for warming than CO₂. Less than 10% of plastic is recycled in the U.S.

Fix it: Recycling won’t work. We need an entirely new pathway to plastics, but even if we achieve it, they’ll still gather in the oceans. Because of all this, I think we should use paper and glass and metal and more reusable containers, but also we should invest heavily in synthetic biology pathways to a new kind of polymer that would quickly biodegrade the way leaves do. Leaves don’t end up as ocean microplastics.

The Future We Make

The upshot: If we are wise, our moonshot science investment should be in studying and inventing materials systems, especially polymers, that don’t degrade our environment, or use excess energy.

And these sectors are just the beginning. Look again at our industrial energy consumption (Figure A) by sub-sector. Can you imagine a better way to do any of these things (just as examples): grinding of materials (0.49 quads), electrochemical processing (0.16 quads), or food processing (1.11 quads)? Do it, and you could be a captain of that new industry.


² Please excuse my Ayn Rand Atlas Shrugged reference.


⁴ Come to think of it this is what most people’s carbon sequestration plans are anyway!