How We Make Things

Our Climate Challenge and Opportunity 2C

How We Make Things - 31% of Emissions

Making things constitutes the majority of our global emissions, which is why it’s so alarming that we’re far behind compared to other sources of emissions. It’s not even that we’re far behind; in some cases, such as cement, we don’t even have a visible path forward!

Emissions from cement, steel, and plastics comprise the majority of emissions in how we make things (5%, 8%, ~1.6%, of total global emissions respectively)1, and their usage will grow immensely as countries develop. For example, China used more cement from 2011-2013, than the US did in all of the 20th century!2 Though there’s a long tail of other emissions sources that come from mining, processing and creating other goods, we’re going to focus on these three areas, since they have the most potential for large-scale emission reductions. 

Previous sections of Our Climate Challenge and Opportunity can be found here.


Cement is a core component of concrete; it serves as the glue that keeps everything together. Cement production today requires calcium; we get calcium by burning limestone, which contains calcium along with carbon and oxygen. As the carbon and oxygen are burned off of the calcium, the carbon and oxygen bind to form CO2. Not only does this process require extremely high temperatures, which have been traditionally achieved by burning fossil fuels, the process itself inherently emits CO2. When you make a ton of cement you get a ton of CO2. Today, nobody knows a way around this. We also do not have an obvious replacement for cement in concrete.  

There are companies, such as CarbonCure (which recently won the Carbon XPRIZE), which inject CO2 into the cement during mixing, storing carbon within the cement. This process actually makes the cement stronger and allows slightly less cement to be required, therefore reducing production amounts. The CO2 captured can come from manufacturing processes (such as when CO2 is produced during the cement-making process). While this is a helpful solution, it is still less desirable than a process that doesn’t emit CO2 at all, as capturing that carbon in the first place requires energy and resources (read money), as we’ll see later when looking at the green premium for clean cement.3

There are also companies making concrete polymers that don’t use traditional Portland cement (again, cement is a primary ingredient in traditional concrete). These concretes use up to 90% less CO2 than Portland cement concrete and are cost-competitive with Portland cement concrete in many use cases. While these polymers have promise to be an important mix in the low carbon concrete space, they need to be scaled up and there are limitations as the materials needed to make them, such as fly ash, are not abundant enough to be used by the entire concrete industry. 

The long-term holy grail will be finding an alternative to limestone to make cement without emitting massive amounts of CO2, which we are still far from.


Steel falls into a similar category to cement, as it needs extremely high temperatures to smelt, and the traditional mixing of materials to make it emits CO2. The traditional way of making steel involves combining iron from iron ore with carbon from coke, which helps gives the steel its strength. The problem is that oxygen from iron ore binds with carbon from the coke in the smelting process, and lots of CO2 is emitted. 

Fortunately, there are clear paths to zero emissions, even if costly today. Some early technologies, such as molten oxide electrolysis, pass electricity through a cell that contains a mixture of liquid iron oxide and other ingredients. The electricity causes the iron oxide to break apart, leaving pure iron needed for steel, and pure oxygen as a by-product. There is no burning and no carbon dioxide produced in the process.4 There are also processes using hydrogen gas in the reduction process, which creates a clean byproduct of water vapor. As with the many breakthroughs that rely on hydrogen, the cost to produce clean hydrogen will need to decrease before this is economically appealing (we’ll be covering hydrogen in a later section).5

A beautiful property of steel is that it can be reused over and over again, by melting and remolding. When processed efficiently, recycled steel is a cost quite cost and emissions effective compared to mining and transporting raw materials, then going through energy-intensive reduction and processing; recycling steel saves ~74% of the energy used to produce it from raw materials!6 This is good news for those using steel in developed countries like the US, though plenty of new steel still needs to be made in growing countries that don’t have old infrastructure to recycle, and overall steel usage is expected to grow as populations grow and the world desires more things.

All of the processes above require extreme heat, oftentimes accomplished by burning fossil fuels and emitting carbon. There have been developments in the ability to generate extremely high temperatures through renewables, such as concentrated solar, which would reduce some of the emissions in the smelting process.

We need a lot of innovation to make cost-effective emission reductions in steel production. Since we’ll be producing 50% more steel by mid-century than we do currently, we need to invest today to bring costs down and scale up clean steel capabilities, especially since it takes decades to overturn expensive processing plants with long life cycles.7


Plastic packaging production is expected to nearly quadruple by 2050.8 Traditional plastics go through multiple steps where they have the potential to emit carbon. Let’s look at some of the more intensive ones:

Fossil fuel usage in creation: Traditionally, fossil fuels are used as cheap ways to bind carbon to hydrogen and other elements. As an alternative, we can use sources like vegetable oils, woodchips, or recycled food waste, to create bioplastics. Today bioplastics are expensive, and some sources used for bioplastics are more harmful to the environment if they take up a lot of land and energy. Researchers and companies are developing cheaper and more climate-friendly ways (ex. using biomass waste) of producing bioplastics.9 

Refinement & production: When we make plastic, ~½ of the carbon stays in the plastic.10 For the rest, we need to utilize point-source carbon capture before it enters the atmosphere. It’s one of the cheaper ways to capture carbon, and declining, though still expensive today. We’ll be covering carbon capture in detail in future sections. 

End of life & recycling: This is where plastics get tricky. Bioplastic emissions look about the same at the end of life as regular plastics (since there is still carbon in bioplastics, even if coming from cleaner sources), so we need to be thoughtful.11 Here are some of the paths plastics can go down after they’ve been used:

Landfills: plastics take hundreds of years to degrade, so landfills are better than some alternatives regarding emissions, however, plastic takes up a lot of space, so many opt for…

Incineration: this is one of the worst outcomes as it related to emissions. Carbon capture may help here, though it’s expensive so it’s better if we can find ways to avoid incineration altogether. 

Leakage: there are about 100 million tons of plastic in our oceans, with 1 million marine animals killed each year, and growing.12 Not only is this bad for life in the ocean, it’s also bad for the climate as the waste of these marine animals serves as food for phytoplankton which play a critical role in capturing carbon.13 

The following are solutions we should be doubling down on to reduce emissions from end-of-life.

Enhanced recycling technology: recycling technology is quite inadequate so we end up relying on humans to decipher recyclables/compostables/waste, which we all know is far from perfect (only ~8.7% of plastic is recycled in the US14). Recycling goes beyond just plastics: aluminum, nickel, copper, lead, paper, and more - think of the savings highlighted when discussing steel recycling above. If we can deploy technologies leveraging computer vision and other ways to sort materials at scale, we can reduce the cost and friction to recycle, making it more economic for waste management plants to resell materials. These materials can then be recycled many times over, dramatically reducing emissions by curbing the amount of new plastics and metals that need to be produced and mined, as well as by avoiding incineration of materials like plastics. Today companies like AMP Robotics and Redwood Materials (they are focused on recycling batteries components, not solely plastics, but mentioning since recycling will be increasingly important in many areas) are pioneering in this space, and the technology is becoming economically viable in an increasing amount of cases.

Additionally, about 25% of plastics are thermoset plastics (as opposed to thermoplastics), which can not traditionally be recycled by heating. In 2020 there were new breakthroughs for breaking down thermosets in the lab15. While these processes will need some iterations before they can be scaled up, they are promising.

Waste to Energy: Anaerobic digesters, which use microbes to break down biodegradable material and turn it into energy sources, have been used for decades on food waste at an economic and climate profit16. The first anaerobic digestion system to turn plastic into energy and fertilizer was developed in South Australia in 2017 and while there are scientific and operational breakthroughs that need to occur, there is a lot of research underway.17

Green Premiums for Plastics, Steel, Cement

Current green premiums for cement, steel, plastic with carbon capture are still very high.18

Changing the way we make things will be one of the hardest parts of our climate challenge. This section of the economy is the biggest emitter, and we have a long way to go until we have the necessary economically feasible alternatives. In the next article, we’ll be covering how we can decarbonize the transportation sector, which fortunately has more solutions that are being scaled up today.



Gates, Bill. How to Avoid a Climate Disaster (p. 104).


Gates, Bill. How to Avoid a Climate Disaster (p. 109).



Gates, Bill. How to Avoid a Climate Disaster (p. 101).



Gates, Bill. How to Avoid a Climate Disaster.







Gates, Bill. How to Avoid a Climate Disaster (p. 107).