It's a key factor in the fight against climate change.

The goal is simple, to reduce carbon dioxide emissions

around the world as soon as possible.

Our planet can not be saved unless we leave fossil fuels

in the ground where they belong.

Decarbonization requires

both sweeping change and incremental steps,

working industry by industry, process by process,

in every major country in the world.

Sound expensive?

It will be.

But the science community agrees

that to avoid global catastrophe,

we have no choice but to mobilize and take on

this monumental challenge. What do we want?

Climate justice!

When do we want it? Now!

Renewable energy, like wind turbines

and solar panels, as well as electric cars,

are the more popular topics in the conversation.

But there are other key sectors that are less-discussed,

and changes there are equally important

for decarbonizing the planet.

Here's three.

Cement, steel, and agriculture.

These three sectors combined

make up almost 40% of all carbon emissions in the world.

What will it take to revolutionize

these three industries without bankrupting them?

Cement is the most widley-used

manmade material in existence.

When combined with water and aggregates,

it can be poured into whatever shape

is needed for construction.

Cement has been used for millennia,

to build structures like the Pantheon and Roman aqueducts,

to highways and parking garages.

Lots of parking garages.

Globally, the production of cement

accounts of 7% of yearly CO2 emissions.

And that's largely because of how cement is created.

The main ingredient to cement is a substance called clinker.

In order to produce this,

limestone is heated to high temperatures.

And usually, this heat is generated

by fossil fuels, releasing CO2.

Meanwhile, the chemical reactions inside the kiln

release even more CO2 in the process.

Companies are working to reduce the amount of clinker used.

Others are testing substitutes, including fly ash,

which is the residue left in chimneys

of coal-burning furnaces, or slag from iron production.

But the drawbacks are serious.

These new techniques come with a price tag

sometimes triple the cost of the traditional process.

And since cement is holding many

of the world's structures together,

alternative recipes make contractors and regulators uneasy.

Steel is just as important as cement,

and as cities grow, global demand

is expected to rise by 50% between 2019 and 2050.

But its process involves purifying iron ore

in blast furnaces, with a refined form of coal called coke.

And just like cement, this production produces a lot of CO2.

In Europe, blast furnace owners

are testing hydrogen as an alternative way

to take the carbon out of iron ore.

But again, so far, it's way too expensive to go mainstream.

About double the cost of using coke.

There's one thing you can do with steel

that you can't do with cement.

And that is recycle.

Instead of producing more steel in the first place,

we can use what we already have.

Increasing the use of steel recycling is now commonly seen

as critical to reducing carbon emissions.

Now agriculture requires a multi-pronged effort,

as it is responsible for nearly 25%

of global CO2 emissions.

The practice of controlled burns after harvests,

the use of inorganic fertilizers

that release methane and nitrous oxide into the air,

the destruction of rainforests for ranching,

and even livestock flatulence, all need to be addressed

to put a dent in agriculture's carbon output.

Some hope can be seen in the US,

as demands for beef products have dropped significantly.

Additionally, interest in alternatives,

like Beyond Meat and Impossible Burgers,

have soared in recent years.

And for those who can't quit beef,

scientists are developing climate-proof cows,

with digestive systems that produce less methane.

But implementing these solutions globally

remains an uphill battle.

Even as more people in Europe and the US

take up vegetarian alternatives,

increased meat demand in China and other developing nations

means that globally, animal product consumption

is expected to rise 60% by 2050.

You are the last best hope of Earth.

We are in the beginning of a mass extinction,

and all you can talk about is money

and fairy tales of eternal economic growth.

How dare you.

It'll take policy makers and companies

years of diligent work and collaboration

to move industry away from its most polluting methods.

But each of these industries is working on answers,

with some executives confident

they can be both green and show a profit.