Most emissions have an electric answer. About a third do not, not yet or not cheaply: making cement and steel, flying, shipping, and farming animals and rice. Each is hard for its own reason, and none of the reasons is laziness. This lesson takes them one at a time.
Limestone at 1,450°C→The rock gives off gas→The powder is cement→Rock gives half the gas
Cement is made by cooking limestone rock in an oven called a kiln until it breaks apart. About half of cement's carbon dioxide does not come from the fuel. It comes out of the rock itself. Run the kiln on clean electricity and that half remains. Cement alone is about 7 in 100 of the world's carbon dioxide.
From the fuel50%
From the rock itself50%
Where a cement kiln's carbon dioxide comes from.
A cement kiln switches from coal to clean electricity. What happens to its carbon dioxide?
About half goes. The half from the rock remains.
Right. Heating the rock cleanly changes where the heat comes from, not what the rock does when it gets hot. Limestone gives off carbon dioxide as it breaks apart, whatever heats it.
None of it. It is the same rock.
Not yet. The rock's half stays, but the fuel's half was real and is gone. Cement on clean power is half as bad, which is a lot, and not all the way.
All of it goes. Nothing is burning any more.
Not yet. The fuel half goes. The rock half is chemistry, not burning: limestone is carbon and calcium and oxygen, and cooking it lets the carbon go. No fuel is involved in that half.
Steel from ore, with coal1.8 tonnes
Steel from scrap, in an electric furnace0.4 tonnes
Carbon dioxide for each tonne of steel made.
Steel is iron with the oxygen taken out. Today coal does the taking, in a furnace, and the oxygen leaves as carbon dioxide: about 1.8 tonnes for every tonne of steel. Hydrogen, a gas, can do the job instead and leave water. Making that hydrogen takes a lot of clean electricity. The first such plants are being built now.
The hard third, by kind. Tap the slice where the gas comes mostly from living things, not from anything burned or cooked.
Tap the part of the picture that answers it.
Cement7%
Steel7%
Chemicals and plastics4%
Planes3%
Ships3%
Cows, rice and fertiliser11%
Everything else: has a plug or a clean swap65%
Cows, rice and fertiliser
Right. Cows belch methane, flooded rice fields breathe it out, and fertiliser gives off a third gas, nitrous oxide. Three gases, none of them from a fire, and no motor to swap in.
Cement
Not yet. Cement's problem is the rock: heat limestone and it gives off carbon dioxide on its own. Chemistry, not a living thing.
Steel
Not yet. Steel's problem is that coal is the chemical pulling oxygen off the iron. Chemistry again.
Chemicals and plastics
Not yet. Most plastics are made from oil, and the oil is the raw material, not just the fuel. Chemistry.
Planes
Not yet. A plane's problem is weight: nothing yet holds as much energy per kilogram as jet fuel.
Ships
Not yet. A ship's problem is distance: weeks at sea with no plug, and a cargo that must not be all battery.
Everything else: has a plug or a clean swap
Not yet. The two thirds with a motor, a heat pump or a clean electricity source waiting. The last lesson was about this part.
Move the control to set how far a 180-seat jet flies. It burns about 3.5 kilograms of fuel a kilometre; a battery holding the same energy weighs about forty times as much as the fuel.
Jet fuel needed1.8 tonnes
Battery holding the same energy70 tonnes
The whole plane, full, at take-off79 tonnes
How far the plane flies: 500 km
500 km needs about 1.8 tonnes of jet fuel. A battery holding the same energy would weigh about 70 tonnes, under the plane's weight.
Jet fuel needed5.3 tonnes
Battery holding the same energy210 tonnes
The whole plane, full, at take-off79 tonnes
How far the plane flies: 1,500 km
1,500 km needs about 5.3 tonnes of jet fuel. A battery holding the same energy would weigh about 210 tonnes, more than the whole loaded plane.
Jet fuel needed17.5 tonnes
Battery holding the same energy700 tonnes
The whole plane, full, at take-off79 tonnes
How far the plane flies: 5,000 km
5,000 km needs about 17.5 tonnes of jet fuel. A battery holding the same energy would weigh about 700 tonnes, more than the whole loaded plane.
Jet fuel needed35 tonnes
Battery holding the same energy1,400 tonnes
The whole plane, full, at take-off79 tonnes
How far the plane flies: 10,000 km
10,000 km needs about 35 tonnes of jet fuel. A battery holding the same energy would weigh about 1,400 tonnes, more than the whole loaded plane.
At what distance does the battery alone weigh more than the whole loaded plane?
Only past 10,000 kilometres.
Not yet. At 10,000 km the battery would weigh 1,400 tonnes, eighteen planes' worth. It passed the plane's own weight long before that, at about 1,500 km.
Never. Batteries get lighter every year.
Not yet. They do, by about 5 in 100 a year. A forty-fold gap at that pace takes many decades to close. The rule from the last chapter makes batteries cheaper fast and lighter slowly.
Already by 1,500 kilometres: 210 tonnes of battery against a 79-tonne plane.
Right. A short hop of 500 km is just about thinkable. Anything further and the battery outweighs the aircraft it is meant to lift. That is why the first electric planes are small and fly short.
Move the control.
Over its first 20 years80×
Over 100 years28×
Methane's heat-catching power, against the same weight of carbon dioxide.
Cows and sheep belch methane as they digest grass. Methane lasts only about twelve years in the air. Over twenty years it catches about 80 times as much heat as carbon dioxide does. Flooded rice fields breathe it out too. Fertiliser gives off a third gas, nitrous oxide. Farming is about 11 in 100 of the world's warming gases.
How much of the world's land that is not ice or desert is used for farming?
Pick one. Nothing is scored.
Farmland50%
Forests37%
Shrub and grassland11%
Towns and roads1%
Lakes and rivers1%
The world's land that is not ice or desert.
About 50 in 100.Half. And of that farmland, more than three quarters is for animals, as grazing or as land growing their feed, giving under a fifth of the world's calories. Keeping forests, growing food and holding carbon all compete for the same land.
Three different walls. Which wall does each of these run into?
One card at a time. Tap the pile it belongs to.
Card 1 of 6
Cement
Steel from ore
Long-distance flights
Cargo ships
Beef
Rice
Cement → Chemistry
Not yet. Cement hits the chemistry wall. The limestone gives off carbon dioxide as it cooks, whatever the fire is.
Steel from ore → Chemistry
Not yet. Steel from ore hits the chemistry wall. Pulling oxygen off iron needs a chemical, and today it is coal.
Long-distance flights → Weight
Not yet. Flights hit the weight wall. A battery that holds enough energy for a long flight is heavier than the plane.
Cargo ships → Weight
Not yet. Ships hit the weight wall. Weeks at sea need a fuel that packs a lot of energy into little weight.
Beef → It is alive
Not yet. Beef hits the alive wall. A cow's stomach makes methane as it digests, whatever the cow is fed.
Rice → It is alive
Not yet. Rice hits the alive wall. Flooded rice fields grow tiny living things that give off methane, and the plant needs the flood.
Chemistrycement, steel
++
Weightflights, ships
++
Alivebeef, rice
One wall each. The fixes are different for each wall.Right. Chemistry: the gas is made by the process, not the fire. Weight: nothing yet holds as much energy per kilogram as a fuel. Alive: a cow's digestion makes methane whatever it is fed, a little less with some feeds and never none.
Solar runs the lights, motors and rollers
++
Coal still pulls the oxygen off the iron
A company says its new factory runs entirely on solar power, so its steel is carbon-free. The factory makes steel from iron ore using coal. What is true?
The solar power cancels out the coal.
Not yet. Clean electricity for the lights does not take back the gas the furnace made. Nothing here cancels; the furnace's carbon dioxide went up and is in the bath.
The steel is carbon-free. The power is solar.
Not yet. The power is one part of a steelworks. The furnace is another, and in it coal is not a fuel but a chemical, doing a job electricity cannot do to iron ore. That job makes the carbon dioxide.
The electricity is clean, but the coal in the furnace still makes about 1.8 tonnes of carbon dioxide for every tonne of steel.
Right. Solar runs the lights, the motors and the rollers. It does not touch the chemistry: coal is still the thing pulling oxygen off the iron, and that is where most of a steelworks' carbon dioxide comes from.
Lesson complete
Cement, steel, planes, ships and farming make about a third of emissions and have no cheap swap yet.