In much of rural India, dinner is still cooked on a mud chulha fed with wood, crop waste and dung cakes, filling the kitchen with smoke.
Factories that make sugar, food, chemicals and paper burn gas in boilers to raise steam, while warm wastewater and vapour go straight down the drain or up the chimney.
Hundreds of millions of rural families cook on smoky wood or dung fires, while manure from their cattle releases methane into the air.
Cement is the glue of modern construction, and about 7% of global CO2 emissions, much of it released by the chemistry of limestone itself.
Making new aluminium from bauxite takes huge amounts of electricity, and where that power comes from coal, each tonne can carry 15 tonnes of CO2 or more.
Every window, glass facade and balcony panel starts in a furnace burning natural gas at around 1,500°C, melting sand, soda ash and limestone.
In Indian cities, an auto-rickshaw or cargo three-wheeler earns money only while it is moving. Waiting four hours to recharge, or queuing at a battery swap station, eats directly into a driver's income.
Lithium-ion batteries have become the default way to shift solar power into the evening, but they wear out with heavy cycling and are usually built for two to four hours of output.
Europe is wasting a growing share of its renewable electricity because there is nowhere to put it when the wind blows hardest. Lithium-ion batteries empty in a few hours, which is not enough for a calm, grey week in winter.
Conventional geothermal power needs hot rock, natural water and permeable ground in the same place, which is why it is concentrated in volcanic regions such as Iceland, Kenya and Indonesia.
For decades, enhanced geothermal systems were the energy technology that was always ten years away: engineer a reservoir in hot, dry rock anywhere, and you could have clean power around the clock.
Most people picture geothermal energy as steaming volcanic power stations. In Sweden, it is a 200-metre hole in the garden and a fridge-sized box in the utility room.
Small modular reactors have been promised for two decades, but very few have moved from paper to concrete.
About Nuclear Power Corporation of India
India has built heavy water reactors since the 1970s, but for decades its standard unit was a modest 220 MW.
Since the 1950s, critics of nuclear power have asked one question: where does the waste go?
Europe installs tens of gigawatts of solar every year but makes only a tiny share of the panels itself.
Almost every solar panel in the world is made from crystalline silicon, and most of that silicon supply chain runs through China.
Most of the surface area of our buildings cannot carry heavy glass solar panels: weak roofs, curved surfaces and tall concrete facades.
Warehouses and factories have huge flat roofs, and solar panels cover many of them, but solar goes quiet in the evenings and in winter.
Construction sites, farms and islands still burn diesel because the grid is full, far away or not there at all.
Wind turbines are mostly steel, copper and concrete that can already be recycled, but their giant composite blades have usually been cut up and buried or burned.
