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.
Refineries, fertiliser plants and steelworks use millions of tonnes of hydrogen made from natural gas, and that hydrogen carries a heavy carbon footprint.
Heating buildings is one of Europe's largest sources of carbon emissions, and most homes still burn gas or oil to do it.
