Using energy: food, materials, mobility and buildings

By the end you will be able to

• Explain the difference between primary, final and useful energy, and give today's rough split of final energy by sector
• Describe how the Haber-Bosch process works, where its energy goes, and how much fossil energy sits in common foods
• Compare the energy cost per tonne of steel, cement, plastics, ammonia and aluminium, and explain why steel and cement emit CO2 from chemistry as well as fuel
• Use weight-to-payload ratios and energy density to explain why cars are easier to electrify than aircraft and ships
• Identify the main energy uses in buildings and explain why cooling, cooking fuels and appliance standards matter for India

Contents

1. Part 1 Where final energy goes

   Energy statistics usually start at the mine, the well and the dam. This part starts at the other end: the factories, vehicles and homes where energy is finally used. Looking at use first explains why some sectors are easy to clean up and others are stubborn, and why the same exajoule can be worth very different amounts depending on what it does.

   • Final energy is split roughly into thirds: industry, transport and buildings
   • We buy energy for heat, motion, light and information, and each service has its own carrier
   • Electrification shrinks the useful-energy gap, which is why demand forecasts look odd
2. Part 2 Food: nitrogen, ammonia and fossil-fuelled farms

   A modern meal is grown with sunlight, but it is also built with natural gas and diesel. The biggest single energy input to farming is not the tractor. It is the factory that pulls nitrogen out of the air. This part explains why nitrogen limits harvests, how the Haber-Bosch process solved that, and how much fossil energy sits inside common foods.

   • Crops are short of nitrogen even though air is mostly nitrogen
   • Haber-Bosch turns natural gas and air into ammonia at a cost of about 28 to 41 GJ a tonne
   • A modern meal embeds fossil fuel, measured best in spoonfuls of diesel
3. Part 3 Materials: steel, cement, plastics and aluminium

   Industry is the largest user of final energy, and a few materials dominate it. Smil names four pillars of modern civilisation: steel, cement, plastics and ammonia. Add aluminium and silicon and you have most of industry's energy bill and a large share of its CO2. This part looks at what each costs in energy and why.

   • A few bulk materials carry most of industry's energy bill
   • Steel and cement are energy-hungry because chemistry, not just heat, is involved
   • Plastics, aluminium and silicon trade small mass for very high energy per tonne
4. Part 4 Moving people and goods

   Transport takes over a quarter of final energy and runs on oil more than any other sector. Smil's way into it is through simple ratios: how heavy the vehicle is relative to what it carries, and how much energy a fuel packs per kilogram. Those ratios explain why cars are easier to electrify than ships and aircraft.

   • Cars move mostly themselves, which is why weight and drivetrain matter
   • Electric cars are now a quarter of global sales, led by China
   • Jets and ships need dense fuels, which is why they are the hardest to electrify
5. Part 5 Buildings and appliances

   Homes, offices, shops and public buildings use about a third of final energy, mostly for heat, cooling and appliances. Unlike steel mills, buildings are millions of small decisions by owners and tenants. That makes efficiency cheap in principle and slow in practice. For India, the story is dominated by cooking fuels and the rise of air conditioning.

   • Building energy is mostly low-temperature heat, but the mix depends on climate and income
   • Cooling is the fastest-growing use in buildings, and the efficiency gap is large
   • Lighting shows how much a better converter can save across a whole chain
6. Wrap-up Key terms, try it in the table, final quiz, sources