4 Strategies to reduce global warming

1. Use public transportation to reduce vehicle exhaust. Vehicles emit large amounts of greenhouse gases (and other pollutants that deplete the ozone layer or form smog), so the use of private vehicles should be minimised as much as possible. Walking, cycling, shared transport, electric vehicles and metro systems help.
2. Improve energy efficiency using energy-efficient technologies in homes and factories (high-efficiency electrical appliances, LED lamps), and switch to clean, renewable energy sources such as solar energy, wind energy and hydropower. Egypt has large solar and wind potential (for example the Benban solar park near Aswan, and wind farms in the Gulf of Suez and Zafarana).
3. Increase green spaces (afforestation). Vegetation increases the amount of photosynthesis that plants perform, which has a fundamental role in absorbing carbon dioxide, the main cause of global warming; so afforestation is one of the most important methods to reduce global warming. (Trees also cool the air by transpiration and shade and reduce dust.)

Further measures: reducing food and material waste; capturing methane from landfills; sustainable agriculture; recycling; carbon capture and storage; international agreements such as the 2015 Paris Agreement (limit the global temperature rise to well below 2 °C and develop renewable energy).

Problem. (a) A car burns 1 litre of petrol (assume pure octane C₈H₁₈, density 0.74 kg/L, M = 114). How much CO₂ is produced? (b) A household replaces five 60 W incandescent lamps by five 9 W LED lamps, each used 5 hours per day. How much electricity and CO₂ is saved in a year if generating 1 kWh emits 0.5 kg CO₂? (c) A tree absorbs about 22 kg CO₂ per year. How many trees are needed to absorb the CO₂ from (a) per 1000 litres?

Solution. (a) 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O. Mass = 0.74 kg = 740 g → 6.49 mol octane → 8 × 6.49 = 51.9 mol CO₂ → 51.9 × 44 = 2285 g ≈ 2.3 kg CO₂ per litre. (b) Power saved = 5 × (60 − 9) = 255 W = 0.255 kW; energy per day = 0.255 × 5 = 1.275 kWh; per year = 1.275 × 365 = 465 kWh; CO₂ saved = 465 × 0.5 = 233 kg. (c) 1000 litres produce 2285 kg of CO₂; one tree absorbs 22 kg per year → 2285/22 = 104 trees for one year (or 104 trees needed to absorb the CO₂ of 1000 litres of petrol every year).

• Air pollution is one of the greatest dangers to the atmosphere and to the health of living organisms.
• The most prominent pollutants are: sulfur oxides (SO₂, SO₃), carbon monoxide (CO) and nitrogen oxides (NO, NO₂).