Incineration means burning waste polymers at high temperature. Polymers are made from hydrocarbons, so they release a lot of energy when they burn. This energy is used to heat water and generate electricity or to heat buildings.For example, the complete combustion of poly(ethene):-[CH2-CH2]-n + 3n O2 → 2n CO2 + 2n H2O so each C2H4 repeat unit needs 3 mol of O2.Advantages: it recovers energy from waste, greatly reduces the volume of waste going to landfill, and can deal with mixed and dirty plastics that are hard to recycle.Problems:
• it produces carbon dioxide, a greenhouse gas
• incomplete combustion produces toxic carbon monoxide and soot
• burning chlorine-containing polymers such as PVC produces hydrogen chloride, HCl, a toxic and acidic gas
• the polymer, made from crude oil, is used up and cannot be reusedRemoving toxic gases: waste gases are passed through a scrubber, where a base neutralises the acidic gases. For example, calcium oxide removes HCl:CaO + 2HCl → CaCl2 + H2O Calcium carbonate can be used in the same way. Removing these toxic waste products is one way chemists make incineration more sustainable.
• it produces carbon dioxide, a greenhouse gas
• incomplete combustion produces toxic carbon monoxide and soot
• burning chlorine-containing polymers such as PVC produces hydrogen chloride, HCl, a toxic and acidic gas
• the polymer, made from crude oil, is used up and cannot be reusedRemoving toxic gases: waste gases are passed through a scrubber, where a base neutralises the acidic gases. For example, calcium oxide removes HCl: