Most polymers end up as waste, and each method of dealing with them has advantages and disadvantages.Landfill
• For: cheap and easy; little sorting needed.
• Against: uses up land; non-biodegradable polyalkenes last for a very long time; decomposing waste can release methane, a greenhouse gas; toxic additives can leach into ground water.Incineration (burning)
• For: greatly reduces the volume of waste; the heat released can generate electricity.
• Against: produces carbon dioxide, a greenhouse gas; incomplete combustion gives toxic carbon monoxide; burning chlorine-containing polymers such as PVC releases toxic HCl, so waste gases must be treated, for example by passing them through a base.Recycling
• Mechanical: sorted plastic is washed, melted and remoulded into new products.
• Chemical: condensation polymers can be hydrolysed back to their monomers, which are purified and polymerised again.
• For: saves crude oil, a finite resource, and energy; reduces landfill and CO2 emissions.
• Against: plastics must be collected and sorted by type, which is costly; recycled polymer is often lower quality, so it can only be reused a limited number of times.Worked example. Suggest why incinerating PVC needs more gas treatment than incinerating poly(ethene). PVC, [-CH2CHCl-]n, contains chlorine, so burning it releases hydrogen chloride. Poly(ethene) contains only C and H, so complete combustion gives only CO2 and H2O.
• For: cheap and easy; little sorting needed.
• Against: uses up land; non-biodegradable polyalkenes last for a very long time; decomposing waste can release methane, a greenhouse gas; toxic additives can leach into ground water.Incineration (burning)
• For: greatly reduces the volume of waste; the heat released can generate electricity.
• Against: produces carbon dioxide, a greenhouse gas; incomplete combustion gives toxic carbon monoxide; burning chlorine-containing polymers such as PVC releases toxic HCl, so waste gases must be treated, for example by passing them through a base.Recycling
• Mechanical: sorted plastic is washed, melted and remoulded into new products.
• Chemical: condensation polymers can be hydrolysed back to their monomers, which are purified and polymerised again.
• For: saves crude oil, a finite resource, and energy; reduces landfill and CO2 emissions.
• Against: plastics must be collected and sorted by type, which is costly; recycled polymer is often lower quality, so it can only be reused a limited number of times.Worked example. Suggest why incinerating PVC needs more gas treatment than incinerating poly(ethene). PVC, [-CH2CHCl-]n, contains chlorine, so burning it releases hydrogen chloride. Poly(ethene) contains only C and H, so complete combustion gives only CO2 and H2O.