UNIT 2 CHEMISTRY · PEARSON AAQ · E1.10
Solutions to Environmental Problems
FREE CHEMISTRY REVISION · TOPIC 68
Solutions to Environmental Problems
Pearson BTEC Level 3 AAQ Applied Science
Unit 2: Principles and Applications of Chemistry · E1.10
What you will learn
- Match solutions to the particular combustion, refrigerant, plastic or ethanol-related problem.
- Explain how each solution works and identify its limitations.
- Use lifecycle reasoning and data to justify a realistic environmental choice.
1. Start with the cause and a measurable goal
An effective environmental solution must target the cause of a problem. Better combustion can reduce CO but does not remove the CO₂ formed from fuel carbon. Replacing a CFC can protect ozone but may introduce a climate, toxicity or flammability trade-off. A polymer being made from plants does not guarantee biodegradation. Identify the pollutant, the route into the environment and the function that still needs to be delivered.
Compare equal service: the same useful heat, the same number of safely packaged meals, or the same cooling duty. Assess manufacture, energy use, transport, use, collection and disposal. State your assumptions and distinguish measured evidence from a claim on a label.
2. Reduce harmful combustion emissions
| Action | Why it helps | Limitation / trade-off |
|---|---|---|
| Maintain burners and improve oxygen mixing | Promotes more complete oxidation, reducing CO, unburned fuel and soot. | Carbon still forms CO₂; hotter combustion can favour NOₓ formation. Appropriate control is needed. |
| Catalytic converters | Suitable catalysts oxidise CO and unburned hydrocarbons and can reduce NOₓ in appropriately controlled exhaust systems. | Require suitable temperature and operating conditions; do not remove all emissions or fuel-derived CO₂. |
| Particle filters | Capture soot particles before release. | Need maintenance and regeneration; do not capture CO₂ as their principal function. |
| Low-sulfur fuels / flue-gas desulfurisation | Reduce sulfur inputs or remove SO₂ from exhaust using a suitable sorbent. | Energy, materials and by-products must be managed. Pure alkanes contain no sulfur. |
| Efficiency and lower-carbon energy | Insulation, efficient equipment and reduced unnecessary transport can reduce fuel demand; low-carbon electricity can replace some combustion. | Manufacture and electricity generation have impacts; performance depends on the system and energy source. |
| Carbon capture for suitable large sources | Separates some CO₂ for controlled transport and long-term storage. | Needs energy and infrastructure, has costs and does not capture every emission or remove other lifecycle impacts. |
3. Chemistry behind emission control
Oxidation of CO: 2CO + O₂ → 2CO₂. This reduces a toxic gas but produces CO₂, so it addresses a different problem from climate mitigation. A simplified reaction between CO and nitric oxide is 2CO + 2NO → 2CO₂ + N₂. Both C=2, O=4 and N=2 are conserved. Real exhaust systems require controlled conditions and multiple reactions; these equations illustrate chemical functions, not a universal conversion efficiency.
A simplified limestone scrubbing equation is CaCO₃ + SO₂ → CaSO₃ + CO₂. C=1, Ca=1, S=1 and O=5 on each side. Industrial systems can further oxidise sulfite to sulfate; sorbent supply and by-products matter. Reducing SO₂ is valuable even when the process is not carbon-free.
4. Replace ozone-depleting refrigerants responsibly
Phase out CFC uses, prevent leaks and recover refrigerants during servicing and disposal. Recovery matters because existing equipment can contain a stored stock of refrigerant even after new production has been restricted. International action such as the Montreal Protocol addresses ozone-depleting substances; this does not mean every old appliance is already harmless.
Many HFC replacements do not deplete ozone because they contain no chlorine or bromine, but many have high global warming potentials. Lower-GWP options can include suitable HFOs, hydrocarbons, CO₂ or ammonia in appropriate systems. These alternatives have different pressure, flammability, toxicity, efficiency and decomposition-product considerations. Use an engineered system suitable for its refrigerant; an alternative is not a universal drop-in substitute.
Compare both direct leakage impact and the indirect impact of energy use. A low-GWP refrigerant in a very inefficient system can lose some of its climate advantage. Preventing leaks, improving efficiency and recovering the refrigerant work together.
5. Prevent plastic waste, retain material value
| Approach | Benefit | What must be checked |
|---|---|---|
| Reduce | Avoid unnecessary material and energy use. | Maintain essential hygiene, safety and food protection. |
| Reuse / refill | Spread manufacture impacts across repeated uses. | Actual reuse count, cleaning energy/water, transport and loss rates. |
| Mechanical recycling | Sort, clean and reprocess compatible thermoplastics into useful products. | Contamination, mixed polymers, additives, quality loss and local acceptance. |
| Chemical recycling / depolymerisation | Some processes recover monomers or useful chemical feedstocks from suitable waste. | Energy use, yield, emissions, solvents and whether products replace virgin material; not all plastics suit every process. |
| Controlled energy recovery | Extract useful energy from non-recyclable waste under managed conditions. | CO₂ emissions, air-pollution control and ash; open burning is not equivalent. |
| Managed disposal | Contains residual waste where recovery is impractical. | Loss of resources, space use and leakage control. Prevention is preferable where feasible. |
Design for collection: use compatible materials, make components separable and avoid unnecessary mixed laminates. A recycling symbol is not proof of local collection. Follow the relevant local waste service’s acceptance rules rather than assuming all polymer items belong in the same stream.
6. Alternative materials: define the conditions
Bio-based means some or all feedstock comes from biological sources. Biodegradable means microorganisms can break the material down under specified conditions and timescales. Compostable materials meet defined composting conditions; industrial compostability does not guarantee rapid breakdown in the sea, soil or a home compost heap. These terms describe different features.
PLA and other suitable biodegradable polyesters may be helpful for particular products with an appropriate collection and treatment system. They are not permission to litter. Compostable packaging can contaminate conventional recycling streams. Check the receiving facility’s requirements and the product’s certification. A bio-based poly(ethene) molecule can still be persistent; a biodegradable polymer can be made from fossil-derived feedstock.
Paper, glass, metal and reusable materials also need resources and energy. Compare total use, breakage, transport mass, cleaning and disposal, rather than assuming a non-plastic label proves a lower impact.
7. Cleaner fuels and processes
For ethanol, choose feedstocks and production routes using lifecycle evidence. Waste or residue feedstocks can reduce competition with food or land, although collection and processing still cost energy. Renewable process heat, efficient distillation and heat recovery can reduce emissions. Crop feedstocks require attention to fertiliser, water, biodiversity and land-use change; renewable does not mean unlimited or impact-free.
For polymer and organic-chemical production, catalysts can improve selectivity and reduce energy requirements; recovering solvents and unreacted monomers can reduce waste. Renewable electricity, heat integration and efficient separations can cut process impacts. Evaluate catalyst manufacture, toxicity, solvent losses and actual yields. A cleaner production route does not solve litter or end-of-life management on its own.
Worked and applied evaluations
Example 1 · CO control versus climate control
A converter changes 2 mol CO into 2 mol CO₂ using oxygen. It reduces CO toxicity. It does not remove fuel carbon from the atmosphere. Pair local pollution control with efficiency and low-carbon energy measures where appropriate.
Example 2 · Refrigerant leakage calculation
Illustrative supplied data: a system contains 2.0 kg refrigerant with GWP 1000 and leaks 5% in a year. Leaked mass = 2.0 × 0.05 = 0.10 kg. Direct climate impact = 0.10 × 1000 = 100 kg CO₂-equivalent. This is not the whole system footprint; electricity use and other lifecycle stages are additional.
Example 3 · Reusable-container threshold
Illustrative data: a reusable item has 1000 g CO₂-equivalent manufacturing impact and washing costs 5 g per use; a single-use alternative costs 30 g per use. At N uses: reusable = 1000 + 5N; single-use = 30N. Equality at N=40. Above 40 actual uses, reuse is lower under these assumptions. Include transport, losses and performance if the question supplies them.
Example 4 · Compostable cup decision
A venue has no collection route to an accepting industrial composting facility. A compostable cup is unlikely to deliver its intended disposal benefit. A well-run reuse system or accepted recyclable design may perform better. Do not put it into ordinary plastic recycling solely because it looks plastic.
Example 5 · Evaluate a bioethanol claim
A producer uses crop sugar and fossil-fuelled distillation. Suggested improvements: recover heat, use lower-carbon process energy and assess residue feedstock. Limitations: capital costs, feedstock availability and farming effects. Conclude using equal useful energy and full lifecycle data, not a claim of zero exhaust CO₂.
Example 6 · Exam-style evaluation: mixed waste
Question: Should all waste plastics be burned for electricity? Model answer: controlled energy recovery can handle some non-recyclable waste and displace other energy, but emits CO₂ and loses polymer material. Reduce, reuse and appropriate recycling can retain more value. Judge the remaining waste stream, plant controls and alternative energy source; “burn everything” is not a justified universal solution.
Common misconceptions and examination tips
- A catalytic converter is not a CO₂ removal device.
- Ozone-safe does not mean climate-neutral; consider GWP, leakage and energy use.
- Bio-based, biodegradable, recyclable and compostable are different claims.
- Specify the waste route, facilities and conditions that make a proposed solution work.
- For calculations, show leaked mass, units and assumptions; CO₂-equivalent is a comparison metric, not a statement that the refrigerant is CO₂.
- End an evaluation with a supported, conditional judgement rather than “there are advantages and disadvantages”.
Check your understanding
Choose one answer, select Check Answer, then read the explanation. Try Again resets the question. Use Tab between controls, arrow keys within a radio group, and Enter or Space on buttons. Answers are not saved.