Cognito · AQA ChemistryLife cycle assessment and the 6Rs
Key facts
Extracting metals — traditional and new methods
Metals extracted from ores by reduction (carbon) or electrolysis (above carbon in reactivity).
Phytoremediation — plants absorb metal compounds through roots; plants harvested and burned, metal extracted from ash.
Bioleaching — bacteria feed on low-grade ores, producing acidic leach solution containing metal ions → metal extracted by displacement or electrolysis.
Both are more sustainable than traditional mining for low-grade ores.
Life Cycle Assessment (LCA)
Assesses environmental impact of a product through its entire life cycle.
Stages: raw material extraction → manufacturing → use → disposal.
Considers: water use, energy use, carbon emissions, waste produced.
Limitations: some stages are difficult to quantify. Subjective — what counts as "environmental impact"?
Used to compare products (e.g. paper vs plastic bags).