Gardeners are investigating two different methods of aerobic composting to see which method decomposes organic plant waste faster: a Standard Bin and an Insulated Hotbin.
They start with two identical piles of green waste and record the mass of the waste at the start and after 30 days.
| Composting method | Mass at start (kg\text{kg}kg) | Mass after 30 days (kg\text{kg}kg) |
|---|---|---|
| Standard Bin | 180018001800 | 115011501150 |
| Insulated Hotbin | 180018001800 | 820820820 |
During aerobic decomposition, gases such as carbon dioxide are released, which accounts for most of the decrease in mass.
Calculate the percentage decrease in the mass of the organic material in the Standard Bin. Give your answer to 2 significant figures.
Calculate the percentage decrease in the mass of the organic material in the Insulated Hotbin. Give your answer to 2 significant figures.
Suggest why insulation in the Hotbin leads to a higher rate of decomposition.
67 exam-style questions on OCR GCSE Biology 4.1 Ecosystems, covering 4.1.1 Cycling of materials in ecosystems, 4.1.2 Microorganisms in cycling materials, 4.1.3 The carbon and water cycles, 4.1.4 Factors affecting decomposition, 4.1.5 Levels of organisation in an ecosystem, 4.1.6 Abiotic and biotic factors affecting communities, 4.1.7 Interdependence and competition, 4.1.8 Trophic levels, 4.1.9 Pyramids of biomass, and 4.1.10 Efficiency of biomass transfers. Each one has a worked solution and a mark scheme showing where the marks go.