Gardeners often turn dead plant material from their garden into compost. They then add this compost to the soil where they are growing plants.
Why do gardeners add compost to their soil?
Tick (✓) one box.
Compost can be made in a composting bin. In the bin aerobic bacteria turn dead plant material into compost.
Some people use a different way of making compost, called bokashi. In this process the compost is made anaerobically.
The drawings show a normal composting bin and a bokashi bin.
Explain the difference in the design of the two composting bins..
Scientists investigate the two methods of making compost.
This is their method:
- Take one large pile of dead plant material
- Divide the material into two samples of equal mass
- Place one sample into the normal composter and place one sample into the bokashi composter
- Measure the temperature in each composter every 10 days
- After 40 days, measure the mass of the compost.
Write down one way that the scientists make sure that they can draw valid conclusions.
Table 18.1 shows the scientists’ temperature readings.
Temperature of the compost (°C) | ||
Time (days) | normal compost | Bokashi compost |
0 | 26 | 26 |
10 | 70 | 27 |
20 | 53 | 29 |
30 | 42 | 31 |
40 | 28 | 28 |
Table 18.2 shows the scientists’ results for the mass of the compost.
Normal compost | Bokashi compost | |
Mass at start (kg) | 1500 | 1500 |
Mass after 40 days (kg) | 750 | 1100 |
A gas is given off in the formation of the compost. This causes most of the decrease in mass.
Calculate the percentage decrease in the mass of the bokashi compost.
Give your answer to 2 significant figures.
Percentage decrease = .......................... % [3]
Use your answer from part (e)(i) to justify the scientists’ conclusion.
[2]
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