4.12.3Additional lessons
Carbon Sequestration — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 101 of 101
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Natural Carbon Sinks
Carbon sequestration is the long-term removal of carbon dioxide from the atmosphere into a store.
Forests
- Forests Trees take in carbon dioxide by photosynthesis and store the carbon in wood, roots and soil for decades.
Peat
- Peat In waterlogged acidic bogs decomposition is slow because oxygen is scarce, so partly decayed plant matter builds up as peat.
Oceans
- Oceans Carbon dioxide dissolves in seawater, and marine organisms build shells of calcium carbonate that sink and form sediment.
Fossil fuels
- Fossil fuels Over millions of years buried organic matter was turned into coal, oil and natural gas, locking carbon away.
| Sink | Typical storage time | Threat |
|---|---|---|
| Forest biomass | Decades to centuries | Felling and fire |
| Peatland | Thousands of years | Drainage and burning |
| Ocean sediment | Very long | Acidification effects |
| Fossil fuel | Millions of years | Extraction and burning |
Part 2 of 5Peat and Fossil Fuel Formation
1
Plants in waterlogged ground die but do not fully decompose because anaerobic and acidic conditions slow decomposers.
2
Layers of partly decayed plant material accumulate as peat, which holds large quantities of carbon.
3
Burial under sediment over millions of years applies heat and pressure that convert organic matter to coal, oil or gas.
4
Burning these fuels reverses the process and returns the stored carbon to the atmosphere as carbon dioxide within a short time.
Part 3 of 5Enhancing Sequestration
Enhancing Sequestration
Afforestation
- Afforestation Planting new forests increases the biomass carbon store, provided that the trees survive and grow.
Peatland protection
- Peatland protection Stopping drainage and restoring wetness keeps stored carbon in place and may resume accumulation.
Carbon capture
- Carbon capture Technology can trap carbon dioxide at power stations and pump it underground, but it is costly.
Evaluation
- Evaluation Most strategies need decades to work, so reducing emissions remains essential.
Part 4 of 5Worked Example
Question
- Clearing 50 hectares of forest that stored 120 tonnes of carbon per hectare releases all carbon as CO₂.
- Calculate the mass of CO₂ produced (C = 12, CO₂ = 44).
- Carbon released = 50 × 120 = 6 000 tonnes.
- Mass of CO₂ = 6 000 × (44 ÷ 12) = 22 000 tonnes.
Answer 22 000 tonnes of CO₂
Part 5 of 5Exam Checklist & Tips
4.12.3 – Key Points for the Exam
- Carbon sink A store that takes in more carbon than it releases.
- Carbon source A store or process that releases more carbon than it takes in.
- Sequestration Long-term removal of carbon from the atmosphere into a store.
- Peat Partly decomposed plant material formed in waterlogged conditions.
- Afforestation Planting trees on land that has not recently been forest.
Common Mistakes
- Stating that forests are permanent stores, when fire, disease or felling can release the carbon.
- Saying peat forms because plants do not decay at all.
- Mixing up a sink with a source.
- Forgetting that burning fossil fuels moves carbon from a very long-term store to the atmosphere.
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