Mitigation of climate change Study Guide

📖 Core Concepts Climate‑change mitigation – Human actions that limit greenhouse‑gas (GHG) emissions or enhance carbon sinks (e.g., forests, soils, DAC). Carbon‑dioxide removal (CDR) – Anthropogenic techniques that pull CO₂ from the air and store it (direct‑air capture, biochar, afforestation, soil carbon). Net‑zero – Balance between emitted and removed CO₂; the IPCC says global net‑zero must be reached 2050 to stay within 1.5 °C. Primary vs secondary measures – Primary: clean energy, transport, industry decarbonisation. Secondary: land‑use change, CDR, carbon‑pricing. Levelized Cost of Electricity (LCOE) – Average cost ($/kWh) to produce electricity over a plant’s lifetime; solar PV ≈ $0.04 /kWh (2024). Heat‑pump COP – Coefficient of performance; typical COP = 3–5 (delivers 3–5 ×  the electricity input as heat). 📌 Must Remember 2020 emissions: 49.8 Gt CO₂‑eq; CO₂ = 72 %, CH₄ = 19 %, N₂O = 6 %. Fuel mix 2020: Coal 39 %, Oil 34 %, Gas 21 %, Cement 4 %. Peak‑by‑2025 rule – Global GHG emissions must peak no later than 2025. 2030 target – ‑43 % emissions needed for a 1.5 °C chance. Solar PV LCOE 2024: $0.039–0.041 /kWh. Wind capacity factor: offshore > onshore; peaks in winter, complementing solar. Heat‑pump advantage: 3–5 × heat for 1 × electricity. Carbon‑pricing coverage (2021): > 21 % of global emissions; EU ETS price ≈ €80/t CO₂ (2022). BECCS potential: up to 22 Gt CO₂ yr⁻¹ (theoretical). Direct Air Capture cost: $100–600 /ton CO₂. Forest carbon storage: intact US forests sequester ≈ 2 × their emissions. 🔄 Key Processes Renewable Integration Workflow Forecast variable output → (a) Transmission to regions with complementary patterns → (b) Storage (pumped hydro / batteries) → (c) Demand‑side management (smart‑grid load shifting). Carbon‑Dioxide Removal (CDR) Pathway Capture (DAC / BECCS / biochar) → Transport (pipeline/compression) → Geologic/soil/ocean storage → Monitoring (MRV). Heat‑Pump Heating Cycle Low‑temperature source (outside air/ground) → Evaporator (absorbs heat) → Compressor (adds work) → Condenser (rejects heat to building) → Expansion valve (returns low‑pressure refrigerant). Carbon Pricing Mechanism Tax: set price $/t CO₂ → emitters pay per tonne. Cap‑and‑Trade: set total cap → allocate allowances → allow buying/selling; price emerges from market. 🔍 Key Comparisons Solar PV vs. Wind Solar: higher output in summer, lower capacity factor, cheapest LCOE. Wind: higher output in winter, better capacity factor, needs more transmission. Natural Gas vs. Coal (electricity) Gas: ½ life‑cycle CO₂ of coal, but methane leaks can erase benefit. Coal: higher CO₂, higher particulate/health impacts, longer plant lifetimes. Carbon Tax vs. Emissions Trading Tax: price certainty, revenue generation; may not guarantee emission caps. ETS: quantity certainty (cap), price volatility; requires robust market oversight. BECCS vs. DAC BECCS: combines energy production with CO₂ capture; land‑use intensive. DAC: location‑flexible, high energy demand, higher cost per tonne. Afforestation vs. Reforestation Afforestation: trees on non‑forest land → slower carbon build‑up, possible land‑competition. Reforestation: restores existing forest soil carbon → faster sequestration, lower cost. ⚠️ Common Misunderstandings “Natural uptake = mitigation” – Only anthropogenic CDR counts; natural photosynthesis without human intervention is not counted as mitigation. “Renewables solve intermittency instantly” – Variable output needs flexible grids, storage, and demand‑side management. “Carbon pricing alone will cut emissions” – Without removing subsidies and complementary regulations, pricing impact is limited. “All bioenergy is carbon‑neutral” – Lifecycle emissions depend on land use, feedstock, and whether CO₂ is captured (BECCS). 🧠 Mental Models / Intuition Energy‑Carbon Triangle: (Supply → Demand → Sink) – every mitigation option either reduces supply (clean energy), lowers demand (efficiency, diet), or enhances sink (forests, soils, CDR). “Stacking” Concept – Layer multiple low‑cost measures (e.g., insulation + LED + smart thermostat) before moving to high‑cost solutions (e.g., nuclear). “Lock‑in Risk” – Investing in long‑lived fossil‑fuel infrastructure (coal, gas) creates a future emissions tail; think of it as a debt that must be repaid. 🚩 Exceptions & Edge Cases Methane leakage threshold – If leakage > 1 % of production, natural‑gas advantage over coal disappears. Solar PV cost spikes – In regions with high land‑use conflicts or supply‑chain bottlenecks, LCOE can rise above $0.06/kWh. Carbon pricing in developing economies – Regulatory instruments (standards, bans) are often more effective than market‑based taxes. Afforestation on water‑scarce land – May increase irrigation demand, offsetting carbon gains. 📍 When to Use Which Choose Solar PV when: high solar irradiance, land availability, need for rapid deployment, and cheap LCOE matter. Choose Wind when: strong wind resources, especially offshore, and seasonal complement to solar is needed. Deploy Energy Storage (batteries) for short‑term (< 24 h) fluctuations; pumped hydro for seasonal (> months) balance. Apply Carbon Tax in economies with strong fiscal capacity and need for revenue; ETS where a clear emissions cap is politically prioritized. Select BECCS when biomass feedstock is abundant and land‑use competition is manageable; DAC for regions lacking suitable land but with cheap renewable electricity. 👀 Patterns to Recognize “Winter peak → Solar dip → Wind high” – Expect higher wind generation when solar output is low. “High‑income diet → > 50 % emissions – Look for questions linking meat consumption to methane. “Policy mix = higher impact – Exams often pair carbon pricing with subsidy reform → synergistic emissions cuts. “Leak‑adjusted gas advantage – Check if methane leakage rates are given; if > 1 %, gas loses its advantage. 🗂️ Exam Traps Distractor: “Natural gas always reduces emissions vs. coal.” – Wrong if methane leakage is high. Distractor: “All bioenergy is carbon‑neutral.” – Ignored lifecycle emissions and land‑use impacts. Distractor: “Carbon pricing guarantees net‑zero.” – Overlooks need for caps, subsidies removal, and technology deployment. Distractor: “Afforestation alone can meet the 1.5 °C target.” – Neglects land‑competition, saturation, and time lag. Distractor: “Solar PV LCOE is $0.02/kWh everywhere.” – LCOE varies with local conditions; $0.039–0.041 is the 2024 global range. --- Use this guide to review key concepts, recall high‑yield facts, and avoid common pitfalls before your exam.