| name | life-cycle-assessment |
| description | Life cycle assessment (LCA) — ISO 14040/14044, system boundary, functional unit, inventory analysis, impact categories (GWP, AP, EP), carbon footprint, eco-design, EPD. |
| metadata | {"priority":7,"promptSignals":{"phrases":["life cycle assessment","LCA","carbon footprint","global warming potential","GWP","environmental impact","eco-design","cradle to grave"],"minScore":3}} |
Life Cycle Assessment (LCA) — Complete Skill
LCA Framework (ISO 14040/14044)
Four Phases
- Goal and Scope definition: purpose, functional unit, system boundary, assumptions
- Life Cycle Inventory (LCI): data collection — all inputs (energy, materials) and outputs (emissions, waste)
- Life Cycle Impact Assessment (LCIA): translate inventory into environmental impact scores
- Interpretation: identify hotspots, sensitivity analysis, conclusions
Functional Unit
Standardizes comparison: e.g., "1 tonne of steel delivered to customer" or "1 passenger-km of transportation"
Must be consistent across compared systems
System Boundaries
Cradle-to-gate: raw material extraction to factory gate (excludes use + disposal)
Cradle-to-grave: includes use phase and end-of-life
Cradle-to-cradle: closed loop; recycling brings material back
Gate-to-gate: process-specific; component manufacturing only
Life Cycle Stages
- Raw material extraction: mining, farming, forestry
- Material processing: refining, alloying, purification
- Manufacturing: machining, welding, assembly, surface treatment
- Transport (logistics): all transportation throughout supply chain
- Use phase: energy consumption in operation, consumables
- End-of-life: recycling, landfill, incineration, reuse
Impact Categories (Midpoint)
| Category | Abbreviation | Unit | Example contributor |
|---|
| Global Warming Potential | GWP | kg CO₂-eq | Combustion, CH₄ |
| Acidification Potential | AP | kg SO₂-eq | SO₂, NOx emissions |
| Eutrophication Potential | EP | kg PO₄³⁻-eq | N, P to water |
| Photochemical Ozone Creation | POCP | kg C₂H₄-eq | VOCs, NOx |
| Ozone Depletion | ODP | kg CFC-11-eq | Refrigerants |
| Resource Depletion (fossil) | ADP_fossil | MJ | Fuel combustion |
| Human Toxicity | HTP | kg 1,4-DCB-eq | Heavy metals, chem |
| Land Use | — | m² yr | Agriculture, mining |
Characterization factors: convert specific substance emissions to impact category units
From IPCC, EDIP, ReCiPe, CML methodologies
Carbon Footprint (GWP100)
Most common LCA metric; Global Warming Potential over 100-year horizon
GWP100 characterization factors (IPCC AR5):
CO₂: 1 kg CO₂-eq/kg
CH₄ (biogenic): 28 kg CO₂-eq/kg
CH₄ (fossil): 36 kg CO₂-eq/kg
N₂O: 265 kg CO₂-eq/kg
HFC-134a: 1430 kg CO₂-eq/kg
SF₆: 23,500 kg CO₂-eq/kg
Material carbon footprints (typical, kg CO₂-eq/kg):
Primary steel: ~2.0; Recycled steel: ~0.4
Primary aluminum: ~11–16; Recycled Al: ~0.6–1.5
CFRP: ~20–35 (energy-intensive fiber production)
Concrete: ~0.1–0.2 (but high volumes)
Plastic (HDPE): ~2.0; ABS: ~3.5
LCI Data Sources
Databases:
ecoinvent: gold standard; Swiss; 18,000+ datasets; commercial license
GaBi (Sphera): industry-oriented; North America, Europe
ELCD (European Commission): free; basic processes
EPD (Environmental Product Declaration): verified manufacturer LCA data
Primary data: measured from specific processes (preferred for foreground)
Secondary data: from databases (background system; upstream)
Energy Carbon Intensity (Electricity)
GWP of electricity varies by grid mix:
| Grid | kg CO₂-eq/kWh |
|---|
| Norway (hydro) | 0.017 |
| France (nuclear) | 0.056 |
| EU average | 0.275 |
| US average | 0.390 |
| Germany | 0.366 |
| India | 0.710 |
| Coal-dominated | 0.9–1.0 |
Use regional grid data for operational phase calculations
LCIA Methods
ReCiPe 2016: comprehensive; hierarchist perspective; midpoint + endpoint
CML 2002: established European; conservative; midpoint only
TRACI 2.1: North American; EPA; different impact categories
ILCD: EU preferred; harmonized
Eco-Design Principles
Identify hotspots → redesign for lower impact:
Material selection: lower embodied carbon (e.g., bio-based, recycled content)
Weight reduction: less material use; lower use-phase energy (automotive, aerospace)
Design for disassembly: separable components → higher recycling rate
Energy efficiency (use phase): often dominates for appliances, vehicles
End-of-life design: single materials, marked polymers, no hazardous coatings
Sensitivity and Uncertainty
Foreground data variation: ±10–30% typical
Background data: ±20–50%
Impact characterization: ±10–40%
Total GWP uncertainty: factor of 1.5–3× typical for product LCA
Environmental Product Declaration (EPD)
Verified third-party LCA disclosure; PCR (Product Category Rules) define scope
ISO 21930 (construction); ISO 14025 (general EPD)
Used in: green building certification (LEED, BREEAM); procurement requirements
Output
Provide: functional unit, system boundary, GWP per functional unit [kg CO₂-eq], top three impact category results (with units), life stage breakdown (% contribution from manufacturing/use/EoL), key hotspots, eco-design recommendation, EPD applicability.
