ACA 101: Airport Carbon Accreditation — What It Is, Who It Covers, and How It Works
The global voluntary carbon certification programme for airports. 800+ accredited across 97 countries. 7 levels from Mapping to Net Zero. Carbon credit integration and compliance with voluntary carbon markets.
By Koorosh Behrang & Abhishek Das • • 8 min read
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800+
Airports Accredited
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7 Levels
Mapping → Net Zero
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2009
Programme Launch
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What Is Airport Carbon Accreditation? |
ACA is the global voluntary carbon certification programme for airport operators, launched in 2009 and now covering 800+ airports across 97 countries. Managed by ACI Europe on behalf of the Airports Council International, ACA provides a structured framework for airports to measure, reduce, and offset emissions.
The programme requires ISO 14064 third-party verification and annual accreditation renewal. It is not a compliance mandate, but rather a market-driven certification that signals carbon management credibility to stakeholders, investors, and airlines.
ACA vs CORSIA Quick Reference
ACA = Airport Operators (voluntary, 7 levels, broad credit eligibility). CORSIA = Airlines (compliance mandate, single offset threshold, restricted credit eligibility). These are complementary frameworks targeting different parts of the aviation value chain.
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Who Is Covered? |
ACA covers airport operators, not airlines. Any airport worldwide can participate, regardless of ACI membership. The framework measures Scope 1 (direct), Scope 2 (purchased energy), and Scope 3 (indirect) emissions. At higher accreditation levels, airports must account for full Scope 3, including aircraft movements and tenant activities.
Airport operations account for roughly 5% of total aviation emissions; aircraft fuel burn makes up the rest. ACA captures the full picture by requiring Scope 3 reporting at higher levels — including aircraft landing and take-off cycles — which is what makes Levels 4+ and 5 so significant for carbon credit demand.
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What Emissions Are Included? |
ACA follows the GHG Protocol corporate standard. The emission scopes an airport must report expand as it progresses through the levels. At Levels 1–2, only Scope 1 and 2 are required. From Level 3 (Optimisation) onward, airports must begin accounting for Scope 3 sources.
Scope 1 — Direct Emissions
Emissions from sources the airport owns or controls directly. This includes on-site heating and cooling (boilers, chillers), airport-owned vehicle fleets (buses, baggage tugs, fire trucks), backup generators, and any fuel combusted on-site. For most airports, Scope 1 represents 10–30% of controllable emissions.
Scope 2 — Purchased Energy
Emissions from purchased electricity, heating, and cooling consumed by the airport. Terminal lighting, baggage handling systems, HVAC, runway lighting, and IT infrastructure all fall here. For large hub airports, Scope 2 is often the single largest controllable emission source (40–60% of Scope 1+2 combined). Reported using both location-based and market-based methods.
Scope 3 — Indirect / Value Chain Emissions
The largest category by far. Includes aircraft landing and take-off cycles (LTO), aircraft auxiliary power units (APUs), surface access transport (passengers and staff travelling to/from the airport), tenant operations (retail, catering, ground handlers), construction and capital goods, and waste. For a major hub, Scope 3 can be 10–50 times larger than Scope 1+2 combined, primarily driven by aircraft fuel burn during LTO.
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Scope 1
Direct
Boilers • Vehicle fleet • Generators • On-site fuel
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Scope 2
Purchased Energy
Grid electricity • Terminal HVAC • Runway lighting • IT
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Scope 3
Value Chain
Aircraft LTO • APUs • Surface access • Tenants • Waste
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Why this matters for credit procurement: At Level 3+ airports offset Scope 1+2 only — typically tens of thousands of tCO2e. At Level 4+ they must also offset staff business travel emissions (a Scope 3 subcategory). At Level 5, airports must engage across broader Scope 3 and use carbon removals for any residual. The scope boundary at each level defines the scale and type of carbon credit demand.
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The 7 Levels — From Mapping to Net Zero |
The ACA framework progresses through seven levels of increasing carbon maturity. Each level represents measurable advancement toward net-zero aviation.
Key insight: Levels 1–3 focus on measurement and reduction. Level 3+ introduces Scope 1+2 offsetting. Level 4+ extends offsetting to include staff business travel. Level 5 requires ≥90% absolute reduction in Scope 1+2 (vs baseline), extensive Scope 3 mapping with a net-zero-by-2050 commitment, and carbon removals only for residual emissions. The progression reflects the science: measure, reduce, offset, then removals for true net zero.
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Offsetting Requirements by Level |
Carbon credit procurement becomes mandatory at Level 3+ and scales with each higher level.
Level 3+ (Neutrality)
Offset all remaining Scope 1+2 and staff business travel emissions. Credits from: Verra, Gold Standard, ACR, CAR, UK Woodland Carbon Code.
Level 4+ (Transition)
Same offset boundary as Level 3+ (Scope 1+2 plus staff travel). Adds absolute reduction requirement and active stakeholder engagement on broader Scope 3. Same approved programmes.
Level 5 (Net Zero)
Achieve ≥90% absolute reduction in Scope 1+2 vs baseline (e.g. 2010). Extensively map all Scope 3 categories and commit to Scope 3 net zero by 2050 or sooner. All residual emissions — Scope 1+2 and staff business travel — neutralised with carbon removals only (DACCS, BECCS, reforestation, soil carbon, biochar). Avoidance/reduction credits do not qualify at this level.
Quality Standards All Credits Must Meet
Additionality • Credible baseline • Monitoring & verification • Permanence • Leakage mitigation • Independent audit. Only high-quality credits pass ACA approval.
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What's Next — Procuring the Right Credits at Each Level |
With 800+ accredited airports progressing through the framework, demand for high-quality carbon credits is substantial and growing. Each offset level has specific credit requirements, approved programmes, and procurement challenges. The next three articles in this series break them down:
ACA Level 3+ — Neutrality: Offset Procurement Guide →
How to source, verify, and retire Scope 1+2 and staff travel offsets from ACA-approved programmes.
ACA Level 4+ — Transition: Full-Scope Offset Strategy →
Extending the offset boundary to include staff business travel, demonstrating absolute reductions, and building a multi-year procurement strategy.
ACA Level 5 — Net Zero: Carbon Removal Requirements →
Why only carbon removals qualify, which pathways meet Level 5, and cost-permanence trade-offs.
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Canopy: Source. Verify. Retire. Report. |
ACA creates structured, level-specific demand for carbon credits and removals. But demand without procurement infrastructure is just an accreditation target on paper. Once your airport knows its level, emission boundary, and offset obligation, you need an end-to-end system that takes you from residual calculation through to audited retirement — not another spreadsheet.
Climate Decode’s Canopy is an AI-powered carbon credit procurement platform built for exactly this challenge — replacing fragmented offset workflows with a single, auditable workspace for managing ACA-compliant credit portfolios.
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Residual Calculation
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AI Credit Curation
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Portfolio Assembly
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Procurement & Retirement
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Reporting & Compliance
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Level 3+ Airports
Canopy calculates residual Scope 1+2 and staff business travel emissions, curates ACA-approved avoidance and reduction credits from Verra, Gold Standard, ACR, CAR, and UK Woodland Carbon Code, and assembles a diversified offset portfolio optimised for cost and quality.
Level 4+ Airports
Canopy extends the offset boundary to include staff business travel emissions, manages multi-vintage procurement strategies across approved programmes, and tracks absolute reduction progress required at the Transformation and Transition tiers.
Level 5 Airports
Canopy separates removal-only credits from avoidance credits, curates biological and technological removal pathways (A/R, biochar, DACCS, BECCS), supports forward contracting for emerging removal technologies, and models cost-permanence trade-offs for the residual ≤10%.
Platform + Expertise
Canopy works seamlessly with Climate Decode’s advisory team. From ACA level assessment and emission boundary mapping through credit procurement, due diligence, and annual accreditation reporting — your advisory team works directly alongside the platform. Canopy’s AI handles discovery and optimisation; our experts handle the nuance and relationships with project developers and registries.
The ACA Advantage
Airports that build their carbon credit procurement infrastructure now — before advancing to higher ACA levels — will secure better pricing on quality credits, establish relationships with verified project developers, and enter each accreditation cycle with portfolios that satisfy both ACA requirements and emerging standards like SBTi and CORSIA.
References
Airports Council International (ACI), Airport Carbon Accreditation Programme. ACI, ACA Accreditation Requirements & Verification Standard. Verra, Carbon Standard. Gold Standard Foundation, Carbon Credit Requirements. American Carbon Registry, Project Standards. Climate Action Reserve, Project Protocols.
Ready to Procure ACA-Compliant Carbon Credits?
Climate Decode's Canopy helps airports at every accreditation level source high-quality offsets and removals aligned with ACA requirements. From Level 3+ to Level 5, Canopy provides end-to-end carbon credit curation, verification, and portfolio management.
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About the Author Koorosh BehrangFounder, Climate Decode Koorosh brings 10+ years of experience in decarbonization strategy, corporate sustainability, and carbon markets. He leads Climate Decode's vision to decode carbon markets for every climate dollar. |
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About the Author Abhishek DasClimate Decode Abhishek specializes in voluntary carbon markets, residual emission procurement strategy, and carbon credit analytics. He helps organizations bridge corporate net-zero targets with carbon credit and removal frameworks. |