목적 (Purpose)
Defines how upstream emissions from purchased goods and services are calculated and how data sources are prioritized.
산정 방법 (Methods)
Category 1 is hybrid: per purchased item, one of three methods is applied by data availability — primary data (supplier-measured per-product intensity; preferred), average-data (quantity × unit weight × product-group LCI intensity), and spend-based (spend × industry-average spend factor, MRIO). An embedded upstream transport leg (supplier→purchasing site) may be computed distance-based.
Data-Source Precedence
By accuracy, primary data → supplier/average intensity → spend-based is preferred. Results are aggregated split into primary, secondary, and no-source emissions to transparently report data quality.
계산 공식 (Formula)
평균·중량기반: 배출 = 수량 × 단위중량 × 배출원단위
지출기반: 배출 = 구매금액 × 지출계수
(+ 내재 운송 = 거리기반 운송 산정)GWP Handling
Category 1 factors are single, already-CO2eq-characterized values (e.g. kgCO2eq/kg, kgCO2eq/currency). Cat 1 therefore has no per-gas split and no separate GWP-set multiplication — effectively GWP=1, with characterization baked into the factor source (LCI / spend-factor DB). This contrasts with Scope 1·2 combustion, which multiplies per-gas emissions by the GWP set. Because Cat 1 factors are pre-characterized, changing the GWP set does not change Cat 1 emissions.
Choosing a Method
The three methods differ in the data they need and in how much weight a requester gives them. Primary (supplier-specific) data is the easiest to defend — boundary, vintage, and grid mix are explicit — and is what CDP/EcoVadis prefer, but suppliers must produce it and smaller ones often cannot. Average/weight-based data lets you start immediately from public factors, but those factors describe another company's product, so they are a proxy: expect to replace them once primary data arrives. Spend-based needs only purchase value but carries the largest error and depends on a spend-factor database (EXIOBASE and similar), most of which are commercially licensed. When using a proxy, state what is lost first; when two suppliers report different values for the same material, check boundary, vintage, unit, and grid factor before deciding either is wrong.
Basis & Standards
표준 정본: GHG Protocol 및 Scope 분류 기준. Basis: Scope 3 Technical Guidance Cat 1 (spend/average/ supplier tiers) and the Scope 3 Standard.
관련 문서 (Related)
- Scope 3 Categories Overview
- Emission Factors — factor types, sources, primary/secondary data
- Cat 4·9 Transport Calculation — the embedded transport leg