A buyer from an automotive OEM sends you a questionnaire and, among the questions, one appears that paralyzes more than one Mexican plant director: "Report your Scope 1, 2, and 3 emissions in tCO₂e for the last fiscal year." The deadline is in six weeks and no one in the company is clear on what goes into each scope, with what factors it is calculated, or who validates the number.
The problem is rarely a lack of technical capability. It is the lack of a clear classification framework. The GHG Protocol —the standard underpinning almost all ESG and SBTi reports, as well as OEM questionnaires— divides greenhouse gas (GHG) emissions into three scopes. Classifying correctly from the start avoids double counting, inflated numbers, and, above all, avoids losing a contract by reporting late or poorly. This guide explains what goes into each scope for a Mexican industrial plant, how it is calculated, and where the real headache lies.
What are Scopes 1, 2, and 3 of the GHG Protocol
The GHG Protocol classifies emissions according to who controls the source that generates them:
- Scope 1 — Direct emissions: those coming from sources your company owns or controls.
- Scope 2 — Indirect emissions from purchased energy: those associated with the electricity (and steam or heat) you buy and consume.
- Scope 3 — Other indirect emissions: everything else in your value chain, upstream and downstream.
The logic is to prevent two companies from reporting the same ton as their own. The electricity that CFE generates by burning gas is Scope 1 for CFE, but Scope 2 for you who consume it. Understanding that boundary is 80% of the work.
Scope 1 in a Mexican plant: what really counts
Scope 1 includes all direct combustion and leakage within your facilities:
- Stationary combustion: natural gas in boilers and furnaces, diesel in emergency generators, LPG, fuel oil.
- Mobile combustion: the company's own fleet of forklifts, trucks, and vehicles.
- Process emissions: chemical reactions, decarbonation in cement, use of fluxes.
- Fugitive emissions: refrigerant leaks (HFC) in air-conditioning and cooling systems, and SF₆ in medium-voltage electrical equipment.
The most common mistake is to forget refrigerants. A single kilogram of leaked R-410A is equivalent to more than 2 tons of CO₂e due to its high global warming potential. A plant with several cooling units can have a far from negligible fugitive Scope 1 that never appears in its inventory.
Scope 2: the SEN emission factor and how to lower it
This is where energy strategy directly touches the ESG report. Your Scope 2 is calculated by multiplying your annual electricity consumption (MWh) by the emission factor of the National Electric System (SEN), which the CRE publishes each year and which in recent years has stood in the range of 0.40 to 0.45 tCO₂e/MWh (reflecting the Mexican mix, high in natural gas).
| Concept | Indicative value (3 MW plant) |
|---|---|
| Annual consumption | 15,000 MWh |
| SEN emission factor (basic supply) | 0.42 tCO₂e/MWh |
| Scope 2 with CFE Basic Supply | 6,300 tCO₂e/year |
| Same consumption with 50% certified renewable energy | ~3,150 tCO₂e/year |
| Same consumption with renewable PPA + CELs (factor ~0) | close to 0 tCO₂e/year |
The lever is clear: migrating to the Wholesale Electricity Market (MEM) as a Qualified User and contracting packages with certified renewable energy allows reporting a lower or zero emission factor for that portion of consumption. It is the contractual ("market-based") method recognized by the GHG Protocol, and it is the reason so many exporters migrate to the MEM. We develop it in the pillar on CELs, RECs and ESG in Mexico 2026 and in ESG and sustainability: how they fit with energy optimization.
Scope 3: the value-chain headache
Scope 3 is the broadest and the one global OEMs increasingly demand from their tier-1 and tier-2 suppliers. It covers 15 categories, but for a manufacturing plant the relevant ones are usually:
- Purchased goods and services (raw materials, steel, aluminum)
- Transportation and distribution (inbound and outbound logistics)
- Waste generated
- Business travel and employee commuting
- Use and end of life of the sold product
Calculating Scope 3 with precision is costly because it depends on third-party data. The reasonable practice is to start with the material categories (those representing the bulk of the footprint) and refine over time. If you are an automotive supplier, this is exactly what your client audits: we cover it in ESG audit for automotive OEM suppliers.
How it is reported and who validates it
Once emissions are classified and calculated, the next step is formal reporting. In Mexico, companies that exceed a certain threshold must report to the National Emissions Registry (RENE) before SEMARNAT —an obligation distinct from an OEM's voluntary questionnaire—. Review the details in RENE SEMARNAT: mandatory GHG reports in Mexico.
For clients and banks, reporting is usually channeled through platforms such as CDP or EcoVadis, and third-party verification by an accredited body is increasingly required. If you export to the European Union, the Scope 1 and 2 inventory per product feeds directly into your CBAM report.
Common mistakes that inflate or invalidate your inventory
- Double counting Scope 2: reporting purchased electricity also as Scope 1.
- Forgetting refrigerant leaks in Scope 1.
- Using an incorrect emission factor: mixing the SEN average with a supplier-specific factor without documenting it.
- Reporting full Scope 3 from day one: it is better to prioritize material categories and declare the measurement boundary.
- Not keeping documentary evidence of the contracted renewable energy (contracts, CELs, attributes).
Next step
Properly classifying your emissions by scope is the foundation of any credible ESG report and of any strategy to lower your emission factor via the electricity market. At Enerlogix we integrate the GHG inventory with the supply strategy within the Plan 360 Management and our sustainable services: we measure your Scope 1 and 2, optimize Scope 2 with certified renewable packages, and connect the data with your reports to OEMs, CBAM, and banks.
Request a free Plan 360 Management evaluation and we will review your current situation with no obligation.
Frequently asked questions
The GHG Protocol classifies emissions according to who controls the source. Scope 1 are direct emissions from sources your company owns or controls, such as combustion in boilers or an owned fleet. Scope 2 are indirect emissions from the electricity, steam, or heat you buy and consume. Scope 3 is everything else in your value chain, upstream and downstream. The logic is to prevent two companies from reporting the same ton as their own.
By multiplying your annual electricity consumption in MWh by the emission factor of the National Electric System or SEN, which the CRE publishes each year and which in recent years has stood between 0.40 and 0.45 tCO2e per MWh, reflecting the Mexican mix high in natural gas. For example, a 3 MW plant consuming 15,000 MWh with a factor of 0.42 reports close to 6,300 tCO2e per year on CFE basic supply.
Yes. Migrating to the Wholesale Electricity Market as a Qualified User and contracting packages with certified renewable energy allows reporting a lower or close-to-zero emission factor for that portion of consumption. It is the contractual or market-based method recognized by the GHG Protocol. In the 3 MW example, moving to 50% certified renewable lowers emissions to about 3,150 tCO2e, and with a renewable PPA plus CELs the factor approaches zero.
Because they are often forgotten and have a very high global warming potential. A single kilogram of leaked R-410A is equivalent to more than 2 tons of CO2e. A plant with several cooling units can have a far from negligible fugitive Scope 1 that never appears in its inventory. Scope 1 also includes stationary and mobile combustion, process emissions, and SF6 leaks in medium-voltage electrical equipment.
Before the National Emissions Registry or RENE of SEMARNAT, the obligation centers on direct and energy-related indirect emissions, that is Scope 1 and 2, when a certain threshold is exceeded. OEMs and voluntary frameworks such as SBTi do request the relevant Scope 3. Scope 3 covers 15 categories, but it is best to start with the material ones and refine over time, not to report it in full from day one.
The greenhouse gas inventory considers seven gases: carbon dioxide or CO2, methane or CH4, nitrous oxide or N2O, the hydrofluorocarbons or HFC, the perfluorocarbons or PFC, sulfur hexafluoride or SF6, and nitrogen trifluoride or NF3. All are converted to CO2 equivalent using their global warming potential, which allows summing them into a single tCO2e figure comparable across sources and plants.
