Carbon Footprint in Mexican Manufacturing: Why the Real Challenge Is the Supply Chain

Mexico is one of the world's major manufacturing hubs, with the automotive industry and the IMMEX programme for the manufacturing, maquiladora and export services industry as its pillars. But when measuring the carbon footprint of these industries, the most common mistake is looking only at the assembly plant.

Most of the footprint is not at the final plant

In the automotive and electrical sectors, most of the carbon footprint is not generated at assembly but in the supply chain: suppliers, raw materials, logistics and earlier production stages. Measuring only scope 1 and 2, meaning direct emissions and those from purchased energy, leaves out the largest share of the real impact, which is scope 3. The full map of those categories is in the guide to the 15 scope 3 categories of the GHG Protocol.

Why this puts Mexico under international scrutiny

• Energy-intensive export manufacturing: much of what is produced in Mexico ends up in the scope 3 inventory of customers in other countries, who need the data broken down by supplier.
• The EU's carbon border adjustment mechanism has been in its definitive regime since 1 January 2026 and requires the embedded carbon of goods such as steel, aluminium, cement and fertilisers to be declared, key inputs for the automotive industry.
• International corporate clients: global automotive brands and large distributors increasingly ask their Mexican suppliers for footprint data as a condition of contract.

What is already mandatory in Mexico: the RENE

Before thinking about the foreign customer, it is worth reviewing the local obligation. The General Law on Climate Change Regulation on the National Emissions Registry expressly includes among the sectors subject to reporting the automotive, metalworking, electronics, electrical, iron and steel, metallurgical, chemical, petrochemical, glass and textile industries, among others. Any establishment in those subsectors whose direct and indirect emissions add up to 25,000 tonnes of CO2 equivalent or more per year must report them between 1 March and 30 June through the Annual Operating Certificate, have them verified every three years by an accredited body and keep the documentation for five years. The detail is in the guide on what the General Law on Climate Change requires from businesses.

What the European customer asks for: real data or default values

CBAM works with a logic that favours the supplier who measures well. Since 2026, an EU importer that exceeds 50 tonnes a year of covered goods needs authorisation as a declarant and must file each year, by 30 September, a declaration with the embedded emissions of what it imported and surrender the corresponding certificates; the first one, covering 2026, is due on 30 September 2027, and certificates go on sale from 1 February 2027. If it has no verified actual data from its supplier, the importer applies default values with a mark-up: 10% in 2026, 20% in 2027 and 30% from 2028, according to the European Commission. In other words, every tonne of steel or aluminium leaving a Mexican plant without a verified figure costs its customer more.

The Commission itself has enabled operators of installations outside the EU to register in the CBAM Registry, have their emissions verified by an accredited verifier and share the data with their importing customers through a standardised template. For a Mexican manufacturer of covered inputs, that registration is the most direct way to turn its measurement into a commercial advantage.

The operational challenge: hundreds of suppliers, one report

Measuring scope 3 in manufacturing means consolidating data from dozens or hundreds of suppliers, each with its own invoice format, spreadsheet or system. Doing it manually does not scale, and the result is usually an inventory with a lot of estimation and little traceability.

What can be automated

• Automatic invoice reading: extracting energy consumption data from PDF invoices without keying them in, even if they come in another language or another currency.
• Importing data that are not invoices: converting the Excel and CSV files suppliers send into the internal format, instead of maintaining manual templates.
• Classification and factor assignment: sorting each purchase into its scope 3 category and assigning the corresponding emission factor, with a record of where each number comes from.

Traceability by supplier, not just an annual total

An annual emissions total is no use for answering a customer asking about the embedded carbon of a specific part, nor for preparing a customs declaration with a carbon figure. What works is data by supplier and by shipment, with its origin documented. Setting it up that way from the start avoids redoing the inventory when the first large customer asks for the breakdown.

Manglai helps manufacturing companies scale scope 3 measurement without relying on manual, supplier-by-supplier work. You can see it in Manglai's carbon footprint software and in its approach for supply chain managers.