MH/T 6138.2-2025 in English

Standard Development Background and Technological Evolution

MH/T 6138.2-2025 is a special standard launched by the Chinese civil aviation industry to quantify the carbon footprint of sustainable aviation fuel (SAF). With the implementation of the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), HEFA-SPK has become the mainstream technology path for second-generation biojet fuel. The accuracy of its carbon footprint calculation directly impacts the assessment of emission reduction benefits. This standard is based on the ISO 14040 series of life cycle assessment frameworks and incorporates the characteristics of China's aviation fuel industry chain, providing industry-specific refinements to GB/T 24067.

Core Terminology Definitions and Scope Definition

This standard applies to kerosene components (HEFA-SPK) produced by the hydroreforming process of esters and fatty acids in accordance with GB 6537. The functional unit is clearly defined as the production of 1 megajoule (MJ) of heat (calculated as lower heating value), and the benchmark flow is 1 ton of HEFA-SPK product. The system boundary adopts a "cradle to grave" full life cycle model, covering four stages: raw material production/collection, processing and production, supply and use.

System boundary and unit process division

Innovation in carbon footprint calculation methodology

The carbon footprint calculation formula (1) proposed in this standard embodies a number of technical innovations:

Of particular note, for waste oil and fat raw materials, only greenhouse gas emissions from transportation are calculated, reflecting the emission reduction advantages of waste resource utilization. For cultivated crop raw materials, changes in carbon stocks caused by direct land-use change must be accounted for.

Data Quality Requirements and Allocation Principles

The standard prioritizes the collection of primary data, particularly core parameters such as energy consumption, raw material consumption, and transportation distance. Secondary data is only permitted for upstream emission factors. Allocation principles follow the provisions of MH/T 6138.1, prioritizing physical allocation (such as energy content allocation) over economic allocation.

GWP Characterization Factor Selection Specifications

The standard explicitly stipulates the use of the 100-year GWP values from the latest IPCC assessment report to ensure alignment with international standards. Non-CO2 greenhouse gases such as methane and nitrous oxide must be converted to CO2 equivalents based on their corresponding GWP values.

Implementation Recommendations and Application Cases

Data Collection System Development: It is recommended that companies establish a comprehensive data monitoring system, particularly online energy consumption monitoring and material balance accounting, to ensure the accuracy and completeness of primary data.

Co-product Allocation Practice: Taking a HEFA-SPK plant as an example, which produces both jet fuel and hydrocarbon-based biodiesel, it is recommended to allocate the carbon footprint based on energy content. The jet fuel allocation coefficient is approximately 0.85-0.90.

Third-Party Verification Preparation: To enhance the credibility of carbon footprint claims, it is recommended to prepare data quality archives in advance, including measurement equipment calibration records and data statistical process documentation.

Industry Impact and Future Development

The implementation of this standard will unify the HEFA-SPK carbon footprint accounting method, providing a reliable basis for airlines to purchase sustainable aviation fuel under the CORSIA framework. It is expected to promote coordinated emission reductions across the entire supply chain and promote the green and low-carbon transformation of my country's aviation transport industry.

With technological advancements and data accumulation, future standards may further refine feedstock classification, update the emission factor database, and potentially expand to include carbon footprint accounting for other types of sustainable aviation fuel.