【未来能源研究所】钢铁和铝工业在产品层面的温室气体排放强度-2024.8_32页_575kb

Greenhouse Gas Emissions Intensities of the Steel and Aluminum Industries at the Product Level

This report by Brian P. Flannery and Jan W. Mares from Resources for the Future (RFF) focuses on greenhouse gas (GHG) emissions intensities (GGIs) across the steel and aluminum industries at the product level. It aims to provide a framework for calculating GHG emissions associated with these industries, addressing challenges for border adjustments under a potential U.S. carbon tax.

Key points include:

1. Data Collection and Reporting: U.S. facilities emitting over 25,000 tonnes of CO₂e annually report GHG emissions to the EPA. Similar programs exist globally, though not universally. Trade associations and firms like CRU collect and publish average GGI values for products such as basic oxygen furnace (BOF) steel, electric arc furnace (EAF) steel, and primary aluminum.
2. GGI Calculation Methodology: GGIs are determined using a "cradle-to-gate" approach, accounting for both direct production emissions and indirect emissions from suppliers of raw materials, electricity, and thermal energy. The process mirrors value-added taxation frameworks, requiring detailed accounting of emissions across supply chains.
3. Product-Specific Emission Ranges:
   • BOF Raw Steel: 2.09–3.04 tonnes CO₂e per tonne of steel.
   • EAF Raw Steel: 0.019–0.645 tonnes CO₂e/tonne.
   • Primary Unwrought Aluminum: 2.12–19.64 tonnes CO₂e/tonne.
   • Secondary Unwrought Aluminum: 0.241–0.534 tonnes CO₂e/tonne.
     These ranges reflect variations in energy sources (e.g., coal vs. natural gas), process efficiency, and raw material usage (e.g., scrap vs. primary inputs).
4. Sectoral and Regional Variability: Emissions intensities differ significantly even among facilities of the same company due to factors like size, age, maintenance, and operational practices. For example, primary aluminum’s GGI is heavily influenced by electricity and thermal energy sources, while secondary aluminum depends on scrap quality and processing efficiency.
5. Data Limitations and Uncertainty: Estimates rely on averages from diverse national and sectoral sources spanning multiple decades. This introduces uncertainty, as current technologies and regulations may have altered emission profiles. The report notes that manufacturers may have improved efficiency or increased emissions to meet environmental or safety standards.
6. Industry and Policy Implications: The authors emphasize that GHG control policies, such as carbon taxes, must apply equally to imported and exported products to avoid competitive distortions. They advocate for transparency, suggesting all GHG-intensive product manufacturers should publicly report GGI values for their customers and regulators.
7. Global Supply Chain Considerations: Scrap usage, energy efficiency, and raw material sourcing (e.g., pet coke for aluminum) are critical variables affecting GGI. For instance, EAF steel production using 100% scrap has a lower GGI, while reliance on primary inputs (like 25% basic oxygen steel) increases it.
8. Need for Updated Metrics: GGI values are dynamic and require annual updates to reflect evolving industrial practices, technologies, and market conditions. Border adjustment mechanisms should include appeals processes to correct inaccuracies or fraud in reported GGIs.
9. Recommendations: The report highlights the importance of using product-specific GGI data rather than sector-wide averages. It also underscores the necessity for standardized methodologies and the inclusion of regional and temporal variations in emission calculations.

The analysis is based on data from the International Aluminium Institute, U.S. EPA, and industry studies, with adjustments for energy and material efficiency. While the results are illustrative, they aim to guide policymakers, industry stakeholders, and trade associations in designing fair and effective GHG accounting systems for international trade. The authors caution that without precise data and updated frameworks, policies risk inefficiencies and disputes.