Embedded emissions: Measurement, trade flows and construction policy

Overview

Embedded emissions, frequently referred to as embodied carbon, represent a method for attributing greenhouse gas emissions to the specific goods being consumed rather than solely to the geographic location of their production. This concept shifts the focus from the territorial origin of emissions to the final consumer, providing a clearer picture of the carbon footprint associated with individual products or services. The distinction between embedded emissions and traditional accounting methods is critical for understanding global climate responsibilities. Under the United Nations Framework Convention on Climate Change (UNFCCC), emissions are primarily measured according to production. This means that the exporting country is credited or debited for the emissions generated during the manufacturing process, regardless of where the final good is ultimately consumed. Consequently, embedded emissions on imported goods are attributed to the exporting nation, which can sometimes obscure the role of importing countries in driving global emission levels.

Production vs. Consumption Accounting

The choice between measuring emissions based on production or consumption is not merely a technical distinction but also a significant issue of equity. It raises the question of who bears the responsibility for the emissions generated in the global supply chain. Production-based accounting, as used by the UNFCCC, assigns emissions to the country where the physical activity occurs. In contrast, consumption-based accounting attributes emissions to the country where the goods are ultimately consumed. This difference can lead to substantial variations in how nations perceive their contribution to global warming. For instance, a manufacturing-heavy country might appear to have higher emissions under production-based accounting, while a consumption-driven nation might see a larger share of its emissions revealed through the lens of embedded emissions. Understanding these nuances is essential for developing effective climate policies and fostering international cooperation.

Implications for Climate Policy

Recognizing embedded emissions allows for a more comprehensive assessment of national carbon footprints. It highlights the interdependence of economies and the flow of emissions across borders. Policies aimed at reducing emissions must consider both production and consumption to avoid carbon leakage, where emissions are shifted from one country to another rather than being reduced globally. By incorporating embedded emissions into climate strategies, nations can better target interventions, such as carbon border adjustments or supply chain optimizations. This approach ensures that efforts to mitigate climate change are equitable and effective, addressing the root causes of emissions in a globalized economic landscape.

How are embedded emissions measured in international trade?

International trade accounting for greenhouse gas emissions primarily distinguishes between production-based and consumption-based methodologies. The United Nations Framework Convention on Climate Change (UNFCCC) traditionally measures emissions according to production, meaning that emissions generated during the manufacturing of a good are attributed to the exporting country rather than the importing country (per UNFCCC guidelines). This creates a divergence between where emissions physically occur and where the final consumption takes place. Embedded emissions refer specifically to the greenhouse gas emissions associated with the goods being consumed, offering an alternative attribution method that shifts responsibility from the producer to the consumer.

Production vs. Consumption Accounting

The choice between production and consumption accounting has significant implications for equity and responsibility. Under production-based accounting, a country’s national inventory includes all emissions released within its territorial boundaries. In contrast, consumption-based accounting adjusts this figure by adding emissions embedded in imports and subtracting emissions embedded in exports. This distinction raises the question of who is responsible for emissions, which is partly an issue of equity. For instance, if Country A manufactures goods for Country B, production accounting attributes the emissions to Country A, while consumption accounting attributes them to Country B.

Spillover Effects and Carbon Leakage

Differences in national climate policies can lead to spillover effects, where the policies of one country to reduce emissions affect emissions in other countries. A key concern in this context is carbon leakage. If an exporting country has less stringent climate policies than the importing country, production may shift to the exporting country, leading to an increase in its emissions. This can undermine global emission reduction efforts, as the total global emissions may not decrease significantly, even if the importing country’s production-based emissions drop. Carbon leakage highlights the importance of considering embedded emissions in international trade to ensure that climate policies do not inadvertently shift emissions rather than reduce them.

Equity Implications for Annex B Countries

Under the Kyoto Protocol, Annex B countries (primarily developed nations) had specific emission reduction targets. The choice of accounting method significantly impacts these countries' progress toward their targets. If Annex B countries adopt consumption-based accounting, they may find that their effective emissions are higher than their production-based figures, as they import many goods with high embedded emissions. This has equity implications, as it suggests that developed countries may be "offloading" some of their emission responsibilities to developing countries through trade. The question of whether to measure emissions on production or consumption is therefore not just a technical issue but also a matter of global equity and responsibility in climate change mitigation.

Global trade flows and regional disparities

The attribution of greenhouse gas emissions to production rather than consumption creates significant discrepancies in global trade flows. Under the United Nations Framework Convention on Climate Change (UNFCCC) methodology, embedded emissions are assigned to the exporting country, meaning the importing nation’s consumption does not directly reduce its production-based emission totals. This framework highlights a major equity issue: the responsibility for emissions often lies with the producer, while the benefit accrues to the consumer. In 2004, embedded emissions accounted for approximately 23% of global emissions, illustrating the substantial portion of the carbon footprint displaced through international trade (UNFCCC).

Major Exporters and Importers

Regional disparities in embedded emissions are pronounced. Major exporters such as China, Russia, and South Africa bear a significant share of the emissions generated for goods consumed elsewhere. Conversely, the United States, Europe, and Japan are primary importers, meaning a large fraction of their consumption-related emissions are technically attributed to the exporting nations. This dynamic results in a 71% difference in regional emissions when comparing production-based metrics against consumption-based metrics, underscoring the complexity of assigning climate responsibility in a globalized economy.

The calculation of these flows often involves input-output analysis, where the total embedded emissions (E) for a country can be expressed as the sum of emissions from domestic production (Edom​) minus the emissions embodied in exports (Eexp​) plus the emissions embodied in imports (Eimp​). This framework reveals that without adjusting for trade, national inventories may understate or overstate the true environmental impact of a region’s consumption patterns.

What are the main types of goods with high embedded emissions?

The carbon footprint of global trade is not distributed evenly across all commodities. Certain sectors and product categories carry significantly higher embedded emissions than others, driven by energy-intensive production processes and complex supply chains. Research conducted by the Carbon Trust in 2011 provided a foundational analysis of these disparities, highlighting how emissions are embedded differently in primary materials versus finished consumer goods.

High-Emission Primary Commodities

Primary commodities such as steel, cement, and chemicals consistently rank among the highest contributors to embedded emissions. These materials are often referred to as "trade-heavy" goods because their production requires substantial energy input, frequently derived from fossil fuels. For instance, the steel industry relies heavily on coal for reduction processes, while cement production involves significant thermal energy and chemical decarbonation. When these materials are exported, the exporting country bears the brunt of the emissions under production-based accounting, even if the final consumption occurs elsewhere.

The Carbon Trust research emphasized that these primary goods form the backbone of global infrastructure and manufacturing. Their high emission intensity means that shifts in global demand for steel or cement can have outsized effects on the carbon footprints of exporting nations. This creates a complex interplay between trade policies and climate equity, as importing countries may benefit from lower domestic emissions while relying on carbon-intensive imports.

Semi-Finished and Finished Products

In contrast to primary commodities, semi-finished and finished products like vehicles, clothing, and machinery exhibit different emission profiles. These goods often involve multiple stages of processing and assembly, spreading emissions across various sectors and regions. For example, a vehicle's embedded emissions include those from steel production, electronics manufacturing, and final assembly. Similarly, clothing items may involve cotton cultivation, textile processing, dyeing, and sewing, each contributing to the total carbon footprint.

The Carbon Trust study noted that while individual items in these categories may have lower per-unit emissions compared to bulk commodities, their cumulative impact is substantial due to high consumption volumes. Additionally, the complexity of supply chains for finished products makes it challenging to attribute emissions accurately. This complexity underscores the importance of consumption-based accounting, which seeks to capture the full lifecycle emissions of goods from cradle to grave.

Understanding these distinctions is crucial for designing effective climate policies. By targeting high-emission commodities and optimizing supply chains for finished products, policymakers can address both production-side and consumption-side emissions. This dual approach helps ensure that efforts to reduce embedded emissions are both equitable and efficient, reflecting the true environmental cost of global trade.

Embodied carbon in construction

The construction sector represents a significant portion of global greenhouse gas emissions, with embedded emissions playing a critical role in the overall carbon footprint of buildings. According to industry analyses, construction accounts for approximately 11% of global emissions, but when considering the full lifecycle of buildings, this figure rises to 75% of total lifecycle emissions. This distinction is crucial for understanding the impact of construction materials and processes on climate change.

World Green Building Council Targets

The World Green Building Council has set ambitious targets to reduce embedded carbon in the construction sector. Their goal is to achieve a 40% reduction in embodied carbon by 2030, compared to a baseline period. This target focuses on the carbon emissions associated with the production, transportation, and installation of building materials, as well as the construction process itself.

The 40% reduction target is part of a broader strategy to make the built environment net-zero carbon. This involves not only reducing operational carbon emissions (from heating, cooling, and lighting) but also addressing the significant contribution of embodied carbon. The target applies to new buildings, retrofits, and the materials used in construction.

The Concept of Re-use

Re-use of building materials and components is a key strategy for reducing embedded emissions. By re-using materials, the carbon emissions associated with extracting, processing, and transporting new materials are avoided. This approach can significantly reduce the overall carbon footprint of a building, especially when combined with other strategies such as efficient design and renewable energy integration.

Re-use can take many forms, including the re-use of structural elements (such as steel beams and concrete slabs), non-structural components (such as windows and doors), and even entire buildings. The effectiveness of re-use depends on factors such as the distance the materials need to be transported, the energy required for processing and installation, and the quality of the materials themselves.

The formula for calculating the carbon savings from re-use can be expressed as: Carbon Savings = (Emissions_New - Emissions_Reused) * Quantity_Reused where Emissions_New is the carbon emissions associated with producing new materials, Emissions_Reused is the carbon emissions associated with re-using materials, and Quantity_Reused is the amount of material re-used. This formula helps quantify the impact of re-use on the overall carbon footprint of a building.

How can embodied carbon be reduced in buildings?

Reducing embodied carbon in buildings requires a multi-faceted approach targeting material selection, structural efficiency, and data transparency. The primary strategy involves minimizing construction mass, often referred to as "less is better." This approach focuses on optimizing structural designs to use the minimum amount of material necessary to achieve required performance metrics, thereby directly reducing the total volume of carbon-intensive inputs. Structural efficiency can be achieved through advanced engineering techniques that reduce the dead load of buildings, allowing for smaller foundations and less steel or concrete usage.

Material Substitution and Low-Carbon Alternatives

Material substitution is a critical lever for lowering embedded emissions. Replacing high-carbon materials like steel and concrete with lower-carbon alternatives can significantly impact the total embodied carbon footprint. Timber, bamboo, and hemp are prominent examples of bio-based materials that sequester carbon during their growth phase and typically require less energy to process than mineral-based materials. The use of timber in multi-story construction, for instance, can reduce the structural embodied carbon compared to traditional steel and concrete frames. Bamboo offers rapid renewability and high tensile strength, making it a viable substitute for steel in certain applications. Hemp-based composites, such as hempcrete, provide insulation and structural benefits while sequestering CO2.

Industrial by-products also play a role in material substitution. Slag, a by-product of iron and steel production, can be used as a partial replacement for cement in concrete mixes. This not only reduces the demand for virgin raw materials but also utilizes waste products, thereby lowering the overall carbon intensity of the concrete. The substitution rate depends on the specific type of slag and the performance requirements of the concrete mix.

Utilizing Environmental Product Declarations (EPDs)

Environmental Product Declarations (EPDs) provide standardized, transparent data on the environmental impact of construction materials. By using EPDs, architects and engineers can make informed decisions about material selection based on verified life-cycle assessment (LCA) data. EPDs allow for the comparison of similar products from different manufacturers, enabling the selection of those with lower embodied carbon. The widespread adoption of EPDs facilitates the tracking of embodied carbon throughout the building's life cycle, from raw material extraction to construction and beyond. This data-driven approach supports the optimization of material choices to minimize the total carbon footprint of the building.

The integration of these strategies—minimizing mass, substituting materials, and leveraging EPDs—creates a comprehensive framework for reducing embodied carbon in buildings. Each strategy addresses different aspects of the building's material composition and lifecycle, contributing to a more sustainable construction industry.

Policy and legislation on embodied carbon

Regulatory frameworks for embedded emissions are evolving from voluntary metrics to binding legislative limits, addressing the equity gap between production-based and consumption-based accounting. In North America, several jurisdictions have implemented procurement policies to drive demand for low-carbon materials. Washington and Oregon have adopted building codes and procurement standards that require embodied carbon declarations and set reduction targets for public projects. Colorado’s HB21-1303 further integrates life-cycle assessment into state infrastructure planning, mandating that agencies consider the full carbon footprint of construction materials. Toronto has established a specific performance benchmark, requiring new residential buildings to achieve an embodied carbon intensity of 350 kg CO2e/m2. This metric provides a clear target for developers to balance operational efficiency with upfront material costs.

European nations are implementing some of the most stringent limits on embodied carbon, leveraging the EU’s broader climate neutrality goals. The Netherlands, Denmark, Sweden, France, and Finland have introduced national strategies that cap the carbon intensity of concrete, steel, and timber in public infrastructure. These policies often utilize carbon pricing mechanisms or mandatory Environmental Product Declarations (EPDs) to standardize reporting. The regulatory landscape reflects a shift toward treating embodied carbon as a primary driver of urban emissions, particularly as operational energy use declines due to electrification and renewable integration.

Key Jurisdictions and Policy Benchmarks

The calculation of these limits often involves complex life-cycle assessment models. The total embodied carbon Etotal​ is typically defined as the sum of emissions across the supply chain:

E_total = Σ (m_i × GWP_i)

where mi​ is the mass of material i and GWPi​ is its global warming potential per unit mass. These formulas allow regulators to standardize comparisons between different material types, such as steel versus timber, ensuring that procurement decisions are based on verifiable emission data rather than proxy metrics.

Worked examples

The distinction between production-based and consumption-based accounting creates significant divergences in national greenhouse gas inventories. To illustrate this, consider the trade dynamics between China and the United States. Under the UNFCCC’s production-based method, emissions from goods manufactured in China but consumed in the United States are attributed to China. This means that if a Chinese factory emits 100 tonnes of CO2 to produce a laptop sold in New York, China’s inventory increases by 100 tonnes, while the US inventory remains unchanged, unless the US adopts consumption-based accounting (per UNFCCC methodology). This attribution highlights the equity issue: the exporting country bears the environmental cost of the importing country’s consumption patterns.

Application in Material Selection via EPDs

Embedded emissions are also critical in construction and manufacturing, where Environmental Product Declarations (EPDs) quantify the lifecycle emissions of materials. When selecting between steel and aluminum for a structural beam, engineers compare the embedded CO2 per kilogram. Suppose an EPD states that recycled aluminum has an embedded emission of 5 kg CO2e/kg, while primary steel has 1.5 kg CO2e/kg. If a project requires 1,000 kg of material, the total embedded emissions for aluminum would be 5,000 kg CO2e, whereas steel would contribute 1,500 kg CO2e. This calculation allows decision-makers to attribute the environmental impact directly to the material choice, facilitating more precise carbon budgeting in infrastructure projects (per standard EPD frameworks).

Policy Implications for Carbon Border Adjustments

The disparity between production and consumption accounting drives policies like the Carbon Border Adjustment Mechanism (CBAM). If Country A has a carbon price of 50/tonneandimportsagoodwith10tonnesofembeddedemissionsfromCountryB,wherethecarbonpriceis20/tonne, the importer must pay the difference. In this case, the cost is (50−20) * 10 = $300. This mechanism ensures that the embedded emissions of imported goods are priced similarly to domestic production, reducing the "leakage" of emissions to countries with lower carbon costs. This approach directly addresses the equity question by assigning responsibility for emissions to the final consumer’s market policies (per EU CBAM regulations).

See also

• Pressurized fluidized bed combustion: Technology, Efficiency, and System Variants
• Diemen Power Station: Thermal Infrastructure in the Netherlands
• Efficient and stable perovskite solar cells prepared in ambient air irrespective of the humidity
• Anaerobic digestion and biogas production
• Redox flow battery cell: US Patent 11316170

References

1. "Embedded emissions" on English Wikipedia
2. ISO 14067:2018 — Greenhouse gases — Carbon footprint of products — Requirements and guidelines for quantification
3. IPCC Guidelines for National Greenhouse Gas Inventories (2006 & 2019)
4. Scope 3 Standard — The Complete Guide to Corporate Value Chain (Scope 3) Emissions Accounting and Reporting
5. Embedded Carbon in Buildings — World Green Building Council