What is Carbon accounting? A guide for businesses

What Is Carbon Accounting? A Guide for Businesses

As requirements for emissions reduction and ESG disclosure continue to gain importance, businesses need to measure, manage, and report greenhouse gas (GHG) emissions generated by their operations. Carbon accounting plays a fundamental role in this process, helping organizations identify emission sources, establish reduction targets, and track progress.

However, implementing carbon accounting involves more than calculating emissions. Businesses must also address challenges related to data management, calculation methodologies, inventory boundaries, and data traceability. This article introduces the fundamental principles of carbon accounting, its implementation process, and the role of technology in improving emissions management.

1. What is carbon accounting?

Carbon accounting, also known as greenhouse gas (GHG) accounting, is the process of measuring, calculating, and reporting direct and indirect greenhouse gas emissions generated by a business or organization within defined boundaries.

In carbon accounting, different greenhouse gases are converted into carbon dioxide equivalents (CO₂e) to establish a consistent measurement basis.

This conversion uses the Global Warming Potential (GWP) of each gas, which measures its contribution to global warming relative to CO₂ over a specified period.

For example, methane (CH₄) has a higher GWP than CO₂. Therefore, one tonne of methane emissions is equivalent to multiple tonnes of CO₂e, depending on the GWP value and assessment period applied.

Through carbon accounting, businesses can:

• Identify total GHG emissions and major emission sources.

• Measure the climate impacts of their business operations.

• Establish emissions baselines and reduction targets.

• Monitor the effectiveness of energy efficiency initiatives, technological improvements, and emissions reduction measures.

• Provide data for ESG reporting, GHG inventories, and disclosure requirements.

Classification of Scope 1, Scope 2, and Scope 3 emissions

One of the most widely used frameworks for carbon accounting is the Greenhouse Gas Protocol (GHG Protocol), developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD).

Under the GHG Protocol Corporate Standard, greenhouse gas emissions are classified into three scopes:

Scope 1 – Direct emissions

Scope 1 includes greenhouse gas emissions from sources owned or controlled by the organization.

Examples include:

• Fuel combustion in boilers, generators, and manufacturing equipment.

• Fuel consumption by vehicles under the company's control.

• Emissions from industrial production processes.

• Refrigerant leakage from air conditioning and refrigeration systems.

Scope 2 – Indirect emissions from purchased energy

Scope 2 includes emissions generated from the production of purchased electricity, steam, heating, or cooling consumed by the organization.

For example, a manufacturing facility purchasing electricity from the national grid accounts for the emissions associated with electricity generation under Scope 2 rather than Scope 1.

Scope 3 – Indirect emissions across the value chain

Scope 3 covers other indirect emissions occurring throughout an organization's value chain from sources that are not owned or directly controlled by the organization and are not included in Scope 2.

These activities may include:

• Production of purchased raw materials and goods.

• Transportation and distribution of products.

• Business travel and employee commuting.

• Treatment and disposal of operational waste.

• Use and end-of-life treatment of sold products.

• Investments and other value chain activities.

Scope 3 emissions are often more difficult to measure because organizations must collect data from numerous external partners and entities. However, they can also represent a significant share of total emissions, particularly in industries with complex supply chains.

2. Why is carbon accounting important for businesses?

Carbon accounting not only supports greenhouse gas inventories but also provides essential data for corporate management and sustainability strategy development.

2.1. Identifying opportunities to reduce emissions and optimize costs

Detailed emissions data enables businesses to identify energy-intensive activities, inefficient fuel consumption, and significant emission sources.

Based on these insights, businesses can prioritize appropriate measures, such as improving equipment efficiency, optimizing production processes, adopting renewable energy, or changing transportation methods.

By continuously monitoring emissions data, businesses can assess achieved reductions, compare results against investment costs, and evaluate the effectiveness of individual initiatives.

2.2. Supporting compliance and ESG disclosure

Greenhouse gas emissions data is a critical component of the Environmental (E) pillar of ESG reporting.

Standards and frameworks such as the GHG Protocol, GRI, IFRS S2, and CDP incorporate or require information related to greenhouse gas emissions, depending on their objectives and scope of application.

Establishing a reliable carbon accounting system helps businesses prepare data to meet current GHG inventory and disclosure requirements while improving their ability to adapt to future changes.

2.3. Meeting investor and supply chain requirements

Investors, financial institutions, and customers are increasingly interested in how businesses manage climate-related risks and achieve emissions reductions.

In particular, companies participating in international supply chains may be required by customers to provide emissions data relating to products, raw materials, or transportation activities.

Maintaining consistent and verifiable carbon data enables businesses to better support supplier assessments, engage with partners, and fulfill disclosure requirements.

2.4. Tracking progress toward Net Zero targets

Carbon accounting provides the foundation for businesses to establish emissions baselines, set targets, and evaluate progress over successive reporting periods.

Rather than relying solely on qualitative commitments, organizations can monitor specific indicators, such as total GHG emissions, emissions intensity per unit of production, or emissions reductions relative to a baseline year.

3. Carbon accounting and greenhouse gas emissions calculation process

To implement carbon accounting effectively, businesses need a consistent process covering inventory boundary definition, data collection, emissions calculation, and reporting.

Step 1. Define inventory boundaries

Businesses must identify the entities, locations, and activities to be included within their carbon accounting boundaries.

Under the GHG Protocol, organizational boundaries may be established using approaches such as equity share, financial control, or operational control.

Businesses then identify emission sources across Scope 1, Scope 2, and Scope 3, based on their actual operations and applicable standards.

Applying a consistent boundary-setting approach is essential to prevent omissions or double counting of emissions.

Step 2. Collect activity data

Activity data provides the inputs required to calculate greenhouse gas emissions.

Depending on the emission source, relevant data may include:

• Fuel consumption by machinery, equipment, and vehicles.

• Purchased electricity, steam, or heating energy.

• Quantities of raw materials and products.

• Transportation distances, vehicle types, and fuel consumption.

• Waste volumes and treatment methods.

• Emissions data provided by suppliers and other value chain partners.

Data may be collected from utility bills, meters, production management systems, enterprise resource planning (ERP) software, or internal reports.

Businesses should prioritize primary source data and establish consistent data collection methods across reporting periods.

Step 3. Select appropriate emission factors

An emission factor represents the quantity of greenhouse gases emitted per unit of activity, such as one kilowatt-hour (kWh) of electricity or one liter of fuel consumed.

Reference sources for emission factors may include:

• Guidelines published by the Intergovernmental Panel on Climate Change (IPCC).

• Emission factors published by national regulatory authorities.

• Databases maintained by the International Energy Agency (IEA).

• Databases provided by the U.S. Environmental Protection Agency (US EPA).

• Emission factor datasets published by the UK's Department for Environment, Food & Rural Affairs (Defra).

Businesses should select emission factors appropriate to the fuel type, technology, geographical location, applicable period, and calculation methodology.

For operations in Vietnam, priority should be given to emission factors that reflect local conditions and regulatory requirements, where available.

Step 4. Calculate and aggregate emissions

A common calculation method involves multiplying activity data by the corresponding emission factor:

GHG emissions = Activity data × Emission factor

If the emission factor is expressed for an individual greenhouse gas rather than CO₂e, an additional conversion using the appropriate GWP value is required.

For example, a facility's electricity consumption can be multiplied by the corresponding grid emission factor to determine its Scope 2 emissions using the location-based method.

Once calculated, emissions are aggregated by emission source, facility, business unit, and reporting scope.

Throughout this process, businesses should verify data completeness, measurement units, consistency, and traceability.

Step 5. Establish emissions baselines and monitor targets

An emissions baseline is a reference point used to assess an organization's emissions reduction performance over time. Businesses should select a baseline year supported by sufficiently reliable data, representative of their operations, and aligned with their emissions reduction targets.

When significant changes occur in organizational structure, inventory boundaries, or calculation methodologies, businesses should consider recalculating the baseline in accordance with established policies and criteria.

Maintaining a consistent baseline helps distinguish actual emissions reductions from fluctuations caused by changes in operational boundaries.

Step 6. Report and disclose results

Carbon accounting results are used to prepare greenhouse gas inventory reports, ESG reports, and other climate-related disclosures.

Reports should clearly present inventory boundaries, reporting periods, calculation methodologies, emission factors, emissions by scope, and relevant assumptions or data limitations.

Businesses should also retain supporting documentation and evidence for internal reviews and independent assurance when required.

4. Key considerations when implementing carbon accounting

Although the fundamental principles of carbon accounting are relatively straightforward, practical implementation can be complex due to differences in emission sources and calculation methodologies.

4.1. Location-based and market-based methods for Scope 2

According to the GHG Protocol Scope 2 Guidance, businesses should consider two methods for calculating emissions associated with purchased energy:

1. Location-based method: Uses emission factors representing the electricity generation system in the geographical area where electricity is consumed, such as the national grid emission factor.

2. Market-based method: Reflects emissions associated with an organization's eligible electricity purchasing choices and contractual instruments, such as electricity supply contracts or Energy Attribute Certificates (EACs).

EACs may include Renewable Energy Certificates (RECs) or Guarantees of Origin (GOs). When applying the market-based method, businesses must assess certificate eligibility, issuance dates, electricity consumption periods, and applicable market boundaries.

Importantly, purchasing renewable electricity or holding certificates does not automatically entitle a business to report zero emissions. Such claims must meet the quality criteria established by the GHG Protocol.

In markets where the relevant conditions apply, the GHG Protocol requires businesses to report Scope 2 emissions using both methods. This approach helps distinguish emissions associated with the electricity system from those reflecting an organization's electricity purchasing choices.

4.2. Collecting data and calculating Scope 3 emissions

Scope 3 is often one of the greatest challenges in carbon accounting because relevant data falls outside an organization's direct management systems.

The GHG Protocol Scope 3 Standard classifies value chain emissions into 15 categories covering upstream and downstream activities.

During the initial stages, businesses may use estimated data and secondary emission factors to identify significant emission categories. As data management systems improve, they can increase the collection of primary data directly from suppliers and partners.

Key activities include:

• Identifying relevant Scope 3 emission categories.

• Assessing data availability and quality.

• Selecting appropriate calculation methods for each category.

• Establishing mechanisms for collecting and updating supplier data.

• Retaining assumptions, emission factors, and supporting evidence.

For manufacturing businesses, purchased raw materials, transportation, and product use may account for a significant proportion of total value chain emissions.

Therefore, Scope 3 accounting not only supports disclosure but also provides a foundation for businesses to collaborate with partners on emissions reduction initiatives.

5. Challenges in implementing carbon accounting

According to IBM, carbon accounting requires businesses to manage large volumes of energy and operational data from multiple sources while maintaining consistency in calculation methodologies across reporting periods.

These challenges often become more complex for organizations operating across multiple locations and subsidiaries.

5.1. Fragmented and disconnected data

Data required for GHG inventories may be distributed across ERP systems, energy management platforms, accounting systems, production management systems, and Excel spreadsheets.

Different departments often use different data storage methods and measurement units, making enterprise-wide data consolidation difficult.

Without a centralized data system, reconciling information and identifying missing data can be time-consuming.

5.2. Inconsistent data quality

Manual data collection and processing increase the risk of input errors, missing information, and inconsistent application of emission factors.

In particular, changes in measurement units, data formats, or emission factor validity periods may lead to significant calculation errors.

Without appropriate controls, businesses may also struggle to trace data back to its original source for verification.

5.3. High reporting costs and time requirements

Collecting, validating, standardizing, and calculating emissions data can require substantial resources when performed entirely through spreadsheets.

For organizations with multiple facilities, data consolidation is repeated during each reporting cycle, increasing workloads and the risk of reporting delays.

5.4. Difficulties in monitoring emissions reduction performance

When data is consolidated only at year-end, businesses may struggle to monitor energy consumption, emissions trends, and the effectiveness of reduction initiatives in a timely manner.

This limits their ability to identify underperforming activities and adjust implementation plans throughout the year.

5.5. Data auditability and assurance requirements

When emissions data is used in ESG reports or official disclosures, businesses must ensure that the information has a clear origin and that calculation methodologies can be verified.

Insufficient supporting documentation, change histories, or clearly assigned responsibilities may create additional challenges during reviews and independent assurance engagements.

6. Building a reliable carbon accounting data system

To improve carbon accounting quality, businesses need to establish data management systems that ensure consistency, traceability, and effective controls.

IBM uses the term finance-grade data to emphasize the importance of reliability, completeness, and auditability in sustainability data.

To achieve this objective, businesses should focus on the following areas.

6.1. Standardizing data structures

Emissions data should be organized in a structure aligned with the organization's management systems and GHG inventory boundaries.

A typical structure may include:

• Accounts and meters: Capture detailed energy consumption data.

• Locations: Consolidate data by factories, offices, or operational facilities.

• Business entities: Manage data for individual companies or subsidiaries.

• Reporting groups: Aggregate data by region, business segment, or reporting boundary.

• Enterprise level: Consolidate data for organization-wide management and disclosure.

This structure should be flexible enough to accommodate changes in organizational structures, locations, and operational boundaries.

It should also support multidimensional analysis, such as by emission source, geographical area, reporting period, or business unit.

6.2. Establishing data management processes and responsibilities

Carbon accounting requires participation from multiple departments, rather than relying solely on the sustainability team.

Businesses should clearly assign responsibility for data provision, validation, approval, and consolidation.

An effective data management process should include regular collection schedules, data completeness checks, procedures for resolving discrepancies, and processes for updating emission factors.

Businesses should also establish data quality indicators, such as the percentage of data submitted on time, data completeness rates, and the number of discrepancies requiring correction.

6.3. Prioritizing source data and automating collection

Businesses should prioritize collecting data directly from original sources, including utility meters, energy bills, and operational management systems.

Where appropriate, integrating data through APIs or automated data transfer methods can reduce manual processing and minimize errors.

For supplier data, businesses can develop standardized templates, define submission procedures, and establish consistent update schedules.

However, the degree of automation should be determined by the connectivity capabilities of each data source and the organization's existing technology infrastructure.

6.4. Maintaining data traceability and auditability

A reliable carbon accounting system should allow emissions results to be traced back to activity data, emission factors, and supporting source documents.

Businesses should retain information such as emission factor versions, adjustment histories, responsible personnel, update timestamps, and reasons for changes.

Maintaining an audit trail supports internal reviews, result reconciliation, and the preparation of data for independent assurance.

6.5. Establishing centralized data management

Rather than storing information across multiple disconnected systems, businesses can use a centralized data management platform to consolidate and share emissions information.

The system should provide appropriate access controls, allowing departments to access data according to their assigned roles and responsibilities.

For multinational businesses or organizations with complex structures, centralized management also helps maintain consistent calculation methodologies across different entities.

7. The role of ESG software in carbon accounting

Spreadsheets may be sufficient for carbon accounting on a small scale. However, as the number of data sources, operational locations, and reporting requirements increases, manual approaches can become increasingly challenging.

Dedicated carbon accounting and ESG reporting software helps businesses manage data systematically, strengthen controls, and reduce manual workloads.

7.1. Automating data collection and consolidation

ESG software can support data integration from multiple sources, standardize measurement units, and consolidate information according to organizational structures.

Depending on the platform's capabilities, businesses may configure data processing rules, automate data imports from source systems, or implement standardized data collection templates.

This enables ESG teams to spend less time consolidating data and more time analyzing performance.

7.2. Supporting emissions calculations using standardized methodologies

Dedicated carbon accounting platforms can support emission factor management and emissions calculations based on activity data.

Key capabilities may include:

• Managing emission factor libraries and update histories.

• Configuring calculation methodologies for different emission sources.

• Calculating Scope 1, Scope 2, and relevant Scope 3 emissions.

• Supporting location-based and market-based calculation methods.

• Aggregating and analyzing emissions across different organizational levels.

Applying standardized formulas and calculation rules helps reduce errors associated with manual processing while supporting consistency across reporting periods.

7.3. Improving data quality and auditability

Dedicated software can support data completeness checks, identify anomalies, and retain supporting evidence for emissions calculations.

Version control, access management, and change tracking features provide businesses with greater control over data collection and processing.

These capabilities provide an important foundation for internal reviews, audits, and independent assurance.

7.4. Monitoring targets and emissions reduction performance

ESG software can help businesses establish key performance indicators (KPIs) and track emissions performance over time.

Indicators may include total GHG emissions, emissions intensity per unit of production, percentage reductions against baseline years, or energy consumption at individual locations.

Through dashboards and analytical tools, businesses can monitor trends, compare performance across entities, and identify priority areas for improvement.

7.5. Supporting ESG reporting and disclosure

Carbon accounting data provides important inputs for various reports and disclosure frameworks.

ESG software can help businesses organize data according to different reporting requirements, reduce repetitive consolidation tasks, and improve the consistency of disclosed information.

However, software alone does not automatically ensure compliance with every standard. Reporting quality still depends on the selection of appropriate methodologies, system configuration, data controls, and clearly assigned responsibilities.

8. Key criteria for selecting carbon accounting software

When selecting carbon accounting software, businesses should evaluate both its emissions calculation capabilities and its compatibility with existing data management systems.

Important selection criteria include:

In addition to technical capabilities, businesses should consider implementation costs, integration with existing systems, the provider's support capabilities, and internal operational resources.

The most suitable solution is not necessarily the one with the greatest number of features, but the one that meets current business needs while supporting long-term scalability.

9. Leveraging technology to improve carbon accounting

For carbon accounting to effectively support management and decision-making, businesses need to transition from periodic emissions calculations toward systematic data management.

This transition can begin with standardizing data sources, establishing collection and control processes, and gradually adopting technology to improve operational efficiency.

For organizations with multiple facilities or complex ESG reporting requirements, platforms such as IBM Envizi ESG Suite can help centralize ESG data, manage environmental information, and monitor sustainability performance.

In addition, solutions specializing in greenhouse gas emissions calculation and visualization, such as Zeroboard, may also be considered depending on an organization's scale and implementation requirements.

The selection of a platform should be based on the organization's actual GHG inventory requirements, data readiness, organizational structure, and target reporting standards.

10. Conclusion

Carbon accounting is not only a tool for measuring greenhouse gas emissions but also a foundation for businesses to manage climate-related risks, develop emissions reduction strategies, and improve the quality of ESG disclosures.

Effective implementation requires a combination of appropriate calculation methodologies, reliable data sources, robust management processes, and active participation from relevant departments.

Adopting carbon accounting software and dedicated ESG management platforms can help automate data collection, improve reporting reliability, and monitor progress toward emissions reduction targets.

EGP Vietnam provides technology solutions for ESG and sustainability data management, including IBM Envizi ESG Suite and Zeroboard, helping businesses gradually digitalize emissions management and ESG reporting.

Learn more here. For a live demonstration, please contact:

• Thai Nguyen

• thai.nguyen@egp.vn

• 0912 500 085

References

• IBM. What Is Carbon Accounting?.

• GHG Protocol. Corporate Accounting and Reporting Standard.

• GHG Protocol. Scope 2 Guidance.

• GHG Protocol. Technical Guidance for Calculating Scope 3 Emissions.