Scope 3 Emissions: The Complete Guide for Singapore Businesses

The third scope: why it is the biggest and the hardest

The GHG Protocol Corporate Standard, published in 2001 and still the foundation of nearly every major sustainability reporting framework, divides corporate greenhouse gas emissions into three scopes. Scope 1 is what you burn directly — diesel in your delivery trucks, gas in your office kitchen, refrigerants leaking from your air-conditioning units. Scope 2 is what you consume indirectly — the electricity you purchase from Singapore Power, which was generated somewhere, by something. These two scopes are measurable, auditable, and already mandatory for SGX-listed companies from FY2025.

Scope 3 is everything else. The carbon in the raw materials your suppliers extracted and processed before delivering them to your loading dock. The emissions generated when your customers drive to your store, use your product, or eventually dispose of it. The flights your team takes to client meetings. The commute your 200 employees make five days a week on the MRT. The servers your cloud provider runs in data centres you have never visited. All of this counts — and for most companies, it dwarfs the other two scopes combined.

A useful way to think about it: Scope 1 and 2 are the emissions you control. Scope 3 are the emissions you influence. That distinction matters enormously for how you approach reduction. You cannot switch off your supplier's coal-fired smelter. But you can choose a supplier who runs a cleaner operation, or use your purchasing power to push your supply chain toward lower-carbon alternatives.

Scope 3 is also harder to measure with precision. Unlike your electricity bill — which gives you a kWh figure you can multiply by an emission factor — Scope 3 requires data from parties outside your organisation who may not measure or disclose it. This is why regulators and frameworks accept a degree of estimation for Scope 3 that they would not accept for Scope 1 and 2. The goal is a reasonable, methodologically consistent estimate, not laboratory-grade accuracy.

The 15 categories mapped

GHG Protocol Technical Guidance for Companies (2011) defines 15 Scope 3 categories, divided into upstream and downstream activities. Here is what each means in practice — and which are most likely to matter for a Singapore business.

Upstream categories cover emissions that occur before your product or service reaches you:

• Category 1: Purchased goods and services.The emissions embedded in everything you buy — raw materials, components, services, office supplies. For most businesses, this is the single largest Scope 3 category. A Singapore F&B company importing food ingredients, a manufacturer sourcing parts from Malaysia and China: Category 1 dominates their Scope 3 footprint.
• Category 2: Capital goods. The embedded carbon in equipment, buildings, and other long-lived assets you purchase. Relevant for capital-intensive industries; less significant for services companies.
• Category 3: Fuel and energy related activities. Emissions from the extraction, production, and transportation of the fuels and electricity you use — beyond what is already counted in Scope 1 and 2. This covers things like the upstream emissions from producing the diesel before it reaches your tank.
• Category 4: Upstream transportation and distribution. The emissions from shipping your purchased goods to your facility. If a supplier in China ships components by sea to Singapore, the shipping emissions go here.
• Category 5: Waste generated in operations. The emissions from disposing of solid and liquid waste produced by your business activities. For a Singapore office, this covers landfill and incineration of paper, food waste, and general waste. Singapore's waste-to-energy infrastructure affects the emission factors applicable here.
• Category 6: Business travel. Flights, hotels, ground transport taken by your employees for business purposes. For Singapore businesses with regional operations, Category 6 can be material — long-haul flights have significant per-passenger emission factors.
• Category 7: Employee commuting. The emissions from your employees travelling between home and work. Singapore's public transport-heavy commuting culture generally makes this lower than regional peers where private car usage is higher. Still worth measuring for completeness.
• Category 8: Upstream leased assets. Emissions from assets leased by your organisation that are not included in Scope 1 or 2.

Downstream categories cover emissions that occur after your product or service leaves your hands:

• Category 9: Downstream transportation and distribution. Shipping your products to customers or distribution points. Relevant for product companies; less so for service businesses.
• Category 10: Processing of sold products. Emissions from processing your intermediate products downstream. Relevant for manufacturers whose products are inputs to other processes.
• Category 11: Use of sold products. Emissions from customers using what you sell. For an electronics manufacturer, this covers the electricity used by customers running your devices over their lifetimes — often the largest single category in consumer electronics companies' footprints.
• Category 12: End-of-life treatment of sold products. The emissions from disposing of your products at end of life — landfill, recycling, incineration.
• Category 13: Downstream leased assets. Emissions from assets you own but lease to others.
• Category 14: Franchises. Emissions from franchisee operations for companies running franchise models.
• Category 15: Investments. Emissions associated with investments you hold. Highly relevant for financial institutions; the financed-emissions calculation methodology is one of the more contested areas of Scope 3 accounting.

What Singapore requires and when

Singapore's Scope 3 disclosure landscape is evolving at the pace of international standard-setting, which has accelerated significantly since IFRS S2 was finalised in June 2023.

For SGX-listed companies, the timeline is:

• FY2025: Mandatory Scope 1 and Scope 2 disclosure, with independent limited assurance required from FY2029.
• FY2026: Scope 3 disclosure expected on a "best-efforts" basis. This is a meaningful phrase. It means SGX expects listed companies to make genuine progress on Scope 3 measurement and disclosure, but recognises that perfect data is not yet achievable across all 15 categories. A company that identifies its most material Scope 3 categories, applies a recognised methodology, discloses the result with appropriate caveats, and documents its methodology is meeting the best-efforts standard.
• FY2030: More structured, comprehensive Scope 3 requirements are anticipated as data availability and methodologies mature.

For non-listed companies, there is currently no mandatory Scope 3 requirement from MAS, SGX, or other Singapore regulators. But "not mandatory" does not mean "irrelevant." Two forces are making Scope 3 practically necessary for Singapore SMEs:

First, supply chain pressure. Your multinational customers — the ones headquartered in Europe, Japan, or the US — are under their own Scope 3 disclosure obligations. Your emissions are their Category 1. When their corporate sustainability team reaches out asking for your carbon footprint data, that is no longer a nice-to-have conversation. It is becoming a procurement condition.

Second, financial access. Sustainability-linked loans from Singapore banks increasingly require borrowers to measure and reduce emissions across all three scopes. As green finance products multiply, emissions data becomes a financial credential.

How to calculate Scope 3 for a Singapore SME

There are two main calculation approaches for Scope 3, and which you use depends on what data you have available.

The spend-based approach multiplies your procurement spend in a category by an emission intensity factor (emissions per dollar of spend in that industry). It is the most practical approach for Category 1 when supplier-specific data is unavailable — which is most of the time for Singapore SMEs. The EXIOBASE database, maintained by a consortium of European research institutes, provides industry-level emission intensity factors that can be applied to spend data by sector. The US EPA also publishes supply chain emission factors. While not perfect, spend-based calculation gives you a defensible estimate that can be refined over time as better data becomes available.

The activity-based approach uses physical activity data multiplied by emission factors. It is more accurate than the spend-based method and is preferred where the data is obtainable:

• Category 5 (waste): Collect waste weight data from your waste contractor (most Singapore licensed waste contractors can provide monthly tonnage by waste type). Multiply by waste-specific emission factors from DEFRA 2025 or Singapore's own NEA emission factors.
• Category 6 (business travel): Collect flight data from your travel management company or expense system. Distance × passenger × DEFRA aviation emission factors (which include a radiative forcing uplift for high-altitude emissions). Hotels add a per-night factor by hotel type.
• Category 7 (employee commuting): Survey your employees on their primary commute transport mode and one-way distance. MRT, bus, taxi, private car, and walking each have distinct emission factors. Aggregate: (employees × mode share × average distance × days worked × emission factor). Singapore's high MRT usage typically produces lower Category 7 figures than comparable regional cities.

A note on accuracy: Scope 3 figures carry inherently higher uncertainty than Scope 1 and 2. The GHG Protocol, IFRS S2, and Singapore regulators all acknowledge this. Your Scope 3 disclosure should include a methodological note explaining what approach you used, which categories are included, and what the key assumptions are. Transparency about methodology is more important — and more credible — than false precision.

The supplier data problem

The most rigorous approach to Category 1 is to obtain actual Scope 1 and Scope 2 emissions data directly from each of your suppliers — what the GHG Protocol calls "supplier-specific activity data." In practice, for most Singapore SMEs, this is not realistic across the full supply base. Your top 10 suppliers might be reachable. Your long tail of 200+ secondary suppliers will not be.

The practical approach is tiered. Start with your top-10 suppliers by spend — these probably account for 70–80% of your procurement expenditure. Ask them directly: do they have a Scope 1 and 2 figure for their Singapore operations? Some will. Many of your larger suppliers in Singapore are themselves SGX-listed or subsidiaries of listed companies, and already publish sustainability reports. Extracting the relevant number from a published report is a legitimate approach.

For the remaining suppliers where direct data is unavailable, apply spend-based factors from EXIOBASE or similar databases, grouped by industry classification. Document clearly which suppliers are estimated versus directly measured. As your procurement team normalises sustainability questions in supplier onboarding and annual reviews, the direct data coverage will expand over time.

The direction of travel is clear: within five years, carbon disclosure will be as routine a part of supplier qualification as price, quality, and delivery performance. Singapore's major manufacturers, retailers, and property companies are already moving in this direction. Starting your supplier engagement now means you are ahead, not reactive.

Business travel and employee commuting in Singapore

Categories 6 and 7 are among the more tractable Scope 3 categories for Singapore businesses because the data is largely within your own systems.

Business travel (Category 6) data lives in your travel management system, expense platform, or corporate credit card statements. For flights, the key variables are origin, destination, class of travel (economy vs business vs first), and number of passengers. DEFRA 2025 emission factors cover international and domestic aviation by route type and include a 1.9x radiative forcing multiplier for high-altitude emissions, which is the methodologically conservative approach recommended by most frameworks. For Singapore businesses with frequent regional travel — Kuala Lumpur, Jakarta, Bangkok, Hong Kong — business travel can be a materially significant category.

Employee commuting (Category 7) requires a survey. A simple annual survey asking employees their primary commute mode and approximate one-way distance gives you the inputs. Singapore's Land Transport Authority (LTA) publishes statistics showing that roughly 60% of morning peak-hour trips are on public transport. Applied to a Singapore office workforce, this skews Category 7 downward compared to regional peers in cities where private car commuting dominates. An MRT commute produces approximately 0.04 kgCO2e per passenger-km; a private car commute produces approximately 0.19 kgCO2e per passenger-km. The difference is significant. Singapore's infrastructure is, in this regard, a genuine sustainability asset for urban businesses.

Remote and hybrid working adds a wrinkle. The GHG Protocol allows companies to count the reduction in commuting emissions from remote working days — but some of that emission shifts to Category 1 (home energy used for work purposes). The accounting is still evolving; the most common approach is to estimate commuting days avoided and apply a partial home-energy offset.

Where to start without getting overwhelmed

The most common Scope 3 mistake is trying to do everything at once. Companies produce a sprawling inventory that is 40% estimates, with methodology that is inconsistently applied across categories, and end up with a number that their sustainability team cannot defend to an assurer or a procurement questionnaire.

A better approach is materiality-first sequencing:

Step 1: Conduct a high-level materiality assessment. Based on your business type, which Scope 3 categories are likely to be significant? An F&B company importing ingredients: Category 1 is dominant, Category 5 is relevant, Category 6 and 7 are smaller. A logistics company: Category 4 (upstream transport) and Category 9 (downstream transport) dominate. A professional services firm: Categories 6 and 7 are the primary categories, with Category 1 (software, office supplies, contracted services) secondary.

Step 2: Build calculation methodology for your top 2–3 material categories. Get the data. Apply appropriate emission factors. Document the method. Produce a number with stated uncertainty ranges and methodology caveats.

Step 3: Report what you have and commit to expanding coverage. The narrative in your sustainability report should say: "We currently report Scope 3 categories 1, 6, and 7, which we have assessed as our most material categories. We are working to expand coverage to additional categories over the next reporting cycle."

Step 4: Build internal infrastructure so that Scope 3 data collection becomes a routine operational process rather than an annual scramble. The companies that achieve clean Scope 3 reporting at scale treat it the same way they treat financial data collection — with defined owners, consistent methodology, and evidence trails that can withstand scrutiny.