What is carbon intensity — and why does it matter?

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Carbon intensity (CI) is a process-level metric that expresses the total greenhouse gas (GHG) emissions of a chemical process normalised to the mass of desired product. Measured in kg CO₂ equivalent per kg of product (kg CO₂eq kg⁻¹), it allows direct comparison of the climate impact of different synthetic routes, energy sources, and scales of production.

GoalMinimise GHG emissions per unit of product — an ideal process would have zero or even negative carbon intensity through carbon capture and use of renewable inputs.

WhyChemistry accounts for ~7% of global GHG emissions. Knowing the carbon intensity of a process identifies where decarbonisation efforts will have the greatest leverage.

HowSwitch to renewable electricity, reduce energy consumption, choose low-carbon feedstocks, eliminate high-emission solvents, and optimise yield to reduce material per kg product.

The formula

$$CI = \frac{\displaystyle\sum_{i} E_i \cdot \text{EF}_{i}^{\text{energy}} + \sum_{j} m_j \cdot \text{EF}_{j}^{\text{material}}}{m_{\text{product}}}$$

Symbol	Term	Units
$CI$	Carbon intensity of the process	kg CO₂eq kg⁻¹ product
$E_i$	Energy consumed from source $i$ (electricity, heat, etc.)	kWh
$\text{EF}_{i}^{\text{energy}}$	Emission factor for energy source $i$	kg CO₂eq kWh⁻¹
$m_j$	Mass of material $j$ used in the process	kg
$\text{EF}_{j}^{\text{material}}$	Cradle-to-gate emission factor for material $j$	kg CO₂eq kg⁻¹
$m_{\text{product}}$	Mass of isolated desired product	kg

Emission factors for electricity depend on the grid mix (country / region and year). The default values here are widely cited literature estimates — update them with site-specific data for the most accurate results.

Typical carbon intensity by process type

Process / Context	Typical CI (kg CO₂eq / kg product)	Key driver
Renewable-powered bulk chemicals	< 0.5	Green electricity, optimised yield
Bulk chemicals (fossil grid)	0.5–3	High-volume, relatively efficient energy use
Fine chemicals	3–30	Energy-intensive steps, solvent emissions
Pharmaceuticals (API)	10–200+	Complex synthesis, low yield, heavy solvent use
Green hydrogen (electrolysis, renewable)	0.4–1	Electrolyser efficiency, grid carbon intensity

Relationship to other green chemistry metrics

Metric	What it captures	CI relationship
E-factor	Mass of waste per mass of product	More waste → more material emissions → higher CI
PMI	Total mass input per mass of product	High PMI means more materials contributing to CI
Carbon Footprint	Total absolute GHG emissions (kg CO₂eq)	CI = Carbon Footprint ÷ Product mass
GWP Horizon	Warming potential of a single substance, and how it changes with time horizon	EF values in CI are GWP100-weighted sums over all emissions
Space–Time Yield	Productivity per reactor volume and time	Higher STY can lower CI by reducing energy per kg product

Scope boundaries

Scope 1 — Direct

Combustion of fuels on-site (gas burners, boilers, steam generation)
Process emissions (CO₂ released during reaction, solvent evaporation losses)
Fugitive emissions (refrigerants, compressed gas leaks)

Scope 2 — Indirect energy

Purchased electricity (grid emission factor × kWh consumed)
Purchased heat or steam from an external supplier
Chilled water or compressed air from an energy utility

Scope 3 (upstream supply chain and downstream use) can also be included by using cradle-to-gate emission factors for raw materials. This tool lets you mix all three scopes freely — label your entries clearly to make the boundary explicit.

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Process details

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Process / reaction name

Researcher(s)

Date

Lab / institution

Reaction type

Primary energy source

Scale

Scope boundary

Reference / DOI

Notes

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Energy inputs

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Enter each energy input (electricity, heating, cooling, compressed air, etc.). Select a preset emission factor or enter a custom value. Energy is converted to kWh for consistency — see the unit helper below if your values are in MJ or BTU.

Unit conversions: 1 MJ = 0.278 kWh · 1 GJ = 277.8 kWh · 1 BTU = 0.000293 kWh · 1 therm = 29.31 kWh

Energy source / type	Preset EF	EF (kg CO₂eq/kWh)	Quantity (kWh)	Emissions (kg CO₂eq)

Σ Energy emissions — kg CO₂eq

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Material emissions

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Enter the mass of each material used (reagents, solvents, catalysts, workup materials) and its cradle-to-gate emission factor. Select a preset from the dropdown or enter a custom value. Use the same units as your product mass in section 05.

Material name	Category	Preset EF	EF (kg CO₂eq/kg)	Mass (kg)	Emissions (kg CO₂eq)

Σ Material emissions — kg CO₂eq

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Product output

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Enter the mass of desired product actually isolated. For co-product allocation, enter only the mass attributed to the product of interest, or use the Notes field above to describe your allocation method.

Product name	Mass isolated (kg)

Σ Product mass — kg denominator of carbon intensity

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Results

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Carbon Intensity

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kg CO₂eq / kg product

Total Emissions

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kg CO₂eq

Carbon intensity scale (lower is better)

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0 (ideal)530100+ kg CO₂eq/kg

Emissions by source type

Emissions by material category

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Detailed breakdown & interpretation

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Source	Type / Category	Quantity	EF (kg CO₂eq / unit)	Emissions (kg CO₂eq)	% of total	Visual
Enter energy and material data above to see breakdown.

Interpretation

Enter your energy inputs, materials, and product mass above to generate an interpretation.

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Save & load sessions

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Sessions are stored in your browser only. No data leaves your device.

No saved sessions yet.

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Export

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Export your carbon intensity calculation as a PDF report or CSV data file. PDF opens in a new tab and uses your browser's print function. CSV downloads directly.

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Where can I read more?

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References are sorted alphabetically by first author.

P. T. Anastas and J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, 1998. ISBN 978-0-19-850698-0. — Original 12 Principles; Principle 6 covers energy efficiency and use of renewable energy.
Ecoinvent Centre, Ecoinvent Database v3, Swiss Centre for Life Cycle Inventories, 2023. ecoinvent.org. — Primary source for cradle-to-gate emission factors used in LCA studies.
IPCC, Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report, Cambridge University Press, 2021. ipcc.ch. — Updated GWP100 values for greenhouse gases used to compute CO₂ equivalents.
C. Jiménez-González et al., Org. Process Res. Dev., 2011, 15, 912–917. DOI. — PMI framework; energy and material contribution to pharmaceutical process footprints.
R. A. Sheldon, Green Chem., 2018, 20, 3953–3954. DOI. — The E-factor at 25; energy efficiency and carbon footprint as emerging green metrics.
UK Government / DESNZ, Greenhouse Gas Reporting: Conversion Factors 2024, Department for Energy Security and Net Zero, 2024. gov.uk. — Official UK grid and fuel emission factors updated annually.

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Contributors

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Roles follow the CRediT taxonomy (Contributor Roles Taxonomy), adapted for educational software. Hover a contributor's name for a summary, or a column header for the definition of that role.

Contributor

This portal was built with the assistance of a large language model (Claude, Anthropic), which was used to generate and refine code, articulate and structure contributed ideas within the defined page format, and support iterative design decisions. All scientific content, conceptual frameworks, pedagogical choices, and final outputs were directed, reviewed, and verified by the contributors listed above.

Whilst every effort has been taken to ensure accuracy, mistakes can happen. If you notice something that doesn’t look quite right, kindly reach out to the DodecaGreen team via the Contact page.

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How do I cite this page?

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If you use this tool in teaching or published work, please cite the DodecaGreen portal as the source.

Reference

BibTeX

Carbon Intensity calculator.