A key component of a Voluntary Monitoring Plan (VMP) for Energy-for-Waste (EfW) operators is to monitor and calculate their greenhouse gas emissions. There are two main UK ETS monitoring approaches: measurement-based and calculation-based. In this latest update, we break these down, explain how to determine biomass versus fossil carbon, and highlight the key factors that influence emissions data.
The Two UK ETS Monitoring Approaches.
UK ETS Monitoring: Measurement-Based Approach
This method uses Continuous Emissions Monitoring Systems (CEMS) to directly measure CO₂ concentrations in flue gases.
- Ideal for sites with existing CEMS infrastructure
- Requires high-quality calibration and maintenance
- Must be able to distinguish fossil vs. biogenic CO₂ (e.g. via C-14 sampling)
UK ETS Monitoring: Calculation-Based Approach
This method estimates emissions using activity data (e.g. fuel/waste input) and emission factors.
- More flexible and cost-effective for smaller or less complex sites
- Requires reliable data on waste composition, calorific value, and biomass fraction
- Must follow tiered accuracy levels based on installation size and complexity
Key Factors for Emission Calculations.
Whether you measure or calculate, operators need to understand the following factors:
- Net Calorific Value (NCV) – the energy content of the waste or fuel
- Emission Factor – the amount of CO₂ emitted per unit of energy or mass
- Oxidation Factor – the proportion of carbon that is oxidised during combustion
- Biomass Fraction – the percentage of biogenic carbon in the waste or fuel stream
Choosing the Right Tier.
The UK ETS uses a tiered system to define the required accuracy for each factor:
- Higher tiers = more precise methods (e.g. lab analysis, direct measurement)
- Lower tiers = acceptable for smaller sites
The tiers range from 1 to 3 and are based on an installation’s size and complexity.
Those installations applying tiers 2a or lower for calculation factors may use default values provided by the UK government.
Operators applying higher tiers must use analysis or sampling to determine calculation factors.
Determining Biomass vs. Fossil Carbon
One of the biggest challenges for EfW operators is distinguishing between fossil-derived and biogenic CO₂. The UK ETS requires this split to ensure only fossil emissions are counted and recommends using one of the following methods:
- C-14 Radiocarbon Analysis
- Waste Composition Studies: Those installations meeting tier 3 for biomass fraction in waste streams must use monthly C-14 analysis based on EN ISO 13833
- Literature-Based Factors (acceptable for lower-tier installations with justification)
The chosen method must be documented in your VMP and supported by written procedures.
Handling Missing Data.
If data is missing or unreliable, operators must apply conservative estimates and document the issue. Your VMP should include a procedure for:
- Identifying missing data
- Estimating values conservatively
- Reporting the issue to regulators
Rounding Data for Emissions Reporting.
Operators should avoid rounding data too early when calculating reportable emissions. All values should be reported to an appropriate number of significant figures however the regulators do not define “appropriate”. We recommend using all available significant figures.
Our next update will explore how to report your emissions quarterly and how to manage data flow and control systems to ensure accuracy and integrity.
Our team of Carbon Consultants are experts in emissions reporting. If you would like us to support you through the voluntary MRV-only period, please contact us here and make sure to follow us on LinkedIn to get notified when the next blog in the EfW series is released.
