Skip to main content
What you’ll learn in this lesson:
  • Understand why emissions must be allocated to individual batches
  • Apply proportional allocation (by mass or carbon content)
  • Apply time-based allocation for periodic costs
  • Use direct allocation for batch-specific emissions
In the previous lesson you learned how to calculate total process emissions. But those totals need to be distributed across individual batches: a monthly electricity bill must be shared among all the deliveries that month. This lesson covers the three main allocation methods.

​
Why allocation is necessary

Batches are the reporting unit. Each batch must carry its fair share of emissions so that its net carbon figure is accurate. Without allocation, you’d have:
  • Some batches with zero emissions (overstated removal)
  • Other batches bearing all emissions (understated removal)
  • Reports that don’t reflect the true per-batch impact

​
Allocation methods

Distribute emissions based on a measurable attribute of each batch, typically mass or carbon content.Formula: batch_emissions = total_emissions × (batch_attribute / sum_of_all_batch_attributes)Example, by mass: Monthly electricity = 4.17 tCO2e. Three deliveries: 3t, 5t, 2t (total 10t).
  • Batch 1: 4.17 × (3/10) = 1.25 tCO2e
  • Batch 2: 4.17 × (5/10) = 2.09 tCO2e
  • Batch 3: 4.17 × (2/10) = 0.83 tCO2e
Best for: Shared resources consumed in proportion to production volume (electricity, facility overhead).

​
Combining allocation methods

In practice, you’ll use multiple methods for different emission sources within the same project:
The allocation method should reflect the causal relationship between the emission source and the batch. If an emission scales with mass, allocate by mass. If it’s tied to a specific event, allocate directly.

​
Building allocation in the model

In the Model Editor, allocation logic is implemented using operators and node references:
1

Calculate total emissions per source

Sum all emission events for the accounting period (e.g., total kWh × grid factor).
2

Calculate the allocation weight

For proportional allocation: batch_mass / total_mass_in_period. This may use the data_point_proportion operator.
3

Apply the allocation

Multiply total emissions by the allocation weight to get the per-batch share.
4

Deduct from gross carbon

Use a difference node: net_carbon = gross_carbon - allocated_emissions.
The data_point_proportion operator in the Model Editor can automatically calculate a batch’s share of a total. This simplifies proportional allocation. You don’t need to manually compute the denominator.

​
Verifying allocation correctness

After building the allocation logic, verify that:
  1. Allocated emissions sum to the total: all per-batch shares should add up to the total emissions for the period
  2. No batch has negative net carbon: if a batch’s emissions exceed its gross carbon, something is likely misconfigured
  3. Proportions are reasonable: larger batches should receive proportionally larger emission shares
A common error is double-counting: allocating the same emission source through both proportional and direct methods. Each emission source should be allocated through exactly one method.

​
Check your understanding

Use proportional allocation for shared resources that scale with production volume (electricity, facility overhead). Use direct allocation for emissions uniquely tied to a specific batch (transport for a specific delivery, batch-specific processing). The choice should reflect the causal relationship between the emission and the batch.
Check three things: (1) Allocated emissions sum to the total: all per-batch shares should equal the total period emissions. (2) No batch has negative net carbon: if emissions exceed gross carbon, the allocation is likely wrong. (3) Proportions are reasonable: larger batches should carry proportionally larger emission shares.
You’re now ready to put batch partitioning and LCA into practice in the Module 3 Exercise: Configure Batch Partitioning with LCA Emissions.