Appendix 9 – Methods for Calculating Energy Use and Greenhouse Gas Emissions

This Appendix details the methods for calculating energy use and greenhouse gas (GHG) emissions as required by Criterion 2.10. It also provides GHG targets to guide development of GHG management plans.

9.1 Introduction

Measurement, reporting, and management of on-site energy use and GHG emissions are data and calculation-intensive processes. ASC strongly recommends the use of the ASC Greenhouse Gas Calculator (https://ghg.asc-aqua.org) to assist in undertaking calculations; it ensures correct methods and provides results consistent with the required reporting format. Other tools or frameworks may be used if it can be demonstrated that they follow the methodological requirements outlined in this Appendix.

9.2 Scope and timeframe for calculating energy use and GHG emissions

Both energy use and GHG emissions are calculated relative to a quantity of production. This requires that production data and input data (feeds, energy inputs, etc.) relate to a consistent timeframe. Given the differences between production cycles of different culture systems and species, two timeframe options may be used for calculations:

Option A. Calculate values for the most recently completed production cycle.

Option B. Calculate values for the three most recent consecutive years of production.

If insufficient data are available for initial audits, the UoC shall demonstrate how they will collect and calculate values once production data are available (after first production cycle if using Option A or, on an interim basis, after one year of continuous production if using Option B).

All energy use and GHG data calculations may be undertaken at a site-specific or multi-site scale. If calculating values for multiple sites together, all sites included shall farm the same species, use the same production method, and be located in the same country.

9.3 On-site energy use (Indicator 2.10.1)

Energy use of production is calculated as megajoules of energy per tonne of net live weight production (MJ/t). The required scope of activities and inputs to include in energy use calculations is provided in Table 1.

Table 1 Energy inputs required in energy consumption calculations for Indicator 2.10.1.

On-site energy use shall be calculated using the following formula:

$E=\frac{(Q_i\times D_i)}{P}$

Where:

To facilitate calculations, energy densities are automatically calculated when submitting energy use data to ASC.

Table 2 Energy density values for calculation of energy consumption.

Source: DESNZ (2022)140140DESNZ (2022). Greenhouse gas reporting: Conversion factors 2022. United Kingdom Department for Energy Security and Net Zero. Available at https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2022

9.4 GHG emissions (Indicator 2.10.2)

GHG emissions are calculated following an attributional life cycle assessment approach (Figure 1). Emissions are calculated and reported in units of kg carbon dioxide-equivalent (CO₂e) per tonne of live weight production and then converted to kg CO₂e per kg of edible product to inform target-setting and tracking the GHG Management Plan.

Figure 1 System boundaries for calculating GHG emissions of aquaculture products, showing included processes for feed (shaded) and farm stages.

Calculation of GHG emissions for ASC is categorised following the emission scopes defined by the Greenhouse Gas Protocol (WRI, 2004141141World Resources Institute (WRI). (2004). The Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard. Washington, D. C.: World Resources Institute.). To ensure comparability of GHG data between ASC-certified sites, a consistent application of these scopes is used, including activities and inputs listed for each in Table 3.

Table 3 Included inputs and activities for GHG emissions calculations according to Greenhouse Gas Protocol scope.

ASC accepts two methods of handling co-product allocation in GHG accounting: mass allocation and economic allocation. This methodological choice affects GHG emission factors for feed ingredients as well as processing of fish products, if applicable. Farms may follow one or both allocation methods. Feed mills are required to provide farms GHG data specific to the allocation method requested. If farms are using the ASC GHG Calculator or another tool that supports both methods, and have data from their feed suppliers reflecting both methods, they shall subsequently report GHG values following both methods.

UoCs are highly encouraged to use the ASC GHG Calculator or another tool to support GHG calculations. If undertaking calculations manually, the following equations shall be used to calculate Scope 1 (Appendix 9 (9.4.1)), Scope 2 (Appendix 9 (9.4.2)) and Scope 3 (Appendix 9 (9.4.3)) emissions. Each calculation requires a combination of input quantities and their corresponding emission factors, which must be documented alongside calculations.

9.4.1 Scope 1 GHG Emissions

Scope 1 GHG emissions shall be calculated using the following formula:

$S_1=\frac{(Q_i\times G_i)}{P}$

Where:

Table 4 Greenhouse gas intensity (kg CO₂e/unit), according to Greenhouse Gas Protocol scope, for calculation of Scope 1 and Scope 3 emissions from on-site energy use.

Source: DESNZ (2022)140140DESNZ (2022). Greenhouse gas reporting: Conversion factors 2022. United Kingdom Department for Energy Security and Net Zero. Available at https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2022

9.4.2 Scope 2 GHG Emissions

Scope 2 GHG emissions shall be calculated using the following formula:

$S_2=\frac{(Q_i\times G_i)}{P}$

Where:

9.4.3 Scope 3 GHG Emissions

Scope 3 emissions associated with feed ingredients and milling shall be calculated using the following formula:

$S_{3\left(\mathrm{Feed}\right)}=\frac{(Q_f\times G_{f,a})}{P}$

Where:

Scope 3 emissions from feed transportation to sites shall be calculated using the following formula:

$S_{3\left(\text{Feed transport}\right)}=\frac{(Q_f\times T_{f,m}\times G_m)}{P}$

Where:

Scope 3 emissions associated with (production of) fuels and other inputs (e.g., liquid oxygen) shall be calculated using the following formula:

$S_{3\left(\mathrm{Other}\right)}=\frac{(Q_i\times G_i)}{P}$

Where:

9.5 Target-setting for GHG management plans (Indicator 2.10.3)

Species-specific targets serve as a basis for understanding the relative emissions of aquaculture production and guiding reduction efforts in GHG management plans (Table 5). These are based on average species-specific estimates of GHG intensity from Gephart et al. (2021)142142Gephart, J. A., Henriksson, P. J., Parker, R. W., Shepon, A., Gorospe, K. D., Bergman, K., … & Troell, M. (2021). Environmental performance of blue foods. Nature, 597(7876), 360-365.. They will be regularly updated based on data submitted to ASC to support target-setting and tracking relevant to different species and production systems. Farms are not required to meet these targets but they serve as guidance to inform reduction efforts in the GHG management plans.

Table 5 Species-specific GHG targets to incorporate into GHG management plans.