There are numerous pathways to produce hydrogen. This document specifies a methodology for different hydrogen production pathways for determining the greenhouse gases (GHG) emissions associated with the hydrogen supply chain from the raw material extraction up to the production gate.

This document considers the GHG emissions associated with hydrogen production up to the production gate. This document applies to and includes every step within the production process up to the production gate (see Figure 2 in the Introduction).

NOTE            Complementary documents in the ISO 19870 series will consider hydrogen conditioning, conversion and transport methods.

ISO 14044 requires the goal and scope of a life cycle assessment (LCA) be clearly defined and be consistent with the intended application. Due to the iterative nature of LCAs, it is possible that the LCA scope needs to be refined during the study. According to ISO 14040:2006, A.2, the goals and scope of LCAs correspond to one of the following two approaches:

1. an approach that assigns elementary flows and potential environmental impacts to a specific product system, typically as an account of the history of the product (see 4.1.2);
2. an approach that studies the environmental consequences of possible (future) changes between alternative product systems (see 4.1.3).

In this document, approach a) is referred to as an attributional approach, while approach b) is referred to as a consequential approach. Complementary information is accessible in the ILCD handbook[4].

A carbon footprint of a product (CFP) (3.1.2) or partial CFP (3.1.3) as defined by ISO 14067 can be estimated using either the attributional or the consequential approach, the latter corresponding to the use of “system expansion via substitution” to avoid allocation when a unit process yields multiple co-products. This document applies to the CFP for hydrogen production.