Understanding Life cycle assessment and sustainability criteria terminology
Disclaimer: This interactive graphic aims to provide a simple explanation of typical words and phrases used in the consideration of sustainability criteria and life cycle assessments of alternative marine fuels. However, no representation or warranty, express or implied, is made as to its accuracy or completeness. The terms as defined are in no way to be considered “agreed definitions” from an IMO perspective, and do not imply the expression of any opinion whatsoever on the part of the IMO.
Lifecycle assessment (LCA) framework for alternative marine fuels
Definition of goal and scope
The goal and scope of the assessment is clearly defined
Define the system boundary and functional unit
Lifecycle inventory (LCI) analysis
The “accounting stage” where all input and output data are collected
Input: Energy and materials consumed, other physical inputs
Output: Waste and pollution, emissions to air, water, and soil, co-products
Lifecycle inventory: Illustrative example
Lifecycle impact assessment (LCIA)
Where the inventory is translated into meaningful results and indicators to assess the environmental impact
- Selection of sustainability criteria
- Selection of impact categories and indicators
- Selection of impact assessment method – For systems with multiple by-products, output allocation could be done by system expansion or co-product allocation
- LCI result classification to impact categories
- Calculation of results for impact indicators
Lifecycle Assessment LCA framework
This is a standardised framework (set out in ISO 14040/44) that allows compilation and evaluation of the inputs, outputs, and the potential environmental impacts of a product system throughout its lifecycle. There are four steps:
- Definition of goal and scope
- Inventory analysis
- Impact assessment
- Interpretation
System Boundaries
The system boundary determines which entities (unit processes) are inside the system and which are outside. It essentially determines which lifecycle/supply chain stages and processes are included in the assessment and need to be in accordance with the goal and scope of the study.
Ideally, the boundary should be as broad as possible, thereby including all the processes that directly and indirectly contribute to the system under consideration, from the extraction of all the raw resources to the intended point of use of the delivered product.
Functional Unit FU
The functional unit represents the reference product or service to which the input and output flows from the lifecycle inventory (LCI) are related.
For example, the functional unit for fuels could be e.g. ‘MJ of delivered energy’, and hence the output flow for emissions could be expressed with the unit: gCO2e/MJ.
Lifecycle Inventory LCI
This is a phase of the lifecycle assessment which involves the compilation and quantification of inputs and outputs for a product throughout its lifecycle.
Lifecycle Impact Assessment LCIA
This is the evaluation phase of the lifecycle assessment which aims to assess the magnitude and significance of the potential environmental impacts for a product system throughout the lifecycle of the product.
Sustainability Criteria
Sustainability criteria are parameters for the production process and quality of a process that must be met to obtain a sustainability status or certification. Often sustainability criteria will consist of multiple impact categories against which a product lifecycle impacts will be assessed.
Impact assessment method
An established methodology to assess impacts e.g.
- EU Renewable Energy Directive (RED II)
- JEC (JRC-EUCAR-Concawe) Well to Wheels study
- GREET Model
- ICAO CORSIA carbon certification
Impact Category
An impact category combines multiple factors that cause the same impact on the environment into a single environmental effect.
For example, carbon dioxide (CO2) and methane (CH4) both lead to the greenhouse effect and can be converted into a single unit (e.g. kg CO2e) that translates into one impact category (e.g., climate change). In LCA, impact categories represent the environmental issue of concern to which a lifecycle inventory analysis (LCIA) may be assigned.
Impact Indicator
An impact indicator may also be known as an “impact metric”. This provides a quantifiable representation of an impact category, which can result in numerical values, expressed in category-specific units.
For example, for climate change (an impact category), the related impact indicator (global warming potential) is expressed in kg CO2e.
Co-product Allocation
Co-product allocation is a method to distribute environmental impacts (e.g. emissions) between two or more products resulting from a process or product system.
Allocation can be done by mass, energy, and economic value of the resulting products. Essentially, this method focuses on the individual product unit, which is assigned a share of the overall environmental impact, rather than considering the system as a whole.
System expansion
System expansion is a method to distribute environmental impacts (e.g. emissions) between two or more products resulting from a process or product system.
Let’s consider this with the figure below. In the system expansion approach, the entire impact of the system (Plant AB) is first calculated, and then the boundary of the multioutput system is expanded to include a set of alternative independent production pathways (Plant B) which are capable of producing outputs that are deemed to be “functionally equivalent” to the various co-products of interest (Product B’ being functionally equivalent to Product B). The impact assigned to one co-product (Product A) is finally calculated as the difference between the entire impact of the original multi-output process (Impact AB), and the sum of the impacts of the alternative independent pathways that produce functional equivalents of all the other co-products (Impact B’).
This approach is part of the consequential lifecycle assessment method that seeks to capture change in environmental impact as a consequence of a certain activity.
ISO 14040 recommends the use of system expansion whenever possible.
