New report sheds light on sustainability and life cycle of alternative fuels

The study, undertaken by Ricardo Energy & Environment, mapped existing standards, regulations and calculation methods and tools, covering Well to Tank (WtT) and Tank to Wake (TtW) emissions. The study aimed to understand the coverage of this governance infrastructure and its applicability to marine fuels.

GHG calculation methodologies and fuel pathway case studies

The study has identified existing standards, regulations and calculation methods and tools related to WtT and WtW, including ‘well to wake’ (or ‘well to wheel’ for road vehicle) methodologies. The review of the landscape of regulations, standards, and methods covering GHG emissions and environmental impacts was carried out across transport sectors and territories to understand the coverage and approaches used.

With most being based on the use of fossil fuels, their focus is on CO2 emissions released TtW, although a small number of methods reflect the increasing use of alternative fuels with coverage of WtT or WtW, and environmental sustainability considerations.

From this, four GHG calculation methods and tools were identified which had sufficient coverage and relevance to be worthy of deep study. The methods and tools identified were:

1. That built into the GREET model, which was developed to simulate energy use and emissions for a range of vehicle and fuel combinations
2. That resulting from the application of the calculation rules and emission factors specified in the RED II policy directive, which sets targets for EU Member States to increase the use of energy from renewable sources
3. That specified in the CORSIA certification scheme, originally developed for Sustainable Aviation Fuels (SAF) and Lower Carbon Aviation Fuels (LCF)
4. That used in the JEC Well-to-Wheel study, which was co-developed by the JRC, EUCAR and Concawe to assess the sustainability of the European vehicle and oil industry

Consideration of wider sustainability criteria

The evaluation of the existing methods and tools showed a focus on GWP aspects, and the methods’ specific coverage of feedstock sourcing and fuel production categories is described below. Overall, this study highlighted the need to comprehensively account for all GHG emissions, including:

• Contribution to global warming potential (GWP) from fuel feedstock sourcing – especially through land use change (LUC) for non-waste biofuels
• Contribution to GWP from fuel production – such as the effectiveness of carbon capture and storage (CCS), fugitive emissions, and the carbon intensity of electricity sources

Additionally, this study also identified the need to consider additional environmental sustainability criteria for several impact categories. The following were assessed to have significant impact potential for fuel WtW pathways:

• Eutrophication Potential – from land use for non-waste biofuels
• Particulate Matter Formation Potential – for liquid hydrocarbon fuels (e.g., biodiesel), which may be similar to some existing fossil fuels
• Ecological and Human Toxicity and Abiotic Depletion – potentially large concerns from material demands associated with electricity as an energy carrier and input to green fuels, and the demand for electric motors, batteries, and fuel cells.

Boundaries for WtW evaluation of marine fuels

When applying life cycle assessment (LCA) principles, consideration should be given to the boundaries to include all relevant factors and allow a fair comparison at the lowest possible complexity level of the calculation. This report considered the appropriate boundaries for assessing marine fuels in different contexts.

When considering the WtW GHG emissions of marine fuels the system boundary may include:

• Fuel/electricity production including sourcing of feedstock, production, and fugitive emissions.
• Fuel distribution and storage, including losses and energy consumption from compression and liquefaction (where applicable), and fugitive emissions.
• Vessel operation phase including fuel conversion/combustion and exhaust and fugitive emissions, covering all fuel use (such as for auxiliary power and multi-fuel systems) and shore power electricity, and including non-CO2 combustion emissions such as CH4 and N2O.

The use of shore power to remove the need to run auxiliary engines in ports may in future be mandated through legislation as is proposed in the EU, and already in place in China and California, for various larger vessel types.

While this means less fuel is consumed on the vessel, it may not mean there are no net GHG emissions. Indeed, the evaluation of the GHG emissions of the electricity used may need to consider whether renewable, grid average or marginal factors are appropriate. Therefore:

• The GHG impact of electricity supplied for shore power or battery charging could be evaluated by measuring the energy provided and the use of an appropriate GHG factor for the electricity source.

With increasing uptake of lower/zero carbon fuels, the proportion of the lifecycle emissions associated with the vessel (construction, modification, and use) increase. This is particularly true for electrified and battery vessels, and not just for GHG but also wider sustainability criteria.

In addition, the effect of future lower density fuels on the “utility” of the vessel (more space used by fuel, less available for cargo), and therefore its sustainability, may not be clear. This can only be assessed for a specific vessel design and usage.

• It is recommended to further study the relative emissions across lifecycle stages for a number of vessel types and energy vectors. This would inform whether guidance or legislation may be required in future.

Establishing accurate data

While the use of common datasets allowed comparison of the methodological differences, the methods and tools also differed in the default data inventories provided. Given the global nature of the marine industry and the future diversity of fuels, production methods and geographies, a wider set of input data and emissions factors may need to be developed to allow more accurate evaluation of variation in WtW emission calculations.

In some cases, this may be a relatively simple task, but in others such as land use change and upstream fugitive emissions, establishing widely accepted data could be challenging. Some data are specific to the fuel pathway, location or vessel and the use of default assumptions may be inappropriate.

• It is recommended that a future study reviews the differences between pathways, production method or locales for specific fuels to determine the differences in WtT emissions for a single fuel. This could then be used to determine whether different WtT factors are needed per pathway or supplier.
• Ongoing monitoring of certain aspects of fuel production is recommended due to differences in technology and process having a significant impact on the GHG intensity of the product.
• Further work could evaluate approaches to quantifying emissions (including fugitive) from alternative fuel production, storage, and distribution.

Considerations for GHG emission assessment methods and standards for alternative marine fuels

From the analysis of existing GHG emission assessment methods and tools, Ricardo recommend that any WtW methodology applied to alternative marine fuels considers the following:

• Inclusion of in-use emissions of CO2, CH4 and N2O, plus potentially black carbon.
• Inclusion of upstream emissions, particularly regarding methane leakage, energy used for production and carbon capture and storage rate.
• CORSIA represents a relevant model for the consideration of land use change, and RED II for considering co-product allocation.
• Any default data, assumptions, or emission factors provided should be conservative and the burden of proof for better values should be on the fuel producer or powertrain supplier.

EXPLORE MORE AT THE REPORT ON ALTERNATIVE FUELS