1 Introduction

The European Union has ambitious goals regarding decarbonization and the transport sector is of great importance in order to become climate neutral by 2050 (Haasza et al. 2018). To reach a higher level of transparency about the origin of greenhouse gas (GHG) emissions in a transport chain, carbon foot printing is an essential pre-requisite (Dobers et al. 2019). Users and providers of freight services need to be aware how much GHG they are emitting to be able to set and deliver carbon reduction targets (McKinnon 2021). This requires further insights into current emission levels and the development of an internationally accepted standard for the calculation of transport chain emissions to support comparisons, and with them the identification of potentials for reducing GHG emissions and best practice (Dobers et al. 2019).

During recent years substantial progress has been made in the measurement, calculation and reporting of transport chain emissions. The subject has generated a large literature of reports and journal papers, techniques for measuring emissions have been refined and there has been much greater harmonization of methodologies, particularly with the wide adoption of the EN 16258 standard and the Global Logistics Emissions Council (GLEC) framework (McKinnon 2021). Nonetheless, at present, a seemingly fragmented landscape of various programs with different methodological approaches exists. The quality of calculated emissions and emission intensities depends on availability, specification, quality and exchange of data. In many cases no complete real-world data are available for carbon footprint calculation. In such cases, it is possible to use aggregated average data (default factors) on emissions to substitute missing data (Dobers et al. 2019). These values, mostly given in gram per tkm vary greatly, especially for inland navigation. In fact, a comparison between available data of IWT, rail and road shows that the IWT sector is lacking behind (Schweighofer and Szalma 2014; Greene and Lewis 2019). For this paper, a literature review was conducted to focus on emission factors along multimodal transport chains and their effects on emission calculation results.

2 Result, Analysis and Discussion

Accounting for emissions from freight transportation requires an understanding of a diverse set of business models, modes of transport, regions and more. For the road sector there is a choice between many sources of reference data and default factors which can lead to comparability issues, whereas for rail and inland waterway transport there are limited data available, leading to very high-level assumptions being made, this time leading to uncertainty and potentially unrepresentative outputs being generated (Greene and Lewis 2019). Raising the GHG emission factors for inland waterway transport is quite extensive in comparison to other modes. The specific energy consumption of an inland vessel in relation to the weight of goods transported and the distance (grams of diesel per ton kilometer) can take on very different dimensions. The width and depth of the waterway including the distance between the side of the ship and the river bottom have a massive influence on the diesel consumption of a ship. Therefore, energy consumption data for individual waterways and the type of ship used are necessary (Bauer et al. 2011). If energy consumption data is not measured, but calculated using default values, then certain assumptions, e.g. about the load utilization of the vehicles, enter the calculation. These assumptions can have a considerable effect on the result but are not always correct (Schmied and Knörr 2012).

There exist large differences between fuel-based emission calculation and calculations using emission-intensity factors based on the volumes and kilometers transported. The use of intensity emission factors is often preferred due to unavailability of real fuel consumption values in companies. The use of these factors should be used with caution as for example in the calculation of a round trip, the distance without freight cannot be calculated. A reason for this is that the emission intensity factors already include a certain utilization and empty running factor. Thus, an upstream calculation with freight and a downstream calculation without freight with the emission intensity factors according to the GLEC Framework is not possible (Lomax 2022).

Another difficulty in calculation is that the vessel types in the GLEC Framework are not specified more precisely. As an example, it is not clear if the tanker vessel is a tank lighter or a motor tanker.

Carbon calculation tools such as EcoTransIT World or CarbonCare strive to simplify the process of calculating. EcoTransIT World is compliant with the EN 16258 and the GLEC framework, but a simple calculation example with a truck and an inland waterway vessel is emerging in different values compared with a calculation including the manual GLEC calculation. A major challenge are the different parameters for the emission calculation: The EcoTransIT World and the GLEC framework have varying vessel categories, differences in the calculation of the kilometers, the load factor, the empty trips and the emission standard of the vessel. To make the differences and obstacles regarding vessel types clearer, here is an example. To calculate the emissions of a tanker from Enns to Vienna with a cargo of 3,100 t, it is only possible to select a large inland cargo vessel Bulk V 1,500–3,000 t in the EcoTransIT vessel categories. However, with a cargo of 3,100 t, two ships would be needed, since no larger ship is available in EcoTransIT.

Simenc (2016) evaluated existing emission calculator that could be used for estimating emissions of inland waterway transport and concluded, that the range of available ready-to-use practical solutions is relatively narrow. There are few options available and even the estimation capabilities of existing ones could be thought of only as educated guesses, at best. They are only as good as the quality of emission factors and other parameters that are considered, over which the prospective users have no influence and are subject to uncertainties regarding the underlying calculation algorithms and ability to produce reliable results.

To further increase the accuracy of logistics emissions in multimodal transport chains, van Liere (2018) calculated the GHG emission factors for representative vessel classes in Europe on the basis of real-life data from barge operators. The data collected by barge owners/inland shipping lines has resulted in lower GHG emission factors in comparison to other recognized studies. As the dataset includes information on only approx. 1% of the vessels operating in Europe, they recommended to continue expanding the dataset with annual information on transport performance (distance covered, load factor, tones transported) and fuel consumption per representative vessel class.

Since 2018 the work is still in progress and some data collection programs are currently being undertaken to get a more accurate picture of the GHG emission per tkm from inland waterways. The work will be reflected in the update to the GLEC Framework by the end of the year 2022 and its resulting worldwide standard ISO 14083 (Quantification and reporting of greenhouse gas emissions arising from operations of transport chains) (Lomax 2022). The improved access to reliable data will help both business and governments make better decisions to collectively reach climate goals.

3 Conclusions

It is important, that the drive for consistency, transparency and comparability is strongly maintained in the future for the collection of freight emission data. This means that the future framework for calculating GHG emissions needs to be reliable, relevant, and accurate to enable adequate comparison of emissions from transport operations, thereby placing all modes and operations on equal footing. The GHG emission factors for inland waterway transport is quite extensive in comparison to other modes, so more effort is needed to ensure a broad database to stay competitive with other transport modes such as road and rail. The inland waterway sector is challenged to ensure a high level of accurate data collection among the GHG of vessels. Nevertheless, it should always be the goal to shift to primary data (primary fuel consumption data). This is the only way to get really reliable factors and to be able to track future progress. Future research should focus not only on the GHG emissions from the transportation, but also those emissions which are related to handling, where the data situation is currently inadequate.