A multi-criteria sustainability assessment for biodiesel and liquefied natural gas as alternative fuels in transport systems

The incorporation of clean-fuel technologies has become essential for the sustainability of the transportation sector. Natural gas technology, especially the use of liquefied natural gas (LNG), has become a possible alternative to diesel oil in freight transport because of its acceptable autonomy and low fuel prices. For the introduction of this alternative fuel, freight companies need tools that allow them to perform an integrated assessment of relevant aspects related to environment, economy and social responsibility. This paper introduces a multi-criteria based methodology that integrates the key factors involved in the transport system: vehicles, infrastructure and fuels, and consideration of the three pillars of sustainability, as well as the reliability of technology, legislation and market issues. In particular, a case study for the impact assessment of LNG in comparison to hydrotreated vegetable oil (HVO) and diesel oil as regular long-haul freight transport fuels in Spain was developed. The information for the comparison process was obtained from peer-reviewed articles and reports from international and Spanish institutions, while the primary data was obtained through semi-structured in-depth interviews to the different stakeholders. A weighted sustainability index for each alternative was developed to integrate the data obtained through the analytic hierarchy process. The results indicate that LNG trucks would be an attractive option compared to diesel oil and HVO, provided that decision-makers give significant weight to social and environmental criteria, and that the government guarantees a legislative security to maintain the low taxes on natural gas. Integration of stakeholders allows making the most appropriate decision according to the objectives of the company. The application of the proposed methodology shows consistent results, which should ensure the success of a long-term alternative in the dynamic market for transportation fuels.