Future diesel-like renewable fuels – A literature review

06 Dec 2022

IFP Energies Nouvelles was commissioned by Concawe to identify novel sustainable liquid fuels pathways by 2030 for heavy duty trucks applications. The study consists of an extensive literature review to address three main topics: (1) the overall fuel production pathways from the resources, the processes, and the renewable components; (2) renewable fuels performances through engine tests and blending behavior; and (3) life cycle and techno-economic assessment of selected pathways. The work is combined with interview sessions of relevant stakeholders involved in fuel production or use.

The study contributed to shed light on opportunities and limitations related to the development of novel renewable diesel-like fuel. Three main constraints were identified for the development of novel fuel production pathways. First, the availability of sustainable feedstock in the 2030 horizon; second, some dedicated fuel conversion processes are potentially mature for certain routes while other require important investments and time to be developed which may not be compatible with the 2030 timeframe; finally, along with the large number of renewable products identified, an evaluation of their “drop-in” capabilities was performed. This evaluation remains partial for most of the compounds, except for the well-known conventional renewable products, i.e. fatty acid methyl esters and paraffinic fuels (e.g. hydrotreated vegetable oil alike). This evaluation includes their overall compatibility with current fuel specifications or more globally their impact on engine/vehicle hardware and emissions.

Two main routes were considered.

First, paraffins and FAME were excluded to identify other sustainable components. This led to highlight dioxolane derivatives and two ethers (di-n-pentylether and dibutoxymethane). It was concluded that while such oxygenated compounds are promising and related to recent research and development studies, they suffer from important shortages including the availability of key reactants. However, encouraging developments were identified and these could contribute to accelerate the development of such pathways in the future beyond the 2030 timeframe.
Second, this work focused on parafins and esters to assess and discuss the advantages or drawbacks of the related production pathways. The latter included hydrotreatment, gasification combined with Fischer Tropsch, esterification, fermentation and e-fuel. The study concludes that fuels arising from these energy pathways could lead to significant CO2 emissions reductions thanks to the resources and processes characteristics but also a high blending potential with respect to the EN590 specification. The main identified constraints are the density or the cold flow properties for increasing the incorporation of such renewable components.

Also included is an evaluation of the production potential of renewable parafins and esters assuming the mobilisation of locally produced European sustainable biomass, leading to a range between 57 and 88 Mtoe by 2030, or between 24% and 37% of the expected energy demand for middle distillates in the transport sector1 (low or high mobilization scenario2 with energy pathways already at industrial scale and expected to become mature by 2030; this evaluation only considers the use of advanced biomass and does not include current mainstream biofuels from food and feed crops (often called “1st generation biofuels”)). These values must be seen as a maximum theoretical potential, pending the development and upscaling of the technologies, the mobilisation of biomass to biorefineries, the necessary investments and development of a profitable business, etc. This maximum theoretical production potential is however highly unlikely to be reached in 2030, as it would require massive investments to be realized in technologies which today do not exist at industrial scale, without waiting for demonstration of a First-Of-A-Kind. Competitions will certainly be present between heavy duty transport and aviation or maritime sectors due to ambitious decarbonation targets by 2050.

Findings of this study were shared with 15 stakeholders involved either in fuel production, fuel logistics, engine manufacturing, fleet operation or representing public authorities. Their views mostly highlight the significant role that renewable liquid fuels will have to play to contribute to the decarbonization of the commercial transport sector in the short term and for the next decades. In this context, this work contributes to assess the strengths and weaknesses related to existing and potential future liquid fuel energy pathways.