Hydrothermal liquefaction-mediated valorization of biomass residues towards novel bio-sourced binders – ALGOROUTE

In the past recent years, tensions have appeared on the asphalt supply for road construction, since cracking of heavy petroleum distillation residues to produce gasoline has become economically competitive due to the high level of the crude oil market. Moreover, the processing conditions of some oxidized bitumen for waterproofing have been recently classified as potentially carcinogen.
As a consequence, it is of high importance for the future that France, which hosts most of the leading companies in the road construction area, anticipates the development of novel technologies to produce alternative binders to petroleum-based bitumen.
In this context, the main objective of Algoroute is to identify, in a medium- to long-term perspective, some processes to valorize biomass residues (from agriculture, food industry…) to anticipate the future tensions on the petroleum market.
In this study, microalgae residues will be used as a model system. Indeed,
- this biomass feedstock has now been investigated for decades, due to significant benefits over other biomass sources (i.e. cellulosic), including low competition for arable land, high per hectare biomass yields, and large harvesting turnovers. Numerous research studies are conducting to produce microalgae biomass for energy and feeding applications and the development of this technology is very likely to result in the production of significant amounts of waste (i.e. the non-valorized solid residues of microalgae).
- the wide variety of microalgae will allow to screen an important chemical diversity. These residues, generated after a first valorization, will be easily accessible because one of the partner is a company specialized in the production and valorization of microalgae.

In that context, hydrothermal liquefaction has been identified as a relevant process to transform biomass residues into bio-sourced road binders with controlled thermochemical and physicochemical properties. The work packages present in the Algoroute proposal will address the main scientific and technical challenges, to make then possible the development of a viable large scale industrial process. This includes (1) a detailed understanding of physical and chemical phenomena taking place during the hydrothermal liquefaction process, and their influence on the rheological behavior of the resulting hydrophobic material, as a function of the nature of the initial biomass residues (2) the multi-criteria optimization of the experimental conditions for the production of bio-bitumen suitable for paving.
In summary, the Algoroute proposal is very innovating since biomass residues are proposed to produce alternative binders, for the first time worldwide. The objective is to valorize a microalgae by-product, as a model system, by developing the understanding and control of the hydrothermal liquefaction process which is considered as a key enabling technology for this sector. Based on the results of the project other categories of biomass residues might be considered.