Integrated Valorization of Biomass: Catalytic Hydrothermal Liquefaction and the Architecture of a Modular Biorefinery

In the absence of massive government subsidies, the economic viability of large-scale thermochemical conversions of biomass to biofuels is tenuous at best. While hydrothermal liquefaction (HTL) is an efficient way to upcycle wet biomass wastes, the resulting biocrudes require significant upgrading, and up to 50% of the feedstocks’ carbon partitions to a low-value solid hydrochar and a difficult-to-separate, organic-laden aqueous phase. A profitable biorefinery to valorize heterogeneous wet wastes requires new in situ catalytic approaches to upstream HTL and the valorization of byproducts. In this talk, we demonstrate how abundant clay minerals such as dolomite partition upwards of 60% of a biomass’ carbon into HTL biocrude, increasing energy recovery by 22% versus non-catalyzed HTL. Dolomite aligns the biocrude’s boiling point distributions to that of petroleum, with a larger fraction of long chain (C15+) components as compared to the abundant phenols and furans found with sand- and illite-catalyzed HTL.

While HTL advocates have long touted the versatility of hydrochars for direct insertion into industrial and environmental applications, our recent work has cast doubt on many of these claims.Yet, the chemical shortcomings of these hydrochars can be leveraged to design industrially viable fuels and high-value porous carbons for use as adsorbents, soil amendments and electrodes in supercapacitors. For example, hydrochars can be upgraded into activated carbons with rigid aromatic structures and Lewis base activity to adsorb up to 90% of their weight in heavy metals from contaminated groundwater, or to recover phosphorus and additional biocrude from the aqueous phase (AP) of HTL. The AP contains organics often beyond their solubility limits. While biological treatment is typically hindered by cytotoxicity, we demonstrate that Gluconobacter oxydans produces valuable biolixiviants when grown on HTL AP. This thermodynamically unconstrained route to valorize fugitive carbon is currently under investigation for its ability to produce bacterial nanocellulose, a high-value carbon scaffold for myriad applications. Together, these studies reframe HTL byproducts as feedstocks for a modular biorefinery, where every carbon atom has a purpose.

Speaker: Jillian Goldfarb, Cornell University