DOE seeks input on barriers to thermochemical liquefaction conversion of biomass to drop-in transportation fuels
The US Department of Energy (DOE) has issued a Request for Information (RFI) (DE-FOA-0000796) to garner input from researchers in industry, academia, and other interested biofuels stakeholders to identify key technical barriers in converting biomass via thermochemical direct liquefaction pathways to transportation fuels in the gasoline, diesel, and jet fuel ranges.
Thermochemical direct liquefaction pathways are unique in their ability to accept readily widely varied non-food, high-impact biomass and to produce bio-oil feedstocks that may be further processed into a range of hydrocarbons that are similar to those found in crude oil derived products, DOE notes. This enables the production of gasoline, diesel, and jet range fuels and other co-products such as heating oil and chemicals. These technologies also have the potential to supplement petroleum-derived streams within a refinery.
For the purpose of this RFI—Carbon, Hydrogen and Separation Efficiencies in Bio-Oil Conversion Pathways (CHASE Bio-Oil Pathways)—thermochemical direct liquefaction pathways include:
In situ catalytic fast pyrolysis (i.e. where biomass is pyrolyzed in a fluidized reactor containing a catalyst);
Ex situ catalytic fast pyrolysis (i.e. where fast pyrolysis products exit a reactor and vapor phase upgrading is performed on the bio-oil vapor);
Hydrothermal liquefaction (i.e. where biomass is liquefied with near-super critical water); and
Solvent liquefaction (i.e. where biomass is liquefied with a solvent system).
These are the six primary thermochemical direct liquefaction pathways currently under development with the support of US DOE funding, all of which share some common problems:
All of the pathways listed produce an intermediate bio-oil of varying stability and longevity. The ability to remove destabilizing components from bio-oils is crucial to achieving improved processes for bioproducts production. Improvements in selective fractionation and separation capabilities in the context of bio-oil production and upgrading are needed.
All of the processes listed above require a hydrogenation step that utilizes either hydrogen gas or a surrogate hydrogen source. Currently, many systems use steam reforming of non-renewable natural gas to generate hydrogen. Little is known about the efficiency of hydrogen use during catalytic upgrading of bio-oil and during hydropyrolysis. The use of hydrogen gas and hydrogen-donor molecules needs to be evaluated and corresponding technologies need to be identified, understood for optimal efficiency, and tested. Improvements in hydrogen production, use, and transfer in biomass liquefaction and bio-oil upgrading are needed.
Several of the processes listed above produce a biphasic bio-oil as the initial product. Typically only the organic phase is processed in subsequent upgrading steps, leaving behind valuable hydrocarbon material in the aqueous phase. Technology needs to be developed to better use aqueous phase hydrocarbons and to minimize hydrocarbon loss to the aqueous fraction of bio-oil.
A recent stakeholder workshop hosted by the Department of Energy’s Office of Biomass Program (OBP) (Conversion Technologies for Advanced Biofuels, CTAB) (earlier post) , identified common technology deficiencies for the pathways:
Developing selective fractionation and separation systems in bio-oil processing;
Improving H2 production, use, and transfer in biomass liquefaction and bio-oil upgrading; and
Developing technologies for use and mitigation of the aqueous fraction of bio-oil.
DOE thus is seeking information regarding the relevancy of these technical barriers, technology readiness level, and resource needs. The information may be used by OBP in support of program planning.
Responses to the RFI are due by 5 December.
DOE had earlier issued a separate RFI regarding technologies for the deconstruction of lignocellulosic biomass to intermediates and for the upgrading of biomass derived intermediates to hydrocarbon transportation fuels and blendstocks. DOE also requested views and opinions regarding the draft Conversion Technologies for Advanced Biofuels (CTAB) Roadmap developed as a result of the DOE CTAB road-mapping workshop held in December 2011.