BACterial conversion of CO2 and renewable H2 inTO bioFUELs

Project Information

Bac-To-Fuel

Grant agreement ID: 825999

DOI

10.3030/825999

Project closed

EC signature date 11 December 2018

Start date 1 January 2019

End date 30 June 2022

Funded under

• SOCIETAL CHALLENGES - Secure, clean and efficient energy

Total cost

€ 2 999 922,50

EU contribution

€ 2 999 919,00

Coordinated by

UNIVERSIDAD DE SANTIAGO DE COMPOSTELA
Spain

Periodic Reporting for period 3 - Bac-To-Fuel (BACterial conversion of CO2 and renewable H2 inTO bioFUELs)

Reporting period: 2021-07-01 to 2022-06-30

Summary of the context and overall objectives of the project

WP1 Results differed from expectations, but after re-orientation they went beyond the state-of-the-art. The planned “in situ” demonstrator was replaced by “in silicon” integration, showing the project’s feasibility & socio-economic impact.

WP2 Monodisperse Cu & Ag AQCs (5 atoms) were the most catalytically active for H2 photoproduction with solar light, when deposited onto semiconductors e.g. TiO2, CeO2, perovskites. AQC synthesis methods were developed & scaled up. AQCs were purified & 0.1 g was produced at a concentration of 10 g/L.

WP3 modelled the stability & electronic structure of Cu5 & Ag5 AQCs on TiO2 & CeO2 surfaces. Mid-gap polaronic states formed by electron transfer from AQCs to the Ti or Ce on the substrates & some hybrid states on Cu & adsorbed O2 atoms. As AQCs could create states within the bulk gap under ambient conditions, this showed that the absorption spectrum of the AQC-semiconductor complex is more closely matched to the peak of the solar spectrum. The AQC-semiconductor complex can be used in solar energy harvesting.

WP4 developed photo-catalysts for H2O splitting. The AQCs & semiconductors were characterised & tested: the concentration & purity of the AQCs were key parameters & the incipient wetness method was best. Elevated temperature (>400°C) & concentrated sunlight (>10-fold) gave optimal STH efficiency. A patent was filed.

WP5 optimised the culture of Clostridium autoethanogenum, & developed conjugation & CRISPR-Cas protocols: aiming to engineer the conversion of H2 & CO2 into biofuel. 2 successful gene knockouts were constructed, but it did not produce more ethanol.

WP6 A lab-scale pressurised 1 L bioreactor was built to convert CO2 & H2 into biofuel. A wild type strain was tested as the CRISPR-Cas modified strains were not ready. The gas diffusion electrodes, for in situ H2 production, were finalised & bioreactor performance was optimised. VFAs & alcohols were produced without the need to pressurise the reactor.

WP7 The original process could not provide pure H2 for anaerobic fermentation. An alternative process, with 2-stage catalytic H2O splitting, was developed to produce highly pure H2. Therefore, a scaled-up demonstrator could not be built. Instead, a digital model demonstrated the integrated process.

WP8’s business plan will maximise exploitation, including through the spin-off HYSUN, which will develop & scale-up the photocatalysis process. The Indian Oil Company aims to commercialise VITO’s gas diffusion electrode.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

WP1 refined the system requirements for producing biofuels & reviewed the lab-scale process components & product targets, the integrated system specification, & the test protocols for the photocatalytic & electrobiocatalytic processes.

WP2 synthesized purified & monodisperse samples of Ag5 & Cu5 in enough quantity to prepare 10 g of cluster@semiconductors’ catalysts per day.

WP3 AQCs (Cu5, Ag5) are predicted to decrease the O2 vacancy formation energies of CeO2, indicating that the operating temperature could be achieved by a solar concentrator. In contrast, AQCs do not affect the O2 vacancy formation energies of TiO2. AQCs transfer electrons to both CeO2 & TiO2 to form polarons on the substrates. Some of these localised electrons on Ce & Ti atoms have higher energies making them more active, so that they can reduce protons to H2 without illumination. Spontaneous H2O splitting was identified on some active sites in the Cu5/TiO2 interface.

WP4 Photocatalytic H2O splitting should use concentrated light at >400°C as STH efficiency is substantially increased compared to ambient conditions.

WP5 Despite constructing different gene knockouts, the organism did not produce more ethanol. A high ethanol yield is essential for a successful bioprocess, therefore further engineering is needed.

WP6’s proof of concept pressurised reactor significantly increased bacterial ethanol production with CO2 & H2 feedstock. Based on this, a lab scale pressurised pilot bioreactor (≤10 bars) was designed, developed, fabricated & tested with a wild type strain of Clostridium. A sparger or a tubular gas diffusion electrode developed at VITO were the most efficient methods for supplying the gaseous feedstocks. A tubular membrane electrode assembly was designed for in situ H2 production. Novel electrodes were fabricated with the inner core (made of Ni) producing H2 & the outer core (made of C/Pt) producing H2. Long term stability tests showed the electrode was stable.

WP7 The H2 quality required for anaerobic fermentation can only be provided in a 2-stage H2O splitting process. Integration between production & utilisation requires a pressurised H2 storage tank. This will be used when sunlight is insufficient for H2 production.

WP8 is ready to scale up the technology. Licenses could be granted to EPC companies & end users. We developed a business plan resulting in the creation of a spin off & a potential commercialisation of the GDE for in situ H2 production.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

WP1 Specifications & requirements for producing biofuels 1) AQC production, 2) photocatalytic & electrobiocatalytic processes, & 3) final efficiencies of the integrated system are beyond the state of the art.

WP2 Highly efficient procedures to prepare pure & monodisperse AQCs (>6 orders of magnitude better than the state of the art), using common wet chemical techniques, were developed, which transformed the application of AQCs at industrial level from a dream to a reality.

WP3’s models suggest that the AQC/metal oxide catalyst Cu5/CeO2 can underpin a sustainable, low cost & environmentally friendly energy vector, based on the photocatalytic production of H2. A 2-step photocatalytic H2O splitting cycle could be used in which O2 is removed from the oxide in the presence of sunlight, followed by H2O splitting in the dark, which regenerates the oxide & releases H2.

WP4 AQC photocatalysts are an alternative to noble metal nanoparticles. When combined with metal oxide semiconductors, they are a sustainable solution for photocatalyst synthesis.

WP5 did not obtain a better ethanol-producing strain, severely hampering development of a bioprocess, converting H2 & CO2 into biofuel. In future, a commercial partner could provide a H2-using ethanol-producing strain.

WP6 advanced the biocatalytic technology for converting CO2 to biofuels e.g. alcohols. Most microbial electrosynthesis studies use mixed cultures, leading to non specific conversion of CO2 to products that are hard to separate, reducing the Faradaic efficiency towards a single product. Our new pressurised reactor uses pure bacterial cultures (wild type or GM) leading to higher conversion efficiency & product yields. The reactor’s in situ H2 production system (tubular electrodes) overcomes H2 availability issues. VITO will pursue further upscaling. VITO had visits from the industry (e.g. Electrochaea) who want to use the H2 production system in future projects e.g. for methane generation.

WP7 A new concept for H2 production, & its use for biofuel manufacture, was shown for use at locations with available land & CO2 sources, but without renewable electricity. Use of this technology makes fuel production more flexible.

WP8 studied the market. We protected the technology, have FTO in most of the process, & have clients interested in buying parts of the technology (AQCs & in situ H2 generation via GDE). A spin off was created.

Improved electrodes for use in the electrochemical synthesis of Cu5 clusters.