Solar Powered Enzymes

February 16th, 2024

We explored the use of nitrogenase within bacteria and purified enzymes to produce ammonia.

Project lead

Dr Trevor Rapson, trevor.rapson@csiro.au

Lead researchers

Dr Jess Bilyj, jess.bilyj@csiro.au

Challenge

There is a growing interest in using ammonia as a liquid carrier of hydrogen for energy applications. Currently, ammonia is produced industrially by the Haber-Bosch process, which requires high temperature and high pressure. In contrast, bacteria have naturally evolved an enzyme known as nitrogenase, that is capable of producing ammonia and hydrogen using energy from the sun at ambient temperature and pressure. Therefore, nitrogenases are attractive as a potentially more efficient means to produce ammonia via harnessing the unique properties of this enzyme.

In recent years, exciting progress has been made in bio-electrocatalysis using nitrogenases to produce ammonia. This project sought to determine if these advances could be utilised industrially.

We explored the use of nitrogenase within bacteria and purified enzymes to produce ammonia.

Ammonia production via nitrogenase biocatalysis compared to the traditional Haber Bosch process

What we did

We explored the use of nitrogenase within bacteria and purified enzymes to produce ammonia. Our goal was to test whether promising results from the literature could be transferred from laboratory scale to a larger scale demonstration. In particular, we sought to tackle the identified bottlenecks of poor stability of the enzymes and low ammonia production rates to increase the TRL of the technology.

Lessons learned

  1. While reports in the literature using bacteria to produce ammonia look promising, a detailed technoeconomic assessment indicated that the costs associated with production at current ammonia production rates make these pathways not viable.
  2. In order to increase the rate of ammonia production a more detailed understanding of catalytic kinetics is required.
  3. Encapsulation of nitrogenase in Metal Organic Frameworks (MOFS) does not improve the stability of nitrogenase enzymes.

Our lessons learnt are now being used in other projects.

Project finish date

June 2022

Relevant project publications

  1. Rapson TD, Gregg CM, Allen, RS, Ju, HK, Doherty, C.M, Mulet, X, Giddey, S, Wood, CC Insights into nitrogenase bioelectrocatalysis for green ammonia production ChemSusChem (2020) 13, 4856-4865 https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cssc.202001433
  2. Rapson TD, Wood, CC Analysis of the ammonia production rates by nitrogenase Catalysts (2022) 12, 844, https://www.mdpi.com/2073-4344/12/8/844
  3. Wiskich A, Rapson TD Economics of emerging ammonia fertilizer production methods (2023) e202300565, https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/cssc.202300565

HyResearch record

Nitrogenase: Enabling Solar-Powered Ammonia – HyResearch (csiro.au)