Researchers Develop Method Of Producing Ammonia From Sunlight

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Originally published on PlanetSave.

A group of scientists led by the US Department of Energy’s National Renewable Energy Laboratory (NREL) and the University of Colorado-Boulder has developed a new, eco-friendly method to produce ammonia, the main ingredient of fertilizers, using light. This study also included researchers from Utah State University (USU) and Montana State University (MSU).

Discovery details

CU-Boulder Assistant Professor Gordana Dukovic

The research team discovered light energy can be used to change dinitrogen (N2), a molecule made of two nitrogen atoms, to ammonia (NH3), a compound of nitrogen and hydrogen. The researchers hope the newly discovered, light-driven chemical process that creates ammonia can lead to future developments that will enhance global agricultural practices while decreasing the dependence of farmers on fossil fuels.

Traditionally there have been two main ways to transform nitrogen, the most common gas in Earth’s atmosphere, for use by living organisms:

  • One is a biological process occurring when atmospheric nitrogen is “fixed” by bacteria found in the roots of some plants like legumes and then converted to ammonia by an enzyme called nitrogenase.
  • The second, called the Haber-Bosch process, is an industrial method developed a century ago changing N2 to ammonia in a complex chain of events requiring high temperatures and pressures. The Haber-Bosch process requires the significant use of fossil fuels and results in a corresponding hike in greenhouse gas emissions.

Led by NREL research scientist Paul King, the new paper appears in the April 22 issue of Science. CU-Boulder co-authors include Assistant Professor Gordana Dukovic of Department of Chemistry and Biochemistry, former doctoral student Molly Wilker, now a faculty member at Luther College in Iowa, and current doctoral student Hayden Hamby.

The team showed nanocrystals of the compound cadmium sulfide can be used to harvest light, which then energizes electrons enough to trigger the transition of N2 into ammonia.

“The key was to combine semiconductor nanocrystals that absorb light with nitrogenase, nature’s catalyst that converts nitrogen to ammonia,” said Dukovic. “By integrating nanoscience and biochemistry, we have created a new, more sustainable method for this age-old reaction.”

Fertilizers and environmental protection

Developing a better environmental footprint concerning the development and use of various fertilizers is a fundamental challenge facing the international agricultural  industry.

As reported by Scientific American, many synthetic chemicals used to produce fertilizers are petroleum-based. While these fertilizers have allowed farmers and gardeners to exercise greater control over the plants they want to grow by enriching the immediate environment and warding off pests, these benefits have come with environmental costs, such as the runoff pollution of many streams, rivers, ponds, lakes, and coastal areas.

“When the excess nutrients from all the fertilizer we use runs off into our waterways, they cause algae blooms sometimes big enough to make waterways impassable. When the algae die, they sink to the bottom and decompose in a process that removes oxygen from the water. Fish and other aquatic species can’t survive in these so-called “dead zones” and so they die or move on to greener underwater pastures.”

This discovery might pave the way for sounder fertilizer-manufacturing methodologies which have a safer environmental impact.

“Using light harvesting to drive difficult catalytic reactions has the potential to create new, more efficient chemical and fuel production technologies,” said NREL Research Scientist Katherine Brown. “This new ammonia-producing process is the first example of how light energy can be directly coupled to enzymatic N2 reduction, meaning sunlight or artificial light can power the reaction.”

Image via University of Colorado

Source: EurekAlert

Reprinted with permission.

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18 thoughts on “Researchers Develop Method Of Producing Ammonia From Sunlight

  • What’s the hydrogen source?

    • Hydrogen is generated in two ways:
      1. Electricity is passed through water separating it into hydrogen and oxygen.
      2. A hydrocarbon fuel (oil or natural gas) is partially burned creating steam and hydrogen.

      nitrogen is extracted from the air using compressors and special filters

      The article states that “reported by Scientific American, many synthetic chemicals used to produce fertilizers are petroleum-based.”

      This is not really true. The first ammonia plants 100 years ago were entirely powered by electricity. Mainly from hydroelectric facilities. After world war II oil was widely used. Since 1970 the energy source of choice is natural gas. We could easily switch back to solar powered ammonia production.

      The other elements used in fertilizers are phosphate, and potassium. phosphate is typically extracted fro ores although there are many other sources. Potassium is typically extracted from mainly used in the mining or phosphate ore and in transporting the materials to processing centers and customers.

      Now some oil is also used to make pesticides. But pesticides are not fertilizers. Furthermore most hydrocarbon chemicals today are made from natural has. So it is my opinion most pesticides are now made today with natural gas not oil.

  • Haber process
    “This conversion is typically conducted at 15–25 MPa (150–250 bar; 2,200–3,600 psi) and between 400–500 °C (752–932 °F), as the gases are passed over four beds of catalyst, with cooling between each pass so as to maintain a reasonable equilibrium constant. On each pass only about 15% conversion occurs, but any unreacted gases are recycled, and eventually an overall conversion of 97% is achieved.”
    Energy Intensive

    • Yes, Haber Bosch reaction is energy intensive. However, this energy could be 100% RE, therefore, the article is weak and not correct. You need hydrogen (electrolysis of water), nitrogen (liquifaction of air) and (RE) energy for ammonia synthesis via the Haber Bosch route.

      Only when the new reaction could be done in large scale at a lower price than a 100% RE Haber Bosch reaction then we can talk. 🙂

      • That’s the wrong way to assess a laboratory innovation against a commercially established process. The question is whether it has the potential to win, after development and rollout. From this report, it looks as if a direct catalytic solar method would use much less energy, so it may well be worth developing. Note also that it could allow more dispersed fertiliser manufacture close to the point of use, with large savings on transport.

        • I second that and since it is using the sun directly I guess it could be quite interesting even from an economic perspective.

        • Sorry, the article claims that it may be an alternative for the Haber Bosch reaction, therefore, we have to wait for a technicum scale reaction. The author compares a lab experiment with large scale reaction. 🙂

          Of course the alternative is in principle interesting as it may solve some issues of Haber Bosch route. However, for me as chemist the party pooper is nanocrytals, so there is a good chance that this will only be a lab experiment. 🙂

  • The budget cuts in the terrific fundamental research work of the NREL are a scandal. Thanks House Republicans and their fossil paymasters.

  • This will do absolutely nothing to address the environmental impacts of runoff on waterways and other ecosystems. Less carbon emissions yes. But if it ultimately makes nitrogen fertilizers cheaper then the other impacts will actually be increased.

    • Thank you for the links much appreciated. A byproduct of cheaper ammonia is that the likes of VW and other frauds now do not have the economic incentive to go without the only really efficient way to neutralize Nox and if you can get cheap ammonia you can also run Diesel engines hotter and thus more efficient.

      • This is already done with other amides in trucks but may be too expensive for cars. 🙂

  • Wonder what the eventual breakdown in costs for solar fuels will be – hydrogen, syngas, ammonia. Rather than batteries use chemical processes to create fuels for combustion at night and low sun periods. It wouldn’t require specific geography like pumped hydro, and there would be a secondary market for industrial and transportation purposes.

    • I’m not optimistic about their ability to be competitive in places where batteries/electricity will do the job. More likely they will be used for niches where batteries won’t be up to the job.

      That said, if batteries increase in capacity above 400 Wh/kg there may not be many niches to fill.

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