Can we make sure we make the most of the promising ideas people come up with to restrain and adapt to the changes we’re making to the climate? I’ve been considering this question thanks to a recent invention seeking to help cut increasing greenhouse gas emissions that arise from feeding the world’s growing population. Stuart Licht’s team at George Washington University in Washington, DC, has worked out how to make a key component of fertiliser – ammonia – that could eliminate emissions and minimise cost. In fact it’s an extension of a method that Stuart told me can also produce zero carbon cement, iron, bleach, magnesium, and capture CO2 directly from the atmosphere. So when will we see this amazing approach in use? I can’t tell you that – because Stuart has no plans to commercialise it.
I became aware of the new ammonia production system when Chemistry World asked me to cover it for them. Ammonia is a simple molecule, comprising only two elements, hydrogen and nitrogen. Humans have been using it in fertiliser since at least the early 19th century, when it was mined, both in mineral form and as bird guano, for delivery to farmers. That was necessary because although nitrogen is hugely abundant – it makes up four-fifths of Earth’s atmosphere – it’s equally as unreactive. Chemists often replace the air above the reactions in their flasks with pure nitrogen when they’re worried that oxygen will affect their results. That stability meant synthetic ammonia was at first elusive.
But in the early 20th century Fritz Haber and Carl Bosch found a way to overcome nitrogen’s reluctance to react. They could take nitrogen from the air, and bring it together with hydrogen gas in the presence of an osmium catalyst at very high pressures and temperatures. During the First World War ammonia’s other main application – as a basis for explosives – saw that ramped up to industrial scale. The Haber-Bosch process has provided fertilisers that have been crucial in feeding Earth’s growing population since then. But it comes with a downside: it requires huge amounts of energy – 2% of the entire world’s consumption – whose generation usually releases the greenhouse gas CO2.
A STEP forward
Stuart’s team, by contrast, has been developing a process called Solar Thermal Electrochemical Production or STEP. STEP uses electricity to reduce the temperatures and eliminate the high pressures the Haber-Bosch process exploits to get the gases to react together. And rather than reacting nitrogen and hydrogen together as gas flows, it brings them together as bubbles in a liquid. Admittedly, it’s an unfamiliar liquid: a mixture of equal parts sodium hydroxide and potassium hydroxide, heated at 200°C to make it molten.
By bubbling steam through this molten liquid and passing electricity through it, STEP breaks the steam into hydrogen and oxygen. Like the Haber-Bosch catalyst, iron nanoparticles included in the mixture help the resulting hydrogen react with nitrogen from air bubbled through the molten liquid. If powered by mains electricity, the process uses just two-thirds of the energy of the Haber process. But that’s where the ‘Solar Thermal’ part of STEP comes in. Stuart’s team has built systems that use solar power to generate both heat and electricity, which could make STEP ammonia emission-free.
The small ‘heliostat’ solar systems that the George Washington University use also embody another kind of promise. If STEP ammonia needs only a heliostat plus air, sunlight and water, it could provide the beginnings of local fertiliser factories in less developed countries. That potential led SciDev.Net – a website looking at science’s role in development – to ask me to do another article on the technology for them. My editor Josh understandably wanted to know when such a wonderful-sounding invention could be deployed.
In answering my question for Chemistry World about whether his team’s approach could displace the Haber-Bosch process Stuart had said: “The deleterious impact of rising sea levels and climate change are growing and drive the need for effective low carbon footprint replacements. We hope that an awareness of the magnitude of the threat will motivate industry and government to implement effective, low CO2 or no-CO2 emitting chemical and industrial processes such as STEP ammonia fertiliser, STEP iron and STEP cement.”
Inspired by Josh’s interest, I pushed harder on what he was doing to make this happen – whether the technology was being developed by existing or newly founded ‘spin-out’ companies. The answer surprised me. “Our focus is on introducing and demonstrating the fundamental viability of the STEP process to decrease atmospheric carbon dioxide concentrations. We are an academic research facility and not geared towards technology spin-out.”
They promised us clean ammonia
While I respect the fact that many scientists prefer to focus on their research than trying to go into business, this immediately lowered my expectations of STEP ammonia. That was reinforced when another of my interviewees, Paul Makepeace, a fertiliser specialist at the International Fertilizer Development Center in Nairobi, Kenya warned ‘it seems it has a long way to go between now and commercialisation’.
For me this is a ‘they promised us jetpacks’ moment. We love new inventions. That’s reflected in the news – including the kind of stories I write – and popular culture, like the stories of futures where jetpacks are a real mode of transport. We remember them and expect them to become reality, without considering the practical barriers, like whether anyone’s actually going to build a factory to produce them in large amounts.
Can the STEP process fulfil its potential? That’s a question I can’t answer, but what I do know is that it’s not the only new electrically-powered route to make ammonia. Paul underlined that a company called NHThree in Richland, Washington, has developed its own ‘electrolytic’ approach. That requires grid power, but claims to use 30% less energy than the Haber process, and if powered by renewable energy could eliminate ammonia-production linked greenhouse gas emissions. Most importantly, NHThree is already building a plant that exploits its technology in Bolivia.
Shifting one of the chemical pillars supporting modern society to production methods that don’t emit greenhouse gases would clearly be a good thing. But even then, more widespread fertiliser use could lead to more problems as my Twitter friend Joe Turner has pointed out. While nitrogen fertiliser can help us feed the world’s growing population, it is also one of the main sources of the powerful greenhouse gas nitrous oxide (N2O), also known as laughing gas. As Eric Davidson, executive director at the Woods Hole Research Center in Falmouth, Massachusetts, told me in 2012, more efficient fertiliser use is therefore essential in controlling climate change.
I continue to be optimistic that human resolve and ingenuity – including that of Stuart Licht and his team – will eventually bring climate change under control. But the STEP saga shows just how much ingenuity is needed. We don’t just need to invent technological fixes – they have to be ones that can be put into practice, and then used in a way that minimises unintended adverse consequences. Unfortunately, despite this blog’s title, together these needs mean the solutions to climate change are not simple.
Licht, S., Cui, B., Wang, B., Li, F., Lau, J., & Liu, S. (2014). Ammonia synthesis by N2 and steam electrolysis in molten hydroxide suspensions of nanoscale Fe2O3 Science, 345 (6197), 637-640 DOI: 10.1126/science.1254234