Can new biomimicry technology lock-up CO2?

| 24th September 2019
Dr Renault de Richtor researching Iron Salt Aerosols
A new proposal to radically reduce concentrations of methane and other greenhouse gases has been proposed by French researcher, Dr Renaud de Richter, at a recent meeting in London.

You asked whether it can be done at a climatically significant scale and yes, we think it can be done to remove between 6 and 12 gigatons of carbon dioxide per year.

"We have run out of time". Speaking at a special meeting at the Institution of Mechanical Engineers in London’s Westminster, Professor Sir David King outlined some of the major challenges that we face in the near and medium-term due to the ever-worsening impacts of extreme climate events.

“Today the CO2 level is around 413 parts per million but if we add in other greenhouse gases such as methane," he said. "It’s more like 480-500 parts per million depending on how you do the calculation.

"A period 3 million years ago, when CO2 levels were last at the levels they are at now, the temperature was around 10-12 degrees [celsius] higher than it is now.”


The lag in the climate system means that we have not yet fully realised the temperature rise that is implied by previous events on Earth. The main challenge we face as a species is one of preserving our civilisation by transitioning to a sustainable way of life that ranges from energy supply, travel and agriculture.

We also need to reduce the current atmospheric greenhouse gas concentrations from what King has stated above to levels that are way below 350 parts per million. It took 27 years from the initial intergovernmental discussions in 1988 to finally reach an agreement on climate change. King emphasised the point saying:

“Dealing with the UN is a painfully slow process. We had time when we started the process but today we have run out of time!… What we set in place over the next ten years will determine the future of humanity.”

Sir David King Showing The Teperture Record
Sir David King speaking at the Institution of Mechanical Engineers 


The real challenge to the scientific community is extreme weather events.

Extreme weather events are improbable events that happen once in a hundred years, or once in a thousand years, but, due to the warming biosphere are increasing in frequency and intensity, and posing a threat to humanity.

Rice crops

To highlight the interconnectedness of the Earth system, King showed how gradual rises in sea-level can lead to a crisis in food production.

The sea-level rise might itself not inundate coastal areas in normal situations, however, in storm conditions, tidal surges are what take lives and destroy low-lying cities and agriculture.

“Rice production was one of the analyses we did. If the temperature of the rice plant, when it is growing, exceeds 30-32ºC the plant produces no rice. So we could easily calculate the probability of that happening going forward in time with the climate change analysis we used and it turns out to be a very big risk.

If the rice crops of China fail they could turn to Indonesia, they could turn to Vietnam, which has very big rice paddy fields. You turn to Vietnam and you find that the rice paddy fields by that time have gone undersea. They will have been salinated from sea-level rise.

So what we see is a series of big challenges around the world driven by baseline increases and then extreme weather events on top of it.”

Reaching 1.5ºC

Looking at Nationally Determined Contributions (NDC’s) when added up, we are meant to be on a trajectory to achieve 1.5-2ºC by the time 2020 COP comes around again in Glasgow.

Post Paris we can compare our policy trajectories with the nationally determined contributions put forward by every state, to see if we are bending the curve round to limiting global heating to 1.5 - 2ºC above the preindustrial baseline. Currently, we are way off where we need to be with global emissions still rising.

Asking aloud if it is likely we will turn this around, he added: “I don’t know what you think but I think it is highly unlikely!”

Tackling methane with iron salt aerosols

Dr Renaud de Richter speaking at the Institute for Mechanical Engineers
Dr Renaud de Richter speaking at the Institution of Mechanical Engineers

One of the potential tools that could be deployable to help stimulate natural processes that are already breaking down methane and other greenhouse gases in the atmosphere is the Iron Salt Aerosol method being developed by Dr Renaud de Richter, a scientific researcher at the Institut Charles Gerhardt in France, and his colleagues.

In this interview with Dr de Richter, we discuss the issues of scalability and safety among many other aspects.

The main focus of the ISA method is to concentrate on non-carbon dioxide greenhouse gases such as methane that pose an ever-growing near-term risk to global heating.

Dr Renaud de Richter: We are interested in removing other greenhouse gases than carbon dioxide because they are very important in a shorter period of time. One of the most important gases is methane because it has a global warming potential over a twenty-year basis of 86 times that of CO2.

So we looked at nature and we wanted to see if we could enhance natural mechanisms to remove methane at a climatically relevant scale.

Nick Breeze: Can you talk a bit about the rate of increase in the amount of methane in the atmosphere?

RR: Both [CO2 and methane] are going up. In fact, there was a stop of rising methane in the years 2000-2007 but then it started rising again very fast and it is still accelerating. Even if the levels of methane are only around 1.8 parts per million in the atmosphere, compared to carbon dioxide that levels out at around 415 parts per million right now, methane is rising faster because the warming increases the release from rice paddies, from wetlands, from the seep area in the thawing permafrost. There is also a big big risk of destabilisation of methane hydrates, which are underwater and can be released in a very short period of time. 

More warming means much more release of methane and much more methane with a very high global warming potential will increase the warming and this will be a vicious cycle.

NB: You have suggested a couple of solutions that could be employed. Which do you think is the most effective?

RR: The most effective one for the moment is the one employing what Mother Nature does, generating chlorine atoms which destroy the methane 16 times faster than hydroxyl radicals that are currently the main sink for methane in the troposphere.

NB: Would you class this as a form of biomimicry, or as a new engineering technique?

RR: No, this is biomimicry. We have proved with recent research in Germany that there are many ways by which Mother Nature generates chlorine atoms and this is probably an existing one but it can be enhanced if we do it purposefully.

So this method is called iron salt aerosols. 

NB: Is it new, or are we stimulating it where it has declined?

RR: No, we are accelerating it and we can do it in specific places where there are huge concentrations of methane release and prevent this methane from mixing and diluting in the global atmosphere. We are targeting localised applications.

NB: There’s a lot of permafrost news at the moment, so might you go somewhere like Canada or Russia, for example, and deploy it there? Can you talk about how it works?

RR: Yes. Over the seas, there is always a natural sea salt spray and it can be natural acidity or manmade acidity (which we call anthropogenic acidity) like combustion processes, like in the stacks of container ships for instance.

They will emit acids, sulphates and nitrous oxides. These acids will mix with the sea salt spray and generate hydrochloric acid. Then this hydrochloric acid in contact with iron salt aerosols will generate chlorine atoms.

NB: There is a lot of natural concern when you talk about acid release. When this kind of thing gets into the public domain, it sounds like the craziest of geoengineering. How would you respond to these kinds of accusations?

RR: Of course I am talking about acidity but we are 100-1000 times less acidic than pH 1 and this is natural acidity that occurs even without manmade intervention. It is very low acidity.

NB: So this is very low-risk?

RR: Yes. It is really just enhancing natural processes.

NB: Can you talk a bit about scale because, in a lot of conversations that I have had, a lot of proposals fail to address the actual scale of the issue? Is your solution one that could be deployed at scale

RR: Yes, because we have already a lot of scientific evidence that desert dust contains iron that is not very soluble. But when the desert dust blows and creates aerosols, the more it stays in the atmosphere by freezing and de-freezing with the humidity of the clouds and by this unnatural or manmade acidity, it will through this process increase its content of soluble iron which is bio-available and will fertilise the oceans.

In fact, these processes are already increasing primary productivity and very recently scientists showed that natural iron salt aerosols from desert dust, from the Sahara for instance, also fertilised the forests, especially the Amazon rainforest.

NB: Okay, would your process mimic that as well?

RR: Yes.

NB: So in the oceans, for example, you are in effect restoring fisheries?

RR: Yes but I don’t want to speak too much about ocean fertilisation because it is a side effect, which is a good side effect of our technology but our technology is mainly for targeting greenhouse gases in the atmosphere like methane and tropospheric ozone. When this iron falls down it will fertilise both the continents and the oceans.

NB: Is there any risk of doing this in the shallow oceans?

RR: We have started a full evaluation of safety and efficiency and so far we have not found any side effect or any deleterious effect. In fact, there is a huge amount of scientific evidence that natural and manmade anthropogenic emissions of iron salt aerosols are already occurring at large-scale. There is absolutely no scientific evidence that these inadvertent iron salt emissions have any deleterious effect.

The experiments that have been done for ocean iron fertilisation that only want to increase the amount of CO2 uptake from the atmosphere by phytoplankton, which enhance the fisheries, and the marine food web, have produced many critics because they can induce some side effects and deleterious effects. 

At the moment there is no proof that iron salt aerosols, which already occur, have the same deleterious effects. In fact, during experiments of ocean iron fertilisation, the concentration of iron sulphate that was released on the top of the sea was very high. The concentration of our iron salt aerosols will be one thousand times lower and when that iron falls down on the oceans it will be much more diluted.

NB: And is it still effective?

RR: Yes. In the regions of the oceans that are depleted in chlorophyll, which are rich in nutrients but missing iron, in these regions the concentrations of bacteria and plankton are very small because there is almost no food.

If you put a lot of food at the same time, I mean a micronutrient which is iron, there is not enough productivity to benefit all this huge concentration. Meanwhile, if you put it in a thousand times more diluted, you always will find plankton to profit off it.

NB: This is dealing with methane. It still leaves us with the atmospheric carbon dioxide problem but that's over a longer period. We have to deal with it but we have more time. Is this what you are saying?

RR: We think about our iron salt aerosol method for removing other greenhouse gases other than carbon dioxide but then one of the side effects, which is a very good one, is that it can also remove carbon dioxide.

You asked earlier whether it can be done at a climatically significant scale and yes, we think it can be done to remove between 6 and 12 gigatons of carbon dioxide equivalents per year.

NB: Is that the maximum scalability?

RR: Not really because the full evaluation of safety and efficiency has not yet been performed. We discovered that it can also remove tropospheric ozone which is a greenhouse gas. It can also remove some halogen methanes which are natural products produced by plankton and bacteria which destroy the ozone layer. Our iron salt aerosols can destroy these natural compounds so that they will not destroy the ozone layer.

So there are several other benefits that are additional and we have not yet done the full evaluation of all the benefits, so I don’t think it is the maximum scale.

We believe there is no panacea to solve the big problem of global warming. We cannot solve the problem with one silver bullet. We need a set of tools to do that and the iron salt aerosols can be one of those tools.

Research and development status

The iron salt aerosol technology falls under the title of Climate Repair that Sir David King is pushing as part of a worldwide effort to address the environmental crisis that politicians are so far failing to address. 

The current status of this project is that funds are needed to expand the research and carry out more thorough analysis and experiments. The team is based between southern France, Germany and Australia and they are in talks with potential partners about financing their work going forward.

This Author

Nick Breeze writes about wine and climate change.  He posts regularly on Secret Sommelier and is an organiser of the Cambridge Climate Lecture Series. He is on Twitter at @NickGBreeze.


The Ecologist has a formidable reputation built on fifty years of investigative journalism and compelling commentary from writers across the world. Now, as we face the compound crises of climate breakdown, biodiversity collapse and social injustice, the need for rigorous, trusted and ethical journalism has never been greater. This is the moment to consolidate, connect and rise to meet the challenges of our changing world. The Ecologist is owned and published by the Resurgence Trust. Support The Resurgence Trust from as little as £1. Thank you. Donate here