Using nanoparticles and phytoplankton to help combat climate change

Scientists believe technology could be developed to farm large phytoplankton blooms in the oceans to remove carbon dioxide from the atmosphere. 

The phytoplankton converts carbon dioxide into biomass - or living tissue - through photosynthesis. Eventually, the phytoplankton sinks to the sea floor, taking its carbon payload with it and where it will stay for centuries to millennia.  
 
To enable the phytoplankton to grow and flourish, however, it needs to be fed a fertiliser, a combination of iron and other nutrients.  
 
But previous attempts to farm phytoplankton blooms have not shown promise to date because fertilisation techniques, which have involved putting nutrients straight into the sea, have not been effective enough - or the blooms that develop have been less efficient in taking carbon dioxide out of the environment through photosynthesis than naturally forming blooms.  
 
A new scientific paper - led by University of Leeds researcher, Dr Peyman Babakhani from the School of Earth and Environment - argues that these problems can be overcome if engineered nanoparticles are used to target delivery of the fertiliser to the phytoplankton, and they may even have extra benefits.  

phytoplankton blooms could be a cost-effective way of reducing carbon dioxide levels

 The paper - Potential use of engineered nanoparticles in ocean fertilization for large-scale atmospheric carbon dioxide removal, which has been published in the journal Nature Nanotechnology - looked at the results of 123 previous studies and conducted new analyses on the costs, risks, and the efficiency of the approach. It concluded that phytoplankton blooms could be a cost-effective way of reducing carbon dioxide levels, although the experts acknowledge full scale implementation of the technology is still a long way off.  The key solution is better delivery of the fertiliser by specifically designed nanoparticle carriers.  

Engineered nanoparticles  

The nanoparticles, which would range in size between 10 and 100 nanometres, where a nanometre is one billionth of a metre, would be designed to carry fertiliser to the phytoplankton, for example:     

• Coated with simple, cheap, and environmentally friendly polymers, they would be buoyant and would stay in the phytoplankton zone in the ocean rather than sink to the seabed. They could also be designed to deliver other key nutrients essential for the continuation of phytoplankton growth.   
   
• The nanoparticles could also be shaped to facilitate fast export of phytoplankton cells containing carbon to the deep sea. And they could be designed to preserve the phytoplankton from being eaten by other marine organisms before sinking to the seafloor.  

Dr Peyman Babakhani, a postdoctoral research fellow working with Prof Caroline Peacock in the Earth Surface Science Institute at Leeds, said: “Ocean fertilisation has been studied for decades as a potential approach to lower atmospheric carbon dioxide concentrations and thus fight global warming.   
 
“However, the use of conventional dissolved nutrients in ocean fertilisation field experiments has not shown desirable outcomes to date. We show that the use of engineered nanoparticles, instead, can enhance the efficiency of the conventional approach and addresses a number of limitations.  

These findings propose a new area of environmental applications for nanotechnology that sparks extensive research into the role of nanoparticles in storing carbon dioxide within the ocean.

“Our study shows that the use of several types of engineered nanoparticles in ocean fertilisation can be promising in terms of costs and carbon dioxide emissions during production and delivery processes, and such nanoparticles can be applied at concentrations lower than those that might cause toxicity to marine ecosystems.   
  
“These findings propose a new area of environmental applications for nanotechnology that sparks extensive research into the role of nanoparticles in storing carbon dioxide within the ocean.”  
  
The paper says there are public and regulatory concerns over the potential toxicity of nanoparticles to marine ecosystems. Nanoparticles exist naturally but the environmental risk of adding engineered particles to the ocean needs to be assessed. But the researchers say these the challenges are not insurmountable.  
 
The article ends with recommendations how to push the research forward.  
 
More information

Read the main article in Nature Nanotechnology here: https://rdcu.be/c1kw6 
Read the Associated Research Briefing here: https://rdcu.be/c1kxr 
The research was supported by the European Research Council through the MinOrg Project led by Prof Peacock.

IMAGE CREDIT: Stephanie King, Pacific Northwest National Laboratory. COVER DESIGN: Amie Fernandez