Research at SINTEF, Status Report July 6, 2022

Gary Wolff, PhD Research at SINTEF

SINTEF researcher

SINTEF Ocean Lab, located in Trondheim Norway, and part of one of the largest research organizations in Europe, is evaluating what will likely happen to Hollow Glass Microspheres (HGMs) if deployed in the Arctic Ocean, and what impact they might have on the Arctic ecosystem. 

The ‘fate and transport’ tests on three types of HGMs are complete. Algae and bacteria did not grow well on the surface of the HGMs, so they will probably stay reflective for years in the Ocean. Two types of HGMs mostly continued to float when tumbled repeatedly in seawater or repeatedly frozen and then thawed. Yet even these two types of HGMs broke at a modest rate. A modest amount of breakage is good since it means that the cooling benefit of spreading HGMs will last many years, but is also a naturally reversible effect. Greenhouse gas emissions have to decline and greenhouse gases in the atmosphere need to be removed as soon as possible. HGM deployment is intended to ‘buy time’ for that to occur; but we do not want to permanently affect the Arctic Ocean. 

Next, three species essential to the Arctic Ocean ecosystem will be exposed to the best performing type of HGM from the fate and transport studies. Billions of Calanus, a microscopic creature, selectively filter feed small bits of algae and other living things near the ocean surface. They are in turn an essential food source for small fish. Will Calanus eat whole or broken HGMs? And if they do, will HGMs kill them or slow their rate of growth? Or pass through without harm? Blue mussels live near shore and also filter feed, but they eat whatever is in the water they filter. Will whole and broken HGMs pass through blue mussels harmlessly?  Polychaetes (worms) live in the mud at the bottom of the Arctic Ocean. Because broken HGMs will fall to the bottom, SINTEF will see if there is any harm to Polychaetes that eat broken HGMs, such as lower growth or reproductive rates. 

The fate and transport, and biological tests, should be ready to submit to one or more peer-reviewed journals by the end of 2022. These results, if positive, will support permit applications for field testing. 

But the results will be valuable even if they are not entirely positive. All HGMs are not the same. So although the best types of HGMs now available are being tested, it may be necessary to ask manufacturers to produce slightly different types of HGMs that are safer. For example, if broken HGMs cause problems but whole ones do not, manufacturers might be able to make an HGM that breaks like safety glass into pieces without sharp edges.  We could then test the re-engineered HGM for safety.      

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2 Comments

  1. Paul Baker

    Based on my experience testing HGM for creating shading films to protect coral from light during bleaching, I would suggest three additional studies:
    1) HGM dissolution studies – the thin glass can dissolve quite quickly in a few weeks or months so that even small surface holes can cause HGM to sink when immersed in interstitial meltwater or sea water.
    2) Surface treatments of HGM – A single layer of HGM with clear glass is not very reflective – multiple layers are required to reflect sun light back into the sky. Surface treatments such as roughening or coarse polishing, or reflective coatings may improve reflectivity so that just one layer of HGM is effective and be more cost effective in materials and deployment effort.
    3) Biological Studies – may need to be repeated to see if surface treatments from 2) increase algae and bacterial adhesion

    Reply
    • Gary Wolff, P.E., Ph.D.

      Hello Paul:

      Thanks for your interesting comments and suggestions. We would love to hear about the tests you have conducted. We are measuring the ‘dissolution’ of various HGMs in seawater. Some did indeed develop holes quickly, as you said. Others did not. We agree that clear HGMs are not very reflective, which is why all of our tests have been with white HGMs. The three species testing described in the Recent Post that you commented on (Research at SINTEF) is on white HGMs, so the algae and bacterial adhesion results should be relevant for a very thin deployment, perhaps as thin as one HGM layer.

      Reply

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