Boat Antifouling Technology: the problems and the green chemistry solutions!

Boat Antifouling Technology: the problems and the green chemistry solutions!

By Alana Rangaswamy (Vice-President, Dalhousie University Green Chemistry Initiative)

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The iconic Halifax Ferry is one of many boats to traverse the Harbour every day.

One great part of attending Dalhousie University is living steps away from the ocean. Much of Halifax’s history and development is due to its access to water, both as a naval base and port of call. With the massive amount of boat traffic seen daily by the harbour, marine industries strive to maximize the efficiency of travel. And one major way to do that is preventing small creatures from hitching a ride on your boat, causing drag and lowering the efficiency of your vessel. Enter antifoulants: coatings that kill organisms or otherwise block their ability to stick onto your ship. Antifouling is a necessary technology, but introducing biocidal agents into a marine environment, unsurprisingly, poses many environmental challenges. Let’s take a look at two commonly used antifoulants, their issues, and how scientists have tried to fix them:

Tributyltin 

You may have heard of tributyltin (TBT) as a biocidal agent. TBT is an excellent poison – effectively nonpolar due to its alkyl groups, it’s able to accumulate in organisms, rapidly killing them due to the high toxicity of SnIII. This property makes TBT an extremely effective antifouling agent, however, it easily leaches from boat hull paint into the ocean where it persists due to its high stability. Fortunately, the dangers TBT have been recognized worldwide and use as a biocidal agent has been banned as of 20081. Canada jumped on the bandwagon slightly earlier, with the last TBT-containing paint product registered in 1999.2 With this restriction, the industry is searching for alternatives that are as effective as TBT, without the environmental drawbacks.

Copper

Copper as a bulk metal is naturally antiseptic, promoting the formation of reactive hydroxyl radical species which lead to cell death in living systems.3 Copper has been used on boat hulls since the 1700s, and now usually shows up in paints as its metal oxide4 or as a suspension of copper powder.5 Although copper is less bioavailable than TBT, it persists and continually forms unstable radical species (and can, therefore. wreak ecological havoc) in a marine environment. Since copper is widely considered the new “gold” standard in antifouling, the sheer amount of it present on (and leaching off of) boat hulls today points to a long-term impact.

New Antifouling Tech

Green chemistry and engineering are all about designing cleaner systems that work as well as, or better than, the existing standard. TBT and copper are high bars to clear, but scientists are up to the challenge. As early as 1996, the environmentally benign Sea-Nine antifouling compound had received the Designing Greener Chemistry Award as part of the US EPA’s Presidential Green Chemistry Challenge.6 Sea-Nine is a derivative of isothiazolinone, a 5-membered heterocycle containing nitrogen and sulfur atoms. The compound is acutely toxic to marine organisms at the surface of boats, but biodegrades rapidly in marine environments through a ring-opening mechanism to form non-toxic by-products. Sea-Nine (and its derivatives) is currently present in commercial boat hull paints,7 however, degradation times may vary based on geographical location and local environment8 so our job isn’t done yet.

There are many newer studies in the works. For instance, investigation has been done into using natural products as antifouling agents. Natural products are secondary metabolites produced by microorganisms as a defence mechanism in response to stress. As such, they often have antimicrobial properties, while being naturally biodegradable. For example, 1-hydroxymyristic acid, a simple alpha-hydroxy fatty acid, was isolated from the marine bacterium Shwanella oneidensis. When panels were coated with paint containing the fatty acid, and subsequently immersed in a marine environment, no growth of foulants was observed even after 1.5 years.9 Other studies have added hydrophobic coatings which disrupt the binding interactions between the microorganism and the vessel’s hull, and promote detachment due to the natural flow of the water over the hull.10 Some research has diverted away from chemical modifiers altogether, using microtextures, which remove the flat surfaces required for spores to settle,10 to deter growth. UV-LEDs11 which are mutagenic and cytotoxic at a small scale, have also been used to reduce growth of foulants.

The long history and many methods developed to prevent boat hull fouling demonstrates that this is an important and challenging problem. But many results are promising, and green chemists and engineers are well on their way to solving it.

References:

  1. http://wwf.panda.org/?145704/tributyltin-canned
  2. Health Canada – Consumer Product Safety Registrar

http://pr-rp.hc-sc.gc.ca/ls-re/result-eng.php?p_search_label=antifouling+paint&searchfield1=ACT&operator1=CONTAIN&criteria1=tin&logicfield1=AND&searchfield2=NONE&operator2=CONTAIN&criteria2=&logicfield2=AND&searchfield3=NONE&operator3=CONTAIN&criteria3=&logicfield3=AND&searchfield4=NONE&operator4=CONTAIN&criteria4=&logicfield4=AND&p_operatordate=%3D&p_criteriadate=&p_status_reg=REGISTERED&p_status_hist=HISTORICAL&p_searchexpdate=EXP

  1. Grass, G., Rensing, C., and Solioz, M. Metallic copper as an antimicrobial surface. Environ. Microbiol. 2011, 77, 1541-1547. DOI: 10.1128/AEM.02766-10.
  2. https://www.chemistryworld.com/news/antifouling-coatings-cling-to-copper/3010011.article
  3. http://coppercoat.com/coppercoat-info/antifoul-how-it-works/
  4. https://www.epa.gov/greenchemistry/presidential-green-chemistry-challenge-1996-designing-greener-chemicals-award
  5. https://www.epaint.com/product/sn-1-antifouling-paint/
  6. Chen, L. and Lam, J. C. W. SeaNine 211 as an antifouling biocide: a coastal pollutant of emerging concern. Environ. Sci., 2017, 61, 68-79. DOI: 10.1016/j.jes.2017.03.040.
  7. Qian, P-Y., Xu, Y. and Fusetani, N. Natural products as antifouling compounds: recent progress and future perspectives. Biofouling, 2009, 26, 223-234. DOI: 10.1080/08927010903470815.
  8. Salta, M. et al. Designing biomimetic antifouling surfaces. Trans. R. Soc. A, 2010, 368, 4729-4757. DOI:10.1098/rsta.2010.0195
  9. https://www.pcimag.com/articles/104484-marine-fouling-prevention-solution-to-use-uv-led-technology

 

 

 

Top 12 Things the GCI Accomplished in 2014

By Melanie Mastronardi, Secretary for the GCI

As the year comes to a close, I thought I would take this opportunity to recount some of the amazing things the GCI has accomplished over the last year. I should preface this list by saying that there are many things the GCI has been up to this year that don’t appear on the list – for example our ongoing trivia activities and the green chemistry seminar series, which are some of our greatest achievements overall – but here I wanted to highlight some of my favorite activities and initiatives that were new for us.

So in no particular order, here they are – my list of the top 12 things the GCI has accomplished in 2014:

1) In February 2014, we launched the 12 principles of green chemistry video campaign, posting our inaugural video about principle #1 on preventing waste. To date, we have produced and published videos outlining the first 4 principles and plan to finish up the remaining 8 in the near future. Be sure to check out all our videos so far on our YouTube channel!

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Behind the scenes at our first video shoot.

2) On May 21-23, 2014 we hosted our second annual workshop, “The Next Steps in Green Chemistry Research”, at the University of Toronto. The workshop was a huge success with 12 invited speakers and over 70 participants attending from across North America.

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Workshop attendees and speakers mingle at the social event.

3) In January 2014, we launched a Waste Awareness Campaign and started tracking the chemical waste produced in Lash Miller. We shared the result of the collected data with the department in September, and then hosted a lecture about waste collection and disposal given by Ken Greaves and Rob Provost.

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Great turnout for the waste disposal talk!

4) We organized a symposium titled “Green Chemistry Initiatives Beyond the Classroom” as part of the 2014 International Conference on Chemical Education held in Toronto in July. The symposium featured 10 presentations that focused on alternative routes to green chemistry education as well as a panel discussion titled “Peer Teaching: Student-Run Sustainability Groups”.

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Student group panel at our ICCE symposium.

5) We developed a list of “Simple Techniques to Make Everyday Lab Work Greener”, which we shared at the GCI workshop in May and have subsequently posted online. Please check out the poster of our list and feel free to share it or post it in your lab as a reminder.

Simple Techniques to Make Everyday Lab Work Greener

Print out this handy guide for your own lab!

6) We re-launched the “Shut It” campaign – a program originally run in the Chemistry Department at UofT in 2008 to promote reducing energy usage by keeping variable-flow fume hoods closed while not in use. During the 4 months the campaign ran this year, we observed an average compliance of 69%, lowered the building’s energy usage, and taught occupants an easy way to conserve energy in the future.

7) Over the course of 2014, we formed a green chemistry education subcommittee, which has completed a review of the green chemistry content being taught in the chemistry undergraduate curriculum at UofT.

8) Throughout 2014, various members of the GCI represented our group and shared our experiences at conferences and events across North America. Laura Hoch presented at the ACS Green Chemistry & Engineering Conference in Washington D.C.; Laura Reyes presented at McGill University, the CSC Canadian Chemistry Conference and Exhibition in Vancouver, and the International Conference on Chemical Education in Toronto; and Ian Mallov presented at the International Conference on Chemical Education in Toronto.

9) We inspired members of our department to start incorporating some of the principles of green chemistry in their research. For example, it recently came to our attention that the Kluger group has switched entirely from using hexanes to the less toxic alternative heptane. As an added benefit, this has lowered the cost of heptane for our department, encouraging even more people to use it!

10) GCI co-founders Laura Hoch and Melanie Mastronardi were invited to present the Sigma Xi Annual General Meeting Lecture as part of their University of Toronto Chapter Distinguished Lecture Series in April 2014.

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Laura and Melanie at the Sigma Xi meeting.

11) We helped design a cover design for the Journal of Chemical Education, for the paper by UofT lecturer Andy Dicks titled “Green Chemistry Decision-Making in an Upper-Level Undergraduate Organic Laboratory”. Learn more about the cover and check out our pictured resources page.

JChemEd cover

We helped create this cover! Our website is featured on the computer screen.

12) In 2014, the GCI joined the Network of Early-career Sustainable Scientists and Engineers (NESSE) as one of their sustainable science groups. Much like the GCI, NESSE aims to empower early-career scientists to tackle today’s environmental and energy challenges, and move towards a sustainable future.

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NESSE members at the 2014 Green Chemistry & Engineering Conference.