Tuesday, November 29, 2016

Using Oyster Shell "Waste" to Scrub Our Earth Clean


by DAVID PLECHL

Ever since I first drove past the small mountains of oyster shells one sees on the way through Nahcotta Bay at the north end of Southwest Washington's wet and wild Long Beach Peninsula, I have wondered what these spent houses for gloppy little morsels could be used for. Well, the first thing I found out was that they are used to "seed" more oysters. They are literally the medium from which new oysters sprout, (after the baby oysters are implanted on them), and so they are recycled to a degree. But because Willapa Bay is one of the leading producers of oysters in the world, boy do they pile up. 

As I dug more into the potential uses and reuses of these shells, I found that in Korea, a nation that produces 270,000 tons of the waste a year, the accumulation of shells has created real problems. The cost of securing landfill sites for the shells means dis-incentivized fishermen have allowed them to pile up in ports where they have polluted local fisheries, created management problems of public water sources, and created health and sanitation issues.

A 2012 joint study performed by three Korean universities and one research development center, examined ways in which these "waste shells," which are composed almost entirely of calcium carbonate, might be utilized for water and air filter mediums, eutrophication control, and even cleaning up toxic waste. The study was a combination of fresh research and an examination of existing literature on the topic. 

                                                                          Oyster shells at Nahcotta, Washington


Some high points—The study found that the shell medium more efficient and less expensive than limestone at the "desulfurization" of exhaust gases from power plants. When used as a soil conditioner, the shell medium showed higher adsorption and desorption of heavy metals than general soil. Amazingly, the study noted "the oyster shell can neutralize acidic waste water from mines very fast and remove 99% of heavy metals."

Somewhat encouraging for the Northwest, was the potential the shells (in the form of a powder) have shown to "remove red tide organism." These are the organisms that have created recurring dead zones off of the Oregon and Washington coastlines. The toxic algae blooms are fed by warmer than usual ocean temperatures and excessive amounts of nitrogen and phosphorus going into the environment from livestock and agricultural run off. The shells could present a viable option in combating what has become an annual menace that is killing fish, denuding maritime environments and affecting the livelihood of those that depend on healthy fisheries. 

I spoke with an official at the local port where I first became fascinated with the mini mountains of shells, and he assured me that they are "highly valuable," but that the value (beyond reseeding) is only recently becoming apparent. He said the port has looked at grinding up the shells and using them to absorb contaminant that have built up in the port due to various industries or also looked to sell them to various groups in an effort to "blunt ocean acidification."

As I was researching material for this post I was delighted to see that here in Astoria, oyster shells were implanted into the tail end of a revamped water treatment process. Now, wastewater and run off from the streets will go through a filter comprised almost entirely of crushed oyster shells. Whether you find them delicious or disgusting, it seems oysters shells are finding second lives making our lives better. 

References:

Jong-Hyeon Jung, Jae-Jeong Lee, Gang-Woo Lee, Kyung-Seun Yoo and Byung-Hyun Shon (2012). Reuse of Waste Shells as a SO2/NOx Removal Sorbent, Material Recycling - Trends and Perspectives, Dr. Dimitris; Available at: http://www.intechopen.com/books/material-recycling-trends-and-perspectives/reuse-of-waste-shells-as-a-so2-nox-removal-sorbent

The Daily Astorian - http://www.dailyastorian.com/Local_News/20161012/port-closes-in-on-new-stormwater-treatment-system

The Port of Peninsula - Interview 



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