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Using engineered filter feeders to clean rivers and their shells as concrete aggregate

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Darko Savic
Darko Savic Jul 18, 2021
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The idea is to genetically engineer a suitable species of shell-producing filter feeders that would then create an ideal shell size/shape to be used as aggregate material in concrete production.

The clams/mussels would be grown in farms, placed in dirty rivers where they would filter the water. When fully grown they would be harvested and used as concrete aggregate, replacing sand and pebbles.

The species would be engineered to maximize shell to meat ratio. Ideally, there would be little meat and a lot of mineral/shell. The species would also be engineered to create the ideal shell shape/size for the envisioned use case scenario. That way, the shells would not need to be processed/crushed. Alternatively, the shells could be further processed into cement.

These could then be grown in kilometers of rivers and result in the following:
  1. Provide water filtration and clean the rivers
  2. Provide concrete building aggregate (substitute for sand/pebbles)
  3. The meaty part could be separated and used as livestock feed or fertilizer (if it can be made safe)
  4. Remove carbon from water/air and store it in concrete for decades
In essence, this is biological conversion of pollution into building material. It would be great if the meaty part could be used as livestock feed but it might not be safe for any organism to consume and bring it closer to our food chain. So into concrete it goes.




Creative contributions

A good way to remove heavy metals from the ecosystem

jnikola Jul 18, 2021
Mussels and other filtering organisms, by being on the lowest place in the feeding chain, are known to accumulate certain heavy metals . I remember being told not to eat a lot of mussels in large quantities, due to the intoxication. I am not sure how possible is that, but with the increasing pollution of rivers, putting a lot of filter feeders in polluted rivers could make a change.

After some time, it would be clever to remove those heavy metals from the environment for good. We could remove the old filter feeders and use them preferably as a concrete aggregate because feeding livestock would return them into the food chain. The only thing to be careful about would be to measure the concentration of heavy metals in the concrete and see if it can affect people somehow. If not, that's a great way to remove them from the food chain.



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Darko Savic
Darko Savic3 years ago
I updated the idea with your references
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Darko Savic
Darko Savic3 years ago
Yes, that's why they would be engineered to minimize the meat to shell ratio. Less meat, more shell:)
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jnikola3 years ago
Darko Savic okay, but then we have a problem. Less meat means less efficient filtering/purifying, and what we need is more efficient filtering organism. The shell size is just good for concrete aggregate repurposing. Am I right?
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Method of removal of microplastics from the ecosystem

jnikola Jul 22, 2021
I agree that filter feeders can clean rivers and later serve as aggregate material. But I recently found an article that supports this idea from one more perspective, and that is - microplastics.
There were already a few sessions (session1, session2) dealing with this problem, but none of them successfully covered the vast amount of microplastics found in the waters. I found a paper that combines these sessions and possibly offers a natural, efficient method for microplastics removal.

The proof-of-concept

Earlier this year, German scientists from the University of Bayreuth analyzed the microplastics of a broad size range in commercially exploited mussels (Figure 1.).

All the mussels were obtained from wilderness or supermarkets. They originated from 12 different countries distributed worldwide. Scientists used highly sensitive technologies of focal plane array (FPA)-based micro- Fourier-transform infrared (FTIR) spectroscopy and micro-Raman spectroscopy and were able to detect tiny microplastics of just 3 μm!

The results showed that microplastics was present in all mussel samples. The number of >50 μm microplastic particles in supermarket samples was between 0.13 and 2.45 particles/g of wet weight of the mussel. On the other hand, the highest number of particles found in wild mussels was 0.97 particles/g w w. Only fiber- and fragment-shaped particles were found. The most common synthetic polymer types detected were polypropylene (PP, 39% ± 6.3%), polyethylene 196 terephthalate (PET, 32% ± 2.8%), polyacrylonitrile (PAN, 8.2% ± 1.4%) and polyethylene (PE, 197 7.2% ± 0.6%), correlating with the ratios of specific types of plastic waste.

This paper showed the accumulation of microplastics in mussels. Next experiments that should be done in order to examine the rate of microplastics accumulation are the time-dependent study on accumulation and a scale-up experiment to see how effective can this be.
Figure 1. The graphical abstract

Important note 1

If mussels show great perspective of being a successful microplastics collector, the amount of microplastics found in each batch should be strictly measured and regulated. If above a certain threshold, they should not be used in commercial purposes, but instead, as @Darko Savic proposed, as a concrete agglomerate material.

Important note 2

If farmed in big quantities and used as a concrete agglomerate material, mussels could help removing the microplastics from the ocean!


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The effect on the ecosystem

jnikola Jul 18, 2021
In the filter feeder video you linked, they talk about "Maryland Oysterman Face Troubled Waters". People overfished the oysters in the Chesapeake bay, which caused a rise in phytoplankton populations. Since they do the photosynthesis, oxygen went dangerously low and killed many species in the bay.

If we plan to put many engineered filter feeders in the river ecosystems, wouldn't we do the same thing? They could change the dynamics of the river and change it drastically. Here is one example of how simple, seemingly insignificant change has a dramatic consequence. In the case of filter feeders, we add a significant number of new species in a balanced ecosystem and that could cause a catastrophe.
Another problem is the removal/collection of the feeders from the river.

Is it maybe more clever to just keep it simple, have a farm, and use old feeders as a concrete aggregate?
If we still want to develop a business that would also help to clean rivers, what parameters would be the key metrics to keep the ecosystem balanced as possible?
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Purifying mussels from heavy metals with zeolite

jnikola Sep 14, 2021
Recently, I listened to a lecture on zeolite and its capabilities to absorb heavy metals and remembered that we had a problem with mussels and their heavy metal accumulation.

After a quick google search, I found papers that studied the selectivity of zeolite in the process of sorption of Pb (II) compared with other heavy metals like Zn (II) and Cd (II). The results confirmed the usage of zeolite as a low-cost material for purifying waters [1]. Another paper reported that increasing the zeolite concentration improved the removal efficiency of heavy metals in the rearing water with adsorption selectivity of Pb˃Cd˃Fe˃Cu˃Zn [2] and thus concluded that it could effectively be done to purify live fish flesh from heavy metals, too. There was also the idea of creating zeolite-based cotton water filters for households that would reduce the heavy metal concentrations [3].

Based on the above-mentioned literature, my ideas to reduce the concentrations of heavy metals from the mussels would be:
  • Farming mussels in pools of seawater with zeolite-based filters.
  • Treating collected mussels with zeolite water to purify them from heavy metals before they go to market or into concrete mixture.
  • Extracting heavy metals from live mussels by zeolite water purification and returning the mussels in the water.
[1] https://www.scielo.br/j/eq/a/hzfj4YdKd8kspFvVsDYLWjj/?lang=en
[2] https://sciendo.com/pdf/10.2478/cjf-2020-0012
[3] https://www.nature.com/articles/s41598-020-61776-8

Do you think it could work? I didn't find the information if the zeolite concentration reduces when it binds to heavy metals. Would it be too expensive?
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Fully sustainable business and a "think-about"

jnikola Jul 18, 2021
I must admit that the idea sounds very promising and viable. With feeders cleaning the rivers, serving as livestock feed and concrete aggregate, we have a fully developed system!

That means that the same company could have filter feeders farms where they produce them in various sizes and meat-to-shell ratios, serving different purposes.
  • Bigger "meaty" feeders could be sold to restaurants and on markets as food.
  • Shells engineered to have less meat and bigger and stronger shells could be transported where needed to clean rivers and lakes. When they reach the appropriate size, they would be collected and used for building purposes as hollow aggregate material, similar to the bubble deck concept.
  • The smallest shells or deformed ones could be crushed into sand and used for creating finer construction materials such as mortar.
Nevertheless, there is one thing I am concerned about.

Is it economic?
We are talking about filter feeders taking the role of current aggregate material - sand or different kinds of stone. To get the stone and sand, you need to have a quarry or dig the sand from the rivers, lakes, and seas. How many filter feeders should you farm and how long would it take to collect enough material for an 8-story building? If you include the transport costs, does it maybe sound like a not-so-economical strategy? Maybe I got it wrong and you imagined it in a different, more sustainable way, so feel free to comment on this.
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Darko Savic
Darko Savic3 years ago
The primary function is to filter/clean the rivers. The aggregate and meat are secondary. I imagine it would take kilometers or filter feeders to make a noticeable difference in a flowing river. That's a lot of aggregate as a side product.
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