<aside> đź’ˇ Using duckweed, a second-generation aquatic species, to produce a more sustainable and scalable polylactide bioplastic that offers the opportunity for increased crop yield and reduced cost.

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Executive Summary

Problem: The sugars used to make bioplastics are often made from crops like corn and sugar cane which consume land out of production needed to feed a rapidly increasing population. 1 kg of PLA requires 2.65 kg of corn, and if the quantity of plastic produced every year came from corn-based sources, that would be over 715 million tonnes. This is a huge portion out of our food supply, and is not plausible especially because of the influence climate change is having on farming in tropical areas.

Solution: This solution leverages duckweed for an enhanced bioplastic. Duckweed is an aquatic species that humans don't consume, thus eliminating the problems of decreasing food supply and usage of farmable land. Duckweed can double its biomass in as little as 16 hours, is very small, and grows nearly all over the world, making it ideal for a material like plastic. Because duckweed produces five to six times as much starch as corn per unit of area, it is a good candidate for polylactide bioplastic.

Outcome: A duckweed-based bioplastic would enable a material that doesn't use fossil fuels or crops that humans consume, all at a maximized yield and decreased price. A by-product of protein could be sold and the duckweed would sequester carbon dioxide and remove mineral contaminants when grown in wastewater, thereby helping to play a role in combatting climate change. 1.4 million pounds of duckweed per hectare annually can be produced, which is 50 times ****more than what is derived from corn.

Why is this a problem?

Plastics are integral to humankind because they have exceptional properties, like malleability, mouldability, strength, durability, weight, and, perhaps most importantly, low price. However, they accumulate in the environment and generate a lot of waste. Within Canada, only 9% of plastic is recycled, the rest going toward landfills, the environment, or incineration. We are polluting the ocean with 12.7 million tonnes of plastic every year, and there are 5.25 trillion pieces of plastic waste estimated to be in our oceans. What’s worse, by 2050, it is predicted that we will be producing three times as much plastic as we do today. That's why bioplastics are emerging as an alternative—but the problem is, even bioplastics aren't as great as they seem.

The vast majority of bioplastics today come from agricultural crops like corn and sugar cane. The compound extraction process is difficult and occupies an enormous portion of our food supply, which is becoming increasingly harder with climate change’s influence. The competition between land and water resources for human consumption would deprive our resources, which is not ideal, scalable, or arguably even sustainable. Studies have been done to show the huge net CO2 emissions that would be generated if rainforests, grasslands, or peatlands were to be converted to agriculture for growing crops for biobased plastic purposes. Using traditional biobased plastic will undoubtedly sky-rocket the land needed for agriculture.

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Status quo for alternatives → algae

The main alternative to duckweed is algae, which is being heavily investigated. Algae is a term that envelopes a group of seaweeds, kelps and photosynthetic eukaryotes. Having high yields, short cultivation times, and the potential to sequester CO2 in the process all provide great reasons for why algae could be used to displace fossil fuels as an energy source. Algae are fast-growing organisms powered by sunlight. When algae are used to clean the environment, the outcome is biomass that can be converted into bioplastic material. Algal bioplastics have more or less the same properties as petroleum-based plastics while also being biodegradable. Unlike other bioplastics which use common crops, algae do not compete with food production for humans, and are tolerant to a variety of environmental conditions meaning they can grow in a range of different areas. They compensate wastewater and use CO2 as biomass production nutrients without emitting it back into the atmosphere. Overall, algae-based plastics would be non-toxic, plastic quality enhancing, and good for the environment.

The barrier here is cost. The production cost is through the roof because of the necessary consumption for labour and water. There’s also the energy needed to circulate gases in photobioreactors (PBRs) where algae can grow as well as dry out the biomass. Producing fuel from algae grown in ponds at scale would cost between $240 to $332 per barrel, which isn’t plausible compared to the inexpensive plastics we use today. Harvesting algae is particularly difficult because of its size and morphology, therefore it has to be pumped with water, centrifuged, and then harvested. There are many scientists looking into genetically modifying algae to reduce the cost, but this will likely take years. Duckweed is actually very similar to algae in that they can both become invasive because of how easily they grow. Often times they are confused with one another. Duckweed shares algae's same benefits of proliferating quickly, growing in water, being tolerant to different environments, and not being consumed by humans—and all at a reduced cost. 1.) there is no need for PBRs, and 2.) duckweed is very easy to harvest; the process is significantly easier than that of algae as all one needs to do is scoop the duckweed out which can be done with something like a skimmer.

What is the opportunity for duckweed?

Duckweed is the smallest flowering plant known to Earth, while also having the capability to double in mass in as little as 16 hours. What’s useful about duckweed is that it is a second-generation food source, meaning humans don't consume it. On top of this, duckweed is abundant in supply, growing in freshwater on every continent except Antarctica. Duckweed can spread very easily, usually through water channels, and once they find stagnant water ****they can proliferate so rapidly that they can cover an acre of surface in ****only ****a month and a half. To add to these advantages, duckweed would allow growing time to be substantially increased, and five to six times more starch than corn per unit of area generated. Duckweed has a high starch content that can reach 75%, which can be manipulated by the conditions and strand. Thus, since polylactide is a starch-based bioplastic, duckweed is more ideal than corn.

Opportunity for vertical farming at a reduced cost

Duckweed is an ideal feedstock for vertical farming. Duckweed does not require farmable land to grow, so hydroponics can be utilized, where crops are grown in water instead of soil. Since the species is so minuscule, you could have layers of duckweed growing in the same footprint. The duckweed would be easier to manage, track, and treat. This has already been proven to work. Planet Duckweed, a company attempting to commercialize a specific strand of duckweed for food, is using vertical faring for duckweed. They use connected trays reliant on gravity for water flow, and skim duckweed from the top of the water. Such a simple system could be built into your basement. The growing system for a bioplastic could be more or less the same design. Traditionally vertical farming can be expensive, but the catch here is that duckweed doesn't need to grow in drinking water and doesn't require strictly regulated conditions.

An incredible property of duckweed is its ability to remove mineral contaminants from wastewater such as those coming from intensive animal industries or sewage treatment facilities. Duckweed acts as a natural water filter, being efficient at uptaking phosphorus, nitrogen, toxins, and pathogens. On top of that, it can sequester CO2 from the atmosphere. This could be especially valuable in developing countries. Duckweed has particularly luxurious growth in nutrient-rich ****districts, like small ponds, swamps, ditches, and even zoos where crocodiles and alligators go (because duckweed can feed on their excrement). Food sources for duckweed can be manure, humus, or compost tea. This means that duckweed could be grown in wastewater and wouldn't require drinkable water, which would be convenient for scalability. Especially with climate change on the rise, having a system that occupies litres of water is not ideal, so the fact that duckweed has this attribute is potentially game-changing.

Other simultaneous advantages

An advantage of using duckweed for bioplastics is that there can be other environmentally positive benefits. On top of sequestering carbon dioxide and having the ability to clean contaminants from wastewater, protein can be sold as a by-product. Duckweed contains over 45% protein, and so instead of discarding the protein when starch is produced, duckweed "protein powder" can be put on the market. Duckweed protein actually has a better array of essential amino acids than most vegetable proteins and very closely resembles animal protein. Cellulose could also potentially be sold as a by-product, which can be used for paper**,** cellophane, rayon, and even cellulosic biofuels.

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PLA's market and the need for a feedstock alternative