Can Duckweed Help Save the World?
What is Duckweed?
While few people may have more than a vague notion of what duckweed is, many have seen it growing on the top of canals, marshes, lakes, and slow moving rivers. Duckweed is the common name for a few different species of floating plants in the Lemnoideae class, family Araceae. It is also called Asian watermeal, khai nam, ducks-meat, fu ping, or water lentils. Duckweed grows wild on every continent except Antarctica. It is easy to grow as an aquatic houseplant or in an aquarium or garden pond. Its many potential uses are currently being studied across the globe.
Here are some interesting properties of duckweed:
- Conserves water
- Removes impurities from water
- Requires no farmland to grow
- Can double its mass in 48 hours
- Provides nutritious food
- Controls pests
Had You Heard of Duckweed?
Duckweed in Water Conservation and Environmental Clean-up
Duckweed benefits the water sources that it covers in several different ways. It helps prevent evaporation by providing shade and by returning droplets of condensation caught in its leaves. It provides a safe habitat near the oxygen-rich surface for fry, tadpoles, and other young. It is a good source of food for all the herbivorous life in the water source. Duckweed also removes ammonia, fecal waste, and harmful bacterial and mineral build ups.
In water treatment, it can purify water in outside holding tanks, filtering out phosphates present in commercial fertilizers common in agriculture run-off. In nature, Duckweed acts as a powerful, natural bioremediator. It removes industrial pollutants like heavy metals from polluted lakes, eventually transforming them into ecosystems fit to support healthy local wildlife.
Duckweed as a Biofuel
Researchers around the world are testing duckweed as a possible source of biofuel. In the United States, the Department of Energy and both Rutgers, and NC State universities have ongoing projects evaluating duckweed as a potential crop for producing clean, efficient, renewable energy. So far it seems a good candidate for biofuel since duckweed grows rapidly, produces about five and a half times as much starch as corn per square foot of growing area and does not require farmland. Plus unlike any fossil fuels, its production is clean and sustainable, removing greenhouse gas instead of adding more.
Duckweed in Food Production
In Asia, people have long used duckweed as a food source, adding it to soups, stir fries, and curries. People have used it all over the world as a cheap source of animal feed to raise everything from ducks, who seem to have discovered the stuff, to chickens, hogs, and tilapia.
Researchers in Germany and India who tested various strains found that all were edible and that one particular species, Wolffia globosa (also known as Asian watermeal) is a major source of protein and omega-3 fatty acids, widely considered the most beneficial fatty acids for good health. The high-protein and good fat content could make Asian watermeal an important crop for combatting food defiencies around the world, especially in areas where malnutrition is due to subsisting on high carbohydrate crops.
The fact it grows wild on six continents means it can be grown easily by anyone in areas that aren't suitable for traditional types of farming. It could be grown on rooftops or by windows in the inner cities or in rocky rural areas with insufficient top soil. It can grow where other fresh green vegetables and sources of vitamin A are difficult to find.
The fact that it doubles itself in 48 hours means that as soon as the plants fill the container once, half the plants can be harvested sustainably every two days, or 182 harvests per year.
Duckweed for Disease Control
There is growing evidence to suggest that duckweed growing on the top of a pool of stagnant water significantly reduces the number of mosquitos that are likely to hatch out of it. One possibility is that fish fry and other young carnivores who find safety in the floating plants devour mosquito eggs, larvae and pupae.
If well managed, introduction of native species of duckweed to canals and other potential mosquito breeding grounds could help prevent the spread of mosquito- borne diseases like malaria, encephalitis, dengue fever, and zika, to name a few. Using duckweed would also limit toxins being introduced to kill mosquitos, while providing other environmental benefits too.
Similarly, Duckweed stops algae from becoming a pestilence within its territory. Harmful algae bloom or HAB has been associated with a number of public health problems.
Drawbacks of Duckweed and Obstacles to Responsible Use
Obviously Duckweed that is intended as a human food product or used for livestock/pet food should be farmed responsibly and tested to maintain quality and safety. It wouldn't do to let unscrupulous people use it for environmental clean-up or sewage treatment then sell it to make animal feed or infant formula.
Also, native duckweed became a pest recently in Florida when flood water from the St. Johns inlet was released into the Everglades. The flood water, heavily polluted with agricultural runoff mainly from cane fields, caused an overgrowth of duckweed which choked out saw grass necessary to the fragile Everglades ecosystem, already in crisis due mainly to countless other man-made mistakes.
The point was well made, though, that care needs to exercised when trying to solve one problem (water management) without causing another (Everglades disaster.)
When introducing duckweed into a new environment, it needs to be done conscientiously. Care should be taken to use the native species most common to the area. In an aquarium, the addition of duckweed can mean some extra work on a continuing basis. In a natural setting, control can be an impossibility. We have to think before we act, and then act so that duckweed is our problem solver, not just another problem.
If you plan to cultivate your own duckweed as an aquatic houseplant, as a plant for your aquarium or garden pond, or as a free food source for your family, pets, or livestock, do your research first. Make sure you really want some duckweed, and if you choose to grow it, can commit to its proper care including responsible disposal (eating or composting) to get rid of the plant when necessary. It grows fast so you will be disposing of a lot of it.
If you decide to give it a try, select a natural local spot to harvest your sample. That way. you know without a doubt that the duckweed is native (or at least already invasive) to your area. You don't have that luxury if you purchase via the internet. Plus, I guarantee you nobody is going to clean the duckweed before they send it to you.
How to Harvest Duckweed From the Wild
Before you leave:
- Use your knowledge of the area, internet savvy, and common sense to scout a collection location. Choose a spot away from highway dust and exhaust, tanneries, and other heavy metal polluters.
- Find a stick in your yard or neighborhood about as big around as a finger, the longer the better. There is never one handy at a collection location. Toss it in your trunk.
- Try to make sure your vehicle will get you there and back again. Check fluids. Make sure you have a blanket, flashlight with new batteries, tool box, emergency kit, some trail mix and bottled water, a full tank of gas and spare tire just in case. It is better to be over-prepared.
- Tell other people where you are going so they will know where to look for you.
Other things you will need:
- Appropriate clothing and sun protection
- Stinky bug repellant to keep off mosquitos and hopefully discourage everything else from wanting to come too near.
- A disposable sandwich container with lid filled about half-full of your tap water from home.
- Another responsible adult who can drive your vehicle and is armed with a fully-charged cell phone.
Always take someone with you when you forage or collect specimens. They can sit in the vehicle and point and laugh so long as they can watch you during the whole process and can respond appropriately if you get bitten by a snake or break your ankle while running bravely away from angry wasps.
When foraging anything, dress for the occasion and the weather. Wear, at the very least, a long sleeve t-shirt and comfortable jeans, crew socks, and sturdy closed-toe shoes. Hiking boots, which offer leg protection from snakes and good traction, are ideal. I always wear sunblock, bug spray, a hat to protect from sun and ticks, sunglasses for eye protection, and gloves of some kind. For duckweed, I'd recommend medical-type thin latex gloves in case you have to touch duckweed or something else out there near it with your finger. Any kind is better than no gloves. Tuck all your clothes into each other and into your socks and boots.
You would prefer creepy crawlies on the outside of your clothes, where you can see them to knock them off during your flail dance. This is better than just feeling something unknown crawling on your skin inside your pant leg. You are going to have to trust me on this one.
If you live in a locale where alligators or crocodiles are your neighbors, be especially careful collecting duckweed which is great at concealing large submerged reptiles. Be aware of your surroundings the whole time.
Harvest at the edge of the water using your stick. When finished, you can just leave the stick out there for the next person who might need it.
Transfer a tiny amount of duckweed off the stick into the water in your box. You only need to collect a few tiny individual plants to start your own duckweed empire. The less you collect from the wild, the better. It means less work to clean it and a lower chance of dragging home unwanted aquatic hitch-hikers, like leaches for example. Make sure that lid is on there tight!
Once you arrive home with your box, take it into your back yard and park it in a shady spot. Don't worry if the plants haven't floated to the top. They are doing fine.
Now, go toss your foraging clothes into the washer, take a shower, and wash your hair carefully to make sure you haven't picked up a tick (I really want to write "or worse" here, but darned if I can think of anything worse than a tick on me.)
After a couple hours, check to see if anything has crawled out onto the sides or lid of the box. Do this with care, obviously. Now look to see if anything is swimming in the bottom. With another pair of disposable rubber gloves, gently transfer just the duckweed plants out into a second container half full with water. Just swishing your finger around generally does the trick. I like to use another disposable sandwich box. I don't return exotically used containers back to the use for which they were intended, but do wash them well by hand, mark them with a sharpie as to their previous use, and reuse them later for similar purposes.
Depending on what you find alive in the first box, dispose of it appropriately. During my foraging history, I've driven creepy crawlies back to my original collection points to be set free and also have, in the case of a tick, drowned it in alcohol and set it on fire. I have a soft spot for most living things. Not a fan of ticks.
When I collected duckweed I brought home, I poured a couple tablespoons of white vinegar into the water and gave it a good shake, let it sit for a while, then transferred it again into plain tap water. Give it another shake to rinse, then let it sit with the lid placed on top to cover but not tightened. The next day, unless you see something other than duckweed it is probably ready for the next step. Determining what that is depends on how you want to use your duckweed.
If I were planning to use it as a water plant for an existing fresh water fish tank, I would start it in a temporary tank first. It is possible that snails or something similar have left sticky eggs attached to the leaves that initial cleaning didn't shift. It would be better to out with a test tank before contaminating your primary tank with a predator or hard-to-get-rid-of pest.
My duckweed ( I harvested about a half a cup and yes, it was a lot of work to clean) went into boiling water. After five minutes, I drained it into a screen colander. Then tossed it all into an all-veggie frittata. Well, I hope there were just veggies and eggs in there. It was good! I have yet to meet a vegetable I didn't like though. I think free food from nature always tastes better than stuff I buy at the grocery store too, which is probably why I am obsessed with foraging even when we're not camping, which is when I first ate duckweed.
Do You Think that Duckweed Can Help Save the World?
Duckweed likely has unknown properties and applications that no one yet has considered. It may have hidden drawbacks too which we need to discover and address. But we can and should use duckweed wisely, in order to help us accomplish much that needs doing, like preventing the spread of disease and ending hunger, including here in America.
It is amazing to think that tiny plants could help solve so many big problems. Just think of all that we may solve as a species, should we one day agree that improving the world for future generations is our most important reason for being here.