Duckweed is the smallest flowering plant in the world. It is an aquatic plant often found in fresh water or wetlands in most parts of the world that do not freeze too frequently. Floating on or just below the surface

of still or slow-moving bodies of water, many around the world perceive it as a pest, claiming it “clogs up lakes or ponds”.

However, duckweed is anything but a pest. It is in fact somewhat more of a super plant. Some people suggest that it has properties that are under-exploited, for example as a bio-fuel and as an effective bio-remediator of wastewater. It is a potent fertiliser; and most importantly for the purposes of this article, it is a rich and sustainable source of protein with the potential for widespread use in animal feed, aqua feed, and as a food source for humans.Question and Answer with Tamra Fakhoorian, International Lemna Assocation

Duckweed expert, Ms Fakhoorian is a biologist, chemist, and co-founder of the International Lemna Association, of which she is the current execu-tive director. Three years ago Ms Fakhoorian founded GreenSun Products, LLC; a company that has developed duckweed production systems, and product lines for both pet and human nutrition.

Q. From my current understanding, it seems as though duckweed would have great potential as an aqua or terrestrial animal feed?A. Yes, while initial commercial marketing focus is on higher value products, duckweed has been used to feed fish and land animals for decades in inte-grated Asian farmer settings. Researchers have been working with duck-weed for nearly fifty years. We know its potential to remediate wastewater and return a large volume of high protein biomass and exceptionally clean water. This pathway is seen as completing the nutrient cycle, a real boon to sustainable production of plant protein for a wide variety of uses includ-ing aqua and terrestrial animal feeds. I love this quote by Peter Marshall:

“Waste itself is a human concept. Everything in nature is eventually used.” Duckweed can help farmers mimic nature in this regard, and reap feed cost savings whilst reusing fresh water over and over.

Q. What is the current state of the duckweed industry?A. Current applications include: - 1. Using the decades-old model of Asian small farm settings to recapture

animal waste nutrient streams and use the resulting duckweed biomass as a fresh feed for ducks, fish, and swine for feed cost savings.

Companies are developing integrated systems including CAFO waste streams for bio methane generation and subsequent duckweed production to be used as fresh feed supplements for cattle, swine, and chickens. (Each species has maximum feed inclusion rates due to each animal’s ability to process the high

A sustainable protein supplement

for the futureby Peter Parker, International Aquafeed Magazine

22 | INTERNATIONAL AQUAFEED | September-October 2015

FEATURE

percentage of water in fresh duckweed.) Dried duckweed meal can be substituted for soya as a protein replacement in 10-30 percent inclusion rates, depending on the animal.

2. As a processed fishmeal replacement-lemna protein concentrate (LPC) for swine, production initially. LPC has gone toe-to-toe with 68 percent soy protein concentrate and found to produce comparable results. This is powerful given duckweed’s ability to produce at least four times the amount of protein per hectare versus that of soya, be GMO-free, and remediate animal waste streams at the same time.

3. Along with GreenSun Products, several companies are working with various strains of duckweed for human nutrition Protein levels of as high at 50 percent and above are being reported on a dry weight basis, with vitamin and mineral content heralded as well above average for green leafy crops. Additional benefits include being non-GMO, gluten-free, and organically produced. Be watching for both fresh and dried products to hit store shelves within the next couple of years.

Q. What is the nutritional make up of duckweed?A. While an older table, this one is fairly reliable as far as ranges:

Organic composition in the Lemnaceae, % of dry weight

protein 6.8 — 45.0

lipid 1.8 — 9.2

crude fiber 5.7 — 16.2

carbohydrate 14.1 — 43.6

ash 12.0 — 27.6

Ms Fakhoorian suggested that the feed industry investigate the potential for duckweed’s nearly complete amino acid profile as being as close to animal protein as the plant kingdom can provide. In addition she provided this quote from Dr John Cross, author of the richly-detailed website, “The Charms of Duckweed.” “The protein content of duckweeds is one of the highest in the plant kingdom, but it is dependent on growth conditions. Typically duckweeds are rich in leucine, threonine, valine, isoleucine and phenylalanine. They tend to be low in cysteine, methionine, and tyrosine.”

Q. What can you tell me about the digestibility of duckweed for salmonids?

A. To answer this Ms Fakhoorian passed the question onto Dr Ron Hardy who is a professor in the Animal and Veterinary Science Department, University of Idaho and Director of the Aquaculture Research Institute. Dr Hardy is also on the Nutrition and Feeds Technical Advisory Committee of Integrated Aquaculture International, he answered as follows:

“Duckweed protein has been shown to be highly digestible to rainbow trout and is therefore likely to be highly digestible to other salmonids. Protein digestibility is on par with many alterna-tive protein ingredients, although slightly lower than high-quality plant proteins, such as soy protein concentrate, and fishmeal. Duckweed protein concentrate containing 65 percent to 70 percent protein has a favorable amino acid profile for fish and has other characteristics, such as high palatability and lack of anti-nutritional factors, that make it an interesting potential component of fish feeds. Keys to future use of duckweed protein concentrate as a fish feed ingredient will be cost and availability.”

September-October 2015 | INTERNATIONAL AQUAFEED | 23

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Q. Do you have any comments on how duckweed might be suited to the aquaculture industry in particular? A. Aquatic plants for aquatic production, it’s a natural fit. Duckweed is highly suited to intensive aquaculture via efficient waste removal and high protein biomass that converts efficiently to live weight carp and tilapia. There are several commercial small to mid-volume duckweed start-ups who are taking a cue from small Asian farmers and producing duckweed to cut feed costs for their own fisheries initially.

As the demand for fishmeal substitutes and non-GMO plant-based proteins grows, the duckweed industry is rapidly developing to meet that demand. Currently, we are able to produce four to ten times the protein production of soy per hectare. As the art of farming duckweed improves, this ratio will go even higher. The hope of sustainable aqua-culture rests with sustainable aquatic plant proteins plus the massive benefits of bioremediation.

Q. What benefits would using duckweed have as a protein supple-ment for animal feed when compared to soya?A. Duckweed has many benefits when compared to soya:• Studies have found that lemna protein concentrate is comparable

to soy protein concentrate for swine• Duckweed produces four to five times the protein per hectare

over soya• Non-GMO• Does not require the use of arable land for production• Soy production relies primarily on artificial fertilisers, whereas

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duckweed can remediate waste nutrients from concentrated animal feedlots, thereby saving costs, cleaning wastewater and producing a valuable feed at the same time

• Duckfeed is virtually free fresh meal

Q. Can you describe feedstock applications of duckweed for aqua-culture? Has there been much research done on this topic and if so, for which species? A. Many studies have been done with duckweed and fish production with 20 percent up to 100 percent inclusion rates giving comparable results to commercial mixes. Work done in the 90’s by Skillicorn, et al showed that carp could be fed solely on farmed fresh duckweed. Interestingly, small farmers have been taking advantage of this “free protein supplement” as per a Bureau of Fisheries and Aquatic Resources Tuguegarao City, Philippines flier describing for fish farm-ers that a 50 percent fresh duckweed and 50 percent commercial pellets would result in heavier gains than pellets alone for tilapia.

Tilapia and carp are not the only fish species that benefit from duckweed feed inclusions. The Burdekin trial conducted by Willett et al, 2003 reared Jade Perch (Scortum barcoo) solely on fresh har-vested duckweed from a municipal effluent stream (average weight gain: 0.7g/da/fish for 102 days). A study conducted by Fletcher and Warburton in 1997 found that decomposed Spirodela was proven effective as commercial pelleted feed for cultured Redclaw Crayfish. Duckweed’s abundance of carotenoids and pigments can stimulate growth as per a study by Landesman et al 2002. The opportunities for duckweed in fisheries are tremendous.

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Q. What limitations does duckweed have in regards to use as an ani-mal feed? Legal regulations? Limited research? Expensive to produce?A. Legal regulations: So far, while duckweed is considered a nuisance plant in some states in the US as well as Australia, purposeful cropping has not been an issue.

Limited research: Need more animal feed research and production research in that protein content varies with nutrient loads and seasonal variances.

Expense: Currently, drying costs are the biggest holdup in commer-cialising production. Solar and hybrid driers can bring the costs down considerably but are early-stage for full-scale production. Processed LPC is foreseen to be competitive with fishmeal prices in the near future.

Q. In our conversation you mentioned that Duckweed has a high water content (92-94 percent water on average) and current drying processes were a limiting factor to the widespread use of duckweed in feed. Is drying the duckweed necessary for aquafeed? Does the drying process alter the nutritional value of the plant?

A. Fresh, wet duckweed is an excellent primary or even sole food source for tilapia and carp. However from a practical standpoint, drying duckweed and including it at up to 50 percent and higher inclusion in various feed formulations, this opens duckweed’s potential in fisheries applications considerably. The cheapest method of drying duckweed is indirect solar dehydration. This retains maximum levels of carotenoids. Efforts are underway to develop hybrid solar gas drying systems to reduce drying costs by 50 percent or more. Other approaches include direct precipitation of protein from lysed duckweed resulting in a lemna protein concentrate (LPC).

Quoting Dr Louis Landesman, “Heat treatments of dried biomass do not affect protein quality. Low temperature drying should preserve the nutritional value of duckweed meal. Duckweed is similar to fresh grains in that it is perishable. Drying or other methods of preservation (ensiling, acid treatment etc.) are necessary to protect its nutritional value. Also most feed mills will only use dried feeds to formulate their feeds.”

Q. Aquaponic systems have been introduced into some RAS fish farms, would it be possible for duckweed to compliment aquaponics in some way? A. A spin-off of RAS is a non-recirculating system I witnessed in the Philippines. It featured a non-discharge open pond tilapia production where the duckweed is actually grown insitu in tilapia ponds with feeding barriers. By the use of photosynthesis via duckweed and normal bacterial breakdown of fish wastes, an ecological balance was achieved.

Tilapia were fed the duckweed as their sole feed input. Grow out periods were stretched for another month, but the trade-off was low to no cost production and a sustainable water system. This approach also works for carp and freshwater shrimp.

Q. You are the owner of GreenSun Products, a company that has developed both pet and human nutritional products from duckweed. Do you have intentions of expanding into the industry of livestock feed?A. My team developed production, harvesting, drying and processing systems for duckweed meal and LPC. GreenSun initially started out in the pet food arena and has a patent pending on formulations with lim-ited sales in certain US states. A year and a half ago, GreenSun turned its attention to research and development for human nutrition and has recently secured funding for that sector. GreenSun has received many inquiries as to supplying bulk tonnage of duckweed meal for livestock, but cannot compete with soy at this time. Long-term goals include mass production of LPC as a fishmeal replacement. GreenSun

is currently expanding productions to include the US, Philippines, and Mexico.

Q. Can you please tell me more about the International Lemna Association?A. The International Lemna Association (ILA) works to develop com-mercial production of duckweed for renewable, sustainable products for a hungry and increasingly fresh water limited world.

ILA was formed in June of 2012 to assist in the development of commercially viable production and processes of duckweed and other aquatic species for renewable, sustainable products. Our membership consists of producers and researchers from around the world.

We are the first trade association in the world dedicated to large-scale production of the aquatic plant commonly known as duckweed. The ILA seeks to bring duckweed and other aquatic species to the limelight of sustainable crops that out-produce terrestrial crops for protein and starches, while utilising waste nutrients and water sources such as municipal and industrial wastewater streams.

You can learn more at www.internationallemnaassociation.org

Q. Can you share an interesting duckweed success story to close this article?A. One company in Argentina, MamaGrande, is remediating municipal wastewater lagoons with duckweed, using a fermentation process to produce polylactic acid and using the residue for high protein animal feedstock.

26 | INTERNATIONAL AQUAFEED | September-October 2015

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