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”.

1. D
uckweed 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 future
by Peter Parker, International Aquafeed Magazine
22 | INTERNATIONAL AQUAFEED | September-October 2015
FEATURE

2. 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
FEATURE

3. 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
SIZE 10
MAXUM
80
1600
NORGREN
MAX.
MIN.
393.31
[9990]
391.31
[9939]
48.00
[1219]
52.19
[1325]
DCC
Inlet
CYL.
Disch.
End of
Head
BIN
Inlet
53.25
[1353]
57.69
[1465]
102.13 [2594]
111.12 [2822]
2
18.00 [457]
1.93 [49]
256T
060
1545
30
195.72 [4971]
F085SHIMPO
64.83
[1647]
108.59
[2759]
15.00
[381]
36.91
[937]
31.19
[792]
29.19
[741]
MAX.
MIN.
19.16
[487]
30.00
[762]
39.00
[991]
Ă12.00
[305]
2.00 NPT [WATER]
2.00 NPT [STEAM]
1
66.5
[168
12.56 [319]
24.59 [625]
15.88 [404]
1.00
NPT
2.00 NPT
3/4 NPT
101.44
[2577]
30.38
[772]
88.00
[2236]
199.38
[5064]
269.88
[6855]
67.28
[1709]
15.00
[381]
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FEATURE

4. 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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FEATURE

5. 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
FEATURE