species. While ozone and microwave disinfection
were used in the long-term commercial operation
of Mirzapur, many feed trials have simply washed
with water, or just harvested duckweed, and have
no report of pathogens (Goopy and Murray 2003;
Skillicorn et al. 1993). Surprisingly, several
studies have found duckweed, including samples
from hospital wastewater to be safe as chicken
and fish feed with regard to E. coli and Salmonella, with no significant differences in the
quantity of five different pathogens in chickens
fed on duckweed compared to control, presumably due to the severe pathogen reduction seen in
wastewater treated by duckweed and its associated microbial communities (Goopy and Murray
2003; van der Spiegel et al. 2013). The feed trials
often use dried duckweed as a percentage of
complete commercial feed or substitute it for a
percentage of the soybean or fishmeal component, with duckweed performing very similarly to
soy in the case of chickens, ducks, and fish, up to
a point where it is suspected that oxalates or other
anti-nutritives inhibit growth (Goopy and Murray
2003; Skillicorn et al. 1993). For tilapia, inclusion
rates of 30% were found equivalent to control,
and 30% replacement of fishmeal component was
seen as the most cost effective (Goopy and Murray 2003). An ecosystem of 5 different carp species or the grass, catla, and mirror carp and tilapia
species individually can be fed on a pure duckweed diet, with a carp yield of 10–15 t/ha yr
(Skillicorn et al. 1993). Duckweed was found to
be beneficial in replacing *15% of the soybean
meal in the feed for chicks or broilers, and 40% in
the case of laying hens (Goopy and Murray 2003;
Skillicorn et al. 1993). In some cases, pig saw
decreased growth in response to small inclusion
rates of duckweed, while the Mong Cai piglets of
Vietnam had higher growth rates than their Large
White counterparts due to higher nitrogen
digestibility (Goopy and Murray 2003; Gwaze
and Mwale 2015). Finally, ruminants have shown
promising results with high nitrogen digestibility
in merino sheep, and cattle consuming and
effectively digesting up to 10% of their weight in
dried duckweed per day (Goopy and Murray
2003). Taken together, these results show the
potential of duckweed to reduce the
environmental impact of livestock by recycling
nitrogen phosphorous and other nutrients that
currently cause eutrophication, while partially
replacing human edible soy and non-sustainable
fishmeal. Furthermore, recycling wastewater to
grow animal feed has been shown in several
economic analyses to raise farmer income, especially in developing countries.
Considering the economic and environmental
benefits, and the success of duckweed as feed for
a variety of livestock species, there will likely be
a rapid expansion of the duckweed agricultural
sector and its use as a sustainable animal feed. In
the FAO’s 2012 estimates, global demand for
non-fish animal protein is expected to increase at
1.3% per year till 2050, with the largest growth
of 4.2% in South Asia, with similar numbers in
the 2030 projection (Alexandratos and Bruinsma
2012). Roughly, half of this increase is expected
to be as poultry (OECD/FAO 2017). Additionally, the largest increase in animal protein supply
will be aquaculture, which was *17% of global
fish supply in 1990, grew largely in Asia between
4 and 10% per year, and is forecasted to exceed
the global catch in 2020 (OECD/FAO 2017). The
livestock sector is, however, very feed, land, and
water intensive, and all reports stress the need to
reduce the environmental impact particularly
through improving the feed supply. With their
ability to treat agricultural wastewater on
non-arable land and provide an affordable
protein-rich feed, a greater number of farmers are
turning to duckweeds as a cheap sustainable feed
source. There are currently several commercial
ventures and hundreds of thousands of
small-scale farmers growing duckweed primarily
in Asia and Central America feeding tilapia,
ducks, chicken, and pigs. Since they are sustainably feeding the livestock species in the
regions where the FAO expects the largest
growth in the world, it is natural to expect this
industry to grow. While working with farmer
education programs in Guatemala and Indonesia,
the ILA, International Lemna Association, has
seen an increase in educational activities for
small-scale farmers and 20% more businesses
seeking to enter the industry for the past 7 years
(Table 1.1, Director of the ILA).
1 Importance of Duckweeds in Basic Research and Their Industrial …
9
were used in the long-term commercial operation
of Mirzapur, many feed trials have simply washed
with water, or just harvested duckweed, and have
no report of pathogens (Goopy and Murray 2003;
Skillicorn et al. 1993). Surprisingly, several
studies have found duckweed, including samples
from hospital wastewater to be safe as chicken
and fish feed with regard to E. coli and Salmonella, with no significant differences in the
quantity of five different pathogens in chickens
fed on duckweed compared to control, presumably due to the severe pathogen reduction seen in
wastewater treated by duckweed and its associated microbial communities (Goopy and Murray
2003; van der Spiegel et al. 2013). The feed trials
often use dried duckweed as a percentage of
complete commercial feed or substitute it for a
percentage of the soybean or fishmeal component, with duckweed performing very similarly to
soy in the case of chickens, ducks, and fish, up to
a point where it is suspected that oxalates or other
anti-nutritives inhibit growth (Goopy and Murray
2003; Skillicorn et al. 1993). For tilapia, inclusion
rates of 30% were found equivalent to control,
and 30% replacement of fishmeal component was
seen as the most cost effective (Goopy and Murray 2003). An ecosystem of 5 different carp species or the grass, catla, and mirror carp and tilapia
species individually can be fed on a pure duckweed diet, with a carp yield of 10–15 t/ha yr
(Skillicorn et al. 1993). Duckweed was found to
be beneficial in replacing *15% of the soybean
meal in the feed for chicks or broilers, and 40% in
the case of laying hens (Goopy and Murray 2003;
Skillicorn et al. 1993). In some cases, pig saw
decreased growth in response to small inclusion
rates of duckweed, while the Mong Cai piglets of
Vietnam had higher growth rates than their Large
White counterparts due to higher nitrogen
digestibility (Goopy and Murray 2003; Gwaze
and Mwale 2015). Finally, ruminants have shown
promising results with high nitrogen digestibility
in merino sheep, and cattle consuming and
effectively digesting up to 10% of their weight in
dried duckweed per day (Goopy and Murray
2003). Taken together, these results show the
potential of duckweed to reduce the
environmental impact of livestock by recycling
nitrogen phosphorous and other nutrients that
currently cause eutrophication, while partially
replacing human edible soy and non-sustainable
fishmeal. Furthermore, recycling wastewater to
grow animal feed has been shown in several
economic analyses to raise farmer income, especially in developing countries.
Considering the economic and environmental
benefits, and the success of duckweed as feed for
a variety of livestock species, there will likely be
a rapid expansion of the duckweed agricultural
sector and its use as a sustainable animal feed. In
the FAO’s 2012 estimates, global demand for
non-fish animal protein is expected to increase at
1.3% per year till 2050, with the largest growth
of 4.2% in South Asia, with similar numbers in
the 2030 projection (Alexandratos and Bruinsma
2012). Roughly, half of this increase is expected
to be as poultry (OECD/FAO 2017). Additionally, the largest increase in animal protein supply
will be aquaculture, which was *17% of global
fish supply in 1990, grew largely in Asia between
4 and 10% per year, and is forecasted to exceed
the global catch in 2020 (OECD/FAO 2017). The
livestock sector is, however, very feed, land, and
water intensive, and all reports stress the need to
reduce the environmental impact particularly
through improving the feed supply. With their
ability to treat agricultural wastewater on
non-arable land and provide an affordable
protein-rich feed, a greater number of farmers are
turning to duckweeds as a cheap sustainable feed
source. There are currently several commercial
ventures and hundreds of thousands of
small-scale farmers growing duckweed primarily
in Asia and Central America feeding tilapia,
ducks, chicken, and pigs. Since they are sustainably feeding the livestock species in the
regions where the FAO expects the largest
growth in the world, it is natural to expect this
industry to grow. While working with farmer
education programs in Guatemala and Indonesia,
the ILA, International Lemna Association, has
seen an increase in educational activities for
small-scale farmers and 20% more businesses
seeking to enter the industry for the past 7 years
(Table 1.1, Director of the ILA).
1 Importance of Duckweeds in Basic Research and Their Industrial …
9