Environmental engineer meets Chinese peasant farmers
Doesnt it sound like a dream to be able to produce a
super-abundance of food with no fertilizers or pesticides and with little or no
greenhouse gas emission? Not if you treat your farm wastes properly to mine the
rich nutrients that can support the production of fish, crops livestock and
more, get biogas energy as by-product, and perhaps most importantly, conserve
and release pure potable water back to the aquifers.
That is what Professor George Chan has spent years perfecting; and he
refers to it as the Integrated Food and Waste Management System (IFWMS).
Chan was born in Mauritius and educated at Imperial College, London
University in the United Kingdom, specializing in environmental engineering. He
was appointed director of two important US federal programmes of the US
Environmental Protection Agency and the US Department of Energy in the US
Commonweath of the Northern Mariana Islands of the North Pacific. On his
retirement, Chan spent 5 years in China among the Chinese peasants, and
confessed he learned just as much there as he did in University.
What he learned was a system of farming and living that inspired him
and many others including Gunter Pauli, the founder and director of the Zero
Emissions Research Initiative (ZERI) (www.zeri.org).
Chan left China in 1989, and continued to work with Gunter and others
in ZERI through consultancy services. This work has taken him to nearly 80
countries and territories, and contributed to evolving IFWMS into a compelling
alternative to conventional farming.
The integrated farm typically consists of crops, livestock and
fishponds. But the nutrients from farm wastes often spill over into supporting
extra production of algae, chickens, earthworms, silkworms, mushrooms, and
other valuables that bring additional income and benefits for the farmers and
the local communities.
Treating wastes with respect
The secret is in treating wastes to minimize the loss of valuable
nutrients that are used as feed to generate further nutrients from algae, fish,
etc., that feed a variety of crops and livestock. At the same time, greenhouse
gases emitted during the first phase of waste treatment are harvested for use
as fuel, while the oxygen required in the second phase of waste treatment -
which gets rid of toxins and pollutants - is generated by photosynthetic algae,
so fish stocks are not suffocated through lack of dissolved oxygen in the
nutrient-rich water entering the ponds.
Livestock wastes are first digested anaerobically (in the absence of
air) to produce biogas (mainly methane). The partially digested wastes are then
treated aerobically (in the presence of air) in shallow basins that support the
growth of green algae. By means of photosynthesis, the algae produce all the
oxygen needed to oxidise the wastes to make them safe for fish. This increases
the fertilizer and feed value in the fishponds without robbing the fish of
dissolved oxygen. All the extra nutrients, therefore, go to improve
productivity. Biogas is used as a clean energy source for cooking, and also
enables farmers to process their produce for preservation and added value,
reducing spoilage and increasing the overall benefits.
IFWMS has revolutionized conventional farming of livestock, aquaculture,
horticulture, agro-industry and allied activities in some countries, especially
in non-arid tropical and subtropical regions. It has solved most of the
existing economic and ecological problems and provided the means of production
such as fuel, fertilizer and feed, increasing productivity many-fold.
"It can turn all those existing disastrous farming systems, especially
in the poorest countries into economically viable and ecologically balanced
systems that not only alleviate but eradicate poverty." Chan says.
Increasing the recycling of nutrients for greater productivity
The ancient practice of combining livestock and crop had helped farmers
almost all over the world. Livestock manure is used as fertilizer, and crop
residues are fed back to the livestock.
Chan points out, however, that most of the manure, when exposed to the
atmosphere, lost up to half its nitrogen as ammonia and nitrogen oxides, before
they can be turned into stable nitrate that plants use as fertilizer (see Box
1). The more recent integration of fish with livestock and crop has helped to
reduce this loss.
The important addition of a second production cycle of nutrients from
fish wastes has enhanced the integration process, and improved the livelihoods
of many small farmers considerably. But too much untreated wastes dumped
directly into the fishpond can rob the fish of oxygen, and end up killing the
How volatile nitrogen is turned into nutrient for plants
Livestock manure contains large amounts of ammonia gas that must
be turned back into stable nitrate before it can be absorbed as nutrient by
plants. Nitrification is the process in which soil bacteria oxidize ammonia
(NH3) sequentially into nitrite
(NO2) and then nitrate (NO3). Ammonia is oxidized into
nitrite by bacteria belonging mainly to the genus Nitrosomonas, but also
Nitrosococcus, Nitrosospira, Nitrosolobus and
Nitrosovibrio. Nitrite is then further oxidized into nitrate by bacteria
belonging mainly to the genus Nitrobacter, but also by bacteria in other
genera such as Nitrospina, Nitrococcus and Nitrospira.
In IFWMS, the anaerobically digested wastes from livestock are treated
aerobically before the nutrients are delivered into the fishponds to fertilize
the natural plankton that feed the fish without depleting oxygen, thereby
increasing fish yield 3- to 4-fold, especially with the polyculture of many
kinds of compatible fish feeding at different levels as practiced in China,
Thailand, Vietnam, India and Bangladesh. The fish produce their own wastes that
are converted naturally into nutrients for crops growing both on the water
surface and on dykes surrounding the ponds.
The most significant innovation of IFWMS is thus the two-stage method
of treating wastes; the anaerobic digester followed by the shallow aerobic
basins containing green algae. Livestock waste contains very unstable organic
matter that decomposes fast, consuming a lot of oxygen. So for any pond, the
quantity of livestock wastes that can be added is limited, as any excess will
deplete the oxygen and affect the fish population adversely, even killing them.
Chan is critical of "erratic proposals" of experts, both local and
foreign, to spread livestock wastes on land to let them rot away and hope that
the small amount of residual nutrients left after tremendous losses that damage
the environment have taken place.
According to the US Environment Protection Agency, up to 70% of nitrous
oxide, N2O, a powerful greenhouse gas with
a global warming potential of 280 (i.e., 280 times that of carbon dioxide)
comes from conventional agriculture. Nitrous oxide is formed as an intermediate
in denitrification, a process in which soil bacteria reduce nitrate ultimately
back to nitrogen gas. Denitrifying bacteria belong to two main genera,
Pseudomonas and Bacillus. Animal manure could be responsible for
nearly half of the N2O emission in agriculture in
Europe, according to some estimates; the remainder coming from inorganic
nitrate fertilizer. Thus, anaerobic digestion not only prevents the loss of
nutrients, it could also substantially reduce greenhouse gas emissions from
Chan further dismisses the practice of composting nutrient-rich
livestock wastes, for this ends up with a low-quality fertilizer that has lost
ammonia and nitrite. Instead of mixing livestock wastes with household garbage
in the compost, Chan recommends produce high-protein feeds such as earthworms
from the garbage, and using worm castings and garbage residues as better soil
conditioners. He is also critical of the outmoded practice of putting manure in
septic tanks for not much financial or other benefits while the badly treated
effluent is just as dangerous as the waste itself.
Instead, the livestock waste digested anaerobically followed by
oxidation in open shallow basins with natural algae before letting the treated
waste effluent flow into the fish pond, can convert almost 100% of the organic
nutrients into inorganic nutrients that will not consume any oxygen to deprive
the fish. So, theoretically, the quantity of waste input into the pond can
increase 10-fold without the risk of pollution. But, Chan cautions, the
nutrients in the waste must be totally used by both fish and crop culture, or
the nutrients can create problems of eutrophication over-enrichment of
plankton - that uses up all the oxygen in the pond, thereby lowering
To close the circle, livestock should be fed with crops and processing
residues, not wastes from restaurants and abattoirs. Earthworms, silkworms,
fungi, insects and other organisms are also encouraged, as some of them produce
high value goods such as silk and mushrooms.
The digester can be as simple as a couple of concentric plastic bags of
5m3 capacity or 200-litre drums for a
small farm, or a complex reinforced concrete steel structure with an anaerobic
sludge blanket to collect the biogas for a big farm or industrial
As the fresh wastes enter the digester, the waste-eating bacteria
transform the unstable ammonia (NH3) and nitrite (NO2) into stable nitrate
(NO3), which is ready for use as
fertilizer. As more wastes are added, the digester also produces an abundant
and inexhaustible supply of biogas - 2/3 methane (CH4) and 1/3 carbon dioxide
(CO2) - a convenient source of free
and renewable energy for domestic, farming and industrial uses (see Box 2). Big
farms, meat and fish-packing plants, distilleries, and various agro-industries
are now self-sufficient in energy, besides having big volumes of nutrient-rich
effluent for fertilizing fishponds, and fertigation (fertilization
and irrigation) of many kinds of crops.
Formation of biogas 
Certain bacteria naturally present in manure produce a combustible
gas (biogas) when they digest organic matter anaerobically (in the absence of
oxygen). Biogas typically contains between 60 and 70 percent methane. Anaerobic
digestion involves two groups of bacteria. The first group of ordinary bacteria
produces organic acids such as acetic acid by fermentation. The second group of
bacteria, the methanogens (methane makers), is special, it breaks down the
organic acids and produces methane as a by-product.
Methanogens cannot tolerate oxygen and are killed when exposed to
oxygen. Instead, they can use the dead end products of fermentation, carbon
dioxide or organic acids such as acetic acid, to generate methane:
Methanogens are found wherever oxygen is depleted, such as
wetland soils, aquatic sediments and in the digestive tracts of animals.
Methane formation is the final step in the decay of organic matter when carbon
dioxide and hydrogen accumulate, and all oxygen and other electron acceptors
are used up.
Proliferating lifecycles for greater productivity
The aerobic treatment in the shallow basins depends on oxygen produced
by the green alga Chlorella. Chlorella is very prolific and can
be harvested as a high-protein feed for chickens, ducks and geese.
When the effluent from the Chlorella basins reaches the
fishpond, little or no organic matter from the livestock waste will remain, and
any residual organic matter will be instantly oxidized by some of the dissolved
oxygen. The nutrients are now readily available for enhancing the prolific
growth of different kinds of natural plankton that feed the polyculture of 5 to
6 species of compatible fish. No artificial feed is necessary, except locally
grown grass for any herbivorous fish.
The fish waste, naturally treated in the big pond, gives nutrients that
are used by crops growing in the pond water and on the dykes.
Fermented rice or other grain, used for producing alcoholic beverages,
or silkworms and their wastes, can also be added to the ponds as further
nutrients, resulting in higher fish and crop productivity, provided the water
quality is not affected.
Trials are taking place with special diffusion pipes carrying
compressed air from biogas-operated pumps to aerate the bottom part of the
pond, to increase plankton and fish yields.
Apart from growing vine-type crops on the edges of the pond and letting
them climb on trellises over the dykes and over the water, some countries grow
aquatic vegetables floating on the water surfaces in lakes and rivers. Others
grow grains, fruits and flowers on bamboo or long-lasting polyurethane floats
over nearly half the surface of the fishpond water without interfering with the
polyculture in the pond itself. Such aquaponic cultures have increased the crop
yields by using half of the millions of hectares of fishponds and lakes in
China. All this is possible because of the excess nutrients from the integrated
Planting patterns have also improved. For example, rice is now
transplanted into modules of 12 identical floats, one every week, and just left
to grow in the pond without having to irrigate of fertilize separately, or to
do any weeding, while it takes 12 weeks to mature. On the 13th week,
the rice is harvested and the seedlings transplanted again to start a new
cycle. It is possible to have 4 rice crops yearly in the warmer parts of the
country, with almost total elimination of the back breaking work previously
Another example is hydroponic cultures of fruits and vegetables in a
series of pipes. The final effluent from the hydroponic cultures is polished in
earthen drains where plants such as Lemna, Azolla, Pistia
and water hyacinth remove all traces of nutrients such as nitrate, phosphate
and potassium before the purified water is released back into the aquifer.
Processing for added value and nutrient release
One big problem with agricultural produce is the drop in prices when
farmers harvest the same crops at the same time. This is solved by the abundant
supply of biogas energy, which enable simple processing to be done such as
smoking, drying, salting, sugaring, and pickling.
Finally, the sludge from the anaerobic digester, the algae,
macrophytes, crop and processing residues are put into plastic bags, sterilized
in steam produced by biogas energy, and then injected with spores for
high-priced mushroom culture.
The mushroom enzymes break down the ligno-cellulose to release the
nutrients and enrich the residues, making them more digestible and more
palatable for livestock. The remaining fibrous residues can still be used for
culturing earthworms, which provide special protein feed for chickens. The
final residues, including the worm casting, are composted and used for soil
conditioning and aeration.
Sustainable development is possible
There has been a widespread misconception that the only alternative to
the dominant model of infinite, unsustainable growth is to have no growth at
all. I have heard some critics refer to sustainable development as a
contradiction in terms. IFWMS, however, is a marvellous demonstration that
sustainable development is possible.
The key is a balanced development and growth thats achieved
by closing the overall production cycle, then using the surplus nutrients and
energy to support as many different cycles of activities as possible while
maintaining internal balance, rather like a developing organism. The
waste from one production activity is resource for another, so
productivity is maximised with the minimum of input and little or no waste is
exported into the environment. It is possible to have sustainable development
after all; the alternative to the dominant model of unlimited, unsustainable
growth is balanced growth.