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Professor George Chan has kindly allowed SCZ to reprint his photos and his detailed November 2003 article explaining the Integrated Farming System for recycling human and animal wastes. He is a sanitation engineer and was formerly of EPA Region 9 - Pacific.

George L. Chan
Environmental Management Consultant


Looking back at the precarious and even risky situation in the farming activities worldwide, we see the poor farmers working hard to feed themselves and trying to make a living from their land, with some livestock and crops. The livestock manure fertilizes the crops, and the crop residues feed the livestock. In order to produce more and improve the quality, they need costly inputs such as chemical fertilizers and artificial feeds, which make their farming activities uneconomic. If they also have to remove the pollution they create, they will not be able to afford it.

Those who added fish to the livestock-crop system have made a very big step forward, not only increasing the fertilizer from the fish wastes, but also enhanced their income from the bigger and quicker yield of fish and their relatively higher market prices. The deeper pond resulted in higher fish productivity, with increased wastes and fertilizer value, but the pond can still be subject to pollution, if it receives too much wastes that deplete the limited dissolved oxygen.

By treating the livestock wastes anaerobically in digesters, with additional production of biogas energy, and aerobically in shallow basins, their amount can be increased ten-fold in the system, increasing the fertilizer and feed in the pond accordingly, but without using any of the dissolved oxygen. Without such abundant, low-cost but much better inputs to improve the farming methods, we cannot expect high-quality produce and better yields.

Provided that all the extra nutrients and feeds are utilized to improve productivity, the benefits can only increase to make the farmers much more prosperous. The energy can also help the farmers to process their produce for preservation and added value, reducing spoilage as well as increasing the overall benefits. This is what the Integrated Farming System is all about.


The Integrated Farming System (IFS) has revolutionized Conventional Farming of Livestock, Aquaculture, Horticulture, Agro-Industry and Allied activities in some countries, especially in tropical and subtropical regions that are not arid. Farming all over the world is not very performing unless relatively big inputs are added to sustain yields and very often compromise the economic viability as well as the ecological sustainability. Evidently, the situation can worsen if high duties are paid on imported materials and energy, and the polluter-payer policy is also applied, as it should well be.

The IFS can remove all these constraints by not only solving most of the existing economic and even ecological problems, but also provide the needed means of production such as fuel, fertilizer and feed, besides 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 will not only alleviate poverty, but can even eradicate this scourge completely.

INTEGRATION The ancient combination of Livestock and Crop activities had helped farmers in the past, almost all over the world, to use the manure as fertilizer for crops, and the crop residues as feed for livestock. However, most of the manure usually lost up to half its nitrogen content before it became nitrate and was readily available as fertilizer to plants. The quantity also became inadequate as the population increased, so chemical fertilizers and artificial feeds had to be purchased, eroding the small profits of the small farmers.

The more recent integration of Fish with the Livestock and Crop has helped to improve both the fertilizer and feed supplies, plus the higher market value of fish as feed and/or food increasing the incomes substantially. Technically, this important addition of a second cycle of nutrients from fish wastes has benefited the enhanced integration process, and has improved the livelihoods of many small farmers considerably. This has now been documented by M. Prein of ICLARM Malaysia in "Integration of Aquaculture into Crop-Animal Systems in Asia".

It should be noted that the first of the two cycles of nutrients from the livestock is used to fertilize the growth of various natural plankton in the pond as fish feeds. Yield of fish was increased up to three- to four-fold with polyculture of many kinds of compatible fish feeding at different trophic levels, as practised in China, Thailand, Vietnam, India and Bangladesh. The fish, after consuming the plankton, produce their own wastes that are converted naturally into the second cycle of nutrients, which is then used to fertilize various crops on both the water surface with floats, as practised in parts of China, and on the surrounding dykes.

However, even if this has been a big step forward, it still required some external input to increase farm productivity and produce processing in agro-industry. So it has remained inadequate to lift the small farmers out of poverty, because of the continuously rising costs of the inputs, such as chemical fertilizer, artificial feed and fossil fuel, which had adverse effects on yield and quality, produce processing, and farming economics. Further innovation as well as increased productivity are necessary to push the integrated farming system almost to perfection. This is what the ZERI (Zero Emission Research Initiative) Integrated Biomass System (IBS) has been trying to do, as documented by Gunter Pauli in "Upsizing".


The most significant innovation is the introduction of the DIGESTER & BASIN in the waste treatment processes of the integrated farming system. One big problem with livestock waste, which contains very unstable organic matter, is that it decomposes fast and consumes oxygen. So for any specific 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 resulting in fish kills.

We should also seriously question the erratic proposals, presently being made by local as well as foreign experts in Mauritius, while ignoring past failures worldwide and wasting scarce funding to repeat the same mistakes, such as:

- spreading the livestock wastes on land to let them rot away and hope that the small amount of residual nutrients left after losses of volatile ammonia and nitrite, if they are not washed away by rain or irrigation water, can improve the soil fertility;
- composting the livestock wastes with household garbage to get a low-quality fertilizer, again because of the ammonia and nitrite losses, instead of digesting the livestock wastes into higher-quality fertilizer, and using the garbage to produce high-protein feeds such as earthworms and having their castings and garbage residues as better soil conditioner; and
- treating the livestock wastes ineffectively as well as inefficiently in outdated septic tanks for not much financial or other benefits, while the badly-treated effluent is just as dangerous as the waste itself.

Digestion of the livestock waste under closed anaerobic conditions, followed by oxidation in open shallow basins with natural algae providing the free oxygen through photosynthesis, before letting the treated waste effluent flow into the fish pond, can convert almost 100% of the organics into inorganics, which will not consume any oxygen to deprive the fish of this important life-sustaining item. So, theoretically, it is possible to increase the quantity of waste ten-fold into the pond without any risk of pollution.

Moreover, the big daily increase in readily usable nutrients can be beneficial to the system, provided that they are totally utilized in both fish and crop cultures, or they can create problems of eutrophication in bodies of water, including the fish ponds themselves, which are then counter-productive.


LIVESTOCK -- Whether it is for production of milk, egg or meat, small and big livestock require properly balanced feeding every day, and cannot continue to rely on rejected grains and their sweepings, cheap offals and residues from abattoirs and packing plants, and food remains from restaurants. It is worth emphasizing that, besides being comfortably housed and kept clean and dry, they must have those well-balanced rations in order to produce quality food products.

They also produce daily wastes, which are valuable renewable resources and will make various farming activities locally sustainable, even without any external inputs such as fossil fuel, chemical fertilizer and artificial feed. Worldwide, the latter have been relied upon to increase yield and even quality but at greater financial risks for those who have the means, but most of them just cannot afford them and remain poor farmers while the integrated farmers become rich by providing their own means of production on their farms.

However, feed can still be a serious problem in both quantity and quality. Most feeds can be locally produced from crops, crop and processing residues, with or without further processing for preservation or enhancement, but more nourishing ones such as earthworms, silkworms, fungi, insects and other organisms should also be constantly encouraged, some of them even producing high-value goods such as silk and mushrooms.

DIGESTER -- It is the most significant addition to farming during the past century, especially with livestock, which is mandatory for integrated farming systems. It 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 or steel structure with UASB (upflow anaerobic sludge blanket) for maximum efficiency for a big farm or industrial enterprise.

It gives the best primary treatment to the livestock or organic wastes through isolation, settling, digestion, liquefaction and solid/liquid separation, with the latter process enhanced with an additional but optional sedimentation tank, for a reduction in biochemical oxygen demand (BOD), which is a measure of the organic content in the waste, of 60% or more. Once the substrate is well conditioned biologically, with the methanogenic bacteria, which are naturally present in the intestines of humans and warm-blooded animals, taking over inside the digester, it is a continuous process.

As the fresh wastes enter the digester, the bacteria 'feed' on the organic content and transform the resulting unstable ammonia (NH3) and nitrite (NO2) into stable nitrate (NO3), which is a nutrient readily usable as fertilizer. It only requires some stirring and clearing of floating matter at the inlet pipe by means of a plunger, with no addition of energy or chemicals.

In fact, as more wastes are added, the digester also produces an abundant and inexhaustible supply of biogas, a mixture of 2/3 combustible methane and 1/3 carbon dioxide, that is a convenient source of free and renewable energy for domestic, farming and industrial uses. Big farms, meat & fish packing plants, distilleries, and various agro-industries are now self-sufficient in energy, besides having big volumes of nutrient-rich effluent for fertilization of fish ponds, and 'fertigation' (fertilization & irrigation) of many kinds of crops, as described more fully below.

OXIDATION -- This oxidation process facilitates further treatment in low-cost shallow basins by aerobic (in presence of oxygen dissolved from the atmosphere or produced by natural algae through photosynthesis) means for another 30% of BOD reduction. So the effluent is almost fully treated when it is ready for discharge into the fish pond. In the tropical, but less in the subtropical, regions the high-protein chlorella algae grow prolifically, while supplying the free oxygen for treatment, and are used as additional feed for chickens, ducks and geese.

FISH POND -- Any residual organic matter from the livestock waste will be instantly oxidized by some of the dissolved oxygen in the fish pond, with hardly any adverse effect on the big fish population. Moreover, the nutrients are readily available for enhancing the prolific growth of different kinds of natural plankton as feeds for polyculture of 5-6 kinds of compatible fish. No artificial feed is necessary, except locally grown grass for any herbivorous fish.

As already mentioned, the fish produce their own wastes that are naturally treated in the big pond to give the second cycle of nutrients, which are then used by crops growing in the pond water and on the dykes. Such a highly-productive bonus is not available in any other farming system.

Where some fermented rice or other grain, used for alcohol production, or silkworms and their wastes used in sericulture, are available they are added to the ponds as a third cycle of nutrients, resulting in higher fish and crop productivity, provided that the water quality is not affected. More research and development are required to find more innovative systems of fish, shellfish and crop cultures to use up these nutrients, because any unused parts are potential pollutants. There is also a possibility to precipitate them and sell them as dry fertilizers.

Special diffusion pipes are now being tried with compressed air from biogas-operated pumps to aerate the bottom part of the pond to increase plankton and fish yields. A deeper pond than 3 metres of water is also being tried for the same objectives.

CROP FIELD -- The IFS has a paradoxal situation where there is too much fertilizer, when it is lacking in other systems. and there is a need to find more ways of using it. 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 have succeeded in growing some aquatic vegetables floating on water surfaces in lakes and rivers. Others have grown grains, fruits and flowers on bamboo or the longer-lasting polyurethane floats over nearly half the surface of the fish pond water, without interfering with the polyculture of 5-6 kinds of fish in the pond itself. Such aquaponic cultures have increased the crop fields by utilizing half of the millions of hectares of fish ponds and lakes in China. All this has been made possible because of the excess nutrients from the integrated farming systems.

Planting patterns have also been improved with the aquaponic culture. 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 or 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 elimination of the back-breaking work.

Another example is to do hydroponic cultures of fruits and similar vegetables in a series of pipes placed in a triangular shape, and have the highly mineralized pond water, enhanced with added missing elements, to run from the top through the other pipes, all holding the plants. This setup allows higher yields per unit surface area of the costly hydroponic building.

The final effluent is polished in earthen drains where macrophytes such as Lemna, Azolla, Pistia, and even Water hyacinth are grown to remove all traces of nutrients such as nitrate, phosphate and potassium before releasing the pure water to the aquifer.

PROCESSING -- One very big problem with market produce is the drop in prices when farmers harvest the same crops at the same time, and the big losses caused by unsold produce because of the glut. Simple processes such as smoking, drying, salting, sugaring, pickling, etc. should be taught to all farmers so that they do not spoil their surplus stocks. With the almost free access to abundant biogas energy, they can now have more sophisticated processing of their produce for both preservation and added value.

The importance of an adequate source of almost free biogas energy in the integrated farming system cannot be stressed enough, as most countries are short of this essential resource for economic as well as social development, especially in remote and isolated areas. Biogas will still be available when fossil fuels run out . . .

RESIDUES -- In the integrated farming system, there are more biomass such as stabilized digester sludge, dead algae, macrophytes, crop and processing residues. Considering that livestock only use 15-20% of the feeds they eat, and excrete the rest in their wastes, the latter can still be quite rich. So everything must be done to recycle them and make better use of their byproducts, which is what the IFS is actually doing.

The sludge, algae, macrophytes, crop and processing residues are put into plastic bags, sterilized in steam produced by biogas energy, and then injected with appropriate spores for high-priced mushroom culture. The mushroom enzymes not only break down the ligno-cellulose to release the nutritive ingredients, but also enrich the residues as more digestible and even more palatable feeds for livestock. The remaining fibrous residues can still be used for culture of earthworms, which then provide special protein feeds for chickens. The final residues, including the abundant worm castings, are composted and used for soil conditioning and aeration.


There is no doubt at all about all the additional benefits that the small, medium or big farmers can derive from the IFS, through the recycling of otherwise unused wastes as renewable resources, providing the essential means of production such as fertilizer, feed and fuel that can make most farming activities economically viable and ecologically sustainable. By ignoring the concept of the IFS, because of criminal ignorance or stupid prejudice, most farmers will remain poor and be deprived of all the benefits that are the basic human rights of every man, woman and child on this earth, which has more than adequate resources for everybody, now and for future generations.


Chaboussou, F., 1980. Les Plantes Malades des Pesticides. Editions Debard, Paris, FRANCE.

Chan, G.L., 1996. The Rural-Urban Connection. World Bank: Sustainable Development Conference Mimeo 18pp, USA.

Chan, G.L., 1993. Aquaculture, Ecological Engineering: Lessons from China. AMBIO, Vol. 22 No. 7, November 1993, pp 491-494. SWEDEN.

Chan, G.L., 1985. Integrated Farming System. Elsevier Science Publications, Amsterdam, NETHERLANDS.

de Zeeuw, H. (ETC), Rijnsburger, J. (WASTE), 1998. Sustainable Wastewater Recycling Management in Support of Community Development. ETC, Leusden, NETHERLANDS.

Kiely, G., Environmental Engineering. McGraw Hill International Editions, USA.

Mulhall, D., Hansen, K., 1998. A Cycle of Cycles -- Guide to Wastewater Recycling in Tropical Regions. Hamburger Umweltinstitut e.V., GERMANY & European Commission, Brussels, BELGIUM.

NACA, 1989. Integrated Fish Farming in China. NACA Technical Manual 7, Bangkok, THAILAND and Asian-Pacific Regional Research & Training Centre, Wuxi, CHINA.

Pauli, G., 1998. UPSIZING: Integrated Biomass System, pp 152-180. Greenleaf Publishing, Sheffield, UK.

Prein, M., ICLARM contribution No. 1611, 2001. Integration of Aquaculture into Crop-Animal Systems in Asia. Agricultural Systems, 71 pp 127-146. Elsevier Science Ltd, Amsterdam, NETHERLANDS.

Zhong, G.F., Wang, Z.Q., Wu, H.S., 1997. Land-Water Interactions of the Dike-Pond System. Presses Universitaires de Namur and Eco-Technologie des Eaux Continentales, BELGIUM.

This Pig Waste Chart is a comparison of treatment required by the US Department of Agriculture, ZERI recommended treatment, and no treatment.

(Webmaster's Note: for more information about Biogas go to:

Beginner's Guide to Biogas an introduction to biogas by Paul Harris of the University of Adelaide, Australia. There are many pertinent references and links in this good summary. Also go to:

The Biogas Forum. This Swiss web site, in English or German, presents information about biogas. It has many important links to other relevent web sites.)

The SeedTree Biogas Web Page.

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