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Field Working Paper 4
Manures and Agro-Industrial By-Products
for Fish-Farming in Ghana

based on the work of

C.E. Agyenim-Boateng (FAO Consultant Sociologist)
M.M.J. Vincke (FAO Senior Aquaculturist)
Ulf N. Wijkstrom (FAO Consultant Economist)

Rome, 1990

1. The need for supplemental feed

The natural productivity of pond-waters is not sufficient to ensure a reasonable and economically rewarding growth of tilapia and/or catfish. Thus, somehow the fish must be provided with additional feed. The alternatives are basically three: (i) enrichment of the nutrient contents through the application of fertilizers, manures or compost; (ii) provision of agro-industrial by-products suitable as fish-feed and, (iii) the provision of complete, manufactured and enriched feed, manufactured for the explicit purpose of feeding fish (or other animals).

While the two first alternatives appear viable, the third does not. The economy of Ghana has not yet reached the capital intensity, and efficiency, required for farmers to be able to afford the costs of manufactured feeds for raising fish.

Thus, it must be ascertained whether agro-industrial by-products and/or agricultural waste are available to be used as feed for fish farming. This annex identifies the manures and agroindustrial by-products which can become the basis for the development of fish-farming in Ghana during the coming decade.

During the coming decade, it is primarily tilapia, and clarias which will be the species of interest.

This following analysis builds on the hypothesis that for a strategy for fish farm development to be worth pursuing, it should be able by the year 2000 to yield an increase in production of about 1000 tons, over and above present production, (estimated to be about 500 tons ). This annex contains an analysis intended to establish which feeds and/or fertilizers are likely to be available to support such a strategy.

2. Possibilities

Satia and Vincke (1989)1 identify ten different categories of agro-industrial by-products which are of interest to the potential fish farmer, as feed or feed ingredients. These categories are: slaughter-house waste, fish meal, residues of wheat and rice milling, brewery waste, waste products from sugar manufacture, vegetable oil cakes, cocoa and coffee waste and, finally, animal feeds. The fish farmer's alternative to these products is basically to fertilize pond waters using chemical fertilizers, animal manures or compost.

1 Satia B. & M.M.J. Vincke Aquaculture Sector Survey, Ghana FAO; 1989.

Fish farmers' possibilities of using the existing supply of agro-industrial by-products, manures or other fertilizers, of course to a large extent depend on the competition for them. That, in turn, is a function of the distances from the source of supply to the user. As the relative costs of transport in Ghana are high (see Field Working Paper 5), the cost of transportation is an important aspect of this problem and will be taken into account.

3. Availability at National level

The analysis of the “effective availability” of feeds and fertilizers for a sustained development of fish farming in Ghana will start at the national level. Once the most suitable materials/ingredients have been identified, the analysis will be broken down by district. This is done with the help of the GIS (see Field Technical Report No. 3).

Agro-industrial by-products and crop waste as bases for fish farming development will be reviewed considering quantity produced, quantity used and cost of transport. The analysis is postulated on the understanding that fish farming is most likely to grow in Ashanti, Eastern Region, the northern part of Central Region, in the Greater Accra area and in irrigation schemes.

3.1 Agro-industrial by-products and agricultural waste


Slaughterhouse waste (stomach contents, blood and bone) can be used to supplement feed (e.g. rice bran), after adequate preparation (drying, grinding). However, the locations of the slaughterhouses - Accra, Bolgatanga and Tema - make it likely that these products will be used only incidentally to supplement fish feed in the centre of Ghana. Fish farmers in the Tono and Vea irrigation schemes are likely to compete with livestock farmers for the products from the Bolgatanga Slaughterhouse.

Slaugher-house waste is unlikely to become a major source of fish feed, given the likely competition from livestock feed manufacturers for this ingredient.

Fish meal

Some fish meal is produced at Tema. Fish meal is also imported for the animal feed complexes in Tema and Winneba. It was sold at Tema for 270 to 280 cedis per kg in April 1990.

Fish meal is an excellent and common ingredient in fish feed, particulary in feeds manufactured for carnivorous species. For pond-raised, as opposed to cage-cultured, tilapia and catfish it is not an essential item. In Ghana it is a costly ingredient. Even at only a 10% inclusion rate, it will account for the major shart of any manufactured feed based essentially on crop by-products. Thus, it can not be considered a strategic item for fish farming development.


Draff (also known as spent grain) and Brewer's yeast are excellent feed for animals and fish. Breweries are located in Accra, Cape Coast, Kumasi and Tamale. The yearly production of beer in Ghana was reported to be 61.4 million litres in 1988.

The combined production of spent grain by the country's breweries amounted to about 7.900 tons in 1988. Poultry and livestock farmers are reported to be purchasing spent grain from these breweries. However, the sales policies - and prices - seem to differ considerably. While one brewery was selling to an intermediary at C. 14 per kg, the other is reported to be selling directly, by the truck-load, to farmers at a token price of less than one cedi per kg.

The production of spent grain (only for three breweries) of about 7.900 tons during 1988, if it was all used as “single” fish food, would contribute about 658 tons of fish. This is based on a conversion factor of 1:12. However, fish farmers would not be able to afford to pay, delivered at the farm, above C. 10 per kg. Therefore, neither does this ingredient seem to be the major strategic input needed for fish farm development.

Wheat processing

Wheat is not grown in Ghana. Imported wheat is milled at two mills in Tema. In 1987 the imports amounted to 140,200 tons. 100.000 tons of wheat would give, when milled, 12,600 tons of wheat bran, as the latter is reported to be equivalent to 9% of the weight of the grain.

Wheat bran is sold for animal feed. The price in April 1990 was reported to be C 700 per bag of 50 kgs. With a transport cost of 50 C/ton-km (see Field Working Paper 5), the average cost of the wheat bran delivered in Kumasi (240 kms) would be about 27 C/kg; in Koforidua it would be about 18 C/kg.

Given a conversion of rate of 5.5 for wheat bran, as single feed, a kg of tilapia in Koforidua would need (5.5 × 18 =) 99 cedis worth of wheat bran; in Kumasi the same kg of tilapia would need wheat bran costing 158 cedis. The latter cost is clearly beyond the economically feasible.

Given that about 5.5 tons of wheat bran would be needed to produce 1 ton of tilapia, the requirement for 1000 tons are 5.500 tons of wheat bran. That would seem to correspond to about 44% of the 1987 supply. Such a share could not be withdrawn from present buyers without causing considerable price increases.

The authors conclude that wheat bran will be used in irrigation based farming in or close to Greater Accra, only if it can compete with rice bran.

Rice Processing

In 1988 the rice production in Ghana is estimated to have been 116.000 metric tons. Rice is grown on wet-lands, utilizing the annual flooding, and in irrigation schemes. The irrigation schemes are on mapped (in Field Technical Report 5, Figure 2). Rain fed rice is produced produced mainly in: Northern, Upper East Region, sourthern part of Upper West Region, the central part of Western region, Brong-Ahafo, parts of Ashanti and part of Eastern region.

Rice bran is sold mainly for pig feed. Mixed with polishings it is used as chicken feed for free-roaming chickens. It is generally sold in (fertilizer) bags containing 35 kgs. The price is reported to move from 6 to 20 C/kg during the year.

Given a bran yield of 2 to 4 %, calculated on the weight of paddy, and a yield of 59 % of rice from the paddy, 58802 metric tons of rice bran should have been produced. The supply is seasonal, tied to the rice harvest between October - December in the northern part of the country and between September - October elsewhere.

However, to produce 1000 tons of tilapia using rice bran as the single feed would require some 5.500 tons of the product, given a conversion factor of 5.5 to 1 kg of fish. That is about equal to the quantity now being produced in the country.

The cost of road transport means that for each 100 kms between the source of the rice bran and the fish pond where it is to be used, about C 5/kg should be added. That is the same as saying that for every 100 kgs of transport, the fish farmer will add about cedis (5.5 × 5=) 28 to the cost of a kg of fish.

Rice bran will not be the final solution to the problem of finding feed for expansion of fish farming However, it is more interesting as a source of feed than is wheat bran, because of the widely distributed supply - implying less transport cost - and the generally lower price.

2 (116 000/0.59 × 0.03)

Sugar Mills

There are two sugar mills in Ghana: Asutuare and Komenda. Neither has been in operation for some time.

Recent data (Jan 1990) from the Ministry of Agriculture show that sugar cane production fluctuated between a high of 205.000 tons to a low of 58.000 tons in the period 1970 to 1983. No data is available for the production during subsequent years.

A production of 100.000 tons would yield about 2.500 tons of molasses. Molasses is not suitable as a “single” feed. In combination with rice bran, 60 % molasses and 40 % rice bran has been reported to give a conversion of 8. Thus, 2.500 tons of molasses (with 1650 tons of rice bran) could yield 520 tons of fish.

Thus, during the next decade it is unlikely that Ghana will produce molasses in quantities sufficent for them to become a major source of feed for tilapia.

Oil mills

In Ghana oil is extracted from: groundnut, palm-kernels, coconut copra, sheanut and cotton-seed. The “oil-cake” that remains after oil is extracted can all be used as supplementary feed for Tilapia nilotica.

(i) Ground-nut

Oil-cake from ground-nut is not a prime candidate as fish feed. Production in 1988 was 230.000 tons (estimated 200.000 for 1989). Part of this production is consumed locally as toasted nuts. Some is processed for oil.

Press-cake normally weighs 50 % of the shelled weight of the ground-nuts, which in turn constitute 70% of the weight in shell. Thus, 200.000 tons of groundnut could result in 70.000 tons of press-cake.

At the village level, however, the resulting oil-cake is used as human food. The industrially produced press-cake is sold for animal feed. Thus, in spite of the relatively large amounts of press cake available, there is no reason to reduce the human consumption in favour of fish feed.

(ii) Oil-palm

Total estimated area planted for oil palm is 125.000 ha (1984 agricultural census) confined mainly to the Ashanti (50%), Western (17%), and Eastern (13%) regions, and the remainder spread between the Volta, Central and Brong-Ahafo regions3. Thus, the oil-palm grows primarily in the forest zone, which coincides with the zone most likely to be the location of an expanding fish farm activity (not considering the irrigation areas).

Oil-palm production is reported to have fluctuated between 281.000 tons (1976) and 1.062.000 tons (1979) during the 1970 -1985 period. In 1985 it reached 643.000 tons.

At the village level the oil palm fruit is subject to artisanal processing to extract the oil for household use. The oil is extracted from the boiled fibres once the kernels have been removed. The resulting press cake of fibres contains considerable quantities of oil since the pressing procedure is not 100% efficient.

The cake is not ideal fish feed but is reported to have a conversion coefficient of 8. Thus, farmers who process oil palm fruits for oil may want to use the freshly pressed fibres as tilapia feed.

(iii) Copra

Coconut production reached a minimum annual figure of 132.000 tons (1977) and a maximum of 432.000 tons (1981), during the 1970 -1985 period. During 1985 the production reached 219.000 tons (ref. UK2). 95% of the total planted area of the country (30.000 ha) is concentrated in the Axim-Takoradi districts. However, the future of the coconut and copra industry in Ghana is uncertain due to the outbreak of Cape St. Paul Wilt Disease (see footnote 3, p 23). Given this situation, it is unlikely that copra by-products will have any future importance as a source of fish feed.

(iv) Sheanut

The Shea Butter Tree is a natural species of the northern savannah vegetation and in recent years COCOBOD has been purchasing the fruit for export. Sheanut production in 1985-86 was exceptionally good with a total pruchase of 40.000 mt compared to 3.000 mt in the previous year. However, the fruit production is unreliable and this needs to be taken into account in any plans for using by-products in fish farming (see footnote 3, p 23).

No information on its use for fish feed is available.

3 Economic and Planning Department; “Report of the Special Programming Mission to Ghana” IFAD; July 1988

(v) Cottonseed

The present production of cotton is limited to that of the Ghana Cotton Company. The company report the following production figures for the last four seasons (12 months periods): 2.400, 3.400, 4.200 and 5.200 tons. The seed is sold to Crystal Oil Mills and a small portion is exported.

No information is available on the relationship between quantity of cotton produced and quantity of cotton seeds obtained, or concerning the use of cotton seed for fish feed.


After having reached 566.000 tons in 1964–65, Ghanaian cocoa production has fallen. In 1983–84 the production was recorded at 154.000 tons. In 1987–88 the production is estimated to have been 270.000 tons. Regional production trends show a gradual shift in production towards the Western region with a decline in the Volta and Central Regions.


No information is available on the quantities of coffee produced.

The COCOBOD has a policy of purchasing only unhulled coffee. Thus, they have a monopoly on hulling.

Coffee hulls used as single-feed have been reported to have a conversion rate of 40. Coffee-pulp can be used in mixtures up to 25% of fish diets.

3.2 Fertilizers and manures

It is evident from the previous section that, under the economic conditions of Ghana in early 1990 and those likely to prevail during the coming decade, feed in the form of agroindustrial by-products is not going to be used as a basis for any major expansion of fresh water fish farming. Fertilizing pond waters containing plankton feeding fish is likely to be the principal method. This section will review the possible use of: (i) chemical fertilizers, (ii) manures and (iii) compost.

3.2.1 Chemical fertilizers

Chemical fertilizers are imported. In the seventies and early 80's the Government encouraged farmers to use them through strong subsidies. Since then the economic rehabilitation programmes have led to a continuous reduction of this subsidy. At the end of 1989, the subsidy was 15 % and planned to be eliminated during 1990. The government had also started to transfer the distribution and marketing of chemical fertilizers to the private sector. The public sector monopoly on imports of fertilizers will be ended in 1991.

The fertilizer prices, per bag of 50 kgs. in April 1990, are shown in the table below. The table also shows what the cost would be for applying fertilizer to one hectare of pond area for a period of 6 months, that normal for culture of tilapia.

  Rate 14 d.Kgs 6 m.Cedis 6 m.
Sulphate of Ammonia:3.1302530018.780
NPK (20-20-0)4.230n/a  
NPK (15-15-15)4.230n/a  

Rates of application are from ref 27; p. 67.

Chemical fertilizers are of interest, particularily as a base for growing males of O. niloticus4. To grow 1,000 tons of tilapia using only Sulphate of Ammonia and superphosphate qwould require about 280 tons of fertilizer5. Imports of fertilizers are of the order of 50,000 to 70,000 tons per year. Thus, use of chemical fertilizers for growing 1,000 tons of fish would involve only a minute part, less than 1%, of current imports.

3.2.2 Manures

Cattle, pig and poultry manures are those of primary interest in Ghana.

(i) Cattle

The cattle population is substantial in Ghana. It is estimated to have numbered 1.12 million in 1986 (see footnote 3). One cow produces about 16 tons of manure (wet weight) per year. Thus, the total cattle population should produce in the range of 10 to 15 million tons of manure during a year.

4 See table 5.19

5 See table 5.18. The calculation is based on mixed sex culture with a per year yield of 5.76 tons/ha for an input of 1.68 tons of fertilizer. The yield with the same input of fertilizer, and growing male O. niloticus, is calculated to be about 9 tons/ha/year.

Cow manure needs to be applied in larger quantities than chemical fertilizers. About 9 tons would be needed to manure a one hectare pond to obtain 2150 kgs of tilapia over a 6 month period. Thus, for a 4.3 tons per hectare/year yield, relying only on cow manure, the relationship would be 4.5 to 1; that is, 4.5 tons of manure would yeild 1 ton of tilapia. Thus, only 4.500 tons would be needed to produce 1000 tons of tilapia. This is only a fraction of the quantities produced in the country or, to be precise, less than 1 tenth of one percent!

However, there are two potential complications: collecting the large quantities needed and the transport of these quantities from the areas where most cattle are found to those areas where fish ponds will be built. Approximately 76% of the cattle are located in the Upper Regions (East and West) and the Northern Region. Cattle are free-roaming and usually “kraaled” at night. This means that manure for fish ponds would most likely be collected from the kraals.

For a small-holder with ten ares (1.000 m2) of pond surface area, the work involved would be to supply 30 kgs of manure per week to these ponds. That is only about 10% of what one cow produces per week. Therefore, it should be possible to collect this amount from the kraal and still have manure for other purposes. It should also be possible for the farmer to pay for this manure. At a cost of C. 15 per kg of manure at the pond-side the cost per kg of fish becomes Cedis (4.000 × 15/1.000=) 60. This, as the farmer would have no feed costs, seems a reasonable expenditure.

Thus, given that cattle are spread over Ghana and the quantities needed (in terms of cows) per unit area of water is small, this manure could become the base for substantial development effort.

(ii) Pig manure

In 1986 the Ghanaian pig population was estimated to have been slightly more than half a million animals. It was growing steadily in the mid-1980s reflecting an increasing acceptability of pork in the Ghanaian diet (see footnote 3, p 34).

Pig-farming in association with fish farming has been well documented. The manures of 100 pigs, continuously applied into one hectare of water has been reported to result in as much as 10 tons of tilapia (males only) per ha/year. Using a yield of 8 tons/ha/year would mean that to produce 1.000 tons of tilapia would require the association of (1000/8 × 100 =) 12.500 pigs6. This represents about 2.5 % of the pig population in 1986.

The mission's investigations did not reveal any extended use of pig manure. In fact, in some areas it is more a nuisance than anything else, and pig farmers would be glad to get rid of it. Thus, the use of pig manure for fish farming is not likely to upset any present patterns of use. However, most likely, if pig manure is to be used, ponds should be located close to the piggery, as transport of pig manure requires either vehicles capable of transporting slurry, or an initial drying procedure and then transport.

(iii) Chicken droppings

Poultry farming is the most advanced and popular animal industry in Ghana. However, its magnitude is much influenced by maize prices. In Ghana the poultry population fluctuates rather drastically in size from year to year. In 1984 it was reported to be 5.9 million, in 1985 10.0 million and in 1986 to have numbered 6.3 million (see footnote 3, p 34). This gives an average of about 7.4 million.

A chicken produces about 19 kgs of droppings per year. In order to achieve an additional production of 1.5 tons/ha/year the farmer should apply an additional 12 tons of droppings per ha/year. This means that 1.000 tons of additional tilapia production could be obtained with the addition of about droppings from about (1000/1.5 × 12 × 1000/19 =) 421.000 chickens7. That number is about 6 % of the average chicken population in 1984 – 1986.

The majority of chickens are free-roaming. Those which are kept by poultry-farmers are usually kept on litters. This means that the droppings are mixed with wood chips. This is not an unsurmountable problem. The droppings can be dried and then sieved, or placed in a container in the pond. The container should be full of holes and shaken at regular intervals to release the nutrients into the water outside the container.

Poultry droppings are generally free, although some quantities are now being sold in Accra. In some areas the situation is similar to that related for pig manure: the farmers do not know what to do with it and would be pleased if someone took it away. Some droppings are used as manure.

6 (1000/8 × 100)

7 (1000/1.5 × 12 × 1000/19 =)

Poultry droppings can be transported but, given the quantity needed to increase tilapia production by 1 ton - 8 tons -, it soon becomes expensive. At a cost of C. 10 per kg by the side of the pond, the farmer in fact pays cedis 80 for every kg of fish produced.

However, no doubt by exploiting the chicken droppings of those farmers who also have the land and water to build fish ponds, a considerable expansion of the farmed fish production can be achieved.

3.2.3 Compost

It appears that compost has not been tried to date in Ghanaian fish farming. Experience in Central Africa indicates that by the use of compost the natural pond productivity of about 200 kgs/ha/year can be increased to about 1.500 kgs/ha/year.

The compost may include: grass, spoiled fruits, waste from soaking cassava, cattle and chicken manure. The farmer, who uses compost, would be using material available on his holding. He would not purchase ingredients but would have to spend time collecting, transporting and piling them. It has been estimated that during a year a farmer may spend 28 hours preparing compost for a pond of 100 m2, with weekly applications of 9 to 10 kgs. At Ghanaian wage rates for casual farm labour, that is equivalent to about (500 × 28/5 =) Cedis 2.800.

This means that preparing compost for one hectare of pond surface area will require about (100 × 28 =) 2.800 hours a year. That is a man-year of labour. A substantial amount of grass and other inputs would be needed. Provided these inputs would be available free of charge (and in particular at no transport cost) the proposition would be viable. However, given the magnitude of the undertaking, it seems likely that only small-scale, subsistence farmers will rely extensively on composting.


Ghana 6.1. Access to feed.

Agro-industrial by-products. Share
needed to produce 1000 tons tilapia/year

Ghana 6.2. Fertilizers.

Share needed to produce 1000 tons of
of tilapia

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