Gabon: producing fertilisers locally
by Alan DEMPSTER
Gabon has put top priority on developing the crop output of its traditional peasant smallholdings and agro-industry! on promoting small and medium-sized enterprises (SME) and on diversifying mining, in which national operators are to play a bigger part.
All three aims came together in a 12-month pilot project to evaluate and demonstrate the working of occurrences of lime and phosphate in the Gabonese Republic, a project which was funded partly by the European Development Fund (ECU 500 000) and partly, by the Gabonese Government (CFAF 50 million, or about ECU 142 000).
The original idea came from the Directorate-General for Mining and Geology (DGMG) at the Ministry of Mining, Industry and Trade, which brought up the possibility of a Lomé-assisted mining scheme in 1985. Various DGMG proposals were discussed with the Commissariat for Planning, Development and Economic Affairs and the EEC Delegation. With agricultural development now the top priority of Lomé, they were looking for a mining project related to that sector and, since Gabon was known to have potash and phosphates, it was decided to look into the possibility of developing the raw materials for fertilisers there.
The study was put out to tender (by restricted invitation) and carried out by geological consultants Crowe Schaffalitzky and Associates Ltd (CSA) of Dublin, Ireland, who spent a month assessing Gabon’s fertiliser requirements and the feasibility of local prospection. The country uses relatively little fertiliser-the average for 19X5-87 was about 6000 tonnes p.a.-but its estimated annual requirements are 30 000 tonnes, 25000 tonnes of it lime and phosphate soil conditioner. As the need for nitrogen and potash fertiliser, particularly of chemical origin, is small (only 2 900 tonnes of urea and complete fertilisers etc. being used in 1987), there was no point in looking for or evaluating the raw materials for these products, because local processing would require enormous investment and not therefore he a paying proposition. It was suggested that it would be better for the Government to start by concentrating on raw materials which could be developed cheaply to meet national requirements.
Both the Gabonese authorities and the Community liked the idea and, after a second mission to Gabon, an invitation to tender was drawn up. The CSA’s suggestion was to move on to a pilot lime, dolomite and phosphate soil conditioner scheme to produce test batches for agricultural projects and agro-industry. The Government wanted practical results for the farm sector as soon as possible and so it selected three known sites near the following agricultural areas:
- Fernan Vaz (Ogooue Maritime): phosphates, lime and dolomite;
These are the three Integrated Operations Zones (OZI) where the existing agricultural operations (farming and farming-herding development projects and large-scale agricultural undertakings) can try out the fertilisers and get them into general use later on.
A private contract for the project was signed with CSA, with a view to getting the benefit of the firm’s experience, bearing in mind the relatively small amount involved. The total budget was ECU 642 000 and 44 % of it was used to purchase equipment (mostly the basic hardware needed to quarry, crush and powder hard rock and bag it for distribution to the farmers). A four-wheel drive vehicle with a trailer and outboard motor and a few items of camping, prospection, geological, laboratory and drawing equipment completed the purchases. The contractor chose all the new items (all of them from the EEC) after restricted consultation, with an eye to the value for money offered by the tenderers.
The orders were placed and work began in the field in June 1988. The reserves and the quality of the occurrences in the three project zones were evaluated during a preliminary phase. The timing of the field work was partly influenced by the seasons, the prospection and evaluation of phosphate, lime and dolomite in the area south of Ndougou (Fernan Vaz), for example, being carried out in the not-so-rainy months of August and September. This region, geologically part of the sedimentary coastal basin, is low-lying and therefore has plenty of lakes, rivers and swamps and the team (of two expatriates and eight Gabonese) often travelled by boat in the course of their investigations. Pitting and drilling techniques were used for the geological study and evaluation of the occurrences and rock samples were analysed for their phosphorous and carbonate content, solubility and neutralising value (NV) in laboratories in Gabon and Ireland.
None of the Fernan Vaz occurrences turned out to be worth exploiting for soil conditioner, so the team moved on to Lebamba to start test working a deposit of magnesian limestone which was suitable (Ca: 30%, MgO: 18%, NV: 95-100). This (Early Precambrian) limestone is very hard and has to be blasted out.
Once the site had been stripped, a quarry face five metres high, in two benches, was developed with a front-end loader and holes 2.50 m deep drilled (at 1.10 m x 1.20 m) for explosives with a pneumatic hammer-drill powered by a portable compressor. The large rocks thus dislodged were reduced to small pieces by blasting or by a rock-crusher (the scoop on the front-end loader being used for this). For reasons of economy, the rock was pulverised in only two stages. A crusher with a grab and a hammer-grinder were mounted on trailers so they could be towed from site to site. Each unit had electric motors and controls, a feeder and a conveyor belt which could be folded away for travelling. Power came from a wheeled 95 kva generator powerful enough to work all the machines at once. The crushers were placed end to end so that conveyor belt could tip the rock straight into the hopper of the grinder. The jaws of the grab on the crusher were fixed at the minimum distance so as to feed finely crushed rock into the grinder-which then tipped the powder into a large (4 m³) storage hopper at the bottom of which there was a semi-automatic bagger regulated to turn out 50 kg packs.
With this equipment, a team of 12 turned out 1-2 tonnes per hour of a standard agricultural lime product (100% finer than 3.5mm and 35% less than 150 microns) and packed into 50 kg plastic bags, sealed with a wire tie. As the fastening could be undone easily, the bags were not damaged and the customer could use them again - a considerable advantage to the small grower.
Most of the output was sold to an agricultural extension project for distribution to the local growers and broken rock was also bought in bulk by local constructors.
Field tests using varying amounts of lime on a variety of crops (groundnuts, maize and cassava) were also run by the agricultural project under an arrangement drawn up by the contractor. Gabon’s soil tends to be very acid and have fairly low fertility as far as agriculture is concerned, but a lime conditioner neutralises the acidity, encouraging microbial activity and releasing oligoelements, thus improving the structure of the soil, which is more fertile as a result and yields bigger crops. Testing of the soil conditioner produced by the Lébamba project will continue over a number of years, but the results already confirm its usefulness to the farmers.
The original idea for the unit to travel from site to site, moving on whenever the annual requirements of a particular area were met, which was why all the major equipment for the project was portable or on trailers. But this has proved impracticable, for the moment at least, and it has been decided to leave the unit at Lébamba, where it is working well, and to look for a promoter willing to take on the existing pilot project as a commercial enterprise. The project-trained team is continuing production at Lébamba until such a promoter is found.
However, the project leaders produced an evaluation report for the Gabonese administration when the project contract came to an end, recommending support for initiatives likely to lead to similar pilot schemes being set up in Lastoursville and N’Toum (near Libreville). Calculations based on the Lébamba scheme suggest that such ventures could well be paying propositions- provided, of course, that there are enough customers. They would be cost-effective if they sold about 1700 tonnes of conditioner p.a. at the fertiliser project’s suggested price of about ECU 140 per tonne (ECU 7 per 50 kg bag). This is much lower than the price of the same imported product and affordable by not only the agroindustrial companies and development and agricultural extension schemes which are currently Gabon’s biggest users of fertiliser, but also by small growers, who are only just beginning to use soil conditioner.
Gabon’s short ( 12 month), low-budget (ECU 642 000), fertiliser project has succeeded in demonstrating that soil conditioner can be produced from local raw materials at low cost and that a small firm could make it a paying proposition. It has also encouraged other small conditioner producers to set up and shown the quality of the local product by demonstrating that it is cheaper than and just as efficient as a similar imported product.
Practical, low-cost pilot projects of this sort are absolutely right for the developing countries where phosphorous and carbonate rocks occur.
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