SUPPLYING THE PFUNDA TEA FACTORY.

Economic study

Some figures

In these evaluations, the following energy equivalents are assumed :
- PCI of a M3 of methane = 34 000 Kj
- PCI of a litre of fuel oil = 42 000 Kj
- I litre of fuel equals 1.25 Nm3 of methane (Nm" at 0°C and at atmospheric pressure)
- 1 MNm3 of methane = 800 tep (tonne equivalent petrol)

The calorific energy of wood (generally eucalyptus in Rwanda) is more difficult to estimate. According to what has been written, the weight/volume ratio for a cubic metre (stere) of wood varies between 300kg per stere and 500 kg per stere. We believe that a value of about 350 kg/stere is close to reality.

The PCI of wood will amount to 15 000 Kj/kg. The comparison between wood and gas on the level of energy works out at : 1 stere of wood is equivalent to 150 Nm3 of gas - that is about 5 GJ.
Prices in Rwanda in August 2004 were as follows :
- 1 stere of wood = 5 000 FRW, that is 7.15 euros or US$8.6
- 1 litre of fuel oil = 350 FRW, that is 0.5 euros or US$0.6 (1 euro = 700 FRW = US$1.2)

Comparison of the price of wood and the price of fuel oil in energy terms
- Fuel oil : 1 GJ = 12 euros = US$14
- Wood : 1 GJ = 1.36 euros = US$1.65

Note that the price of fuel oil is currently 8 or 9 times higher than wood, a fact which cannot be discounted in looking at the economic reality of the country : it would be difficult for methane to be cost competitive with wood. Methane would however be exceptionally competitive as a substitute for fuel oil.

Prices given above may vary considerably with time. One can foresee a continuous exponential increase in the price of wood with the decrease in reserves and the increase in need. On the other hand it is difficult to foresee the future concerning the price of fuel oil (a barrel of oil cost around US$ 45 at the beginning of September 2004)

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Evaluation of energy needs of the Pfunda tea factory

Tea production is a seasonal occupation : so production at the Pfunda factory varies throughout the year. Energy consumption shows this clearly, with a peak in March (178% of the monthly average) and a low point in August (32% of the monthly average). The capacity for supplying methane should thus be calculated on the period when most wood is used. Currently, during March, in the middle of the rainy season, wood consumption for drying the tea is about 20 steres per day.
Thus the methane extraction unit should be proportioned so as to supply 20x150 = 3000 Nm3 of methane a day, that is about 1.1 MNm3 of gas per year. The present management of Pfunda have told us that there are plans for the tea drying plant to expand in the coming years. We envisage the setting up of an extraction station with a capacity of 1.5 MNm3 of methane, thus replacing the use of 27 steres of wood per day during the rainy season.

Due to the wide variation in tea production over a year (see figure below) there will be a surplus of methane available during the dry season. This gas could be sold by UPEGAZ to Bralirwa, replacing fuel oil (in current conditions which is 90%of the price of fuel oil, equivalent PCI)
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Annual wood consumption of wood by Pfunda was of about 4300 steres in 2003. This quantity would take the equivalent of 650 000 Nm3 of methane, thus leaving an excess of 950 000 Nm3 of gas, the equivalent of 760 000 litres of fuel oil.

Figures for wood consumption 2004 - 2009 are even higher, because provisions envisage 5800 steres of wood per year (which would correspond to a maximum consumption of 27 steres per day). Thus the quantity of methane which could be sold to Bralirwa would be 730 000 Nm3 per year, the equivalent of 585 000 litres of fuel oil.

Calculating on the basis of the present price of fuel oil of 0.5 euros a litre and taking into account the reduction of 90% compared to fuel oil, the sale to Bralirwa would bring UPEGAZ : - in the present situation 760 000 x 0.5 X 0.9 = 342 000 euros a year; - in the hypothesis of expansion : 585 x 0.5 x 0.9 = 263 000 euros a year.

Furthermore, for other parts of the production process, the Pfunda factory uses about 1 950 000 KWh of electricity per year (information obtained from the management in October 2003, with an average consumption of 1 500 000 KWh in 2002 for tea production of 1 020 tonnes and an electricity bill of 63 M FRW, or US$ 105 000), a consumption unequallty spread over the year. The factory also has a 450 Kva generator which goes into service during power cuts or when the grid is not available, (periods which account for 2 or 3 % of the time in 2003 (and probably much more at present, in a period of electricity shortage). This amount of energy corresponds to an additional consumption of about 58 000 KWh by the generator and a fuel oil consumption of about 1.7 M FRW or US$ 2 800.
One can thus suggest adding further value to the project by integrating a gas powered electricity generator, the factory thus profiting from the advent of cheap fuel. This could be accomplished - either by transforming the diesel generator into one powered by gas (at a cost of between US$ 50 000 and 60 000 if it were done on site) - or by installing a new 300 KW generator (which could moreover be equipped with a heat retrieval system, usable for preheating the boiler) - and by conserving as a back up the link to the grid (to which excess capacity could moreover be sold, on the condition that a legal arrangement for this reselling could be found during the feasible limits of the project).
The consumption of gas for a 450 KW generator (or 300 KW if new) to supply electricity to the factory would be about 25 000 GJ or 750 000 Nm3 per year.

Technical project for substituting methane for wood

Extraction of methane from Lake Kivu.
The process of extracting gas from the deep waters of Lake Kivu, then the enrichment of the methane has been treated elsewhere (cf. Data Environment Report "Exploitation of Lake Kivu's methane : pilot station project", June 2003°. A synthesis is included as an Appendix. A preliminary study was done for an extraction plant of a size able to produce 1.5 MNm3 per year. Compared with the previously studied pilot station, which had a capacity of 3.5 to 4 MNm3 per year, the proposed project would allow us to validate our calculations and to determine parameters which remain uncertain.
Remember that our previous experiments at Lake Nyos in Cameroon never used an extraction column with a larger diameter than 140 mm.
The pilot station proposed in the 2003 document foresees a diameter of 440 mm. The diameter of the Pfunda station column will be 280 mm, which would act as a 'half-way house', always desirable in a largely unexplored technical field.

Transport of gas from Cape Rubona to the Pfunda factory

The methane extraction plant will be a site chosen offshore from Cape rubona, about 1.5 km from the banks.