35 



seem to be so harmful as in the case of certain other species of bamboo. Two 

 important points however, require to be cleared up, namely : (1) Is there any 

 season of the year in which felling should be prohibited ? and (2) How long 

 will the bamboo take to re-stock a clear-felled area completely and to reach 

 its original size, vigour and density? These two questions can be answered 

 only by carrying out careful experiments. As regards (1), I would 

 suggest clear-felling a number of test plots at different seasons, say, in March, 

 June, September and December, and observing the results. As regards (2), 

 clear-felled plots in different localities should be kept under observation until 

 reliable results are obtained. Meanwhile, if a bamboo concession is given 

 out, clear- felling should be permitted on a rotation of not less than 10 years 

 until it is proved that a shorter rotation will have no harmful effect on the 

 bamboos, when the rotation may be reduced. 



42. FUEL. For a pulp factory in Kenya Colony wood fuel will have to 

 to be relied on. For the manufacture of 1 ton of air-dry pulp the consump - 

 tion of wood fuel may be estimated at 4 tons, of which \ ton would be required 

 for lime-burning. 



In the case of eucalyptus plantations in a favourable locality, one acre 

 clear-felled may be estimated to produce 160 tons of dry fuel if worked as 

 coppice on a rotation of 15 years, giving 10-6 tons per acre per annum. Thus 

 a factory producing 20,000 tons of air-dry pulp a year will require 7,547, or, 

 say, 7,600 acres of eucalyptus plantation of good quality, a correspondingly 

 larger area of plantation of poorer quality, and a much larger area of natural 

 forest. Of the 7,600 acres, about 950 acres would be required for fuel for 

 lime-burning. Although some of the bamboo tracts have considerable areas 

 of natural forest near them, it is doubtful if these could satisfy fuel require- 

 ments for more than a limited period of time; for permanent requirements 

 the establishment of eucalyptus plantations in close proximity to the factory 

 will be an essential item in the scheme of working. 



Under present conditions the cost of fuel may be roughly estimated at 

 16s. per ton delivered at the factory, that is,- 3 4s. per ton of air-dry pulp : 

 of this, 8s. would be absorbed by lime-burning and 2 16s. by factory and 

 other combustion. When plantations conveniently situated come under 

 regular working it should be possible to reduce the cost. 



43. CHEMICALS. The chief chemical processes used in the manufac- 

 ture of paper pulp are : 



(1) The sulphite process, employing bi-sulphite of lime and SO^ 

 gas. The production of liquor is less costly than in the other processes, 

 but bleaching is more difficult, and SOg may prove too volatile for use. 

 in Africa. 



(2) The soda process, employing caustic soda (sodium hydroxide, 

 NaOH). Recovery of spent liquors is possible to the extent of 80 to 90 

 per cent. The process is satisfactory, but expensive, and the bleach 

 consumption is high. 



(3) The sulphate process. A modification of (2) with sulphate of 

 soda used in the recovery of spent liquors : the active constituents are 

 NaOH and Na 2 S (sodium sulphide). According to Raitt it is cheaper 

 than the soda process, and is the best method for bamboo, both in cost 

 and in quality of pulp. It has the disadvantage of giving off a disagree- 

 able smell of sulphuretted hydrogen. 



The two raw products required are soda and lime, the quantities required 

 for 1 ton of unbleached air-dried pulp being approximately : 



Soda 5 cwt. of Magadi quality. 



Limestone 1 ton, equivalent to \ ton of lime after it is burnt. 



[243466] DA 



