The original factory, designed and constructed by Fletcher and Stewart, had a rated milling capacity of 80 tons of cane per hour (tch) which translated to 45,000 tons of sugar per year. The first bag of sugar rolled from the conveyor line on July 1, 1973, just one year after the Factory was constructed. The Factory had provision for expansion of its crushing capacity to 125 tch (75,000 tons of sugar per year). It was originally intended to implement this expansion during the 1978/79 financial year but owing to the Company’s good performance, the Government brought forward the expansion program to 1975/76. Milling at 125 tch rate began in July, 1976.
Improved Factory performance encouraged the Government to consider further Factory expansion to between 170 tch and 300 tch. Following a decision to expand it to 300 tch, there was need to construct a new Factory to meet the new demand. In August, 1976 contracts for the supply of equipment and construction of the Factory were signed and Government approval obtained during the 1979/80 financial year. Factory construction was completed in early 1985 giving Mumias a potential capacity of 210,000 tons of sugar per year. The construction was financed mainly by loans from the Commonwealth Development Corporation amounting to 3.25 million sterling pounds and a further 19,720,000 million sterling pounds from the National Westminster Bank Limited.
The new Factory design capacity was reached and surpassed for the first time in 1986/87. From then on, production stabilized at between 210,000 and 220,000 tons of cane per year. Production increased every year save for a brief interruption in 1982 when low cane yields affected cane supply until 1986/87 when the situation improved. During the first year of sugar production in 1973, Mumias produced a total 20,891 tons from 194,217 tons of mill cane.