Use of Biogas From Brewery Waste Water:a Case Study of Kenya Breweries Limited

Abstract

Rising global challenges of energy generation, especially green energy, sustainability and cost, has triggered immense research on alternative energy sources and technologies in the current times. Energy costs represent a significant expense in beer brewing industry, and it is in a company’s best interest to minimize these costs. In the year 2015 Kenya Breweries Limited total energy cost was Ksh.1020.69Million. Kenya Breweries Limited utilizes an anaerobic waste water treatment which produces biogas as a by-product and flared up because it has no use at the moment. This project focused on estimating the volume of biogas flared up at Kenya Breweries Limited waste water treatment plant and its viability as an alternative source of fuel for boilers. Data was collected at the effluent treatment plant during waste water treatment and the boiler plant during steam production. The data was analysed using flow duration curve method. Values at 50% confidence levels were obtained and used to estimate the volume of biogas produced in a day after waste water treatment. The study revealed that at optimum conditions and 50% confidence levels, loading the UASB digester with a COD load of 19,761kg/day, an estimated biogas volume of 9,973m3/day containing Methane gas of volume 6,383m3/day was produced. The methane gas produced can run the boilers for only 3.4 hours per day to produce estimated steam of 57.6tonnes, while HFO can run the boilers for the next 19 hours to produce an estimated steam of 316.2tonnes. By using methane gas for 3.4 hours in a day, 4,250litres of Heavy Fuel Oil can be saved, which amounts to Ksh. 63,750,000.00 savings in one year. The study demonstrated that boiler burner modification would be the most cost-effective method of using the flared biogas. To adopt the power saving/ recovery strategy, it was observed that the existing boiler burner need to be replaced by a dual fuel rotary cup burner, preferably type SKVGD Saacke. Other system modifications would include modification of the existing bio-filter to act as a water scrubber, installation of a compressor (type GG 90 VSD (50/60 Hz) for compressing gas for storage, and installation of Varec Biogas 245Automatic Drip Tap to remove Condensate or water vapor along the gas pipes.