Windhoek brewery installs biomass boiler

The country’s major brewer, Namibia Breweries (NBL), has invested NAD 53 million (USD 3.3 million) in a biomass boiler at its Windhoek plant.

The boiler, which was imported from Austria where wood-fuelled heating systems are fairly common, will allow the brewery to replace 80 percent of the 3600 tonnes of heavy fuel currently being used per year with wood chips available in abundance in Namibia.

NBL’s Windhoek brewery has a capacity of 3 million hl. The plan is to use 7500 tonnes of wood chips per year to replace 3100 tonnes of oil.

When the plant was commissioned it was with a view to reduce costs, as then the price of oil was fairly high. Since then the price has plummeted which will extend NBL’s return on investment. However, the investment in biomass technology was primarily driven by NBL’s commitment to reducing its carbon footprint, as the new boiler will deliver about 8000 tonnes reduction in carbon emissions per year, it was reported.

The wood chips are produced from invader bush which grows in abundance on the farms surrounding Windhoek. Farmers are more than glad to see the bush go, especially at no cost to them, as it limits their cattle grazing areas. Wood harvesting is done by an O&L subsidiary Organic Energy Solutions, which has bought the necessary machinery to harvest invader bush.

NBL also reports that the biomass boiler is capable of burning the spend grain from the brewery. The spend grain is first de-watered in a special screwpress to about 60 percent moisture and then mixed with the wood chips at a maximum ratio of 20 percent.

Although the spend grain is fairly moist and thus has a low colorific value, it is still cost effective to burn the spend grain, as at the moment there is no demand in Namibia for it. Burning spend grain in isolation is a challenge due to the high moisture content, but blending it with the wood chips makes it a viable option. NBL thinks it is an ideal solution to use the brewery’s waste as a fuel source which generates heat energy and reduces the overall carbon footprint of the brewery by to up to 40 percent.

Another challenge of the new biomass boiler was matching the supply of heat energy to the fluctuating energy demands of a brewery. Especially the brewing process has a fluctuation heating demand, which represents a bit of a test to a biomass boiler as it tends to react slowly when increasing or reducing the output. NBL overcame this problem with the help of inline buffer vessels, which can release additional heat energy when a spike occurs.

Great care was taken in the sizing of the biomass boiler. In the past, many biomass boilers failed because they were oversized and could not operate under partial or low load conditions. NBL’s biomass boiler is sized to operate at 80 percent of its load during most times, thus reaching thermal efficiencies of 93 percent, NBL says. When the biomass boiler together with the buffers is not capable of supplying the required heating demand, as it can happen, the heavy fuel boiler is activated. Thanks to this configuration a continuous and optimal running efficiency of the biomass boiler can be achieved.

The biomass project was started last June and was up and running when I visited the brewery on 27 May 2016.