SAB Miller, South African grown, second largest brewer in the world has introduced anaerobic digestion to treat the waste leaving its Alrode Brewery in Gauteng, South Africa. Anaerobic fermentation of organic material produces methane, which is used to reduce the consumption of fossil fuel based energy.

Trappist Brewhouse

Copper brewhouse in a Trappist brewery

Brewery Waste & Biogas

In the brewery the waste is a collection of unavoidable losses of carbohydrate and protein rich materials, which would otherwise be sold as beer or byproduct and the large quantities of water used to maintain a hygienic operation.This waste is normally fed to standard industrial effluent treatment plants, either in the brewery or at the local authority, where physical and aerobic fermentation processes are used to remove the organic material. The cost of this treatment or the fee paid is directly related to the organic level and volume of the waste.

In the biogas recovery project the brewery’s effluent is treated by converting organic material into methane gas by means of the anaerobic digestion process. The anaerobic digestion process converts 90% of the 25 tons a day of organic material leaving the Alrode brewery in five million litres of effluent. This produces 9,000 m³ ( 320,000 cubic feet) of biogas containing 85% methane. The biogas is fed to a boiler where it is burnt to produce steam that is used to power the brewing process. The biogas saves the consumption of 10.4 tons per day of coal a saving of around R 7,000 ($1,000) a day.

At the same time there is a saving in effluent tariffs and costs as well as electricity which would otherwise have been used to power the activated sludge process.

Other Opportunities

Many industries in South Africa use anaerobic digesters in their waste water treatment but Alrode is the only of its kind to make optimal use of its biogas. This installation is likely to act as a model for other breweries in the group.

In South Africa food manufacturing is concentrated in the urban areas and the plants effluent is mainly, possibly with some pretreatment, discharged to the municipal sewers. With the increasing load on these systems and the national concern about South Africa’s water resources the tariffs charged by municipalities are certain to escalate in the short and medium term. This along with increases in energy costs is certain to increase the attractiveness of anaerobic effluent treatment both as a cost saver and a contribution to combatting global warming.

Biogas can be used to generate either electrical and/or thermal energy depending on the demands of each installation. It is also possible for electricity produced from biogas to be sold into the grid at a realistic price that will be determined by the second set of feed in tariffs about to be announced by NERSA (Mational Energy Regulator of South Africa).

This is the sixth in a series of posts that aim to provide information on the development of renewable energy in Sub-Saharan Africa and South Africa in particular. These are

Photo by Luca Galuzzi – in Wikimedia Commons under a Creative Commons license.