Fertiliser and electricity from a mall


By Liezl Vercueil | 7 March 2019
fertiliser
Photo: www.african-utility-week.com

The N1 City mall in South Africa’s Cape Town is pre-empting future regulation changes around the removal of organic waste from operating buildings to landfills by installing an anaerobic digester. Cape Town intends to reduce organic waste going to landfills by 100% by 2027.

Growthpoint Properties, which owns the shopping centre, is partnering with Dutch firm Waste Transformers to convert organic waste on site to produce fertiliser, hot water and electricity. “Landfills produce methane gas, which is worse for the environment than CO² emissions,” says Gavin Jones, Growthpoint Properties’ Regional Retail Asset Manager for the Western Cape Province.

The unit is made up of four large containers that occupies about seven parking bays. “Within our shopping centre environment, we collect organic waste material from restaurants and from food supermarket operators in separate bins and separate it from the recycled goods. We then process it in the first stage of the machine, which is the macerator which chops up the organic waste matter into a usable size. A grey water mix is added, and this mixture is then pumped into the anaerobic digester. With added enzymes, this digester pretty much functions like a stomach which produces methane gas as well as a by-product of hot water,” says Jones.

The hot water is used to clean the plant and waste areas, the methane is harvested, filtered and kept in the gas component and is used to power an electric generator that feeds electricity back to the mall. The liquid fertiliser produced by the digester will be used for landscaping by Growthpoint’s properties in the area, as well as by non-profit organisations, hospitals and the Parow golf course. “We have an end goal in mind to begin a micro enterprise to sell this fertiliser into the market.”

The installation’s capacity at present is about 6 kVA/day, which powers 10 to 11 small shops in the mall. “What’s exciting about this unit is that the generator runs the system by itself, so it is a self-sustained modulated system, it does not require an external power source for it to run. The main benefit of the system remains in the production of fertiliser, which is a sellable product which we can use in our own property portfolio and for external supply.”

A case study on the system will be presented at the 19th African Utility Week and Powergen conference at the CTICC in Cape Town in May 2019. The expo and conference take place from 14 to 16 May, while 17 May is set aside for site visits.

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