Page 38 - Energize February 2021

TECHNICAL

Figure 5: Food waste is sorted by hand at the Bayside small plant. 5

hot water and fertiliser, at its N1 City Mall property (Figure 6).
The Waste Transformers unit is a modular structure comprising
four large containers which run several processes and occupies
about six or seven parking bays onsite. Table 4 shows the
performance of the unit.
The unit is currently running at a level of approximately 6 kVA
which is sufficient to power ten small shops in the mall. Organic
waste material is collected from restaurants and from food
supermarket operators in separate bins. After final sorting it is fed
into the first stage of the machine, the macerator, which reduces
the organic waste matter into a size suitable for the digestor. A
grey water and enzyme mix is added, and this mixture is then Figure 6: Food waste biodigester at NI City Mall (NI City Mall)
pumped into the anaerobic digestor.
The methane gas is harvested, filtered, and housed in the gas
component of the installation. This gas is then used to run an 3. GP Jordaan: “Evaluating the sustainable potential of biogas
electric generator which feeds electricity into the shopping centre generation in South Africa”, MSc Thesis, Stellenbosch
grid. The last product of the system is a liquid fertiliser and is University, 2018.
distributed for landscaping at all of properties in the company 4. R Zhang, et al: “Characterization of food waste as feedstock for
portfolio in the area, and to many non-profit organisations and anaerobic digestion”, Bioresource Technology 98, 2007
hospitals as well as to the Parow golf course. n 5. M Vice: “Bayside mall sustainability”, African Utility Week,
2016, https://d1jbg4la8qhw2x.cloudfront.net/wp-
References content/uploads/2016/05/Michael-Vice-.pdf
1. Averda:“South Africa wastes 10-million tonnes of food every 6. K Paritosh, et al: "Food Waste to Energy: An Overview of
year”, Averda.co.za, November 2019. Sustainable Approaches for Food Waste Management and
2. CJ Banks, S Heaven, Y Zhang, and U Baier: “Food waste Nutrient Recycling", BioMed Research international, 2017.
digestion: Anaerobic Digestion of Food Waste for a Circular
Economy”, . IEA Bioenergy Task 37, 2018. Send your comments to rogerl@nowmedia.co.za

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