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Evaluation of the Biomethane potential of different types of organic wastes in Cape Town

Objectives

This was an exploratory study, involving both sample collection at points of waste generation, and laboratory work, generously hosted by CeBER. The main objective was to develop an understanding of the range of organic wastes available in Cape Town, and what their key properties are if they are to be considered for energy recovery via anaerobic digestion. A secondary objective was to learn how to do biomethane characterizations in the laboratory. Experiments were done in 100 ml serum bottles.

Students and Staff Involved

Gracia Munganga, Rethabile Melamu, Harro von Blottnitz

Project Partners

Funded by the Solid Waste Department, City of Cape Town. Support from Saliem Haider and Noel Johanneson

Publications

“Biomethane potential of 17 different types of organic wastes disposed in or with municipal solid waste in Cape Town”; Munganga, G., R. Melamu and H. von Blottnitz, for the City of Cape Town, 2010.

“Experimental investigation of the suitability of various organic fractions of municipal solid waste for energy recovery through biomethanation”; Munganga, G., R. Melamu, H. von Blottnitz and M. Nontangana; WasteCon2010, 4-8 October 2010, Johannesburg, ISBN: 978-1-920017-49-1.

Main Lessons Learnt

There are many different types of organic waste!
The waste left at the end of the dirty MRF at the Athlone Refuse Transfer Station contains much more than organics – but it’s fine, food and green components are all suitable for anaerobic digestion.
Carbon to nitrogen ratio is important in AD, esp. if there is too much nitrogen, AD is inhibited.
For experimental work, the ratio of inoculum to susbstrate must be sufficiently high, otherwise the experiment goes sour and produces suboptimal methane quantities.

Follow Up Work

Gracia Munganga selected food waste and abattoir waste for further characterization of behavior in anaerobic digestion, with fed-batch reactors at the 2 litre scale.