An innovative solution to extend the lifespan of Devon Valley Landfill Site

Submitted by: Nadia Shah, Wednesday, February 18, 2015

Stellenbosch Local Municipality have commissioned a pilot project which aims to extend the lifespan of their landfill site, Devon Valley Landfill Site, by diverting building rubble and clay stockpiles onsite to manufacture environmentally friendly building blocks. Over the next year this will potentially result in the freeing up of five percent of the landfill’s capacity.

The challenge

The Devon Valley Landfill Site consists of three cells where waste is filled in and compacted. The first two cells were built in the mid-1960’s and are full. The third cell, commissioned in April 2013, spans five hectares with a maximum height of 135 metres above mean sea level.  This cell has already reached 40% of its 600,000m3 capacity. According to Saliem Haider, the Manager of Solid Waste Management at Stellenbosch Local Municipality, this creates a significant challenge since there is no new landfill airspace in Stellenbosch. “If a new landfill site were to be established it would be at least 50kms away which would have huge cost implications,” explained Haider.

In line with Stellenbosch Local Municipality’s strategic objective to be “The Innovation Capital of South Africa”, in 2014 the municipality advertised a tender for service providers interested in implementing a creative solution to extend the lifespan of Devon Valley Landfill Site by beneficiating the excess builders’ rubble and clay onsite .

The solution

This is only one of many innovative solutions under review, including a landfill gas to energy project, the treatment of informal sector organic waste, and, a waste to food project. Selecting the best solution required an understanding of the waste streams present. Haider highlighted the importance of undertaking a waste characterisation study and stated that the data generated played an invaluable role in informing the way forward. The studies revealed that building rubble made up 25-30% of the waste disposed at Devon Valley Landfill Site. Based on this finding, the bid was awarded to USE-IT, an NGO which specialises in projects which promote waste diversion and job creation. USE-IT proposed using the building rubble and clay stockpiles onsite to manufacture compressed earth blocks which are an environmentally friendly alternative to conventional cement blocks. Not only do compressed earth blocks promote the diversion of waste, they are also cheaper and yield a higher compression strength compared to concrete blocks. In addition, due to their thermal insulative capacity they result in energy savings as the homes built will be kept warmer in winter and cooler in summer.

It is envisioned that this pilot project will produce 480,000 compressed earth blocks over a 12 month period, which can be used to build  the equivalent of 160 homes. In effect the project will free up five percent of Devon Valley Landfill Site’s capacity. According to Haider, the pilot project has huge potential, “There is enough material on site to construct 22 million blocks (8,000 houses equivalent), over a 15 year period, so a three to four year extension is possible with just this initiative in place.”

The way forward

The success of the pilot project is likely to determine the way forward. Stellenbosch Local Municipality are also interested in investigating other options for waste beneficiation, as mentioned previously.  “This project will only take care of a certain component of the waste stream. There is no one-stop shop in waste treatment technologies, and each one will have its rightful place – some are just more expensive than others,” explained Haider. Haider notes that Stellenbosch Local Municipality hopes to set an example that will inspire other South African municipalities to adopt innovative approaches to waste management, “There are tremendous opportunities, but it requires vision, drive and support from both the public and private sector,” he said.

For more information on USE-IT’s compressed earth blocks, visit the USE-IT website

To keep updated with sustainability news subscribe to the fortnightly Urban Earth Newsletter.