Durban’s closed loop landill site

I recently wrote this case study about the Mariannhill Landfill Conservancy in KwaZulu-Natal, South Africafor UN Habitat’s 2012 report “Urban Patterns for a Green Economy: Optimizing Infrastructure”.

About 450 tons of waste arrives daily at the Mariannhill Landfill Site, 20 kilometres from Durban, South Africa. Far from an ecological hazard, this CDM project sets new standards for sustainable urban infrastructure by combining natural, robust and low-cost technologies.

The end result might not have been as positive without the dedication of the Mariannhill community, who set up a monitoring committee after discovering the city’s intent to establish a landfill in the area (Winn 2008). Their persistent concern about the ecological impact motivated the engineers at Durban Solid Waste (DSW) and the environmental department at the eThekwini Municipality to pursue a more sustainable design (Parkin 2011). These engineers are equally deserving of praise; they acknowledged the problems associated with conventional landfills, and were open to trying new methods to prevent environmental degradation (Parkin 2011).

The project began with an Environmental Impact Assessment, the first landfill in South Africa to undergo such a study (Parkin 2011). It found a need to restore local ecosystem functioning, minimise the loss of biodiversity, and connect the site to other nature reserves to support natural migration patterns (Strachan 2007). The Mariannhill landfill had to be designed to prevent environmental contamination, and restore damaged areas (Harvard Kennedy School 2006). The key aims of the project were to collect and treat harmful landfill emissions using natural, robust and low-cost methods, and to rescue soil and indigenous vegetation removed during construction and store it in a nursery on site (Strachan 2007). Other objectives were to help mitigate climate change by reducing greenhouse gas emissions, and to provide an income to the city through the sale of electricity and carbon credits generated from the captured methane (SAGoodNews 2007).

The design of the Mariannhill landfill thus included three core aspects:

  • The ‘naturalistic’ containment, treatment and reuse of leachate

Conventional landfill design is responsible for leachate, a liquid waste that can become toxic and contaminate land and water (Strachan 2007). In collaboration with Enviros UK, DSW designed a treatment system whereby the cells of the Mariannhill landfill are lined with a geomembrane that prevents the escape of leachate, while above the lining a layer of rock and sand allows it to drain off and be collected in a reservoir (Strachan 2007). Here 30m3 are treated by aeration and settlement daily, before being passed through a reedbed (Taylor 2009, Kadalie 2011). This ‘polished’ leachate is reused for on-site irrigation (Taylor 2009). In addition, constructed wetlands help to remove toxic material (Moodley 2007). This closed-loop approach means that environmental contamination by toxic leachate is prevented, and water and energy costs of piped council water are significantly reduced.

  • The capture of landfill gas for electricity generation

Traditional landfills are also responsible for significant methane emissions, ten times as potent as carbon dioxide in their global warming effect. The Mariannhill landfill, however, turns this hazardous waste product into a resource by using the methane to generate between 450,000 kWh and 650,000 kWh of electricity per month (Wright 2011). Monthly power sales are approximately R200,000 at a power purchase tariff of between R0.24/kWh (off-peak) and R0.36/kWh (peak) (Wright 2011). Income from the sale of Certified Emission Reductions (CERs) has not yet been received due to the lengthy CDM process, but about R40 million worth of CERs have been destroyed since 2007 by the 1MW Mariannhill and 6.5MW Bisasar Road plants together (Strachan & Pass 2010, Wright 2011). The capital cost of the combined gas-to-electricity project has been approximately R130 million, with operational costs of about R10 million per year (Wright 2011). These have been partly covered by a R58.74 million loan from the French Development Bank, and a R17.7 million donation from the South African Department of Trade and Industry (SAGoodNews 2007).

  • The protection and restoration of indigenous vegetation

The restoration of the original vegetation to closed cells and border areas of the site is another example of how the Mariannhill design surpasses that of conventional landfills (Harvard Kennedy School 2006). Where existing vegetation is usually destroyed during construction, the Mariannhill design included an onsite nursery called the Plant Rescue Unit (PRUNIT), to save displaced indigenous plants. PRUNIT now also provides low-cost rehabilitation to other closed dumps in the area (Strachan 2007). The saving and propagation of indigenous vegetation supports local biodiversity, and has also provided jobs for people previously unemployed. PRUNIT has also saved the municipality more than R3 million on new plants (Kadalie 2011). It was the community’s monitoring committee who convinced DSW to start a plant rescue process in 1998 (Winn 2008). The committee also worked towards registering the site as a national conservancy, which was achieved in 2002 – a world first for an operational landfill (Strachan 2007).

Contribution to urban sustainability

The Mariannhill Landfill Site is a significant contributor to urban sustainability. Dependence on fossil fuels and greenhouse gas emissions are reduced by the generation of electricity from landfill gas, the supply of indigenous plants by the on-site nursery, and the re-use of water cleaned biologically on site. Local biodiversity is protected by the restoration of indigenous vegetation, the removal of alien plants, and the creation of wetlands and migration corridors. Economic sustainability is improved by the sale of electricity and carbon credits as well as the cost savings associated with on-site landfill rehabilitation and reuse of water. The creation of employment, realisation of skills development opportunities, and effective education programme each contribute to social sustainability.

The Mariannhill Landfill Site is regularly evaluated for effectiveness. It is audited twice a year to retain its permit to operate, and the Conservancies Organisation frequently assesses whether the site should retain its status as a conservancy. The gas-to-electricity project at the landfill is also audited annually to produce mandatory CDM Monitoring Reports.

The landmark nature of the Mariannhill Landfill Site meant that there were significant obstacles along the way. Municipal bureaucracy and the obligations of the Municipal Finance Management Act (MFMA) impaired the design team’s ability to find innovative solutions and required time-consuming reports (Parkin 2011). The MFMA was a particular constraint on the development of the CDM project and on the sale of carbon credits (Strachan & Pass 2010). The rate at which the World Bank’s Prototype Carbon Fund agreed to buy the Emission Reductions was in retrospect too low to make the project financially sustainable, and the UN’s CDM compliance process was also “exhausting” (Wright 2011). A lack of financial sustainability also saw the Materials Recovery Facility at the landfill closing in November 2010 (Parkin 2011). Finally, South Africa continues to lack technical skills required to design and maintain landfills as well as gas-to-electricity plants (Wright 2011).

Despite these obstacles and disappointments, a committed and enduring management team and a dedicated monitoring committee have meant that the Mariannhill Landfill Site has achieved its key aims (Garner 2009, Parkin 2011). A willingness from the municipal engineers to think outside the box, and persevere despite the ‘red tape’ have been vital to the project’s success. Perhaps Mariannhill’s greatest value is the model it has provided for other landfills to build upon, such as Bisasar Road, a much more successful site in terms of its gas-to-electricity production (Wright 2011).

While the technical aspects of the Mariannhill Landfill Site are easily replicable, it might be more difficult to find a management team and community group as willing to push through bureaucratic barriers (Garner 2009). From this case study, it is clear that managerial commitment and a community-driven demand for accountability are critical to the success of sustainable urban infrastructure.

Bibliography

Garner, E. (2009) An Assessment of Waste Management Practices in South Africa: A Case Study of Mariannhill Landfill Site, eThekwini Municipality. Master’s thesis. University of KwaZulu-Natal, South Africa.

Havard Kennedy School. (2006) Mariannhill Landfill Conservancy. Available: http://www.innovations.harvard.edu/awards.html?id=42981. Accessed online: 12 July 2011.

Kadalie, R. 2011. Mariannhill – a dump with a massive difference. The New Age. Available: http://thenewage.co.za/blogdetail.aspx?mid=186&blog_id=961. Accessed online 22 July 2011.

Moodley, S. (2007) Turning a landfill into an asset. Delivery (11) 70-71. String Communication, Cape Town.

Parkin, J. (2011) Email to N. Mayer. Re: Mariannhill Landfill Conservancy – Case study questions. 12 July 2011.

SA Good News. (2007)Durban launches Africa’s first landfill gas to electricity project. Available: http://www.sagoodnews.co.za/environment/durban_launches_africas_first_landfill_gas_to_electricity_project.html. Accessed online: 12 July 2011.

Strachan, L. (2005) Grid connected Renewable Energy Projects – Case Study: Durban (eThekwini) Landfill. Available: http://www.cityenergy.org.za/files/resources/re/case_ethekwini.pdf. Accessed online: 18 July 2011.

Strachan, L.  (2007) Mariannhill Landfill Conservancy – A ‘Closed Loop’ Design. Available: http://www.durban.gov.za/durban/services/cleansing/gastoelec/fill. Accessed online: 12 July 2011.

Strachan, L. & Pass, J. (2010) Ch. 18: Energy from waste: An overview of Africa’s first landfill gas to energy Clean Development Mechanism projects. From The Waste Revolution Handbook. Pp130-135. Durban, South Africa.

Taylor, Y. (2009) Toxic Landfill sites! Perhaps not… Available: http://www.earthorganization.org/articles/Library/Toxic_landfill_sites_perhaps_not/default.aspx. Accessed online: 12 July 2011.

Winn, R. (2008) Mariannhill Landfill Conservancy: History. Available: http://www.landfillconservancies.com/mlc_history.htm. Accessed online: 15 July 2011.

Wright, M. (2011) Phone interview with eThekwini’s gas-to-electricity Project Manager, Marc Wright, by the author. Cape Town, 22 July 2011.

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