Mariannhill Landfill Conservancy

The Mariannhill Landfill currently receives 450 tonnes of general municipal waste per day from the Pinetown, Westville, Queensborough and Kloof areas, representing 15% of the e'Thekwini municipalities total waste. From inception the goal was to create a landfill that coexisted with the surrounding community and natural environment. Durban Solid Waste (DSW) held meetings with the community and various NGOs including the Wildlife and Environment Society of South Africa (WESSA) so that all concerns about creating a landfill in their area, could be listened to and addressed. The next step was to convince the City Council that the initial expenditure, which was more than a traditional landfill would be prudent. It was pointed out that the total cost of Mariannhill over its expected 25-year lifespan would not be higher than standard landfills. The Mariannhill landfill overturns the idea that landfills cannot be successfully managed and operated within an urban context whilst being environmentally sustainable. Urban landfills typically impact negatively on the welfare of surrounding communities, specifically letting off bad smells. This is not the case with Mariannhill.

Innovation

Using existing technology and an approach called a "closed loop system", Mariannhill is now much more than a landfill, it is in fact an ecosystem restoration project. A closed loop system is defined as one in which some or all of its output is used as its input. DSW achieved this by establishing five key initiatives, namely the Landfill Conservancy, Construction of Cells & Buffer Zones, the Plant Rescue Unit (PRUNIT), Leachate Treatment Plant, and the Gas to Electriciuty Plant.

    * The Landfill Conservancy

Population growth results in the loss of natural ecosystems, either through development, or through inappropriate land use. South Africa generates 40 million tons of solid waste per year and landfills will remain a part of waste management for a long time yet. It is for these reasons that Mariannhill places such importance on restoration because it is an essential tool for improving ecosystems, boosting biodiversity and increasing the connectivity in nature reserve networks.

    * Construction of Cells & Buffer Zones

The landfill consists of a number of pieces of land, or cells, used one at a time for the disposal of waste. When a cell has reached its capacity, it is closed up and another cell is dug up and prepared for waste disposal. A four-tier barrier system is in place to protect the soil and water table from leachate. The first consists of a stabilised sand layer with a geo-membrane (Flexible Poly Propylene) liner and a geo-grid. Secondly, a stabilised sand protection layer is then constructed on top of the liner. Crushed rock aggregate is then placed on this protection layer to facilitate the collection and removal of leachate. Fourthly, two low permeability clay layers, between which a layer of 19mm of stone is placed, are constructed below the system described previously.  The ‘sandwiched’ stone layer is a leachate leakage detection system, and provides further environmental protection. There is also a mandatory 200 metre buffer zone which separates the site from a surrounding middle-income area as well as a low-cost housing location. These buffer zones are filled with indigenous plants and trees.

    * Leachate Treatment Plant

The landfill has a full treatment plant for leachate, which is the contaminated liquid that seeps from waste when mixed with water or other liquids, causing standard landfills unpleasant smells. At Mariannhill the leachate is treated onsite at a biological treatment facility. Although the final discharge is not potable it is used as irrigation and dust control. Because the plant can treat up to 50 cubic metres of leachate daily, the load on the municipal sewer system is greatly reduced.

    * The Plant Rescue Unit (PRUNIT)

The value of the soil profile at the Mariannhill Landfill was identified early on during the conception of the conservancy creation plan.  The soil is a vital component to environmental equation that needed to be rescued for effective rehabilitation to take place. This lead to the creation of a large holding nursery for the storage of all indigenous vegetation, along with the surrounding soil, rescued from within the landfill. The plants grown and the top soil saved here are used to rehabilitate cells when they are filled. It is estimated that the plants have saved more than R2 million in rehabilitation costs.

    * Landfill Gas to Electricity

Once landfill cells have reached capacity, the extraction and treatment of harmful landfill gas takes place. Methane, a particularly harmful greenhouse gas is now harvested and converted to electricity on site. Initially the plant was capable of generating 1000 kilowatt hours of electricity which was enough to power 2000 households. It is hoped that eventually it will produce 10 Megawatts of electricity per year. The project is expected to bring in millions of Rands in revenue to Durban via the sale of electricity and carbon credits to industrialised countries.

Effectiveness

Mariannhill was the first landfill site, to be incorporated into an ecosystem restoration site and be a registered as a National Conservancy. The "closed loop" system and the maintenance of the indigenous ecosystem minimises biodiversity loss in the area. Environmentalists and organisations now approach landfill management to breed indigenous and endangered species. It is a rehabilitation area for the black-headed dwarf chameleon. It is the only landfill, arguably in the world that serves as an important natural corridor for species migration. Today the site has a bird hide and a conservation area with nature trails. Other services such as an educational component are thriving. Its educational Boma overlooking the landfill and the conservation area is used as an outdoor classroom, and hosts between 60 and 120 children each week. Topics include waste management, recycling, biodiversity and conservation. To date more than 2000 people have attended these lectures.

From a technological process perspective all units are operating beyond their initial expectation. The process of rehabilitating individual cells as they are filled, preserves all but the currently operating cell as green space. This minimises the impact of the site on area wildlife and makes it less noticeable to surrounding communities. PRUNIT has proven to be both environmentally and economically successful. It has provided the indigenous vegetation for the rehabilitation of both the cells and the buffer zones. The unit has also contributed to the remediation of several defunct landfill sites throughout the eThekwini Municipal area and saved more than R2 million in rehab costs.  The leachate treatment plant makes the landfill almost independent of city water supplies. The gas-to-electricity plant will ensure the financial viability of the entire project as well as provide a large section of Durban with electricity not derived from burning coal.

Poverty Impact

The Mariannhill project demonstrates that brown and green issues can be addressed holistically and feed off the strengths and weeknesses of the other over a duration of a project. Development is not mutually exclusive from sustainability. Even though the cost to initiate Mariannhill was higher than that of other landfills, initiatives such as the continuous rehabilitation of cells, the leachate control systems, and the gas-to-electricity plant contribute to significant short and long-term cost savings for the e’Thekwini Municipality. Money which would have needed to be spent on the rehabilitation of the landfill site at the end of its life span typically 25-30 years can be spent other social delivery programmes. The electicity generated from the landfill can potentially be distributed to people in low-income brackets and those who have yet to receive electricity from then national grid and Eskom. Over the long-term this project will certainly improve the lives of the poor and will make an even bigger impact if it is replicated in Durban and other parts of South Africa.

Sustainability

Landfill-gas-to-electricity generation is financial viable. This is due to the recent signing of the Host Country agreement by South Africa with the World Bank. After a meeting with the World Bank in 2002, the landfill implemented a Clean Development Mechanism (CDM) project specifically to convert gas to electricity. Under the CDM framework it is estimated that the Municipality will receive R50 million from the sale of carbon credits over the next 10 years.

Replication

Visits by municipal officials from around the country to Mariannhill are a sign that other municipalities are exploring the options presented by Mariannhill. Site Manager, John Parkin says that individuals have expressed immense interest, and there is now a group of people comprising residents, officials and representatives of NGOs who meet on a regular basis to discuss the landfill site. It shows that integrated landfill management is not only environmentally and economically viable but essential in order to reduce the impact on the environment to a minimum. The approach will certainly help reduce the harmful effects of traditional landfills and assist other municipalities to adopt similar approaches.

Partnerships

• World Bank

Visit www.durban.gov.za for more information