Landfill Sites, Transfer Stations and Compost Plants

3.
Landfill Sites, Transfer Stations and Compost Plants

The CoCT operates four landfill sites (three general and one hazardous), two refuse transfer stations and two compost plants. Until 2004 six landfills were operational, but two had to close due to a fatal flaw on one of the facilities and the other due to lack of airspace. A fatal flaw is a risk posed by the landfill that no engineering can rectify or guarantee potential pollution to the surrounding environment. By 2013, a regional landfill site should be operational, as two further landfills would have closed by then.

Landfills as a disposal option of last resort has a place in any Integrated Waste Management strategy, but if not correctly operated, can be both environmentally destructive and economically wasteful. South Africa still disposes 90% of its waste in landfills. Despite increasing environmental legislation, waste disposal by landfill is still the cheapest form of disposal, but managing landfills properly can be both demanding and expensive. Two environmental concerns for landfill operators are leachate management and gas management, methane gas in particular. Although both have their negative effects, they could also prove to be beneficial if properly utilised. Leachate could be treated and used as a dust suppressant, whereas methane gas, although explosive, is a clean burning fuel source and could be harvested for energy or electricity.

Where landfills are located too far away for a collection vehicle to dispose of its waste, refuse transfer stations are established to reduce wear of the vehicle and it reduce travel distances. This will also enable the collection vehicles to complete its collection beat as well. The waste at the transfer stations are then fed onto a conveyor system, from where it goes into a hopper and then compacted into a closed container. These containers are then transported either via road network or rail infrastructure to the landfill. Where landfills are closer to the transfer station, road transport seems more economically viable, but when the landfill is a huge distance away, rail transport may be favourable. The break-even point between road vs rail is between 25-40km. Anything less than 25km implies road transport is better and anything over 40km implies rail to be favourable. It is useful to have both options available, in order for the transportation cost to be competitive. As landfill sites close, the need to construct a waste transfer station becomes greater. However, in line with the Polekwane Declaration and the National Waste Management Strategy (NWMS), waste needs to be minimised and all future transfer stations would need to have a waste minimisation component, be it a materials recovery facility (MRF), compost plant, rubble crushing operation, chipping of green waste, etc.

Composting can be defined as the biological decomposition of organic wastes under controlled aerobic conditions, and at elevated temperatures. Composting stabilizes degradable materials and reduces their volume, conserving landfill airspace and decreases the risk of pollution from landfill gas and leachate. By the end of the process, most of the original contents of the heap have been broken down and mixed together to produce a rich, healthy soil conditioner for the garden. There are many different options for composting. They include the use of windrows, forced aeration composting and mechanical composting systems. Trenching, worm composting and layering are more conventional home-composting methods. Ideal material to compost would be annual weeds, cut grass, leaves and soft prunings, most kitchen waste, newspapers, sawdust, horse and cow manure, rabbit droppings and seaweed. Avoid using tough perennial weeds, plants treated with weed-killer, prickly or hard prunings, cooked food, magazines and colour newsprint, dog and cat waste.

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Core Notes for Module 6 (Elective) of the Course
“Environmental Engineering – Sustainable Development in Coastal Areas”
Cape Peninsula University of Technology (CPUT)
Cape Town, South Africa
2006
Available to Distance Learners on www.dlist-benguela.org