Waste lives on in the landfill
It’s easy to think of waste buried in the Landfill as being ‘gone and forgotten’. Yet some waste hasn’t finished its lifecycle. Within the Landfill organic material such as food, paper, timber and clothing made from natural fibres, for example wool and cotton, undergoes a further process of transformation. Over time this waste breaks down into two main components – landfill gas and liquid (called leachate which is collected and treated). The Landfill gas is made up of several individual gases, but is mainly methane and carbon dioxide. Carbon dioxide occurs naturally in decomposition of all organic waste and is required by plants for their growth (photosynthesis). Methane, however, has a high potential impact on global warming if it escapes into the atmosphere.
That’s why at the Kate Valley Landfill as the waste is deposited and compacted a series of gas extraction wells are installed. All the wells are connected to a network of collection pipes. By applying a vacuum to the pipe network, gas is extracted from the Landfill in a controlled way rather than allowing the gas to escape into the atmosphere.
… The story doesn’t end there.
The gas extracted from the Landfill is mainly methane (50-60%) and carbon dioxide. At Kate Valley we’re committed to capture and destroy methane in line with New Zealand’s Emissions Trading Scheme. While burning the gases would destroy them, there’s a better option and that’s to use methane as a fuel to run internal combustion engines and produce renewable energy – electricity – the option we chose. That’s why we set up the Gareth James Energy Park at Kate Valley to turn an unwanted and dangerous waste by-product into a valuable renewable resource.