On Monday, we had a guest speaker come and talk to the class about mining waste and how to effectively use all components when mining. We learned that while mining, usually only 50% can be used as slabs, were you need to find alternative uses for the other 50%. This alternative methods include artificial reefs, furniture components, but mostly being used as crushed material for civil engineering (i.e. foundation layers) and in ceramic and glass industries. The guest speaker talked about different methods of extracting various chemicals, and the efficiency of each methods. He also had a very deep voice and reminded me of my freshman humanities teacher!
The next day, we woke up bright and early to go to a Serdiana Landfill. This landfill has gone through quite the transformation since 2006 when it was denied the permit to continue accepting organic waste from the city. Now, only one landfill in Sardinia accepts organic waste. This landfill mainly accepts ash and bottom ash from incinerators. Since the 1990's, this landfill started extracting the biogas when it was still receiving MSW (one of the first landfills in Italy to do so). The electricity extracted from the biogas generates 3 MW. In their landfills, they have both horizontal and vertical gas collection vents.
This picture above shows the leachate collection tanks, which collects the horizontal drainage system that is gravity feed from the landfill. This leachate is then sent to a waste water treatment plant.
Here is a image of their current landfills. Because there is no organic waste, they will not be extracting biogas for electricity from this landfill. However, in their landfills that do extract biogas, they have 1 pump for the 3 biogas producing landfills. Within this system, there is a back up flare to burn off the methane gas. The landfill has a control system to measure the biogas to check the chemical composition.
This is another view of their one active landfill. They are actually building this landfill on top of a closed MSW landfill. They do not have to cover this landfill daily though because there is no smell or odor to attract birds.
Picture of the tractor moving and placing the ash.
One and half miles away, there is the biogas converter. The pipes that run from the landfill are steel above ground, and PVC underground. The picture above shows the water vapor being separated from the biogas in a heat exchanger (the water will condense at the bottom). The gas is then sent directly to produce electricity from the excess heat. All the electricity generated is sold to the grid. Since they didn't receive the permit to continue accepting MSW, they built a solar farm.
A little shout out to my next co-op for designing the system that converts the biogas to electricity!
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