Solid Waste Management City and County Council of Honolulu

Hawaii is facing significant challenges in solid waste management as they have limited land and are isolated in the middle of the pacific ocean. The island need to manage the municipal waste disposal of more than 850,000 residents and more than six million visitors to the island each year. Currently Hawaii have 3 operating sanitary landfills and 1 incinerator on the island of Oahu. We visited one of the sanitary landfill which are the Waimanalo Gulch Landfill. The landfill is operated by a private company under the permit granted by the City Council. It is amazing as the landfill do not have any smell as what we expected it to be. The reason for this is because they choose a location which received minimum average volume of rain and they capture the methane gas which makes the smell produced by the sanitary landfill. The methane gas is sufficient to power thousand of home on the island and is used for generating electricity for the facility. The City Council owns the gas as it is their land and they planned to use it for an alternative energy source on the island. For now, they are still collecting the gas as they need a certain amount of gas before it can be used to generate electricity for the city to ensure sustainable supply. At the bottom of the sanitary landfill, they placed a high-density polyethalene plastic and they placed it on top of it after it is full to minimise the leakages into the water table underground. They also have a facility to capture all the leakages underground into a tank before sending it to the waste water treatment plant. An independent laboratory will conduct the groundwater test on a regular basis as required by the Health Department. All the roads at the sanitary landfills were built by the trash itself. The trash are buried underground, layer by layer and they use soil from various construction sites to cover the wastes. A compacter which cost about $800,000 is used to spread and squash the waste to ensure efficiency of space use.

After visiting the sanitary landfill, we went to the incinerator called HPOWER. It is owned by the state and the tax payers but is operated by a private company. Beside the facility, there are a coal power plant and the coal was imported from Malaysia. The HPOWER is built to burn trash and change it into energy to power the island. The main goal is to reduce the trash by 90%. However, the remaining 10% which is in the form of ash will be sent to the sanitary landfill. The facility converts 2,160 tons of waste per day into electricity to power more than 40,000 area homes and businesses. The facility utilises refuse-derived fuel technology. The waste is prepared and cleaned of non-processible and non-burnable materials through a series of conveyors, trommels and shredders. Waste is then combusted in furnaces at temperature of 982 degree celcius and reduced to an inert ash residue, which is significantly less than the original volume. Exhaust flue gasses are cleaned through a sophisticated pollution control system before reaching the stack. First, acid gases are neutralised and treated by a dry flue gas scrubber. Then the gases pass through an electrostatic precipitator where the micron-0sized dust particles are removed. As the cornerstone of the islands's integrated waste management system, the facility complements community recyling, waste reduction efforts, and landfilling. The facility recovers and recycles thousands of tons of ferrous and non-ferrous metal as part of its waste to energy process.