Pollution levels are modest and costs are not as high as opponents say.
Reading time: 5 minutes.
We the people and our activities generate a lot of:
Trash including food, paper and plastic waste
Defecate captured as sludge at wastewater treatment plants
Yard, landscaping and related green waste
Wood and textile based waste such as discarded home parts and furniture
Agricultural waste (bagasse, manure, dead animals and animal parts)
Used oils from frying pans and fryers to oil charges of cars, trucks and Navy ships
All this is trash and treasure at the same time. Almost any combination of the wastes listed above has a thermal content that is higher than lower grade coal such as lignite. There are dozens of plants in Australia, China, Germany, Greece and others that burn lignite to produce steam to spin turbines to generate electric power.
Burning trash is a very old idea for sanitation and volume reduction. Incinerators were developed in the early 1900s. By 1990 waste-to-energy (WtE) was a fully developed technology for combusting waste of all kinds and generate heat. Heat can be used directly to provide hot water to industry and homes, or as steam to generate electricity. A typical waste-to-energy plant generates about 500 to 600 kWh per ton of waste.
Waste to energy is a reliable and tested method for minimizing landfills, minimizing groundwater pollution and generating both energy and usable byproducts. Even the ash from the combustion process (bottom ash) and the flume (fly ash) can be used instead of cement and as an ingredient in road building and foundations.
Although municipal and agricultural waste is a renewable source of energy and a huge environmental problem, many environmentalists oppose WtE because it generates CO2, a greenhouse gas. Pollution from a WtE plant is similar or less than the pollution along a busy road. In other words, pollution levels are modest and WtE plants can be located near residential areas. Paris has a modern WtE plant within walking distance from Notre Dame. As shown in this schematic, a very large part of a WtE plant is pollution control.
Opponents also bring up cost. They say WtE plants are expensive whereas sun and wind is free. There is some truth to this. Honolulu’s H-Power third boiler rated at approximately 50 MW cost about $300 million. However, trash costs less than sun and wind. Here is why.
We pay $100 to buy a barrel of oil to burn it and make electric power. This is very costly.
We pay nothing to get a day of solar radiation. This is good but only part time and affected by clouds.
We get paid $100 to dispose one truckload of trash.
Do you see it now? The cost of trash to the WtE plant is minus $100.
As a result, the long term economy of WtE plants is very good. There is plenty fuel (trash, waste and biomass). Municipalities pay the WtE plant to take their trash. The utility pays the WtE plant for the mega-watts of electricity it produces. Trash volume reduces 6 to 10 times so landfill demand is minimized.
What does all this mean for Hawaii? Firstly kudos to Mayor Fasi for starting H-Power on Oahu, and to mayor Hannemann for doubling its capability.
Sweden imports waste from other Europe to fuel its WtE program. Maui should install a WtE plant and bring in trash from Big Island, Lanai and Molokai. Oahu should plan for another 100 MW of WtE (about half of it tuned to burn biomass, sludge and manure) and bring in trash from Kauai. Barges return to Honolulu from Kauai practically empty.
Both Oahu and Maui should consider ordering a sophisticated MRF, or Materials Recovery Facility, to better sort materials such as glass (by color), stones and similar inert materials, and all types of metals out of the trash. This would result in a cleaner burn at the WtE plant and revenue from recyclables, e.g., mixed glass is nearly worthless but glass sorted by color has value. So do sorted metals.
To make Oahu more sustainable we should revise what we currently trash and what we recycle at home in the BLACK, GREEN and BLUE bins, as in this slideshow.
About the author:Panos Prevedouros is a University of Hawaii professor whose areas of expertise include transportation engineering, traffic analysis and simulation, demand forecasting, and intelligent transportation systems. He has twice run for Honolulu mayor.
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