Waste to Energy — What Can We Learn From the Dutch?
The Netherlands has a reputation for being progressive, from the environment to social initiatives. About twice the size of New Jersey, a large proportion of its landmass is below sea level. Protected (at least for the moment) by an elaborate system of dikes, the country is a center of creativity, efficiency, and diversity. It’s a place that is open-minded and broad thinking on everything from social programs to wind energy. A recent trip to Amsterdam also unveiled it is equally creative with its approach to waste management and water reclamation.
Waste management in the Netherlands is tricky. With limited land area available to landfill, conventional waste is either incinerated to produce energy or exported elsewhere for disposal. In the way of waste-to-energy (W2E), Amsterdam has created an incredibly efficient Afval Energie Bedrijf (AEB) plant capable of producing 1 million MWh of electricity annually. Beyond the energy factor, the plant is also being used to create district heating for several communities around Amsterdam, and produces 300,000 gigajoules of heat annually.
It gets better. Right next door to the W2E plant is the Waternet water treatment plant . The two plants work symbiotically: the incineration plant supplies energy and heat for water treatment processes; the water treatment plant injects its sludge and biogas into the incineration plant as an additional fuel source. In one narrow corridor of industrial landscape, Amsterdam manages a large chunk of its municipal functions.
The process looks like this: annually, 1.4 million tons of waste is brought to the W2E plant. This amounts to 600 trucks and 1 freight train per day of refuse from the Amsterdam metropolitan area. The trash is deposited into a large sorting room where it is sifted and put into the incineration process. When trash is burnt, the heat is used to boil water. The superheated steam from this process is used to turn several turbines to generate electricity. Aware of the environmental effects of the gasses from this process, the Dutch have installed a complex process of scrubbing the flue gasses. It starts with an E-filter to separate the fly-ash. Next, gas passes through a fabric filter to remove other residues before being passed to an economizer.
The gas then passes through a series of other scrubbers to remove harmful gasses and particulates so they do not become airborne: an HCl scrubber yields calcium-chloride, SO2 scrubber produces gypsum, and a polishing scrubber takes out much of the remaining water vapor.
For many of these byproducts, attempts are being made to close the loop so the material can be used in other industrial processes—from trace elements for manufacturing, to fly ash for construction. Whatever material is left becomes landfill.
By the time the gas makes it out the flue, what remains is mostly water vapor and clean flue gas. Any other emissions are monitored, and so far have been kept well within Dutch legal limits. Dioxin from the incineration process is captured and safely disposed.
Attention to carbon emissions has been a special focus of the W2E plant and its designers. As the plant performs several functions (elimination of waste, generation of electricity and heat) simultaneously, it stacks up positively to other disposal methods, actually avoiding 438 kilotons of CO2 per year. Because of these combined processes, the process reduces the net amount of carbon going into the atmosphere.
As an alternative scenario, if the same 1 million tons of waste were put in landfill, the amount of equivalent CO2 emissions per year would be 1036 kilotons. This would mainly be as a result of methane gasses developing at the landfill. If these gasses were either captured or burned off, it would reduce the total emissions to 404 kilotons—still a fairly large amount.
The efficiency of the W2E plant is a major positive factor in the equation. If waste across the European Union were handled in a similar fashion, engineers estimate that W2E plants could generate 8% of the total EU electrical production by burning 182 megatons of waste, and in the process avoiding 200 million tons of CO2 per year. It would also free up large amounts of land for other purposes, as from the U.K. to eastern Europe, landfill is unfortunately still the disposal method of choice.
The benefits of the W2E plant are compounded when you plug the Waternet plant into the equation. Waternet handles waste water for 1 million population equivalents, and sludge (e.g. effluents from toilets etc.) for another 2 million population equivalents per year.
The water treatment concept uses biological methods rather than chemical ones to remove phosphate and nitrogen from the water. Sludge digestion means that energy recovery from biogas is possible in the deep aeration tanks. This biogas is currently being used at the W2E plant, to provide gas to the natural gas grid, and also to power a small pilot fleet of 120 biogas vehicles. Annually, Waternet digester gas production equates to 7.5 million cubic meters of natural gas, enough for 5000 households and 3500 cars.
By looking holistically at the processes, services, inputs, and outputs of both the W2E and Waternet plants, the Dutch have come up with an elegant solution to many complex problems. There’s been a clear attempt to close the loop on byproducts, whether it be flue gas particles or biogas from water reclamation. Careful integration of both waste and water management processes has yielded many efficiencies and benefits that would not be possible under other conventional, stand alone systems. With this attention to detail and maximizing benefits across the board, both Afval Energie Bedrijf W2E and Waternet stand as excellent examples of what can be achieved with some careful infrastructure planning.
One would hope in the future that Dutch officials would spend equal time and attention to reducing the amount of “waste” that is produced to begin with, and give more emphasis to reduction, elimination, recycling, and composting initiatives.
By Chris Tobias, appearing courtesy of Celsias.
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