This paper summarizes developments made in the field of waste-to-energy technology between the 1980s and the present. In the USA, many waste-to-energy systems were developed in the 1980s and early 1990s. These plants generated power relatively efficiently (typically 23%) in 60 bar/ 443 degrees C boilers. Unfortunately, the development came to a stop when the US Supreme Court rejected the practice of waste flow control in 1994. Consequently, waste was directed to mega-landfills, associated with very negative environmental impacts. However, given landfill taxes and increased fuel prices, new waste-to-energy projects have recently been developed. Attractive premiums for renewable power production from municipal waste have been introduced in several European countries. This triggered important innovations in the field of improved energy recovery. Examples of modern waste-to-energy plants are Brescia and Amsterdam with net efficiencies of 24 and 30%, respectively. Incineration is traditionally preferred in Japan due to space constraints. New legislation promoted ash melting or gasification to obtain improved ash quality. However, these processes reduce the efficiency in terms of energy, cost and availability. A new oxygen-enriched waste-to-energy system is under development in order to better achieve the required inert ash quality.

Waste-to-energy (WtE) plants are traditionally designed for clean and economical disposal of waste. Design for output on the other hand was the guideline when projecting the HRC (HoogRendement Centrale) block of Afval Energie Bedrijf Amsterdam. Since commissioning of the plant in 2007, operation has continuously improved. In December 2010, the block's running average subsidy efficiency for one year exceeded 30% for the first time. The plant can increase its efficiency even further by raising the steam temperature to 480°C. In addition, the plant throughput can be increased by 10% to reduce the total cost of ownership. In order to take these steps, good preparation is required in areas such as change in heat transfer in the boiler and the resulting higher temperature upstream of the super heaters. A solution was found in the form of combining measured data with a computational fluid dynamics (CFD) model. Suction and acoustic pyrometers are used to obtain a clear picture of the temperature distribution in the first boiler pass. With the help of the CFD model, the change in heat transfer and vertical temperature distribution was predicted. For the increased load, the temperature is increased by 100°C; this implies a higher heat transfer in the first and second boiler passes. Even though the new block was designed beyond state-of-the art in waste-to-energy technology, margins remain for pushing energy efficiency and economy even further.

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