Waste incineration is an old and established method for treating waste. But it has developed significantly since its inception. For those unfamiliar with this technology and those wishing to ‘brush up’ on some of the basics, this article is prepared as a primer on waste-to-energy (WTE) technology and its role in modern solid waste management. The focus is on developments in Europe, which act as a useful benchmark for global activity in this sector.
Now and the future
Despite a long tradition of incineration, the WTE industry today aims for a cyclic flow of resources. There is one objective for waste incineration in an ‘eco-cycle’ society – and that is energy recovery. Volume reduction is not an objective, though it remains an important parameter when comparing environmental impact. And incineration is only justified when the method is at least as favourable as other recycling or recovery alternatives.
The WTE industry in Europe is developing at a pace. Due to the EU goal to minimize landfilling and the EU Directives on Waste Incineration and Landfilling, many European countries have built (and are building new) WTE plants. They are also upgrading existing plants to meet the directives and requirements for the environmentally acceptable treatment of burnable waste. Most European countries plan to increase their incineration capacity, including those which do not have WTE plants. It should also be noted that, due to the EU Directive on Waste Incineration, a number of small plants will be closed down, as they cannot meet the directives at a reasonable cost.
Emission guidelines and flue gas cleaning systems
All Member States of the EU have to, at a minimum, comply with the Directives on Waste Incineration, but can have stricter limits. To meet the directives and national guidelines advanced flue gas cleaning systems have to be installed. The emission directives can be reached by using the best available technology and state-of-the-art cleaning techniques. Almost all incineration plants have some kind of advanced flue gas cleaning system and several have more than one.
Waste-to-energy and dioxins
While dioxins exist naturally in the environment, the man-made ones come from a variety of combustion processes, including power plants, cement kilns, diesel vehicles, buses, open fires, bonfires, barbeques, jet engines and forest fires. Emissions from WTE plants represent just a tiny fraction of such emissions.
In 1990 one third of all dioxin emissions in Germany came from WTE plants, but in 2000 the figure was less than 1.5%. Today it is even lower. In Europe the contribution of WTE plants to national dioxin emissions is 0.07%.
 Figure 1. The reduction in emissions of dioxins to the air from Swedish WTE plants, 1985–2006. Source: Avfall Sverige |
Figure 1 shows the comparisons between the amount of waste incinerated, energy produced and the dioxin emissions, for Swedish WTE plants between 1985 and 2006. The incinerated amount has been doubled, the energy production has been quadrupled, and the emissions have decreased by about 99%.
Waste-to-energy and climate change
WTE avoids CO2 and methane emissions from landfills. The application of the Landfill Directive in the EU Member States will reduce 74 million tonnes of equivalent CO2 emissions by 2016, according to the German Ministry of Environment.¹
WTE also contributes to climate protection through the substitution of fossil fuels as used by traditional power plants. Compared with traditional power stations (coal, oil and gas fired), CO2 emissions from WTE plants perform very favourably. Only gas fired power stations perform better than those WTE plants generating just electricity (a minority in Europe). The majority of WTE plants generate heat or combined heat and power and perform even better than gas fired power plants. Compared with coal and oil fired power stations all WTE plants (including the electricity only plants) emit less fossil CO2 – according to a report from Eunomia 2006.²
Energy from waste substitutes imported fossil fuels used by power plants. Currently, Europe’s WTE plants can supply 20 million people with electricity and 32 million with heat.
The technology is one of the most robust and effective alternative energy options to reduce CO2 emissions and to save limited fossil fuel resources. Professor Bilitewski et al calculated that the cost of avoiding one tonne of CO2 with WTE is between €7 and €20, whereas the cost of avoiding one tonne of CO2 with biomass is €80.3 WTE definitely has an important role to play in the efforts to move away from the dependence on fossil fuels.
Energy recovery
In almost every country with waste incineration plants there is some kind of energy recovery. In general, the Scandinavian countries use a high percentage of the recovered energy to produce hot water for district heating, whereas other countries mainly produce steam for electricity production, mostly without usage of the remaining energy, which has to be cooled off. However, there is a significant change towards the better use of produced heat outside Scandinavia, as well as a significant tendency in the Scandinavian countries for more combined production and use of heat as well as electricity.
Development and new technology
Much of the development takes place within already existing technologies, improving processes already in place. There are, to some extent, new technologies for flue gas cleaning, but even these are mostly adaptations of existing systems.
 A 10 m³ crane lifts waste into the feed chute. Source: Andreas Offesson |
Incineration on grates is still the dominant technology, with fluidized beds in different concepts as the alternative. Most of the WTE processes take place in large units and in large plants, but interesting installations with grates in small units and small plants have been introduced and operated in recent years. This small-scale technology can be of great interest to smaller cities, municipalities and for different industries.
For a long time efforts have been made to develop and introduce gasification and pyrolysis as methods for thermal treatment of waste, but with limited success so far.
WTE is an established and effective method for waste treatment and energy recovery. Due to far-reaching restrictions on landfilling of in many countries there will be an increased need for it, as a complement to recycling and biological treatment of waste. New plants will be equipped for using the produced energy for heating purposes as well as for electricity production.
Håkan Rylander is CEO of Sysav, past President ISWA 1996–98, Chairman ISWA Working Group Thermal Treatment and Deputy Chairman CEWEP.
e-mail: e-post@sysav.se
References
1. German Ministry of Environment: Waste Incineration – A Potential Danger? The contribution of waste management to sustainable development in Germany
2. Eunomia 2006: A changing climate for energy from waste
3. Documentation on waste-to-energy from CEWEP and ISWA Prof Bilitewski et al, EdDe-Dokumentation 10, 2005.
