From the Pipeline: Protecting the environment

There are people who talk about the environment and its protection and there are those who do something about it. One of the least environmental hazards talked about is household waste and its impact on citizens and their environment. We seem to take this lightly since in most cities rubbish is collected and we often do not care about what happens next.

The city of Vienna is one of those that has decided to do things differently. First it has encouraged citizens to think that it is in their best interest to cooperate with the municipality and segregate household waste in such a way that recyclable materials are collected separately.

Therefore, paper, for instance, is collected separately and Austria prides itself on recycling 70 per cent of the paper it uses.

Similarly, glass bottles, plastics and metals are also collected separately for recycling. Even some biological waste, such as grass cuttings from gardens, is used locally for compost.

All these activities are not only good by themselves but are also meant to reduce the total volume of household waste and the cost associated with its collection and treatment. This, eventually, will reduce the taxes paid by households for that purpose.

Vienna has also decided to go one step farther. Instead of dumping household waste in landfills and suffer the associated risks involved in this operation, such as leaching into waterways and methane emissions from decomposition, Vienna opted to use household waste for incineration and energy generation. There are two plants in Vienna for this purpose that make money for the city.

One of them is Spitelau, close to the famous and beautiful city centre, close to some of the buildings of Vienna University and two kilometres from the largest hospital in the city.

It is a tourist attraction and visitors are encouraged to visit the plant, specially decorated by the famous Austrian artist Friedensreich Hundertwasser. The other plant is Flotzersteig, on the western edge of the city. In 2003, the two plants incinerated about 476 thousand tonnes of household waste collected and delivered by 97,000 truck loads where 450 trucks work for five days a week and eight hours a day.

Combustion chamber

The incineration process is simple and straight forward. The waste in Spitelau is tipped by the trucks into a 7,000 cubic metre bunker, where it is mixed mechanically by huge hydraulic tongs and fed directly to the combustion chamber to be burned at more than 800 degrees Celsius.

The hot flue gases are passed through waste heat boilers to generate high pressure steam for power generation or hot water to supply the district heating network of Vienna, which covers most of the city with 980 kilometres of pipes.

he flue gases are then passed through electrostatic precipitators and water scrubbers and finally reheated and passed through a catalytic converter to get rid of nitrogen oxides and dioxins before discharge to the atmosphere. The emissions are continuously monitored to be in line with the Austrian Clean Air Act.

The slag from the combustion process is passed close to magnets to recover ferrous metals and then transported for use in concrete. The waste water from scrubbing is treated back to river quality and the filter cake generated is used for filling disused salt mines in Germany.

The story is not complete unless we consider industrial waste as well. This consists of the sludge of sewage treatment, waste industrial oils, waste paints, animal meal and fat, waste solvents, contaminated soils, polluted metals and plastics as well as unsorted expired medications and other similarly hazardous materials, such as small household batteries.

Special hospital waste is also treated after delivery in special and sealed combustible containers. These wastes are also incinerated for the purpose of protecting the environment and heat recovery for power or hot-water generation.

The delivery is usually made by special tank trucks or drums, where the liquids are stored for sampling in tanks.

The wastes are then fed to rotary kilns and burned at temperatures close to 1,200 degrees Celsius. The flue gases are passed through waste heat recovery boilers and so on as in the household waste treatment plants. The sludge of the sewage treatment plant is pumped directly from the nearby plant for dewatering first before incineration.

This operation is conducted in a special plant built for the purpose in Simmeringer Haide on the outskirts of Vienna. In 2003, the plant processed more than 100,000 tonnes of industrial waste in addition to the equivalent of 455,000 tonnes of dry matter from the sewage treatment.

The plant also receives waste from other European countries for incineration and can also burn household waste if necessary.

Though the three plants belong to the municipality of Vienna they do operate in a commercial way where the city pays a rate per tonne of waste and the industry pays for each tonne of treated waste.

The average rate is close to 350 euros per tonne and the range is 50 to 1,250 euros per tonne depending on the nature and delivery method of the waste. The treatment of waste is sometimes more expensive than the original fresh material.

The plants get the rest of their revenues from the sale of electric power or hot water for the district heating.

In 2003, the heat recovered from incineration in the three plants amounted to 841 GWh where three quarters came from the two household waste incineration plants.

New technology

This amount is equivalent to the heat from burning about 340,000 tonnes of extra light fuel oil and the city may have saved close to 185 million euros in the process. With today's oil prices, the saving must be much higher.

We have to remember that these plants supply only 20 per cent of the annual heating load in Vienna and the rest comes from normal power generation or hot-water plants and, therefore, they are used as base load plants working regularly throughout the year.

The purpose of writing this column is not only to pay tribute to Vienna where I lived for eight years while working for Opec, but also intended to generate interest in our own (Middle East) region to the potential use of waste as a resource in addition to the protection of the environment.

It is true that many areas here are close to the desert and landfills may be cheap. However, environmental hazards still exist, and the economy of power generation from waste is quite feasible.

One or two plants strategically located here may generate power and water for an ever expanding demand for both.

Following the commercial example of Vienna might even convince the Mideast private sector to invest in this industry which should also be given maximum incentives by the authorities. There are unforeseen or unintended savings as well. A better environment will reduce the healthcare bill, create more jobs and transfer a new technology to the region.

The writer is the former head of the Energy Studies Department at the Opec Secretariat and is working as an adviser.