Electric pigs use sun for dry cleaning

According to UPI, robotic 'pigs' drive German drying plants. These electrical pigs, which look like child-sized Volkswagen Beetles, have only one task to perform: clean the 60 million tons of sewage sludge produced every year in Germany alone. Using solar energy to dry mud, these robots are environmentally friendly and cost-effective.

According to UPI, robotic 'pigs' drive German drying plants. These electrical pigs, which look like child-sized Volkswagen Beetles, have only one task to perform: clean the 60 million tons of sewage sludge produced every year in Germany alone. Using solar energy to dry mud, these robots are environmentally friendly and cost-effective. There are currently 100 of them in use around the world, and more are being installed every month.

Here is the introduction of the UPI story.

Some 100 electrical pigs [built by German company Thermo-System GmbH] are operating all over the world: Each is named and works day and night to reduce sewer sludge disposal costs and protect the environment.
Based in Filderstadt near Stuttgart, Thermo-System was founded in 1997 by four up-and-coming scientists from the University of Hohenheim, after the students developed a cost-effective and environmentally friendly solar drying process, which may solve waste disposal problems of sewage plants all over in the world.

These 'pigs' are also known as electric 'moles' and look like Volkswagen Beetles, as you can see on the picture below (Credit: Thermo-System GmbH).

Electric mole when clean

And here is a picture of the Electric Mole at work in the mud (Credit: Thermo-System GmbH).

Electric mole at work

So how does such a 'pig' work?

Conventional drying processes burn up non-renewable energy, but Thermo-System harvests the sun's infinite resources to dry the mud.
The sludge absorbs the heat from the solar rays, and an innovative ventilation system based on sensors and microprocessors keeps the air inside the shed warm and dry. In comes the electrical pig, a fully automated robot. With its mixing tools, it turns over and aerates the microbiologically highly active sludge and thus accelerates the drying process and helps prevent rotting. The whole system works fully automatically, uses up very little energy and can be easily maintained.

And are solar drying plants a good investment?

"Germany alone produces roughly 60 million tons of sewage sludge per year," [Tilo Conrad, the company's founder,] sitting in his spacious office in an industrial district building in Filderstadt-Bernhausen, told United Press International. "Given the fact that it costs between 75 and 100 euros to get rid of 1 ton, communities can save a considerable amount of money."

Compared to these costs of several billions euros, these solar drying systems don't look expensive.

A small sludge drying system starts at roughly $180,000; the biggest, which can cover a city of 300,000, costs roughly $1.8 million. The company has sold plants to more than 60 locations in Germany, France, Brazil, Australia and Austria.

For more information about these technologies, here are two links to a description of the Electric Mole (PDF format, 4 pages, 918 KB) and a brochure describing the Solar Drying of Sludge (PDF format, 10 pages, 951 KB).

Sources: Stefan Nicola, UPI, March 11, 2006; and Thermo-System web site

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