College of Science and Engineering at the University of Minnesota
College of Science and Engineering
http://cse.umn.edu/

Garbage Power

Yesterday, we visited the Vestforbraending Incineration Plant, which incinerates 20,000 to 50,000 tons of waste a week and turns it into electricity and district heat for nearly one sixth of the population of Denmark.

The Danes have realized that modern consumption habits generate an enormous amount of waste, and that even what we normally consider to be useless waste represents a valuable resource. The Vestforbraending station takes in the waste from 19 Danish communities, including parts of Copenhagen, separates out 29 different materials for recycling (paper, glass, various plastics, and various metals) and incinerates the rest. It's especially important to separate out the metals, both because they don't burn in the incinerator, instead just melting and clogging it up, but also because producing new metal from ore is an extremely energy-intensive task. Producing a single ton of aluminum requires mining 65 tons of bauxite ore, using various acid baths to reduce it to aluminum oxide, and running prodigious amounts of electrical current through the oxide to separate out the elemental aluminum. On the other hand, recycled aluminum can be simply melted down and recast, a much more energy-efficient process. To this end, the plant asks the citizens of its communities to sort as many of the recyclables out of their waste as possible before they're sent to the incinerator.

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Suiting up in safety gear for our site visit
The incinerator is capable of burning 70 tons of waste an hour in its two boilers, generating 36 MW of electricity to power the surrounding communities. By comparison, the HERC incinerator near Target Field in downtown Minneapolis only burns 50 tons an hour.

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Garbage goes in...
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And hot water and electricity come out!

In addition to generating electricity, the incineration plant also is a district heat plant, generating steam that is run through pipes to heat every building in the surrounding towns from a central source. District heat is also used in Minnesota in downtown Minneapolis and St. Paul, as well as many university campuses. District heat is used extensively in Denmark, with more than 62% of Danish homes using such a system. Incineration is one of the most versatile types of renewable power generation we'll be looking at on this trip. Next up is wind turbines!


 

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