Ecopolis Part 3: Waste

Episode three of Ecopolis deals with the waste from cities. Journalist Elizabeth Royte published her treatise on waste in 2005’s Garbage Land: On the Secret Trail of Trash. Royte takes an in depth look at our trash, where it goes and how it is handled. In the third installment of Ecopolis, four projects are considered as humans try to deal with the mounting rubbish we produce. Each day Americans generate 4.5lbs (2kg) of waste per person. One project Kammen reviewed uses the garbage to construct off-shore islands. A second proposal destroys waste using gas-plasma technology as seen in this YouTube clip. Another option Kammen considered is being implemented for the 2010 Winter Olympics. This proposal involves recovering heat from sewage through use of a heat exchanger.

Of the four projects, Kammen chose to focus on one that has its roots in an ancient Amazonian practice of burning organic waste in a low oxygen environment to produce terra petra (dark earth). Mixing the terra preta, or biochar, with the existing soil creates a rich, fertile substrate. Of the 100,000 tons of garbage produced each day, up to half is said to be organic matter, which could become fodder for producing biochar. The reason this proposal is so appealing is that the average American uses 24 acres of natural resources a day according to the video below. This over consumption of resources leads to the need for petroleum based fertilizers to replenish the soil. Producing biochar also has the added benefit of generating an energy rich gas as a byproduct. Burning the energy rich gas generates a source of renewable electricity, while waste heat recovered from the combustion of the organic material is used to dry the charcoal. As a further benefit, carbon can be sequestered in soil for the long term. With all of these features, the calculated cut in carbon dioxide emissions would be 21%.

Perhaps the most significant part of this proposal is the fact that all facets of the process represent energy savings and manifold benefits. In the future, it is essential that humans design systems that are interconnected and able to work in concert with each other. These systems save money and resources while providing jobs.

-Eric Wilson