More on Urban use of biochar

Looking past the unfortunate terminology describing biochar as "fertilizer", this article should be of interest for urban environments...

Chicago landscapers turn to ancient Amazonian fertilizer

... “It seemed like a beautifully ecological and non-chemical fertilizer,” Jacobs said. He had seen evidence that biochar improved agricultural productivity, but nothing for landscaping. “We took a leap of faith.” In the first year the honey locusts grew 24 inches, or about twice what Jacobs expected. Two years later, “They have continued to grow like... weeds,” he said.
Urban soils often lack carbon and struggle to sustain the diverse microbial communities that are essential to plant growth. Essentially charcoal, biochar is loaded with carbon and fosters microorganisms so well that it has been called a coral reef for soil.
Jacobs is quick to note that every site is different, and that his project isn’t a scientific study. But the cost difference is negligible, he said, and “something is making those trees grow better.” He now uses biochar in most of his downtown landscaping projects, as well as in his own garden. ...
http://www.wbez.org/blogs/chris-bentley/2013-06/chicago-landscapers-turn-ancient-amazonian-fertilizer-107645