What an interesting link! I assume you thought I would like it because my coop is in my garden bed?
My husband and I are composters. My husband has a bumper sticker that says "Compost Happens!"
In a nutshell that's about adding granite dust to your garden soil. As a soil amendment like lime. Can also put some in the animal feed. You can get it at a gravel operation (quarry) where it's a by product of gravel crushing. Back up your pickup truck and they'll say, take it we don't want it. (Not all gravel operations crush granite rock)
Granite = volcanic. Many trace minerals from deep in the earth that the soil microorganisms feast on. Organic soil is a living, fermenting "brew" same as your compost pile. Depending on a region's rainfall these trace minerals get washed down and out of the reach of plant roots over thousands of years.
A study from 1942 showed higher protein wheat from dry West Kansas than from wetter East Kansas. All had to do with trace minerals and calcium in the soil. Trace minerals were more intact in West Kansas soils with it's lower precipitation over thousands of years meaning fewer trace minerals washed away.
http://www.soilandhealth.org/01aglibrary/010143albpap/010143csiro.htm