Posts Tagged ‘composting’

The Magical World of Composting

by | September 10th, 2010

Here’s something to ponder when you’re sitting there, stuck in traffic. What does the Zoo do with all that animal poop? Do we bury it or ship it overseas? Or do we simply flush it? Hey, there isn’t a toilet big enough for that job! The answer? We make soil out if it! The Oakland Zoo’s on-site composting program, which has been underway for several years now, successfully diverts tons of waste from landfills and provides us with a valuable new resource: organic compost!

The Raw Material

It’s a big job, but here’s how we do it: Manure from elephants, giraffes, zebras and other herbivores, along with straw (soiled animal bedding) is collected daily around the Zoo. Included with this are scraps of fruit and vegetables, eggshells and other items discarded from the animal kitchens. It takes several truck loads.

Inside the Scrapper

Everything would be much simpler if it wasn’t for the straw. It makes up a huge percentage of our compostable material—somewhere in the neighborhood of ninety percent! Early on, this was causing us problems, as we discovered that straw is much slower to decompose than manure. So the Scrapper was brought in to the rescue. The Scrapper is a six-foot long bin with rotating blades that chew up the straw into smaller, more easily digestible bits—sort of like the way your teeth help out your stomach by breaking down the food in your mouth before you swallow it.

The Ag-Bag Machine

Once this is done, the material is ready to be sent to the composting machine. Visualize a giant mechanical sausage-stuffer and you’ll get the idea. Using a small Bobcat tractor, we dump this chopped material into the hopper of the machine (also known as the Ag-Bag.)  Here, it’s mixed with a special liquid to accelerate the breakdown process. Then, a hydraulic compression ram stuffs the mixture into a tube-like plastic bag (imagine a long trash bag open at both ends.) The Ag-Bag machine has wheels which allow it to be pulled slowly along the ground by the Bobcat, as it leaves the filled portion of the bag behind it, like a tail. A plastic hose is attached to the far end of the bag through which air is pumped, providing circulation. Later, the bag is fitted with a series of small vents to release the waste gases that are produced.

Bags Soaking up the Sun

For several weeks, this bag continues to be filled until it reaches a length of about 75 feet. Then, the end is sealed and a new bag is started alongside. These long gray bags sit in the sun, allowing the mixture inside to heat up. When it gets to a temperature of 130-150 degrees Fahrenheit, pathogens are destroyed. During the following months, the material breaks down, gradually becoming less like straw and manure, and more like soil. It’s basically the same process that has created topsoil for the earth for millions of years! After three or four months, the bags are opened.

The finished product is an incredibly rich, 100% organic compound that amends the soil and allows our horticulture department to grow healthy and beautiful plants throughout the zoo grounds.

But don’t think that you have to be a zoo in order to participate in the composting process. Anyone can start their own compost pile right at home. It’s very simple. Just alternate layers of waste produce with dried leaves, cover it up and let the worms do the rest. In fact, I’ve been doing that very thing for years now, using this compost to enrich the vegetable garden in my backyard. It’s good to know that nothing goes to waste—it’s all part of the ongoing cycle of life!