Wide World of Composting

Hello compost fans! I’m Pete Moss, at a backyard in the Greater Vancouver Regional District with nutrient cyclist Rhoda Dendron. How are you feeling about your chances of breaking down an apple core?

Fabulous, Pete. The key will be the performance of my microbes, particularly the bacteria. I’ve got billions of these little single-celled, sphere–, rod–, and spiral-shaped guys from all over. They’ve trained for eons to evolve enzymes that break down just about anything organic.

Great. Looks like you’ve got a wonderful venue.

Absolutely. This shiny black plastic bin is big enough to keep in heat, but not too big for good ventilation. Most municipalities distribute them at a subsidized price. I added wire mesh underneath to keep the rodents out. Invertebrates, like worms, can still get in to help break things down.

Great. Now let’s go to footage of you setting things up a few months ago.

Well, Pete here I’m adding the apple core and other kitchen scraps, like celery tops, coffee grounds and egg shells. They’re called greens, even though they’re not all green. My bacteria use the nitrogen to build the proteins needed for their growth.

You didn’t include any meat, fish, dairy or greasy cooked stuff.

The fats smell bad and attract rodents.

All right. Next you added some soil and then covered them with dried leaves.

The soil adds microbe reinforcements. The leaves are called browns, leftover from the fall. They provide carbon, the main fuel for my bacteria. Covering greens with browns also helps absorb smells, balance the moisture, and smother fly eggs.

Great. Now to the compost cam, for a close-up of the action in the first period. I see the bacteria are cloning themselves!

That’s right Pete. They reproduce through binary fission. With a proper balance of carbon, nitrogen, air and moisture, they can put up big numbers in no time. When things are cooler, the psychrophilic (cool loving) bacteria are in control. They can survive down to - 20C, but do their best work around 13C. Their activity generated heat, setting the stage for another team.

And who would that be?

From 0 to 40C, the mesophilic (medium temperature loving) bacteria dominated. I mixed the pile once a week to keep them aerated. If we run out of oxygen, anaerobic bacteria take over and cause a stink. We don’t want that.

Understandable. Then things just got hotter, didn’t they?

We were really on our game and when it got over 40C, the thermophilic (hot loving) bacteria squad took over. They can really break down stuff fast. At these temperatures, even weed seeds and plant diseases get killed off, but you can’t always count on them to work.

Amazing. But it looks like your hot lovers couldn’t keep it up.

Eventually it got too hot even for them. When they died off, things cooled down. Sometimes they run out of food. Either way, the mesophiles pick up the ball again.

Then you brought in specialty teams?

Right. Moulds and other fungi got into the action. As well, the actinomycetes, who are between fungi and bacteria, help break down cellulose. They give off the “earthy” smelling geosmin.

Okay. Now how about we check on that apple core you put in a few months ago. It’s completely broken down into humus. You must be very pleased.

That’ll help keep the soil in my garden moist, aerated and fertile. and you know, the satisfaction is not just recycling the nutrients of an apple core, but knowing I’m helping cut down on the garbage trucked to landfills.

Great work, Rhoda. Well, I’m afraid that’s all the time we have today. Tune in next time when we look at worm composting as a 2010 demonstration sport. This is Pete Moss, saying, “Think dirty.”