Composting shortcuts lure rats

Carrie Sturrock By Carrie Sturrock The Oregonian
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on February 19, 2010 at 2:00 AM, updated February 24, 2010 at 1:39 PM
compostor_9.JPGHealthy compost happens with the right proportions of debris.
My worst composting fear came true:

Rats in the composter. They actually chewed through the black plastic Earth Machine I bought from Metro.

At first I didn't want to believe it, although I am well aware that rats have adapted to urban life and thrive in cities.

When my husband noticed the side vents of the composter gnawed clean through, I e-mailed Carl Grimm, Metro's natural gardening specialist, and asked if mice, a much more tolerable rodent, had teeth strong enough to chew through plastic. After all, a mouse had scurried from the compost bin in December.

Nope. You've got rats, he told me.

Could it be a raccoon? I asked hopefully.

Not likely.

Gross. So gross, I initially thought, that's it for me and composting. I'm done.

Composting had offered some feeling of redemption in the form of my own tiny carbon offset. I might drive my car around spewing CO2 , but at least my carrot peels rot in my own backyard instead of in a landfill, where they release potent greenhouse gases.

I had been careful, too, not to put in any grains, grease, dairy or meat. What I wasn't careful about is what likely attracted the rats, I've learned from composting veterans.

I was lazy. Rarely did I take the time to shred or cut up kitchen scraps, and I didn't think anything of dumping in a whole pumpkin or half a cantaloupe rind. It takes much longer for big fruits and vegetables to break down and makes the compost more alluring to rats. Rodents don't just dig meat and dairy; they scavenge smelly, half-rotted fruits and vegetables, too.

Also, I did what Grimm warns against: the "dump and run." I would only occasionally stir the compost or poke holes in it with a pitchfork to get oxygen in there to help break down materials faster.

And finally, I rarely mixed twigs, leaves or wood shavings -- the "browns" needed for a healthy compost stew -- except for once in late fall when I raked my front yard. As a general rule, a healthy compost pile needs two parts brown matter for every bucket of green -- which means kitchen scraps or grass. The brown keeps the compost light and fluffy so it doesn't turn into a dense, gooey, smelly anaerobic mass. (To further speed composting, add spring garden soil, bone meal, blood meal or fireplace ashes on the pile.)

"It really is important to follow the basic simple rules of composting," Grimm said. "Chopping and mixing browns and (nitrogen-rich) greens and maintaining the moisture as damp as a wrung-out sponge. If you don't chop it up, it can get smelly."

So, how often do rats chew through Earth Machines? Rarely, I learned.

Chris Roberts, a public health vector specialist with Multnomah County, says if they do get in it's mostly by tunneling under the composters when people haven't purchased the companion floor grate. I purchased that floor grate, which means I guess I'm just lucky. (The No. 1 reason people have rats? The seed from bird feeders. Composting without the floor grate is No. 2.)

The county provides free home inspections as well as free box traps that prevent house pets and other animals from getting hurt. The catch is that you have to dispose of the dead rat yourself, clean the trap and re-bait it. Cheaper than hiring an exterminator, which can cost from $80 to $200 for an initial visit, but much, much grosser.

Roberts came to my house and inspected my chewed-into compost machine, which I haven't dumped fresh scraps in since we first suspected rats. Even though my husband had just stirred it two days before and there was no new food in it, the rats had recently visited. Roberts pointed out a burrow in the compost and a path through the dark mass as well as a gnawed walnut shell.

I asked if he minded giving the compost a quick stir to see if anything ran out. He kindly did. Nothing moved.

What if I just stopped composting for a while? Would the rats go away and forget about my composter?

No, he said. Rats are smart and they remember.

He told the story of one Portlander who found rats outside his bird feeder. The man got rid of the bird feeder. The next week he saw them in his compost. He got rid of the composter. After that he found them feeding in his garden, something rats won't typically do because freshly growing food isn't as fragrant. If the man had trapped them or hired someone to trap them, the problem wouldn't have escalated.

Roberts basically said it's my responsibility to deal with the rats so they don't bother me anymore and don't go elsewhere. Then he offered me one of those box traps. I wilted.

Later, as I sat in my living room staring at the trap and trying to picture myself coolly releasing a squished rat into a garbage bag, I realized I might as well imagine leaping a tall building in a single bound. That's when I decided to spend the money to hire an exterminator.

I'm going to give composting another go because clearly I wasn't doing it correctly, and secondly I like it, except for the rat part. The first step is to rid my yard of rodents.

Then, I have to decide whether I'm going to get a new Earth Machine (the replacement barrel is $15) and line the vents with metal mesh or get one of those round, above-ground barrel composters. I made a lot more work for myself by taking a cavalier attitude toward composting.

"Things are always a little more complex than we think they are," Grimm told me.

How true.
- Carrie Sturrock