Category Archives: Environment

Why I don’t use compost from the city in my vegetable garden.

Here's what hidden pesticides in city compost can do to your tomato plants.

Here’s what hidden pesticides in city compost can do to your tomato plants. Why risk it?

I was recently copied on an email to a community garden regarding the safety of city compost. The email pretty much said “Don’t worry, the city says that the compost is OMRI (the Organic Review Materials Institute) approved, therefore it’s safe.”

But it turns out that OMRI doesn’t require testing for herbicides or pesticides! So you could have city compost with nasty stuff in it, even though it has passed all OMRI requirements.

And this isn’t hypothetical problem: a quick search of the internet turns up a number of incidents where nasty persistent chemicals, both pesticides and herbicides, have been found in city compost and have caused big problems for backyard gardeners. Persistent chemicals are ones that survive the composting process and remain in the soil for years.

I found a very relevant article on the topic that shares important information and perspective:

When you think about it, it’s not surprising that city compost contains these products. Practically every garden store has a full assortment of herbicides and pesticides, and people buy them and use them. Even if vegetable gardeners are less likely to use them, you’ve got the lawn industry, which is probably 100 to 1000 times larger than the vegetable gardening industry.

All of this yard waste, and the chemical residue on them, go into the collection bin, which goes into the shared city compost. Many of these chemicals are not broken down by the composting process, and they can go on to cause terrible problems for the vegetable gardener.

It’s critical to understand, as well, that OMRI doesn’t require testing for pesticides:

The nonprofit Organic Materials Review Institute, which reviews organic inputs, requires approved composts to be tested for heavy metals and pathogens every five years. The US Composting Council operates a voluntary accreditation program in which the largest participants must submit to similar metals and pathogen tests once a month. Neither program requires testing for pesticide residues.

So unless we see 3rd party tests on Recology compost for persistent herbicides and pesticides, that show at what ppb (parts per billion) they were detected, then we have to assume they’re present and that they could cause a problem. I imagine that there is a standard ppb threshold at which the presence of a pesticide becomes a concern.

This is NOT a hypothetical concern! From Mother Jones:

Composting Council executive director Stuart Buckner believes that the EPA still hasn’t learned its lesson from the early aughts, when the herbicide Clopyralid was banned for lawn use after turning up in damaging levels in compost.

Here’s a study of what Clopyralid does to plants:

pesticide clopyralid 3 pics

To me it’s just common sense: given where the raw materials comes from, I assume that city compost contains harmful pesticides and herbicides, unless proven otherwise. Why take the very real risk on city compost, when you can make your own compost from known good materials?

Worm Composting: Learnings from the First Two Years

It’s been over two years since I bought a worm bag, and then subsequently made one of my own. Here’s what I wish someone had shared with me two years ago.

Pay Attention to Moisture

Moisture balance is one of the key aspects of having happy worms. This is the genius of having a warm bag instead of a plastic worm bin. The bag really does breathe in a way that makes it impossible to overwater, and that seems to facilitate worm health.

Shredded paper makes for fine bedding

One of the challenges when you’re getting started in something like worm composting is that there are lots of people running around telling you that you need to use expensive bedding ingredients in order to get satisfactory results. I’ve been doing just great using regular shredded paper.

I avoid envelopes with windows in them, glossy paper, and anything that just doesn’t feel right.

I particularly like the unbleached brown paper that often comes as a packing material. I also like torn up cardboard egg cartons.

I’m not a huge fan of newspaper because I find that it tends to clump, but I think it’s fine to use it if that’s convenient for you. I would just advise shredding it if you can because that will make it a lot more fluffy and less likely to clump.

I’ve never used coconut coir, and I’m sure it works great, but I just can’t get over the energy cost of shipping it from India. Folks, that’s not nearly sustainable unless you live near the production! And besides, it’s unnecessary– we’ve got plenty of trees and paper here, which work just fine.

Your Worm Bin Shouldn’t Smell

If all is going well, your worm bin will have a pleasant smell like soil. It shouldn’t stink. I have observed that I can add smelly stuff to a well-functioning worm bin, and by the next day the smell will largely be gone. So if you’re been smells, you have probably added too much food or you’ve added too much water, and in doing so you’ve thrown off the moisture balance. Try adding more bedding.

Don’t add these things to your compost

Envelopes with windows

You know those envelopes you receive in the mail with the window that shows your address? Word to the wise: don’t shred those and put them in your compost bin. The plastic doesn’t break down in any timeframe I’ve observed. Although I’ve done a combination of tossing compost and filtering, I still find some little annoying pieces of envelope windows now and then. Ugg. On the upside, I better understand why composting matters.

Banana peels

In my early worm composting days I was annoyed to find a lot of little black flies coming out of my compost bag. How did they get in there? I looked it up, and apparently banana peels have fly eggs in them (who knew?) and so if you put them into your worm composting, you’ll eventually hatch little black flies. On the upside, they break down food as well.

Sure enough, once I stopped adding banana peels, the flies went away. I put them into the regular compost pile now.

Too much food all at once

I think of the balance in a compost bin as being like a titration. You can add, and add, and add, and then suddenly it all goes downhill. Experiment, but be conservative until you have a good handle on how much the worms can take. In my experience the moisture balance is a critical factor that can upset the balance.

Compost that smells awful

A little bit of bad is fine, but it’s truly awful, don’t do it! The worms can handle some amount of nastiness, but don’t push your luck.


I never pushed my luck on this, but everyone says to avoid putting citrus peels in your worm composting. I’d have to agree.

Keep these critters out of your compost


Let’s face it: rats are pretty much everywhere. They are hungry, smart, and persistent. Rats eventually discovered my compost bags, identified a weak spot, and chewed their way in. In addition to eating the compost materials, *they ate my worms*. Yes.

Fortunately I realized what was happening before all of my worms were gone from my second bag, and so I was able to somewhat recover.

The good news is that on my “made from an old gym bag” version, the outer shell didn’t get chewed on, and seems rat-proof enough. What happened is that I’d left one of the side pockets opened, exposing a soft inner liner that separates the main chamber from the side pocket. I have since zippered and fastened closed that side pocket, and so I should be fine.

Along those lines, don’t leave any feed around your bags, for instance to put in later. Put it in right away, or you’re asking for trouble from rats.


So the ants occasionally get very interested in my worm bins, and no matter how securely I try to close them, they find a way in. The good news is that they’ve never stay long term—they come, do whatever they came to do, and then leave within a few days or weeks.

Nonetheless, I find it annoying. An easy fix that I learned from a bee keeping neighbor is to put each let of your stand into a container of water. The ants don’t swim (right?) and so that’ll keep them out. You’ll also need to take care that no part of your bin or stand is otherwise touching a wall. And that you don’t let the containers dry out.

There’s something to be said for benign neglect

Worms aren’t like pets that you need to fuss over. As long as there is a sufficient level of moisture, and not too much heat, and no rats to eat them, the worms will make do. If you are consistent about having bedding in your worm then, they will eventually eat that.

So if you get your bag well set up and well situated, you can in fact forget about it for weeks and months at a time, and come back and find that things are better than when you left them. It would make a habit of this but it’s good to know.