Worm Bin & Worm Breeding

The first of our cinder-block worm bins now has a layer of coconut bedding, worms, and slightly-composted food! While the initial batch of worms are acclimating to the conditions at the city garden, more worms are breeding in dedicated trays with horse manure as food.


A worm breeding tray

Sidebar on Persistent Herbicides

A note — Most (nearly all) hay grown in the USA has been sprayed with at least one persistent herbicide so we are very careful not to mix castings from manure with castings from food waste (we poisoned our home tomatoes a few years ago and learned this lesson the hard way).

Persistent pyridine carboxylic acid herbicides and their residue remain active even after the hay is digested and the manure composted in a hot aerobic pile. These four are bad, but we are also concerned about the presence of long-lived non-persistent broadleaf herbicides such as dicamba & 2,4-d. The US Composting Council publishes a series of fact sheets on the topic. Here’s one.

So we have worms breeding in bins in our basement, hopefully happily producing many cocoons each one of which will hatch multiple baby worms. With them fully engaged we set up a cinder block bin in the shadiest spot on the garden plot a few weeks ago.

Our bin is 4’ x 8’ from outer edge to outer edge, with the air space inside the blocks hopefully stabilizing temperature inside. At a usable ~12 sq ft, we want to start with no less than 15 lbs of worms.


Cinder block worm bin

Worms are fantastic decomposers but they’re also apparently delicious, so we wanted to make sure we didn’t attract birds, raccoons, possum, etc, and topped the bin with a lid.


And with the lid

Eager to use our new trommel, we took the time to screen a previous worm bin, using a 1/2” and 1/4” screen in sequence.

Adult worms that didn’t fit through the 1/4” mesh, along with the larger items from their environment

Adult worms that didn’t fit through the 1/4” mesh, along with the larger items from their environment

A production worm bin needs 1 to 2 pounds of worms per square foot of surface area, so until we stock the bin at this level we’re rationing the food waste. Our plan is to take partially-composted food waste from the main working pile after several days, which will not only homogenize the food and jumpstart the decomposition, but also pseudo-pasteurize the worm food by cooking it at ~135 degrees for 3 days.

I can’t rush the worm breeding, but it’s hard not to check their progress twice a day. They’re such nifty animals!