How to harvest worm-compost

Since we installed the Can-O-Worms vermicomposting bin on our balcony in August 2008, we have had 2 harvests. The first one in January this year (so after 6 months but it can take up to 12 months), resulting in 8 kilos of natural worm compost (worm castings) that served us as fertiliser for the plants. The second harvest took less time (less than 3 months) as by then the worms and other organisms had reproduced, which helped speed up the composting process. So our second harvest took place in March and resulted in 9 kilos of compost.

Here is how you harvest the worm-compost:

Recycling your organic waste with the Can-O-Worms is easy: start by feeding the worms with food leftovers and plant clippings in the first tray, and when it fills up, start adding a second tray on top of the first one. Once you filled the second tray, add the third and last tray to the urban compost bin. When this last tray is full up [1], it’s time to harvest your first natural, home-made compost.

It is amazing to see that when you extract the bottom tray [2], what before has been pieces of vegetable, eggshell, etc. has been converted into brown, homogeneous compost, similar to coffee ground [3]. The worms have moved from one tray to another, leaving behind mature compost to feed on the fresh organic waste.

So take the matured compost out of the bottom tray and add the compost to your plants or save it for future needs. Then, simply add that empty tray to the top, add a bit of compost and worms and start adding food scraps like before [4]. It is a cyclic process where you simply keep adding the empty tray to the top.

Here some additional tips:

• Always make sure to fill up the trays enough so that the top of the food scraps touches the tray above so that the worms can migrate later on to the one above (they are not good at jumping).

• Don’t feed the worms any meat; they are vegetarians and would explode if they ate any meat!

• If your compost is too humid, add bits of paper or shaving from untreated wood.

• To avoid attracting fruit flies, always cover the new leftovers with matured compost from the same tray.

Although you might think you produce a lot of organic waste, we were surprised to see the compost absorb ALL our kitchen waste; 2 people eating regularly at home, with at least 5 kilos a week of organic vegetables from Recapte, our local vegetable box service. The reason why we don’t end up with masses of compost is because most of the kitchen waste consists of water and is released through the tap of the Can-O-Worms, which serves as liquid fertiliser. That way the volume of the waste is reduced by 70% in the compost bin. We have been using the compost as fertiliser for our 20 pot plants but if you really produce too much, make a friend or neighbour with plants happy by giving the compost away.

For more information about vermicomposting, check out our previous article and video about how to get started with the Can-O-Worms. And in case you wonder about the lion head behind the Can-O-Worms; it is a protective cover to shield the worms from too much sun and rain, made from a recycled advertisement banner from Barcelona’s Zoo.