From kitchen scraps to 'black gold'? How a Wormery on My Balcony Transformed My Food Waste

A journey to making top quality worm compost on my balcony - with some distressing worm disasters on the way!

It’s the spin off benefits that make growing food at home so rich and rewarding - the delicious, nutritious food, of course, but also the potential for community connections, the wildlife that visits, the beauty and joy of watching plants grow and the opportunity to recycle food waste and put it to good use - to name a few. I plan to celebrate all of these, as well as the nitty gritty of growing in containers, as this Substack evolves.

Today, I want to tell you a little bit more about worms, wormeries, and how they completely changed my attitude to food waste and helped my plants grow stronger and healthier.

It’s so rewarding to transform kitchen scraps into a free, amazing fertiliser. Womeries also take up little space and - if managed well - produce no noticeable smells. And they enable you to witness nature’s miracle of recycling organic matter at first hand.

Wormeries come in all shapes and sizes and can be very attractive. This one, made by Ken at Bubble House Worm Farm, doubles up as bench.

Chucking food scraps without thinking…

Prior to 2009, my family and me used to scrape all our kitchen scraps in the bin without a second thought. We lived in London, in a flat with a small balcony and no garden. We had no space for a conventional compost heap and the idea of any other type of composting hadn’t even crossed our minds.

A couple of years later, our attitudes had changed completely. Our kitchen scraps had become precious organic material for our plants and food for the worms. I was even known to collect up random banana skins to feed them with when out on walks. After a bumpy start (see below), the small box wormery on our balcony started turning out amazing quality compost. When applied to my plants, they started visibly growing stronger, healthier and faster.

The wider food waste mess we’re in

Today, in the UK, only about 17% of household food waste is recycled according to WRAP, with over 4 million tonnes going to landfill each year. Not only is this a waste of precious organic material and landfill space, but it also accounts for an estimated 25 million tonnes of CO₂ equivalent (CO₂e) annually — that’s very roughly equivalent to the annual emissions of between 5 - 10 million cars. This is because food in landfill rots down anaerobically and release large amounts of methane, a potent greenhouse gas.

How much waste do most households produce?

The average household in the UK throws away around 1kg of kitchen scraps a day or nearly 1/3 of a tonne each year. The figure in the US is nearly double this.

As a family we try to minimise food waste. We eat leftovers for lunch, and rarely let fruit or veg go off. So I asked myself: can we really produce a kilo of organic waste a day?

I started weighing our scraps every day to find out. To my surprise we are close: an average of roughly 800g a day (or, staggeringly, over a quarter of a tonne a year). It’s made up of a mix of things like coffee grounds, tea bags, banana and onion skins, porridge scrapings, pea and bean pods, rhubarb leaves, strawberry hulls, artichoke hearts and sweet corn husks - all varying with season, of course.

I was pleased to observe that there was little ‘edible food’ in our caddy - and nearly all of it resulted from cooking from scratch. But still precious, organic waste, nonetheless. Rather alarmingly, edible food (or food that was edible before going mouldy) makes up around 75% of household food waste in the UK.

A bumpy start with worms

My adventures with worms started in 2009 when I first heard about wormeries (aka ‘worm composting bins’). It sounded like an ideal system for our 6 x 8 foot balcony. So I purchased a wormery online that was described as ‘ideal for flats and studios’. What could possibly go wrong? As it turned out, quite a lot.

In a few short months, I became responsible for two mass worm deaths. Not only were these deaths distressing, the contents of the wormery became putrid, and cleaning it out was a most unpleasant experience. It was also expensive - with new worms being purchased each time. I was close to giving up.

But luckily I spent a bit of time trying to understand why these attempts failed. I discovered that my first wormery was too small for our needs, it had poor airflow (worms need air to breathe) and poor drainage. Basically it was a bad design. But there was user error, too: I was feeding it too much too soon.

I bought another, slightly larger wormery with more breathing holes. I fed it more carefully and mixed in more browns (cardboard) with the food scraps. It turned out that, like riding a bicycle, keeping worms becomes easy once you know how.

My first successful wormery that transformed my balcony growing

Five most common pitfalls

I’m far from alone in experiencing difficulties in starting a successful wormery - if you already run a wormery it would be interesting to learn how you’ve found it, and whether it was all plain sailing or you had any hiccups.

Sadly some people do give up. Which is a shame, as nearly all the common pitfalls aren’t too difficult to avoid once you know how.

Here are the five problems I come across most often.

1. Feeding too much too soon. This is the most common mistake. You need to feed little and often to begin with (you almost certainly won’t be able to add all your food waste to it initially), and always mix in a few browns (shredded cardboard is ideal) each time you feed.
2. Waterlogged. Many commercial designs of wormery have holes in the lid that let rain in. The holes aid airflow (that worms need) but increases the risk of flooding if the wormery is sitting outside, exposed. The contents need to be damp - but not waterlogged. The best solution is to shelter the wormery from rain (eg under a table) if possible. Otherwise, leaving the tap open will help prevent bad cases of flooding and drowned worms - but is not ideal as valuable nutrients will also be washed out. Alternatively, look for a model without holes in the lid (although these are rarer than you might think!).
3. Not adding enough browns. Wormeries need a mix of ‘greens’ (kitchen waste) and ‘browns’ (shredded brown cardboard or composted woodchip) to remain healthy. Too many greens and the worm bin will become soggy, anaerobic and smelly. However, too many browns are not harmful - the only downside is that they will slow down the composting process. If in doubt, add more browns.
4. Feeding too little. Once people are aware that it’s easy to overfeed, they sometimes over compensate and feed too little. In order to keep healthy worms and make maximum amounts of worm compost, you want to feed as much as the worms will happily eat. You can add more food as soon as the last batch has visibly started to decompose (at this stage these bits will still be clearly recognisable as food scraps) and the worms are scouting around on the surface.
5. Starting with too few worms. An established wormery will commonly have several thousand worms. Worms will double in numbers every three months, provided the conditions are good for them. The more worms you start with, the quicker your wormery will be fully operational, and the easier it is. Start with at least 1,000 worms if you can, 500 minimum.

An established wormery has LOTS of worms!

It’s also a good idea to do some careful research before buying a wormery. Some of the marketing blurb I’ve seen is misleading, so try to find independent reviews or personal recommendations if you can. Alternatively, a simple home made wormery (like the ones below) will work just as well as most models you can buy - and better than a good number of them.

A harvest of worm compost (in the green trays in the foreground) from the black plastic wormery behind. A simple DIY wormery made from a plastic box with air holes drilled in the base will work just as well as most commercial models.

Over the years, I’ve become unashamedly evangelical about worms and their benefits for food growing and our planet. I give talks (including Worms and Wine evenings 🤣), run workshops, and an online course once a year. 

Wormeries are not the best option for every situation or everyone… particularly if you have a phobia of worms! However, if you want to recycle your kitchen scraps on a balcony, patio or any other small space - and make fantastic compost for your plants - I highly recommend considering one.

I’ll write more about the benefits of using worm compost in container gardening another time.