Worms

Some years ago, the UK government completed a study on the food people bought and ate, and came up with a sobering result: in a time when global hunger is increasing, one-third of food in the UK is thrown away uneaten. That is about three billion pounds a year wasted – a part of the estimated one metric tonne of waste per household per year.

Of course, everyone will have some kitchen waste – no one wants to eat the potato peelings or woody stems – but throwing it in with the rest of the rubbish isn’t the best solution either. There are different kinds of decay, and when organic material is trapped away from oxygen and insects it decomposes slowly and anaerobically, releasing methane – which smells foul and contributes to climate change.

Many people would like to grow their own food, but need help with the earth, which in many yards is builders’ waste covered in a thin veneer or topsoil and turf. To grow things properly, many people need to build up their soil with organic waste.

Fortunately, all three of these problems can solve each other, and there are already volunteers ready to help in your neighbourhood. They will work hard for you 24 hours a day without complaint, they are experts at turning kitchen waste into great soil and they work for free. They are worms.

We got a wormery for Christmas this year, and it came in an easy-to-assemble kit – the bin, a stand, an interior tray and – snug in a plastic bag with air holes – the worms. We lay them gently in the tray inside the bin, spread a bit of peaty earth, shredded newspaper and a bit of kitchen waste around them, and then let them settle in.

A medium-sized wormery can process several pounds of organic waste a day – that’s several pounds you don’t have to put in bins, wrap in plastic and put outside in the cold; that won’t take up space in the landfill; and that won’t worsen climate change.

When it’s cold my daughter and I wrap insulation around the bin and placed cardboard over the top to keep them warm, and they keep going. According to worm experts, they slow down below eight degrees Centigrade (46 Fahrenheit) and stop altogether below five degrees (41 Fahrenheit). The outside temperature can go five or ten degrees below that, however, and they can still be all right if the wormery is sufficiently insulated. If you live where it regularly goes below freezing in the winter, you can bring it inside or into the shed – a well-maintained wormery should not smell foul.

A few things are not suitable for the worms. They don’t like high-protein dishes like meat, cheese or beans, acidic waste like citrus peels, too much grass, or pet poo. A little bit of these things can be okay, but not much. Most wormeries also come with an alkali powder of some kind in case the compost gets too acidic, and I'm told that seaweed, crushed eggshells or fireplace ash will also help. You can tell if it starts to smell or if you see tiny, threadlike worms. The worms – called potworms in Britain – are harmless themselves, but an indication of a problem.

One nice thing about a wormery bin is that most have a valve at the base for draining excess water. The liquid is called “worm tea,” and is about the colour of tea – dilute it and use it to water your plants.

Ordinary composting, however, has some disadvantages that every gardener knows well. One can’t simply add bones or meat – and some gardeners even avoid eggshells – for fear of attracting vermin. Also, plants that have gone to seed cannot be added, or the resulting soil will be peppered with the beginning of next year’s weeds. You can’t add diseased plants, or the diseases might remain in the resulting soil, ready to infect next year’s crops. Also, it takes a long time, and one loses much of the kitchen waste volume in the process of rotting down.

If you have enough waste, you might also try a different kind of composting, enough to heat all the hot water of your house. Called the “Berkeley Method,” it involves adding the right combination of carbon-rich and nitrogen-rich materials, and flipping it occasionally to give it enough oxygen – which grows kinds of bacteria that generate heat. This “hot composting,” generates too much heat for worms. That’s for another column, but something you should look into.