Dig in!

Hi again, Martina here. Welcome back for the third and final post on cutting waste by home composting. This week, we’ll look at how to know when your compost is ready to be dug into your garden and also how to troubleshoot problems, should any arise.

Predicting when your compost will be finished is a tricky business. Even the well-established, healthy compost heap – that’s teaming with tiger worms – will speed up and slow down at different times of the year because of factors like temperature, moisture and oxygen.

Unfortunately, we can’t do much about temperature. Although Scotland’s north-east coast boasts a rugged beauty, we who live here know that it doesn’t often enjoy balmy temperatures. As a result, the composting process tends to be fairly slow – so remember the old adage that says ‘patience is a virtue’. It will likely take between six and twelve months to get finished compost.

The second two factors – moisture and oxygen – can be controlled, to some degree. By getting the balance right between wet and dry materials, it will help to ensure the right moisture level. Also, mixing the materials in your compost heap, once every few months, will help increase the level of oxygen.

So, how do you know when your compost is ready? Well, look for a dark brown layer at the bottom of your compost heap. Eventually, this…
Orange on compost heap

will turn into this…


You’ll probably find that some materials haven’t entirely rotted down and these can be removed and put back into your compost bin. Once you have your finished compost, dig it in to your garden or allotment. And be assured that your soil will thank you – compost adds nutrients, helps to retain moisture and suppresses weeds. It’s magic!

So what happens when your compost heap starts to look and smell bad, and needs rescuing? Follow these simple steps and it’ll be back to normal in no time. Keep calm and compost on…

Wet and slimy compost – This is a sign that there is too much moisture in your compost bin so add dry materials such as toilet roll tubes, cardboard egg boxes and shredded cardboards. These will help absorb some of the moisture and bring it back to a balanced level. It might help to mix the dry materials throughout your compost heap. Also check that drainage is ok; your compost bin should be on a flat and well-draining spot.

Dry compost with little or no sign of rotting – This is the opposite problem where there is not enough moisture in your compost heap and the dryness is stopping the decomposition process from happening effectively. Add lots of wet materials such as fruit and vegetable peelings, grass cuttings and cut flowers.

Bad smells – It might be that your compost heap doesn’t have enough oxygen. When this happens, the process of decomposition changes to ‘anaerobic’ which means that rotting is happening without oxygen. When this happens, your compost heap will start to give off methane, a powerful greenhouse gas. The solution is simple. Mix the materials in your compost heap to help it re-oxygenate. You can also add small twigs, toilet roll tubes and cardboard egg boxes (resist the urge to scrunch) and these will create small air pockets to help oxygen circulate.

Flies – healthy compost heaps don’t normally have flies, or at least not too many. Ensure you keep food waste – such as fruit and vegetable peelings – covered at all times. It might help to put a layer of garden waste – such as grass clippings and cut flowers – on top of food waste to keep the flies away. Check that moisture levels are balanced and mix up materials to bring it back to a healthy state.

Visit Zero Waste Scotland for more information on home composting.

Although composting is nature’s sophisticated recycling system for transforming organic waste into a nutrient-rich soil improver, not everyone has the outdoor space to do it, especially those who live in flats in urban areas. Fortunately, Aberdeen City Council is currently rolling out a food recycling service to flats, and all properties will have the service by January 2016. Recycled food undergoes a process called In-Vessel Composting (IVC) at a reprocessing facility in Aberdeenshire. There, it is turned into compost and used by local farmers to grow food. Watch a short video about this process.

Thanks for joining me in this series on home composting. Whether you’re a master composter or new to the game, we’d love to hear your top tips and handy hints, so please do drop us a line on wasteaware@aberdeencity.gov.uk or leave a comment!


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