Mouse eviction! Or how to fix up an under-active compost bin

Probably the most common problem that can occur with backyard composting is attracting pests, particularly the rodent kind. The inside of a plastic compost bin is insulated from the elements and full of tasty treats so it’s easy to see why they are attracted to it. Another aspect of the average backyard composter is that although it may be a nice warm mouse house it’s not HOT, as in hot composting. Even if you regularly forget about those veggies in the fridge and end up wasting quite a few of them, or cook most of your meals from scratch it’s unlikely that you will generate enough nitrogen rich veggie scraps on a regular basis to start generating heat in your compost bin. This is true even for households of 5 or so people, including little ones who may generate more scraps in the form of half eaten snacks etc. Why does it matter if the compost bin gets hot or not? This determines how quickly the scraps break down. A handful of scraps thrown into a cold composting system may no longer be food safe for us humans but they can remain fresh enough to be attractive to mice and rats for weeks. Whereas a bulk amount of the same veggie scraps in a hot composting system will generate heat and in turn hasten the degradation even more by essentially cooking the veggie scraps. In a day or two they will no longer resemble veggies and the mice and rats will no longer be interested. They also may not find it so comfortable once the interior of the compost bin is up around 60-70 degrees Celsius!

cute! but preventing compost from being made

So besides wasting heaps of veggies (which would be a terrible idea for many reasons) what are you to do? Limit access and make it uncomfortable for the little thieves! The presence of mice or rats may also indicate a compost bin that is too dry. Nothing will break down to any great extent if there is not enough water. All of the bacteria and fungi that do the hard work need water to survive, after all. Don’t just flood the mice out though, as too much water in the compost will also slow things down, and produce bad smells along with methane and other greenhouse gases.

When a HCC contributor sent me the above photo it was easy to suggest a course of action. Peter does the right thing and sends the really tasty kitchen wastes like bread crusts and leftover rice to the HCC, but composts most of the vegetable waste in his own bin. If you’ve ever heard anyone say ‘you can’t compost bread’, what they actually mean is ‘bread is great in compost, it breaks down easily, but unless you have a pest proof system then you’ll end up attracting mice/rats as they love the stuff’. Peter’s heap must not be completely pest proof yet. It’s surprising how small of a hole mice can fit through. Someone once told me they only need about a square centimeter to squeeze through. The best way that I’ve found to keep them out of a plastic composter is to ensure that the base is impenetrable with a few inches of soil piled up against it. Just like making a sand castle, just pile it up around the base of the unit and pat it down to compact it slightly. Yes, the critters can technically still dig through, but they are more likely to run off and investigate other options before they bother.

You can also make the scraps inaccessible from the top (in case they’re running up the sides and squeezing into a lid that’s slightly ajar, for instance). If there are lots of tasty scraps in the bin, you can cover them all up with, what else? compost! The HCC ‘semi-compost’ is perfect for this. ‘Semi-compost’ is what I have started to refer to when there is a pile of material that has cycled through the compost bays yet still needs to break down quite a bit.

the pile in front is ‘semi-compost’, the pile in back is just leaves!

And while you’re adding semi-compost why not heat things up a bit? For Peter’s heap I supplied a nice big bag of coffee grounds, as well as a pile of semi-compost. The idea is to add a nitrogen source that will speed up the decomposition of the whole. Watering this in is a good idea, especially if the pile is dry, but also to distribute the coffee grounds down through the existing mass. Then the whole lot can be topped off with the semi-compost, which the mice won’t be inclined to dig through to get to the tasty bits and will also inoculate the heap with good bacteria and fungi. You can also use grass clippings or a thin layer of manure for a nitrogen rich boost. Finally, (and perhaps waiting a day for the mice to vacate), build your ‘soil moat’ around the base, packing it up against the composter walls to secure the perimeter. Easy peasy! I would then let this whole lot sit for a few weeks, and then turn the whole lot over.

coffee grinds (as shown with portafilter), followed by water and a nice big pile of semi-compost and the mice will vacate! Pack soil around the base for extra reinforcement

If you have a compost bin in a similar situation I’d be happy to supply the semi-compost and even do all the hard work for you. All with the aim of diverting more kitchen scraps from landfill! I would ask for a donation to keep the HCC chugging away. If you think it’s worth it to keep the scraps out of landfill (and to not expand the rodent population) then you can enquire at



Sharing the bucket love with a far-reaching network

Door to (back)door delivery – HCCers meet Marie-Helene

The ‘Hackett’ Compost Collective is a bit of a misnomer because you don’t have to be a Hackett resident to contribute! The name is there as more of a legacy and also a reminder that community composting works best on the local scale.

Contributor Marie-Helene shows us all that the HCC can help reduce waste to landfill not only in our own homes but by allowing others to be involved also. Marie-Helene has been a HCC member since last July when she heard all about the HCC in the SEE-Change newsletter. At the time she was living in North Ainslie. I was more than happy to take a small detour off the bike path to pick up her bucket of scraps on a regular basis. Since then, something drew her to move to Hackett. Funnily enough it was around the same time that another HCC member (Caitlin in Lyneham) moved to Hackett also! I’ve always had in mind expanding the HCC to other suburbs but I didn’t imagine that other suburbs would come to us!

Marie-Helene actually keeps three buckets on hand, one for the kitchen bench, a larger one outside that she empties into, and a third that she takes to work. She’s noticed that the small amounts of organic waste generated in the work place, from coffee grounds to banana peels, add up. And while a banana peel here and there might not seem like much the small bucket has been appreciated by many. Indeed, while Marie-Helene was moving house she took a break from scraps collections (understandable!) but her colleagues, including her director, missed the opportunity to send their waste somewhere worthwhile. Marie-Helene is settled into Hackett now and the three bucket system is working great.

Scott and I also take buckets to our workplaces to get them filled with goodies. In Scott’s case he works with lots of younger people living in apartments so it’s not unheard of that he is bringing home 4 or more buckets full of scraps in his bike panniers on any given day. All of these HCC contributors are valued. And like Marie-Helene, all of them feel better knowing that their scraps are not ending up in landfill. A win-win all round!

Marie-Helene is originally from Canada and she’s certainly not afraid of a little weather. As a side note: I love getting the perspective from people from different climates, to think that I used to hold off on riding my bike if it looked like rain! So it didn’t bother her at all that she walked over with her full buckets during the wettest part of this Queen’s birthday holiday (the skies are clearing now as I write this). It’s fantastic when people in the same local community can help each other out. In the same way, Marie-Helene would like to get her own compost heap started and I’d love to help with that. As Marie-Helene and her family live in a unit she needs to arrange permission with the body corporate first. After all, there can be concerns with pests and odours when it comes to composting. But with proper management it really is the best way to manage our wastes and turn them into something wonderful. At the very least I can share some semi-composted materials with Marie-Helene to serve as ‘activator’ in a new heap, as well as plenty of tips for a productive heap. In the meantime we’ll keep the full and empty buckets circulating, and anyone is welcome to help us fill them up 🙂