If you have a garden, there’s a good chance you also have a compost. Perhaps it’s a bin, maybe it’s just a pile, or a few containers nailed together by a former resident in the corner of the backyard.

It might be buried under a mound of weeds, or overflowing with kitchen scraps. Perhaps it grows a few free pumpkins each year.

But when was the last time you dug under there?

Looks can be deceiving, and much like an iceberg, most of your humble compost pile isn’t visible from above.

If it’s been a while, perhaps it’s time to pull off the topmost layers. You might just find something special.

1. Free compost

If you’re buying in compost, it can run you between $5 and $15 a bag – depending on quality and where you source it from. And that’s assuming you even have the resources to transport enough of it home.

Even buying in bulk and getting a trailer or truck load dumped off is still an investment.

But it’s possible there’s a little black gold mine under your humble backyard compost bin – and you won’t know for sure until you start digging.

I pulled out two 72 litre wheelbarrows full of compost from my bin earlier this week. Roughly $25 worth of free organic matter for improving the soils in my bugnet house.

And I didn’t have to travel or spend any money to get it.

2. Find your lost things

While emptying my compost bin this week I unearthed:

• An underwire from a bra
• A small dipping bowl
• An entire packet of McDonald’s ketchup

I’m pretty sure we can blame the ketchup on being under some napkins in a paper bag. I must have missed it.

But the underwire and the bowl? I cannot explain that. I don’t think I lost a bra – at the very least I would have found elastic (possibly another underwire too).

The bowl is part of a set I have. But how or why it got to the compost bin? Mystery to me. I’m happy to have it back though. I use them to measure catnip while making Fluffy Balls.

Who knows what lost treasures you’ll find? A teaspoon? Secateurs? The potato peeler? Only one way to find out!

3. Evict the pests

It helps a lot if you have a dog or cat on stand-by while you dig your compost up.

We had a mouse, who had built a fairly extensive warren under the compost bin. But our dog Roxy was very much on hand to evict it.

Now we’ve cleared everything out and taken care of the pest, we should be fine for a little while at least.

One of the most effective ways to evict vermin from your compost pile is to destroy their home and use it to grow vegetables instead.

4. It needs turning

While there was 140 litres of compost in my bin, I also pulled out a lot of stuff that hadn’t thoroughly decomposed.

Compost happens when you have the ideal mix of nitrogen-rich materials, carbon-rich materials, water, and air. Oxygen and water are important factors in this process and sometimes there are pockets they simply can’t access. It becomes too dry or compacted to decompose.

When this happens, your ingredients won’t break down. They’ll just stubbornly stay identifiable as paper, or a branch, for a very long time. The solution to this problem is to turn your compost.

Of course, only the most dedicated composters actually go out and regularly turn their compost. That’s why you don’t even know what’s under your pile – you’ve not looked!

As I shovelled out the compost, I sifted through it and threw the larger pieces into a second wheelbarrow. After the compost had been emptied, the stuff that still needed time to break down went back into the bin again.

That effectively turned it over, creating new air pockets and mixing everything up, starting the process for the next time I think to lift it up.

Put on some gloves, and go look

Here’s what you do: take off the material on top that hasn’t broken down, and put it on a tarp, or in a wheelbarrow.

Eventually, you’ll get to the point where you’re looking at thick dark soil. Use a fork or spade to put it into a second wheelbarrow or bucket (we have wheelbarrow privilege, but if you only have one wheelbarrow, use it for this step).

Sift through your compost with your hands. Anything you can still identify should be set aside in your first wheelbarrow/pile to go back. Unless it’s accidentally non-organic, then set it aside to throw away or rejoin its proper place.

Keep going until your compost is empty, and any vermin are evicted. Distribute your compost throughout your gardens.

Replace the materials you set aside back in the compost bin. Continue to throw stuff on top like always.

Come back and do this all over again in a year or two.