Harvesting and sifting your compost: method, equipment, and storage

Print

Your compost has passed the maturity tests: it is dark, it smells like the forest floor, and it crumbles between your fingers. All that's left is to get it out of the composter without disturbing what is still breaking down, refine it if needed, and store it properly until you use it.

If you're not yet sure it's ready, start with our guide How to tell if your compost is mature. For worm composters, the method is different: it is explained in our guide Harvesting vermicompost and worm tea.

Where should you harvest from?

The principle is always the same: the oldest, and therefore most mature, compost is at the bottom, and recent additions stay on top. How you reach it depends on your equipment.

In a bin with an access door

Most compost bins have one or more access doors at the base of the sides. Open them and take the finished compost out from the bottom with a shovel or a hand cultivator, leaving the top to keep working. The contents gradually settle, and you can come back for another harvest a few months later.

In a bin without a door, or to empty it completely

Remove the top layer, which is still only partly broken down, and set it aside on a tarp. Then collect the finished compost from the bottom. Finally, put the material you set aside back into the bin: it will start a new cycle, along with the worms and microorganisms it contains.

With two or more bins

The first bin receives fresh scraps, and the second is used for curing. When the first one is full, its contents are transferred to the second. Keep the materials in the order they went in when you transfer them: the oldest should end up at the bottom. This second bin is where you will harvest the finished compost.

In a pile

Move aside the outer layer and the top of the pile, which are often less advanced, and take the core and the base. The rest will be used to start the next pile.

Tumbler composters

With a dual-chamber tumbler, you fill one side, then keep turning it without adding anything while you fill the other. When the first side no longer contains any recognizable scraps, empty it into a wheelbarrow or a cart.

Keep in mind: what you get is fresh, still coarse compost, not finished compost. Let it finish curing in a pile for 3 to 5 months, or spread it over bare soil in the fall. Used too early around plants, it can turn them yellow. Piled directly on the ground, it can be colonized by earthworms from the soil, which can't live in the drum. You'll find all the details in our guide Tumbler composters: how they work and their real limits.

Sifting: what is it for?

Sifting isn't required. For mulching, enriching the base of trees, or working compost into the surface of the vegetable garden, unsifted compost works perfectly well. Sifting becomes useful when you need a fine, even material: top-dressing the lawn, seed-starting and potting mixes, window boxes.

Equipment

A simple wooden frame covered with wire mesh will do the job. For everyday use, a mesh of about 0.4 in (1 cm) gives good results, with compost fine enough for the lawn and containers. For a very fine seed-starting mix, you can run the compost through a hand sieve with a finer mesh.

Method

• Lean the frame at an angle against a wall or set it on a wheelbarrow;
• toss the compost onto it with a shovel, or rub it through with a gloved hand;
• collect the fine compost that falls through, and set the leftovers aside;
• work in small batches rather than all at once.

Willy's tip

Sift in dry weather, using compost that has been left to dry out for a few days under a lid. Soggy compost sticks to the mesh and clogs it; compost that just feels cool and slightly damp to the touch goes through much more easily.

Remember to wear gloves, plus a dust mask if the compost is dry: it's a simple precaution against health risks that are rare but real. Wash your hands after harvesting, as you would after any yard work.

What should you do with the coarse pieces?

Eggshells, fruit pits, cabbage stems, bits of branches: these leftovers aren't waste, they're materials that simply need one or two more cycles. You have two options:

• put them back in the composter, on top of the compost in progress. Rich in microorganisms and carbon, they help kick-start decomposition again and balance the mix;
• use them as mulch, around shrubs, hedges, or in the paths of the vegetable garden.

Only items that should never have been in there, such as plastic fruit stickers or a forgotten bag, go in the trash can.

Storing your finished compost

Ideally, you should use your compost within a few weeks of harvesting it. If you need to keep it longer, two enemies lie in wait: rain, which washes its nutrients down into the soil, and drought, which kills off its microbial life.

• For a few weeks to a few months, pile it up and cover it with a tarp weighed down with a few stones, or with a layer of straw about 4 in (10 cm) thick;
• for small amounts, a bin or trash can with a loose-fitting, non-airtight lid works very well;
• for long-term storage, check from time to time that it stays slightly moist, and turn it if needed.

To move your harvest to the vegetable garden without lugging it by hand, our 14.5-gallon (55-liter) compost collection cart slides right under the base of the composter.

Shared composters: harvesting together

With a composter outside an apartment building or in a neighborhood, people don't each harvest on their own. The harvest is organized by the site coordinators once the curing bin is ready. It's often a friendly get-together: everyone sifts together, the compost is shared among the participants, and the leftovers go back into the drop-off bin. If your building doesn't have enough green space to use it all, the surplus can go to planters in the common areas or to a nearby community garden. We explain how these sites are run in our guide Shared composters: a how-to guide.

Key takeaways

Always harvest from the bottom, where the oldest compost is. Only sift for uses that call for fine compost, put the leftovers back in the composter, and protect your harvest from the rain if you store it.

In a nutshell

Harvesting your compost means getting the oldest material from the bottom of the bin, through the access door or by setting the top layer aside. Compost from a tumbler, on the other hand, still needs to cure for a few months in a pile. Sifting, with a mesh of about 0.4 in (1 cm), is only useful for the lawn, seed starting, and containers; the coarse pieces simply go back into the composter. Covered and slightly moist, your compost will keep just fine until it's time to head out to the garden: for the right amounts, see our guide Using your compost in the garden.

Related products

Compost collector cart 55 liters

Collect and transport your compost

$73.50 €65.83

EASY-TURN handle for Maze 245L rotating composter

Less effort thanks to the 3-gear system

$37.12 €33.25

Preorder

245L Maze Rotating Composter with Dual Chambers

Effortless outdoor composting

$231.67 €207.50

Maze 180L Dual-Chamber Rotating Composter

Effortless outdoor composting

$166.55 €149.17

Other topics in the guide

Vermicomposting30 fact sheets →Bokashi24 fact sheets →EM microorganisms26 fact sheets →