Garden Myth: Are Compost Accelerators Really Useful?

Almost every garden center (and many hardware stores) sells a product called variously compost accelerator, compost activator, compost stimulator or compost inoculant.

The idea behind these products is that you add them to your compost bin or compost heap when you start it and then again each spring to reactivate the process of decomposition. True enough, these products are not expensive… but are they even worth the few dollars they cost?

They contain microorganisms and sometimes also organic materials and minerals that are supposed to boost composting. However, only the manufacturers’ websites seem to find them the slightest bit helpful. Nowhere else will you find experts who recommend them or even studies that back up their effectiveness. In fact, whether you add or not a “compost accelerator” to your compost seems to make no difference whatsoever. Some studies even indicate that the microorganisms included in the product (commercially reproducible bacteria and fungal spores) are absent from the final product (compost), having been replaced by native strains.

And that’s the crux of the matter: microorganisms that stimulate decomposition are already omnipresent in nature and local strains, better suited to your conditions, inevitably take over… and in fact, do so very quickly. Even the remains of vegetables and fruits that you carefully washed will be rapidly recontaminated by spores carried by the wind or found on surfaces and tools that touch them. Yes, they’re even present on your hands!

If you pile up any kind of vegetable waste or even you just place it on the ground, either the microorganisms are already there or else they’ll move in within minutes. Why then pay for something that Mother Nature offers you free of charge?

A Homemade Compost Activator

If you want to be absolutely sure that the right native microorganisms are finding your composter, remember that the compost you made the previous year—or garden soil found anywhere on your property—already contains all microorganisms needed to get composting started. So add a handful of soil or compost at the beginning of the composting season or whenever you add a massive amount of new products to the bin or pile.

Even this effort is probably unnecessary, but if doing it reassures you…