The timeline for cultivating finished compost varies according to a number of factors. Composting practices occur on a spectrum, but can be described according to three basic approaches: more passive composting, more active composting, and hot composting. Passive composting (also referred to as cool, continuous composting) requires the lowest levels of engagement for pile set-up and maintenance and accordingly, takes the longest to produce finished compost, usually sometime between 6-18 months. Active composting requires more time and effort for set-up and maintenance, but can produce compost in 5-6 months. Hot composting is the most time and labor intensive of the methods, but yields finished compost in the shortest period of time, usually in 3-4 months.
The following are some facets to consider when estimating how long your pile will take to fully decompose:
Particle Size – Chopping pile contents into small pieces increases the surface area of the material, allowing for more rapid decomposition.
Volume of Material- Filling or nearly filling a bin at the start (as is common practice in hot composting) supports a larger community of microorganisms (especially heat-loving bacteria) and creates an environment that fosters more efficient decomposition. In general, piles with higher internal temperatures produce finished product more rapidly.
Water- Keeping a pile evenly moist supports a more efficient community of decomposers, and is essential to speedy decomposition. Aim for the contents to be the dampness of a wrung-out sponge.
Turning- Turning a pile approximately once or twice a month helps to mix materials and create air pockets, which support a more diverse and fruitful decomposer population and increases the speed at which materials break down.
Curing- Immature compost can kill seedlings and beneficial organisms, so you want to make sure compost has cured before use. Curing is the penultimate stage of composting, referring to a period where pile contents cool, rest, and complete decomposition without the addition of new materials. Curing phases usually last about 2-4 weeks.