Essentials for a Healthy Compost

Macro- and micro-organisms are the workers that alter and decompose those rotting vegetables and raked leaves, into the earth smelling, dark brown crumbly substance that we call compost.  The quality of the finished compost depends on the environment we create for the organisms that do the decomposing business (a.k.a decomposers).  Just like ideal environments for many living species,  compost should provide an environment with sufficient food, temperature, water, and air.  This article briefly introduces each of these environment essentials needed for a healthy compost. 


The organic materials we add to compost can have a wide range of nutrients and minerals.  These nutritious components are why compost is considered a natural fertilizer for gardens and fields.  A healthy diet for decomposers consists of a mix of materials that contain carbon and nitrogen.  Materials such as dry fall leaves, straw, wood shavings, pine needles, twigs, newsprint, and shredded paper are high carbon sources.  Materials that have a lot of carbon are also considered “browns” in composting terminology.  These high carbon or “browns” are carbohydrate-rich and provide the energy for the decomposers.  Food scraps, livestock mortalities ( in the case of farm animal operations), grass clippings, egg shells, and coffee grounds are materials that are considered “greens” in composting terminology. These green materials contain high amounts of nitrogen, which provides protein for decomposers and helps these organisms multiply.  Both types of materials – greens and browns – should be layered and mixed to build the decomposer community and allow them to continually turn your organic waste into compost.  For instance, 1 lb of vegetable waste should be combined with at least 1 lb of newsprint.


With a good mix of materials and sufficient water and air, compost temperature should increase quickly.  The process of organisms decomposing materials causes the temperature of compost to rise quickly (within a few days).  Compost temperature while decomposing can range from 13°C to 71°C.  Throughout the composting process, different microbial communities take over decomposing materials, and each community prefers a different temperature range.  The ideal temperature range for efficient composting is between 32-55°C.  Below 32°C, the process of decomposition occurs but is slow.  Having compost reaches 55°C or above, the majority of microorganisms cannot survive. However, compost reaching 55°C or above for at least three days aids in sterilizing weed seeds and destroy pathogens.  


Decomposers prefer compost to have between 40% – 60% moisture.  If the compost is too dry, decomposition will slow down.  If the compost is too dry, water may need to be added or materials with a lot of moisture. More often, composts can end up being too wet. Composts with greater than 60% moisture create an anaerobic environment (low oxygen) that is inviting for undesirable micro-organisms that release bad smells in the compost.  Adding very dry “browns” to the compost mixture helps prevent the compost from becoming too wet.


Aerobic decomposers (oxygen-loving organisms) are preferred for composting.  Keeping within the ideal moisture range, and turning the compost will ensure there is enough oxygen for the decomposers. Turning a batch composter every time materials are added, or once a week will help keep the compost aerated.  Furthermore, turning helps break up materials, and improves decomposers access to recently added materials. 

Managing these four factors – food, temperature, moisture, and air – are key to creating quality compost in a timely manner. Composting is not a complicated process, but these four factors should be considered if your compost starts to smell bad or if the decomposition process is slow or stagnant.