A compost starter, often called an accelerator or activator, is a substance added to organic waste to accelerate decomposition. It works by introducing or stimulating the microbial populations that break down materials into finished compost. The goal is to quickly establish ideal conditions for bacteria and fungi to thrive, transforming waste into a nutrient-rich soil amendment. Effective use requires understanding the starter’s composition, preparing ingredients correctly, and maintaining the pile’s environment to support the activated microbes.
Types of Compost Starters
Commercial starters are typically sold as powders, pellets, or liquids containing a concentrated mix of beneficial bacteria, fungi, and enzymes. These products often include a nitrogen source, such as alfalfa or feather meal, to provide immediate food for the dormant microbes once introduced to the pile.
Natural accelerants utilize readily available, nitrogen-rich organic matter to achieve the necessary microbial boost. Materials like aged animal manure, fresh grass clippings, or coffee grounds contain high levels of nitrogen that fuel the reproduction of decomposers. Finished compost or garden soil can also act as a starter by inoculating a new pile with established microbial colonies.
Preparing Materials for Starter Use
Before introducing the starter, all ingredients should be chopped, shredded, or broken down to increase the surface area available for microbial colonization. Reducing the particle size allows bacteria and fungi to access carbon and nitrogen compounds more quickly, leading to faster breakdown.
Proper structuring of the pile is necessary to create a habitable environment for the decomposers. This involves balancing carbon-rich “browns” (like dried leaves or straw) with nitrogen-rich “greens” (like food scraps or grass clippings) at an ideal Carbon-to-Nitrogen (C:N) ratio of approximately 30:1. Materials should be layered, alternating between browns and greens, to ensure a uniform distribution of energy and protein sources. If the C:N ratio is too high, decomposition slows; if too low, nitrogen can be lost as ammonia gas, creating unpleasant odors.
Step-by-Step Application
Applying the compost starter should be done strategically as the pile is being built. The best time to apply is when initiating a new pile or adding a substantial new layer of material to an existing one. Starters should be integrated in thin layers rather than concentrated in one spot to ensure even microbial distribution.
Layering the Starter
As you layer your prepared organic materials, sprinkle the starter over every layer of new material, typically every six to twelve inches of depth. For granular or powdered starters, gently rake or lightly mix the powder into the top few inches of the layer. Liquid starters should be diluted according to product instructions and evenly sprayed over the new layer until the surface is visibly moistened.
Activating with Moisture
Immediate watering after application is necessary to activate the dormant microbes in the starter. The entire layer must be uniformly moistened to the consistency of a wrung-out sponge, corresponding to a moisture content of about 40 to 60 percent. This moisture level is required for microbial life to begin feeding and reproducing. Insufficient moisture causes the starter to remain inactive, while excessive moisture displaces the oxygen needed for aerobic decomposition.
Ensuring Starter Effectiveness
The starter’s effectiveness relies on maintaining a consistent environment that supports the microbial population. Aeration is a primary factor, as the decomposers introduced are aerobic organisms that require oxygen to function efficiently. The pile should be turned regularly, generally every one to two weeks, to introduce fresh air and prevent anaerobic pockets, which cause odors and slow the process.
Monitoring the temperature of the pile provides a direct indication of the starter’s success in stimulating microbial activity. A well-activated pile will quickly heat up, potentially reaching temperatures between 130°F and 160°F (55°C to 71°C). If the temperature remains low, it may suggest a moisture or nitrogen imbalance that needs correction.