Lemons and their peels are compostable, but they require different handling than most vegetable scraps. Composting is the natural process where microorganisms break down organic materials into a nutrient-rich soil amendment. Lemons’ unique biological structure means they decompose slowly and can disrupt the natural balance of a composting system if added improperly.
The Core Issue: Why Lemons Pose a Composting Problem
The hesitation about composting lemons stems from two biological factors: high acidity and the presence of oil in the rind. The pulp and juice contain citric acid, which can temporarily lower the pH level of a compost pile. A rapid drop in pH slows the activity of the beneficial bacteria and fungi responsible for breaking down the organic matter.
The peel contains volatile organic compounds, most notably d-limonene, a natural solvent and insecticide. This compound is antimicrobial and acts as a defense mechanism for the fruit, making the peel resistant to microbial breakdown. Since d-limonene deters decay, it significantly slows the decomposition rate compared to softer materials.
This aromatic oil also deters macro-decomposers, particularly composting worms. In vermicomposting systems, a high concentration of citrus peels makes the environment inhospitable for the worms. While a traditional compost heap can manage small amounts, the antimicrobial nature of the oil and the dense structure of the peel make it a slow-to-decompose material.
Practical Steps for Successfully Composting Citrus
Successfully incorporating lemon waste relies on mitigating slow breakdown and balancing acidity. Maximizing the surface area of the peels before adding them is the most effective step. Chopping, slicing, or blending the peels into smaller fragments allows the microbial community greater access, accelerating the decomposition process.
To neutralize the acidic effect, maintain an appropriate carbon-to-nitrogen ratio. Lemon peels are a “green” material, rich in nitrogen, so they must be balanced with a larger proportion of carbon-rich “brown” materials. Examples of brown materials include dry leaves, shredded paper, or sawdust. This ensures the pile remains balanced and prevents the pH from dropping too low.
Placement is also important for efficient breakdown. Burying smaller citrus pieces deep inside a large, actively heating pile exposes them to the highest working temperatures. These elevated temperatures help break down the resilient d-limonene oil faster than in a cool or passive pile.
Vermicomposting Considerations
For those engaging in vermicomposting, avoid adding citrus peels altogether to protect the worm population. If small amounts are added, they should be pre-composted until partially broken down or mixed with an alkaline material like crushed eggshells. This measure ensures the worms are not exposed to high concentrations of the acidic, oil-containing material.
Alternative Uses for Lemon Waste
If you wish to avoid potential composting issues, lemon waste can be repurposed in several useful ways. The d-limonene in the peel makes it an excellent natural degreaser for household cleaning.
Household Cleaner
Peels can be steeped in white vinegar for several weeks to create a powerful, lemon-scented, all-purpose cleaning solution. This solution effectively cuts through grease and grime.
Natural Pest Deterrent
The peels also serve as a natural pest deterrent in the garden, used outside of the compost bin. Boiling the peels and straining the liquid creates a concentrated spray. This spray repels soft-bodied insects like aphids and ants from vulnerable plants.
Fire Starters
Dried lemon peels can be used as fragrant, natural fire starters. By drying the rinds completely, their volatile oils become flammable, making them an aromatic addition to kindling for a fireplace or campfire.