How to Recycle Eggshells
Chicken, duck, and quail shells. Real agricultural lime by chemistry, but only at particle sizes and quantities most kitchens never reach.
Quick answer
Eggshells can go in backyard compost or worm bins. Crushing helps them break down faster, but grinding to powder is not required for ordinary composting; finely ground shells are more useful when applying them as a soil amendment. Check your municipal organics program's accepted-items list before adding shells to its collection. Before you go, confirm that a local recycling center accepts the material in its current condition.
- Recycling route
- Check locally
- Typical value
- No meaningful resale value. Their worth is as a free liming and grit material, and only when ground fine.
How to Prepare
- 1Add shells to a backyard pile or worm bin; crushing is optional and can speed breakdown
- 2Rinsing is optional for composting; if saving shells indoors, a quick rinse can reduce residue and odor
- 3No oven-drying step is needed for composting; air-dry only if you want to store shells
- 4Use finely ground shells as a soil amendment only where the soil needs calcium or lime
- 5For a worm bin, Oregon State suggests about 1/2 cup of grit per 14-gallon bin every couple of months; pulverized eggshells are one option
- 6For municipal organics, follow the program's accepted-items and preparation instructions
Where to Recycle
- Home compost bins
- Worm bins, where pulverized shell serves as gizzard grit
- Municipal food waste programs
- Backyard chicken feed as a calcium supplement
- Direct garden application, ground fine
Special Instructions
The size of the pieces is the whole story. Illinois Extension found coarsely ground shells were not much better than nothing at all, while finely ground shells performed as well as pure calcium. Gardeners routinely pull tomatoes at the end of a season and find the shells they buried in the same condition they went in. A University of Georgia pot test tracked soil calcium from a 3,996 lb/acre control up to 4,890 with eggshell tea, 6,123 crumbled, and 11,270 ground. Eggshells are genuinely effective lime: a 54-month Iowa State field trial concluded ground eggshells are an effective liming source and that the standard test actually underestimates them by two to two and a half times. Quantity is where it falls apart. At about 400 lb ECCE per ton against agricultural lime's 1,871, a modest liming rate works out to roughly 900 to 1,000 shells per 100 square feet, and a household going through a dozen eggs a week produces about 600 shells a year. Treat them as a soil contribution, not a fertilizer.
Environmental Impact
EPA lists crushed eggshells as suitable for backyard composting and vermicomposting. Municipal organics programs set their own accepted-material rules, so check locally. Cover food scraps with browns and maintain the pile or worm bin as directed to discourage pests. A well-maintained backyard pile may reach temperatures that help reduce pathogens, but household piles do not guarantee that all material reaches a specific treatment temperature.
Sustainable Alternatives
- Grind and feed back to laying hens as a calcium supplement
- Add pulverized shell to a worm bin as grit; extension services call this their best use
- Work fine powder into garden beds where a soil test shows you need lime
- Use halved shells as biodegradable seed-starting pots
Official guidance and resources
Accepted items and drop-off rules can vary by location. Check the destination before you go.
What’s Accepted
Accepted
- Chicken eggshells
- Duck and quail eggshells
- Any other bird eggshells
- Shells with membrane still attached
Not Accepted
- Dyed or decorated shells (some programs exclude them)
- Shells with substantial raw egg left in them (rinse first, to avoid odor)
Donation & Take‑Back Options
Estimated value: No meaningful resale value. Their worth is as a free liming and grit material, and only when ground fine.
FAQs
Do eggshells need to be washed before composting?
Rinsing is optional for composting. If you store shells before adding them, a quick rinse can reduce leftover egg residue and odor. Cover them with bedding in a worm bin or with browns in a backyard pile, and follow your local program's rules for collected organics.
How long do eggshells take to decompose?
Eggshell pieces may remain visible in finished compost; EPA notes that shells can be screened out and returned to an active pile. Crushing increases surface area and can speed breakdown, but powder is not required for composting. Fine grinding is more useful when applying shells as a soil amendment.
Can eggshells go in worm bins?
Yes, and this is arguably their best use. Worms have no teeth and need grit in the gizzard to process food. Oregon State recommends about half a cup of pulverized eggshell per 14-gallon bin every couple of months, and EPA, Illinois Extension, and UF/IFAS all list crushed eggshells as worm bin material.
Do eggshells keep slugs away?
No. A Royal Horticultural Society field trial ringed lettuces with crushed eggshells, copper tape, sharp grit, pine bark, and wool pellets, and after six weeks found no difference in damage between protected plants and unprotected ones. Some barriers do work in a lab; they fail in a real garden. What Oregon State found effective is a 1 to 2 percent brewed coffee solution used as a drench.
Will eggshells prevent blossom end rot in tomatoes?
No. Blossom end rot is a calcium transport problem driven by inconsistent watering, not a shortage of calcium in the soil, and University of Minnesota Extension states plainly that eggshells do not prevent it. Steady watering and mulch address the actual cause.
Should I worry about salmonella from raw eggshells?
EPA includes crushed eggshells in backyard and worm-bin composting guidance. EPA says a well-maintained pile may reach 130 to 160 degrees F and that higher temperatures help reduce pathogens; this is not a guarantee that every part of a home pile is heated evenly. Cover food scraps and keep the bin maintained, and use your municipal program's handling instructions if you collect organics.
Recycle eggshells
Search recycling centers by city or ZIP, or explore more food waste materials.