The Finishing Process
After our compost has fully cured—a stage where the material is stable, mature, and cool to the touch—we begin the finishing process.
Why Is Curing Important?
Curing is the final stage of composting where active decomposition slows, heat subsides, and microbial communities stabilize. It ensures the compost is fully mature, safe for plants, and won't rob soil of nitrogen. It’s a vital resting phase that transforms hot, semi-finished compost into a garden-ready product.
Our 5-Step Finishing Process:
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Rough Sieving – We pass the compost through a rough screen to remove large chunks, un-composted material, or rocks.
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Contaminant Check – We inspect for any missed plastic, wire, or non-organic debris.
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Microwave in Small Batches – Compost is heat-treated to 180°F for pathogen and seed control.
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Cooling – Treated compost is allowed to cool before bagging.
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Bagging – Once cooled, compost is portioned into individual bags ready for distribution to households.
Each step ensures that the compost you receive is safe, clean, and ready to enrich your garden.
Why We Heat-Treat Our Finished Compost
At the Greenwich Composting Project, we love rich, living compost—but we also care deeply about safety. That’s why we take the extra step of heat-treating our finished compost before it’s distributed to the community.
What Is Heat-Treating?
Heat-treating is the process of raising the internal temperature of compost to at least 180°F using a standard household microwave. We do this in small batches, checking each one with a thermometer to ensure it reaches the target temperature.
Why Do We Do It?
Heat-treating helps ensure that our compost is:
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Free of pathogens that could harm plants or humans
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Clear of weed seeds that might sprout in your garden
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Safe and consistent for all types of use, including vegetable beds, lawns, and planters
Especially in a shared community project, this extra step helps protect everyone’s soil and crops.
What Happens to Microbes?
Heat-treating at 180°F does reduce or eliminate microbial life in the finished compost. Both harmful and beneficial microbes are sensitive to heat. But don’t worry—nature bounces back!
Once compost is added to your garden soil:
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Airborne microbes begin recolonizing immediately
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Worms and insects introduce soil life
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Contact with living soil restores microbial diversity
Your compost quickly becomes biologically active again, full of the good microbes your garden loves.
What About Nutrients?
Nutrients like nitrogen, phosphorus, and potassium are not affected by heat-treating. The compost still provides essential food for your plants and improves soil structure, drainage, and moisture retention.
Compost Q&A
Q: Does microwaving compost kill the good microbes?
A: Yes, heat-treating reduces microbial life. But microbes recolonize quickly once compost is added to soil.
Q: Does heat-treating remove nutrients?
A: No! Nutrients are heat-stable and remain available to feed your plants.
Q: Why not just skip this step?
A: For household compost it might be fine, but since we share compost with many families, heat-treating adds a layer of safety for everyone.
Q: How do you know microbes return?
A: Soil science shows that sterile compost gets recolonized naturally via air, insects, and contact with soil within days.