Coffee chaff is valuable as a compost accelerator
Are you aware that with every shot of coffee, ground beans have already generated a waste known as chaff? The potential of reusing waste chaff is largely ignored.
Is coffee chaff useful for my garden?
Chaff is the skins of coffee beans that detach when beans are roasted to develop coffee flavour. It is often discarded by coffee roasters.
Waste chaff has relatively high levels of nutrients which can be returned to garden soil. Recycling it into compost enables you to nourish and improve your soil for growing healthy plants while working towards a sustainable future.
How do I reuse coffee chaff?
Coffee chaff is also known as silver skin. It is lightweight and blows around easily, so spreading dry chaff on the ground as a mulch can be frustrating. Watering can cause it to mat and create a different problem.
A word of caution. Chaff contains phytotoxic (plant-toxic) compounds, which restricts its heavy use for mulching. Fortunately, composting chaff removes the toxins.
An even better news is that coffee chaff can be reused as a natural compost accelerator. Our trials showed that chaff boosts the composting of non-woody garden waste:
- Spread the chaff as a thin layer (above a layer of garden waste).
- Moisten the dry chaff to make it wet enough for composting.
- Cover the wetted chaff with a new layer of garden waste.
- Repeat steps 1 to 3 as required.
We also found chaff can enrich kitchen waste. Our composting trials involved adding 2 cups of chaff every time a 7L kitchen caddy was emptied into Bioverter, which is a compact, self-contained compost bin.
Availability of waste chaff
A nearby eco-friendly coffee roaster may willingly give away chaff for recycling into compost. Give the roaster and yourself a big tick for taking another step towards sustainability.