Compost vs Coir

Gardeners have been using compost containing peat moss for years, unknowingly contributing to carbon emissions by depleting some of the planet’s great carbon sinks. The peat bogs across the world do more to take carbon out of the air than the tropical rainforests. And they are being harvested at an unsustainable rate.

Sadly, most gardeners are not aware that they are using a peat compost mixture.

Many compost mixtures on the market can contain peat. Unless it's labelled 'peat-free', these mixtures can contain between 70% and 100% peat.

Why Gardeners use Peat

In garden beds, peat moss retains moisture and aerates compost and soil by making it "fluffier". New lawns are commonly seeded and covered with a peat/compost mix but it is ineffective for two reasons: the first hard rain washes the peat off the lawn. Second, Peat is acidic - most gardens and lawns don't need more acidic soil.

In the search for a peat moss alternative, coir (also called coco coir), is the one that is most often discussed.

What is Coco Coir?

A coconut consists of two main parts, the inner coconut kernel which we eat, and the outer husk. The outer husk consists of fibre’s and corky material found between the fibres. The fibres are extracted and used for many applications including floor mats, doormats, brushes and mattresses. The remaining dust and short fibres are known as coir pith.

In horticulture, the term coir is used interchangeably with the term coir pith and is sometimes called coir peat, coir dust, coir meal or coco peat. The material is brown, sawdust-like and looks similar to dry peat moss.

In some cases, the husk is simply broken into chucks without removing the fibre and sold as potting media for plants like orchids. The exceptional water holding capacity and airiness of the material make it a perfect media for such plants.

Why use Coir as an Alternative

Coir has many of the same properties as peat moss including an ability to hold a lot of water. It is sold dry, but after soaking in water it expands 3-4 times in size as it soaks up all the water. Coir tends to have high levels of potassium and low levels of calcium and keeps the soil aerated and moist.

There are two areas where coir wins over compost: seed starting and container plantings.  

Compost vs Coir

There is no definitive data on compost vs coir and which is more eco-friendly.

Multi-purpose compost containing peat moss affects climate change and resources the most. The impacts by peat include transportation, land use change, CO2 production, and aquatic eutrophication (loss of bogs).

Pure peat free compost can contain foreign objects such as glass, plastic, metals and other sharp objects which becomes mixed into the compost but cannot be composted down.

The impacts by coir are due to transportation, electricity consumption and production.

Conclusion

Many gardeners are making the switch to coir from compost mixtures.

During our own growing trials, we noted that seedlings and bulbs do tend to get a boost in growth when started in coir. We believe this is due the slow release of water to the young plants and the added benefit of coir having great drainage which prevents rotting.

Compost mixtures can have more nutritional benefits but gardeners can overlook this if using coir as they add natural feeds and fertilisers, which are readily available on the market and tailored to different plant species.