Take a closer look at Coir

There is now a wide understanding amongst gardeners and garden professionals that the use of peat in horticulture must end. For many years it was common to find peat in all manner of garden compost mixes, as it was used for its water retaining properties and nutrient holding, often used in potting mixes and as a soil improver. 

However, as useful as peat was found to be in the garden, it is even more crucial left in situ. We now know that peat bogs are an essential ecosystem and a key carbon store, the removal and destruction of which has a huge impact on climate change and biodiversity loss in the UK. A shocking 94% of this unique wetland habitat has been destroyed, used not just in horticulture but for fuel. Burning peat releases enormous amounts of carbon into the atmosphere and is still practised, albeit not widely, to produce commercial energy.

Thankfully, sites such as the Humberhead peatlands, now a Special Area of Conservation are being restored to their former condition with the help of LIFE+Nature and the EU. These threatened wetlands will slowly regenerate and provide an essential habitat for rare plants and birds, but as horticulture turns its back on peat, are we keeping an eye on what we are using to replace it?

In recent years, a popular alternative to peat has been the processed husk of coconut, or Coir. Widely seen as a waste product from the commercial production of coconut and coconut products, it felt like coir was the sustainable answer to the peat problem. A lightweight, rehydratable by product with great water and nutrient holding capacity was just what we needed, and it is now firmly in the mainstream. Seed starting blocks and compost pellets are available in most garden centres and coir is recommended by experts and personalities alike. Look closer however and Coir, is not all that it seems. 

Around 650,000 tonnes of coir is produced annually, predominantly from India and Sri Lanka, but it is also an important economic product for Brazil, Indonesia, Vietnam and the Philippines. 

The processing of coir takes time. Smaller producers using traditional methods remove the fibres from the husks and spend around 6 months stabilising them so natural sodium, tannin and other phenolic compounds are removed. In order to do this the fibres are soaked in calcium nitrate and washed, ready to be further processed. In larger scale, mechanised operations the processing time is reduced to only 5 days, but the methods are the same. The husks are washed and then treated with calcium nitrate.

It has been estimated that a minimum of 300 litres of water is used to wash just one cubic metre of coir, making this a very water intensive product. All this while water scarcity in India is becoming a bigger problem, and around 76 million people in the country do not have access to safe drinking water.  

Aside from the high levels of water usage in coir processing, the problem with this treatment is the removal and disposal of this processing water. Contaminated with nitrates, it more often than not finds its way into local rivers and wells, polluting ground water and thusly, the local water supply. Nitrates in drinking water are key risk factors in developing gastric and intestinal cancers. 

The rise in the popularity of coir products will in turn increase the amount of coir that is processed in these areas, which will increase the water usage and the potential for catastrophic pollution of this scarce and essential resource. Yet coir is also contributing to the degradation of the very groves from which it comes.

Once, when coir was just a by -product of coconut production, the spent husks and fibres where returned to the soil underneath the trees they came from, as a mulch and soil improver in an excellent closed-loop system. In agricultural and horticultural terms, a perfect use for any such by-product, but as coir becomes a more sought after commodity, the husks and fibres are not making their way back to the farms but being sold for processing, leaving the farmers either without their sustainable fertilizer or having to transport in alternative, often synthetic fertilizers. 

This coir paradox is just one of the dark sides of our new quest for sustainability, one which is not revealed to the consumer or influencer but is contributing to the already heavy environmental impact of modern horticulture. Ultimately, it is essential that we do not reduce our carbon footprint here in the UK by protecting our unique and degraded peatlands, at the expense of another countries soil stability, water supply and public health.