Last updated: April 2015
Spotlight on coir pith
Environmental damage caused by peat mining and the intensifying search for alternatives has led to coir pith becoming a key component of some peat-free growing media. Joanna Long looks into the debate about coir pith to find out how sustainable it really is.
Coir pith, also known as coco peat, is the material found between coconut husk fibres and is a
by-product of the coconut industry. The largest producers of coir fibre (and therefore coir pith) are India and Sri Lanka. Coir pith has been growing in popularity as a component of growing media since the early 1990s but quality tended to vary and relatively little was known about the supply chains through which coir pith made its way to the UK.
Following the Natural Environment White Paper (2011), which included plans to phase out peat usage by 2030, the Sustainable Growing Media Task Force (SGMTF) was established to look into alternatives to peat and ensure that one unsustainable material was not replaced with another. As part of this, the group commissioned a study into coir pith: an apparently too-good-to-be-true alternative growing media that not only challenged peat in growing effectiveness but solved waste problems elsewhere in the world. 
Coir pith processing
When coconuts are harvested they are separated into kernel and husk. The kernel (or copra) is either used directly as food or processed into other food products or oil. The husk, meanwhile, is sent to fibre mills to be processed and then used to make mattresses, geotextiles and products for the automotive industry. The by-product of this fibre processing stage is coir pith, which historically would have been burned or simply left outside the fibre mill to rot, but is now itself being processed and shipped to horticultural markets in Europe, Australia and the USA.
Processing coir pith is a multi-stage process. First the pith is matured for up to 6 months to reduce the salt, tannin and phenol content, to gain a more favourable carbon-to-nitrogen ratio, and to change the pH from acidic to neutral. The pith is then sieved to remove physical contaminants and then washed with water to reduce the salt content further. The pith may also be ‘buffered’, that is, washed with a mixture of water and calcium nitrate, to displace sodium and balance the naturallyoccurring potassium. The pith is then dried and packaged for export.
The most obvious area of concern regarding coir pith is water consumption and pollution. Sri Lanka has few issues with water availability but in India the main coir pith processing plants are in Tamil Nadu, which suffers from water stress and scarcity.
The SGMTF study found that few pith processing plants were making efforts to conserve water or implement water management practices. Also, the process of washing and buffering coir pith happens simply by hosing or spraying mounds of coir pith.
If untreated or simply allowed to trickle away, the run-off (containing salts and other chemical, microbial and physical contaminants) can affect surface water, groundwater and soils. Some factories do wash coir pith on concrete floors in order to collect and treat the run-off but such practices do not appear to be widespread.
Another key area of concern in the coir pith industry are working conditions. Coir particles are very fine and lightweight, making them easily carried on the air and creating very dusty working conditions. Keeping floors and machinery free of dust and the use of personal protective equipment helped alleviate the problem, although the latter is very uncomfortable in the hot and humid climates of India and Sri Lanka.
The SGMTF study also found that workers in coir pith factories were often working six-day weeks with multiple shifts and, although India and Sri Lanka were deemed to have ‘adequate labour legislation’, this was only enforced in the formal, industrial sector and did not include informal sectors of the coir industry.
Another sustainability question mark for coir pith concerns the costs associated with transporting it from the processing sites in India and Sri Lanka to Western markets. However, coir pith can be compressed into blocks for longdistance transport meaning that it can be transported at a fraction of the size of its usable form.
According to Tom de Vesci of Horticultural Coir Ltd, a single pallet carries 2.7m3 of coir blocks weighing around 950kg. Once hydrated by the UK seller or end user, the contents of this pallet will reconstitute to 12-14m3 or more depending on the quality of the product. 
Similarly, Fertile Fibre claims that less fuel per tonne is used to transport its coir pith from Sri Lanka to the UK than is used transporting the coir between port and factory within the UK. 
A DEFRA taskforce is currently working to quantify the transport costs for coir more precisely but figures have yet to be released.
The SGMTF study also noted water issues elsewhere in the coir pith supply chain, such as the use of ‘retting’ (soaking husks) in coir fibre production and irrigation of coconut plantations. However, given that the coir pith sector comprises 50% of the coir fibre industry and just 5% of the overall coconut industry, the impact any changes to the coir pith supply chain could have were deemed to be too low to have much wider influence. It also seems unlikely that horticultural demand for coir pith will drive unsustainable practices in the coconut industry in general, as coir pith remains a waste product for coconut and coir fibre producers and existing supply is abundant.
All the same, supply chain management appears to be a low priority, not just in the coir industry but in the compost industry more generally, as only one of the companies reviewed in our product guide to peat free compost had a supply chain policy.
In the early years of development of the coir pith industry products tended to be of variable quality and therefore of limited use in horticulture. However, as the economic value of coir pith has
increased due to the intensifying search for alternatives to peat, the quality has improved.
That said, many coir blocks on sale in the UK are unbranded or unlabelled making it difficult to establish what you are buying and from whom. However, Fertile Fibre, Traidcraft and the Eden Project all sell their own brand of coir blocks and have therefore been included on in our guide to peat free compost.