The environmental sustainability of the textile and clothing supply chain depends significantly on the way that fibres are grown or manufactured and the raw materials used, according to a report in the latest issue of Global Apparel Markets from the business information company Textiles Intelligence. Fibres represent only the starting point of the textile and apparel supply chain. But it is in these areas where much of the damage to the environment is caused. In the case of wool, the problems start with the rearing of sheep. Manure generated from livestock, for example, has contributed significantly to the increase in atmospheric greenhouse gases over the last 250 years, and faecal matter has been known to contaminate waterways in areas where sheep are farmed. Also, high stock numbers can be a cause of significant soil erosion which can trigger desertification. In the case of cotton, there is a problem of water usage -- it is said that around 8,500 litres of water are needed to grow the cotton used in the manufacture of a T-shirt and a pair of jeans. Also, extensive use is made of pesticides, synthetic fertilisers and other chemicals which can cause damage to the environment. Moreover, pesticides can cause considerable harm to human health. If cotton is going to be produced in significant quantities for the foreseeable future, there will be rising pressure to find ways of improving the environmental sustainability of cotton growing. A variety of initiatives have emerged with this objective in mind, including the Better Cotton Initiative (BCI), organic cotton, Cotton made in Africa (CmiA) and Fairtrade certified cotton. Despite these initiatives, these so-called "identity cottons" account for only a small proportion of total cotton production. In 2015 organic cotton accounted for a mere 0.5%. And even when other types of sustainable cotton are added, the total is only 16%. Admittedly, this share is expected to reach 35% by 2020. But most identity cottons fall short of the standards of organic cotton in terms of environmental sustainability as they still involve the use of artificial pesticides and fertilisers. Set against these issues, man-made fibres would appear to provide a more environmentally friendly alternative. In the manufacture of man-made cellulosic fibres -- such as cuprammonium rayon (cupro), lyocell, modal and viscose -- most of the raw material used is wood pulp, which can be obtained from a naturally occurring renewable resource in the form of trees. Moreover, there is scope for making the raw material even more environmentally friendly by sourcing the trees from managed forests. However, most cellulosic fibres are made using a process which is unfriendly to the environment -- with the notable exception of lyocell fibres, which are produced using a closed loop solvent spinning process. In the manufacture of synthetic fibres, the raw materials are less environmentally friendly than those used in the production of cellulosic fibres as the bulk are derived from the petrochemical industry, starting with non-renewable fossil fuels. But a number of initiatives are under way to make synthetic fibres from sources which are more sustainable. Recycling initiatives are gathering pace, and an increasing volume of fibres is being made from polymers derived by processing industrial waste generated in factories -- or from polymers obtained by processing post-consumer polyethylene terephthalate (PET) drinks bottles. Also, synthetic fibres such as Ingeo are being made from agricultural crops. However, critics argue that the use of agricultural crops as raw materials for synthetic fibres uses land which should be devoted to feeding the world's growing population. The textile and apparel supply industry still has a long way to go. Despite efforts aimed at improving the environmental sustainability of the supply chain, sustainable fibres account for only a small proportion of the 89 million tons of fibres produced globally.