A Monthly Publication

 By Peter J James

 The first of these collisions was a Cathy-Heathcliff embrace writ large and it has already lasted for some fifty million years

This embrace was, of course, the collision between the Indo-Australian plate and the Eurasion plate, which thrust up the Himalayas and produced a spectacular geography as complex as any on the planet.  The second collision, or rather an annual series of repeated collisions, is an indirect consequence of the first.  The annual monsoons which sweep out of the Bay of Bengal and deluge Northern India and Bangladesh every summer result from warm, moisture laden air smashing into the Himalayan low pressure troughs.  This air is forced upwards and as it rises it cools and its burden of water vapour condenses as torrential rain.  In fact, the monsoon season rainfall exceeds the total annual rainfall of the Amazonian rain forest.  The dramatic quantity of warm rain falling in so short a time provides a set of unique climatic conditions which favour a characteristic type of vegetation.  This brings us to recyclable bags!

As I write this article the Copenhagen Conference on Climatic Change is just beginning and David Attenborough is asking leading questions such as ‘How many people live on planet earth? (Wednesday 9^th December 2009 BBC 2).  Our own High Street shops are making their contribution to salve our ‘green’ consciences by giving away recyclable carrier bags made from jute.  There we have our ‘two collision’ connection. 

Jute is a fibre derived from herbaceous annuals of the genus Corchorus (family, Sparrmaniaceae [Brownlowiaceae], some say), which require some three to four inches of rain during its growing season.  Small wonder then that monsoon soaked Bangladesh and Northern India supply about 85% of the world demand with the rest coming from China, Thailand and Myanmar, a massive total of three thousand million metric tonnes of the stuff!  Each bag that SPAR gives us weighs 120.00grams.  I can’t, I’m afraid, be bothered to work out that one as a percentage of world production but at least we are ‘doing our bit’.

If any of you watched ‘University Challenge’ between Warwick and Jesus College, Oxford on 7^th December 2009, you will know that jute, as well as flax and hemp are phloem or ‘bast’ fibres and that when separated from the plant resemble braided hair, the Bengali word for which is, jute.

Phloem fibres indeed!  We need a little botany here.  Any living organism living on the land, animal or plant must contend with the force of gravity.  Everyone is familiar with arthropod and vertebrate skeletons made of chitin and bone respectively but plant support systems are less obvious.  However, try chewing an undercooked vegetable or one that has been growing for too long without sufficient water and you’ll realise the meaning of the word ‘fibre’!  Plant fibres are long cells ranging in length from a few millimetres to twenty two centimetres in ramie, with tapered ends which allow them to fit neatly together.  They occur, in commercial quantities, in stems and leaves, just as you might expect in structures which give support.  Before synthetic fibres displaced natural fibres, every culture used the fibres of its own native flora for matting, cordage, sail-cloth, textiles and a host of other applications.  Fibre plants include palms, cacti and grasses but the ‘Big Three’ jute, flax and hemp are all annual dicotyledons and their fibres are derived from the outermost parts of the stem – the phloem or ‘bast’. 

Plants, of course, can often be used for more than one product and flax and hemp are no exceptions.  Flax may be grown for its fibre and was used on the Sandringham Estate during the war.  Its seed is used for linseed oil.  Hemp, for its sins, produces not only fibres but the politically sensitive, cannabis resin.  Jute, as far as I am aware, is grown only for its fibre.

The chemistry of plant fibres is very complex but essentially the cell walls are composed of a mixture of cellulose and lignin and this coupled with fibre length, defines the quality of the fibre and its usage.  The composition also determines its potential to be recycled.

This brings me back to those monsoons and Spar’s free carrier bags.  The warm, wet climate allows two or three crops of jute to be grown a year and this fast growth keeps the lignin content of the fibre low.  Hence, because cellulose is much easier to biodegrade than lignin, materials made from jute, such as carrier bags, are recyclable.

So, as we come to the end of the International Year of Natural Fibres, it is Thank you for those two collisions which have made us ‘greener’ and free from that irritating noise made by the crinkling of plastic bags.