Caffeine from Tea waste

Published on 01/11/2011

For centuries, tea and coffee have been most popular beverages. This is not because primarily they are easily available but they contain the stimulant caffeine which stimulates respiration, the heart, and the Central Nervous System (CNS) of human body and is also known to be a diuretic (promotes urination).  Caffeine has both positive and negative impact on human body. It has been seen that due to its deficiency in the body, it can cause nervousness and insomnia. In the case of different kind of people belonging to different workgroups, like many drugs, consumption of tea and coffee can be addictive, making it difficult to reduce the daily dose.  If we take the case of a regular coffee drinker who consumes just four cups per day can experience headache, insomnia, and even nausea when the dosage is made limited. On the other hand, it helps people to pay attention, to concentrate on sharp work and can sharpen moderately complex mental skills as well as prolong the ability to exercise.

What is Caffeine?

The IUPAC name of caffeine is 1,3,7-trimethylxanthine, and is obtained from tea waste or coffee, or from the dried leaves of Cameelia sinensis. Chemical composition of caffeine suggests that it is an alkaloid which is primarily a class of naturally occurring compounds containing nitrogen. They have the properties of an organic amine base together with nitrogen hence it is an alkaloid.  Some of the typical alkaloids are caffeine, nicotine, morphine, codeine, and cocaine. Caffeine exists as an odorless compound which appears as white powder silky glistening needles. The taste of caffeine is bitter. Caffeine acts on the central nervous system facilitating performance of muscular work and capable of increasing total work which can be performed by muscle. This also acts on cardiac muscle and muscle of kidneys.

Caffeine may be the most widely used and abused drug in the United States.  During the course of the day an average person may unwittingly consume up to a gram of this substance.  The caffeine content of some common foods and drugs is given in table below.

Process of extraction of Caffeine from tea waste

Caffeine also comes from tea leaves and other tea wastes. The isolation of caffeine from tea leaves is a difficult task and presents the chemist with a major problem. Caffeine does not occur alone in tea leaves, but is accompanied by other natural substances like cellulose, tannins, flavonoid pigments and chlorophyll from which it must be separated. This separation can be very costly due to involvement of many chemicals and sophisticated laboratory is needed. Apart from this caffeine can also be recovered from the waste tea or from the residue left behind after the preparation of the tea.

Tea waste can be used at broad level to recover the residual caffeine. For this purpose firstly the source from where the tea waste is generated has to be identified. Regarding this tea waste generated from various tea processing industries has to be collected and brought to the extraction plant for extraction of caffeine. The extraction of caffeine is known to be a multi-stage counter-current extraction technique. The extraction plant is broadly sub-divided into three sections, namely:

• Pre-treatment section.
• Extraction section.
• Post-treatment section.

Extraction of caffeine from tea waste is a three stage process which are described one by one below:

1. Pre Treatment Section

The very first step of extraction is called pre-treatment. For this purpose, in the pre-treatment section, tea waste, lime and water are mixed. The mixing ratio of these three ingredients is pre-fixed and always kept constant. After mixing them in the predefined ratio, the mixture prepared is then cooked at elevated temperature in a mixing device called cooker-cum-mixer. The purpose of the pre-treatment is that by cooking the tissues of the tea waste gets loosen which helps in the efficient extraction of caffeine in the extractor. This is the main reason why pre-treatment is done.

2.  Extraction Section

In this section, a suitable solvent is used to extract caffeine tea waste. In this process, the solvent is recovered subsequently and recycled back to the system. The addition of the solvent leads to the generation of crude caffeine. Complete operation in this section is carried out in a continuous mode other than batch operation. A continuous feed of waste is given to the reactor to maintain the continuity of the reactor system. Inside the extractor, the waste comes in contact with the solvent in counter-current way which leads to the extraction of caffeine in stage-wise manner.  Caffeine is recovered from the miscella, a mixture of lime tea waste and water which is stored in the balancing tank in the form of crude caffeine. During this storage all the solvent is removed from the crude caffeine. The removal of solvent from crude caffeine occurs by a solvent recovery method called evaporation. The solvent recovered in this process is recycled back to the extractor. Before it is recycled back to the extractor it is separated from water in solvent-water separator. Crude caffeine is then subjected to the post-treatment which gives pure caffeine.

The residual decaffeinated tea waste from the extractor moves to the desolventizer where the entrapped solvent in the tea waste is removed by heating. Solvent recovered through this process  is recycled back to the system extractor.

3.  Post Treatment

In the last step, crude caffeine obtained from extraction section which is kept in the storage tank is processed further in order to obtain the final purified caffeine. Here, in this section, crude caffeine is firstly made to dissolve in hot water to separate it from wax. After that, the remaining coloured solution which contains caffeine is treated with activated charcoal and filtered. The activated charcoal being capable of absorbing all impurities absorbs all the impurities and color. The decolorized caffeine solution left behind is then concentrated by means of evaporation and allowed to crystallize. Caffeine crystals are then separated from mother liquor by centrifuging. By centrifuge the small crystals of caffeine tends to agglomerate and thus caffeine is obtained. The caffeine thus obtained is dried further in a drier and pulverized to convert it into powder form before its packing.

The Way Ahead

Extraction of caffeine from tea waste is an environmentally safe practice which leads to the caffeine generation as well as waste management and minimization.