* Tea cartel aims to ensure price stability by boosting demand
* Six producers face labour shortages, climate change
* Cartel may also work against producers
MUMBAI, Jan 28 (Reuters) - Brewing a tea cartel is proving more difficult than a cuppa for six major producers of the world's most widely consumed beverage, who last week decided to join forces without explaining exactly what they planned to do.
India, Kenya, Indonesia, Malawi, Rwanda and Sri Lanka, which account for more than 80 percent of the world's tea output, agreed in Colombo to form the International Tea Producers Forum, an organisation they said was aimed at stabilising prices, promoting the beverage and ensuring sustainable production.
Their manifesto, however, had few precise mechanisms -- an executive committee would be set up in November -- and industry experts say any attempts to act like a real cartel and control prices or limit production will be stymied by the complexity of the commodity and the piecemeal nature of its market.
The forum's founding nations, which produce about 1.9 billion kg of tea per year, face similar challenges such as labour shortages, climate change and a need to improve agricultural practices.
They are unlikely, however, to agree on production quotas or price fixing mechanisms due to the different varieties, and amounts, that each nation produces.
"Nobody will accept a quota. What you produce, you have to sell. Tea cannot be stored. Tea is perishable commodity. So no country will ever accept a quota," said Deepak Atal, managing director of Amalgamated Plantations, the second biggest tea producer in India, the world's third biggest tea exporter.
"You will compete in the world market and sell your tea."
Kenya is the world's biggest tea exporter, according to the latest data from the U.N. food organisation, followed by China, which has been invited to join the forum as an observer.
The forum is the first attempt to create unity among the world's main tea producers since a cartel was formed 80 years ago to lift price by curbing exports. The measure worked, and prices rose by more than a quarter within six months.
Back then, British firms such as Finlays controlled most of the tea trade, but today's tea market is filled with a plethora of sellers hawking a vast array of varieties, which complicates any attempt to control exports and prices.
"In 1930s, the industry was controlled by few British companies. They owned tea gardens in multiple countries. That's why it was easier to agree on exports curbs," said a TEA? broker based in Kolkata, capital of West Bengal state which is one of the country's main tea growing areas.
"Today there are hundreds of tea garden owners and exporters."
THE PERFECT PRICE FOR TEA
Unlike other commodities such as rubber or sugar, tea has no futures market and no benchmark grade, which makes pricing largely arbitrary. Physical tea is often sold on a weekly basis, via auction.
According to the Tea Board of India, tea prices in India have risen about 40 percent in the last five years, but during the same period, rubber, wheat and sugar cane prices have more than doubled. Average Indian black tea prices stood at $2.25 a kg in 2012, slightly higher than $2.23 a year ago.
"The quality of tea is different in each country, and even within a country, so benchmarking them is not possible," said Gopal Poddar, chairman, Limtex India, a producer and exporter based in Kolkata.
Past experiences also show that a cartel could work against the producers.
The International Natural Rubber Organization broke up in 2000 after major producers Thailand and Malaysia pulled out, saying the forum was not doing enough to support prices.
The now defunct Association of Coffee Producing Countries tried to stop prices from falling by proposing producers hold back 20 percent of exportable coffee in a plan agreed in May 2000. The scheme was scrapped 16 months later because it failed to have an impact.
"Governments can discuss issues and form organizations, but trade takes place between companies. Convincing them to sacrifice their profits is not possible," said a veteran Indian tea industry official, referring to the cartel.
Against all these odds, industry experts say the cartel is likely to succeed in its goal of maintaining tea's popularity, but only because it really is the world's favourite brew.
Global tea consumption growth slowed down in 2007 before picking up three years later at about six percent, compared with coffee at about 4 percent.
World tea production is estimated to grow at 1.87 percent annually in the next 10 years, the United Nations' Food and Agriculture Organization said in 2012, slightly lower than the 1.99 percent pace over the previous decade to reach 3.28 million tonnes by 2021.
"We are trying to achieve a growth in the world market so tea can become more popular and that can stabilize the prices with a consistent growth," said Amalgamated Plantations managing director Atal.
"There should be cooperation on common issues, common channel for promotion of tea as a generic commodity." (Additional reporting by Ranga Sirilal in COLOMBO; editing by Lewa Pardomuan and Miral Fahmy)