* Need to ramp up cocoa output to 4 mln T, from 3 mln T now -Petra exec
* Global cocoa prices currently at $2,100 per tonne
By Michael Taylor
JAKARTA, March 26 (Reuters) - Global cocoa prices could more than double by 2020, rallying to a level last seen 36 years ago, if production fails to catch up with demand, a director at Singapore-based Petra Foods said on Tuesday.
Cocoa demand is forecast to exceed production by 45,000 tonnes in the season to September 2013, according to the International Cocoa Organization, with grindings expected to rise 1.5 percent to 4.01 million tonnes.
"We have mass market products. We cannot afford a cocoa price of $5,000 a tonne. With that you will get boom and bust, which is the worst scenario for everyone in the cocoa industry," said Marc Donaldson, Petra's director of cocoa sustainability.
Global output needs to hit at least 4 million tonnes by 2020, which is 1 million more than now, to prevent a spike in cocoa prices, he said at the Asia Choco Congress in Jakarta.
Petra Foods was the world's third largest supplier of cocoa ingredients before it sold its cocoa business to Swiss chocolate maker Barry Callebaut in a deal announced in December.
Benchmark New York cocoa futures are currently hovering around $2,100 a tonne, well below a 32-year high around $3,800 struck in early 2011 and a peak of about $5,300 hit in 1977, according to Reuters data.
Prices may, however, soon get a boost as chocolate makers will start replenishing cocoa bean stocks this year after eating through a mountain of cocoa butter built up more than a year ago, boosting demand for chocolate's main ingredient.
Rising global cocoa demand is linked to economic growth, Donaldson said, adding that consumers in Asia are expected to switch to chocolate products with higher cocoa powder content.
Even though the industry has spent more than $1.2 billion on sustainability efforts over the last five years to boost output, results have been far from satisfactory, said Donaldson.
But delegates at the cocoa gathering believe that third-largest producer Indonesia could help fill the output gap, even though the country's ambitious plan to boost production to 1 million tonnes by 2020 has suffered a setback after hundreds of newly-planted trees died.
Indonesia's output could rise by 11 percent to as high as 500,000 tonnes in 2013 from last year due to better farming techniques, although recent wet weather will delay harvests, according to the Indonesian Cocoa Association.
Multinational firms such as Cargill and Barry Callebaut, the world's top chocolate maker, have already built grinding projects in Indonesia.
On next year's global supply prospects, Petra's Donaldson said it was difficult to predict whether there will be a deficit until results of Ivory Coast's mid-crop are known after May.
In Ivory Coast, the world's top cocoa producer, rainfall diminished across the main cocoa growing regions last week, and some growers were worried that extreme heat could hinder the development of the April-to-September mid-crop.