As much as one-third of the total amount of food produced worldwide is wasted, costing the global economy about $750 billion on an annual basis, a new UN Food and Agriculture Organization (FAO) report claims.

The amount of food that goes to waste makes it the third largest source of greenhouse gas and a bigger source of carbon emissions than any country in the world, except for China and the United States. Wasted food is estimated to result in the release of 3.3 billion tons of greenhouse gases, the FAO said.

While 870 million people worldwide are starving, 1.3 billion tons of edible food is being wasted every year. The world cannot afford such waste, not just because of its economic implications but because of its effect on climate change, the report noted.

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The UN estimated that by 2050, the world's population will have increased by another 2 billion people. Feeding the entire population on Earth will become impossible, bearing in mind that one-third of farmland is occupied by produce that is being wasted.

The report explained that more than half of the waste occurs during upstream production — in harvesting, post-harvest handling and storage. About 46% of the waste occurs downstream, during the processing, distribution and consumption stages.

Food that is produced but not consumed also contributes to water waste, since production requires the use of water. The FAO calculated that food waste results in water waste equivalent to the annual flow of the Volga River in Russia.