ROME: A study for the UN Food and Agriculture Organization (FAO) and the European Commission's Joint Research Centre says the world's food systems are responsible for more than a third of global anthropogenic greenhouse gas (GHG) emissions.

Ranging from land-use change and agricultural production to packaging and waste management, food system emissions were estimated at 18 billion tonnes of CO2e in 2015. Top emitters were, and are, China, Indonesia, US, Brazil, the European Union and India.

The Intergovernmental Panel on Climate Change Special Report on Climate Change and Land estimates annual global food system emissions are 11 to 19 billion tonnes.

The new UN study, co-authored by Francesco Tubiello, a senior statistician and climate-change specialist at the FAO, and EC researchers in Ispra, Italy, highlights how global food systems are becoming more energy intensive, reflecting trends in retail, packaging, transport and processing.

Production stages that bring foodstuffs to the farm gate - including fertilizers - are 39 percent of emissions, followed by land use at 38 percent and distribution at 29 percent, a share that is expected to rise.

Food packaging now contributes about 5.4 percent of related emissions, more than any other supply chain factor including transportation. However, emissions intensity varies by product, with wine and beer accounting for a "significant share of packaging impacts", according to the study, while bananas and beet sugar have higher transportation emissions.

Industrialized countries have increased emissions of fluorinated greenhouse gases used in refrigeration, now responsible for nearly half of the energy consumption by the retail and supermarket sector, where emissions have grown 400 percent in Europe since 1990.

Worldwide cold chain activities now account for around 5.0 percent of global food system emissions, a figure expected to increase says the UN.