Each year, food that's produced but not consumed adds 3.3 billion metric tons of greenhouse gas to the atmosphere and can use significant amounts of water, according to the UN Food and Agriculture Organization's latest report, Food Wastage Imprint: Impacts on Natural Resources.
FAO touts its food wastage study as the first to look at the impacts of wasted food from an environmental perspective – studying impacts on climate, water and land use.
It says that producers often suffer the consequences of food wastage that may not occur by any fault of their own. In fact, FAO estimates, waste costs producers $750 billion annually.
"All of us - farmers and fishers; food processors and supermarkets; local and national governments; individual consumers -- must make changes at every link of the human food chain to prevent food wastage from happening in the first place, and re-use or recycle it when we can't," FAO Director-General José Graziano da Silva said in a statement this week.
Part of the problem of wastage, aside from economic and environmental effects, is that wasted food could otherwise be used.
"We simply cannot allow one-third of all the food we produce to go to waste or be lost because of inappropriate practices, when 870 million people go hungry every day," he added.
FAO explains in its latest study that 54% the world's food wastage occurs "upstream" during production, post-harvest handling and storage, and 46% of it happens "downstream," at the processing, distribution and consumption stages.
Food wastage also depends on the region it happens in and what the economic status of the region is, FAO said. For example, developing countries suffer more food losses during agricultural production, while food waste at the retail and consumer level tends to be higher in middle- and high-income regions.
The type of food wasted also makes a difference in its impact, FAO says. Meat, for example, can make a larger impact on the environment when it is wasted due to the time and energy it takes to produce it. In addition, fruit wastage contributes significantly to water waste in Asia, Latin America, and Europe.
FAO says the best ways to tackle the problem of food wastage will be stopping it before it starts, reusing products within the human food chain and recycling or recovering otherwise wasted food.
The report estimates that a combination of consumer behavior and lack of communication in the supply chain underlies the higher levels of food waste in affluent societies especially. Consumers fail to plan their shopping, overpurchase, or over-react to "best-before-dates," while quality and aesthetic standards lead retailers to reject large amounts of perfectly edible food.
FAO recommends the highest priority in limiting waste be given to balancing food production with demand – meaning avoiding using natural resources to produce un-needed food in the first place.
The report also suggests finding secondary markets such as diversion to livestock feed, for food surpluses.
Lastly, FAO says anaerobic digestion and composting are final efforts to recover energy from un-needed or uneaten foods.
Read the full report here.