Growing food creates greenhouse gas emissions both directly – through fuel used for agricultural machinery, methane produced (famously) by cows, and packaging and transportation – and indirectly due to the loss of carbon sinks, like forests and grasslands, to create land for crops and grazing. Plus, when unwanted food breaks down, it also emits the potent greenhouse gas methane.
So wasting food means a lot of emissions, and unnecessary ones at that. Food waste is estimated to account for a whopping 10% of all greenhouse gas emissions.
The same is true of the water that feeds the crops and livestock that are farmed but never eaten. Wasted food uses 760km³ of water every year – enough to fill 304,000,000 Olympic swimming pools.