Food

There are currently about 7.1 billion people on the planet¹.  The average American eats about ton of food per year, and the poorest average about half that².

That works out to 4.8x10¹²kg, which, compacted, would make a ball about 2km in diameter³.

Here it is compared to some other objects:

name	diameter	mass
Great Pyramid of Cheops	0.14x0.23km	5.4x109kg
Three Gorges Dam	0.18x2km	3.4x1010kg
just the meat4	0.76km	2.7x1011kg
asteroid: 1999 KW4	1.5km	2.4x1012kg
asteroid: 1620 Geographos	2.0km	4x1012kg
how much we eat in a year	2.0km	4.8x1012kg
asteroid: 2002 CE26	3.5km	2x1013kg
Halley's comet	8-15km	3x1014kg

To further help comprehend the dimensions, here is a list of the world's tallest buildings.

¹ - world population
² - average food consumption (I used the average of the two numbers)
³ - mean density of compacted food waste is about 1029 kg/m³.
⁴ - The size of the meatball we consume each year, as a species. See source.