In the United States, it is estimated that 40% of food is wasted. Food is thrown out from store shelves, because it has passed “best by” dates—which some have pointed out are arbitrary and not really related to food safety. Consumers who buy more than they eat, or forget their tomatoes or leftover take-out Chinese food in the back of their fridge until it is too old to eat also throw out food. Food waste is also rampant in the restaurant industry, especially due to overly large portioning. Even if the most wasteful aspects of food “waste” were dealt with, however, there will always be organic materials from food preparation and consumption that require disposal. Onion peels. Tomato stems. Fish bones. Right now, this mostly goes into trash streams, aka landfills.
The other post-consumption waste, as mentioned, is human urine and feces. What do we do with it? Well, considering human waste disposal is the “big necessity” of civilization, we’ve been remarkably irresponsible (stupid?) with our approaches. For those in the developed world, water-based sewage infrastructure takes our shit away quickly and easily—which is great for public health reasons—but does so with massive waste of clean (often potable) water, and requires additionally expensive and large infrastructure to process that waste and find somewhere to put it. Some municipal wastewater treatment programs produce what they euphemistically call “biosolids”; in some places this is used on landscapes as fertilizer, in others it is incinerated, or landfilled. In some cases, wastewater is simply dumped into bodies of water such as rivers, bays, and seas.
In the developing world there are major issues of sanitation in the absence of the above infrastructure. Open-air sewage near villages often causes outbreaks of preventable communicable diseases. Latrines built by well-meaning “development” projects often are converted to other uses, or used until filled and then never used again (development projects all too often pay for implementation but not maintenance/upkeep). Yet, the use of human waste in an ecologically sound manner does exist, notably in China, where “night soil” (another euphemism) still is collected, composted, and used as an agricultural amendment locally. The need to deal with waste in a way that benefits the sustainability of farming systems (that is, the soil!) will be taken up further in the “solutions” section.