Which of the following is NOT typically considered an inorganic waste?

The correct answer identifies coffee grounds as an organic waste rather than an inorganic one. Organic wastes are typically derived from living organisms, which includes materials that can decompose naturally, like food scraps such as coffee grounds. Being primarily composed of organic matter, these materials contribute to the nutrient load in wastewater and can be subject to biological treatment processes.

In contrast, inorganic wastes do not come from living organisms. Options like sand, iron, and calcium are all classified as inorganic materials. Sand is a naturally occurring mineral, while iron and calcium are elements found in nature. These substances do not break down biologically, reinforcing their classification as inorganic waste. Thus, coffee grounds stand out as the only material in the list that is not classified as inorganic.