5 NOTES

1. It’s Not Just Gross—It’s Useful! Sewage sludge can be processed and turned into fertilizer, helping grow crops instead of just getting tossed out.
2. Sludge Powers Cities! Some wastewater treatment plants convert sludge into biogas, which can be used to generate electricity and heat.
3. It Can Be Full of Metals! Industrial sludge sometimes contains heavy metals like lead or mercury—so it has to be handled carefully to avoid pollution.
4. There’s Sludge in Cheese? Kind of! In cheese making, “milk sludge” or curd forms when milk solids separate from the liquid—it's part of how cheese is born.
5. It Helped Clean Up Space Toilets! NASA has researched using treated sludge for nutrient recycling in space, possibly turning astronaut waste into fertilizer for growing food on long missions.