including engine sludge. Engine sludge — sometimes called oil sludge — is a thick, jelly-like substance that can form inside of your engine if the oil becomes contaminated, or you go too long ...

Biosolids, or sewage sludge, are the solid byproducts of the wastewater treatment process. Rich in nutrients, they can be used as fertilizer on agricultural fields or compost on lawns. But the ...