Manufacturing a single book produces around 7.5 kg of CO₂ and requires about 25 litres of fresh water, with an average total carbon footprint of 12 kg per copy. And in Spain alone, around 180 million copies are printed every year. Borrowing a book from the library spreads that footprint across every reader who shares it, turning a single-user object into a collective resource that generates zero extra CO₂ and requires no additional trees to be felled.