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Using manure to make sustainable paper

Not the first thing you think of when you see elephant dung, but this material turns out to be an excellent source of cellulose for paper manufacturing, scientists report. And in regions with plenty of farm animals, upcycling manure into paper products could be a cheap and environmentally sound method to use manure.

The idea for the project germinated on Crete, where Dr. Alexander Bismarck, with the University of Vienna, Austria, noticed goats munching on summer-dry grass during his vacation.

“I realized what comes out in the end is partially digested plant matter, so there must be cellulose in there,” he recalls. “Depending on the animal, up to 40 percent of that manure is cellulose, which is then easily accessible.”

Less energy and fewer chemical treatments should be needed to turn this partially digested material into cellulose nanofibers, relative to starting with raw wood, he conjectured.

After working with goat manure, Bismarck moved on to dung from horses, cows and, eventually, elephants. The supply of raw material is substantial – hundreds of elephants in Africa produce tons of dung every day.

The researchers treat the manure with a sodium hydroxide solution, which partially removes lignin plus other impurities. To fully remove lignin and to produce white pulp for making paper, the material has to be bleached with sodium hypochlorite. The purified cellulose requires little grinding to break it down into nanofibers in preparation for use in paper.

The dung-derived nanopaper could be used in many applications, including as reinforcement for polymer composites or filters that can clean wastewater before it’s discharged into the environment, Bismarck says. The nanopaper could also be used to write on, he says.