 Look around you. There are so many paper products from the sheets of paper that you write on, to the pages of your textbook, to ink cartons, to newspapers, to certain grocery bags, to cardboard boxes, and the list continues. The important fact here is that paper is an essential part of our lives. You may know that paper usually comes from trees. They must first be chopped down and then subjected to an industrial process called pulping, which removes lignin, the polymer that gives trees their strong hard structure. Obviously, the paper production process has led to mass deforestation. The main issue here is that the trees are not being replanted, or if they are being replanted, they will not grow fast enough to replace the trees that are being cut. This is a serious environmental issue because it destroys habitats, disrupts food chains, and food webs is a severe eyesore and indirectly leads to increased carbon dioxide content in the atmosphere. It could also lead to erosion of hillsides with the consequence of flooding. An obvious solution is to recycle these paper products. In this lesson, we will learn about recycling paper and the advantages and disadvantages to this industrial process. Paper is in fact layers of cross-linked cellulose fibers. Recall that cellulose is a polymer of glucose monomer units. If you tear a piece of paper and look closely, you will see fine hairs sticking out. These fine hairs are cellulose fibers. When paper products are recycled, these cellulose fibers are merely pulled apart and rearranged into new paper products. In some countries, paper recycling is highly encouraged by having specialized waste containers just for paper waste. The paper waste is then collected and separated according to their properties. Sheets of paper are recycled with other sheets of paper, and cardboard boxes are recycled with other cardboard boxes. Now, right before the paper can be recycled, any ink needs to be removed. This process is called de-inking. Most inks are petroleum-based inks which are derived from crude oil products and can be difficult to remove. Currently, in development, are soy-based inks which are derived from a renewable resource and makes it easier for the paper to be de-inked. Metal parts such as staples and paper clips need to be removed with a magnet, and glues are removed with a chemical wash. Bleach is sometimes added to whiten the slurry, and therefore the resulting paper product will be brighter. The cellulose fibers in the slurry are mixed with new pulp, and then allowed to settle on a gauze and rolled to form the new sheets of paper. This step also removes any excess water from the slurry before it is air dried. The main disadvantage with recycling paper is that it can only be done a few times. Recycled paper is usually used to make kitchen rolls, toilet paper, and packaging materials. Each time a paper product is recycled, the cellulose fibers become shorter, thereby rendering the recycled paper product a little bit less useful than the original. However, this can be used for another purpose. Can you remember what cellulase is? Hint, it is an enzyme. Please pause the lesson to think about this and resume when you are ready. Cellulase is the enzyme that breaks cellulose apart into its glucose monomers. Currently, the industrial usage of cellulase is to break down cellulose into glucose. The glucose obtained can then be fermented by certain bacteria to produce ethanol, which can then be used as a biofuel. In summary, recycling paper products help to reduce the rate of deforestation and consumes a lot less energy. Although paper can only be recycled a few times, the cellulose fibers can be broken apart into glucose monomers, which can then be used for other environmentally friendly applications.