No matter what you’ve read or heard, paper isn't going away anytime soon. I know people who print their email. (Honestly sometimes, I kind of think it's a good idea.) However, paper comes from trees, and honestly that isn't the best idea, since trees grow slowly which makes sustainability difficult.
What we need is a way to make semi-natural cellulose fibers out of a sustainable, renewable material. Optimally it needs to be a perennial legume. The problem is plants like that produce short often branched chain cellulose instead of the more desirable long chain (woody) structural cellulose.
Right now there is a lot of research going into enzymes that can cleave cellulose into sugar so yeast can be used to ferment biomass into ethanol for fuel. We need research in the other direction, where short cellulose molecules are linked to make long molecules. The branching chains could then be cleaved and the long molecules cross linked, to make them more rigid. The resulting fibers could be used as pulp for paper making. Since the fibers are not from trees they will be naturally whiter and free of lignin, so they will require fewer chemical treatments.
Possibly the fibers could spun like cotton to make renewable cloth. Cotton may be a great cash crop but due to its high fertilizer, water and pest spraying needs it isn't that great for the environment. Even if the fibers are too coarse for spinning they could be used in engineered wood products to reduce the need for farmed trees. Engineered wood products are actually a better possible use of semi-natural cellulose. By replacing whole wood products with a sustainable material it could really help make forestry a more sustainable industry.
Ok you might be thinking great where do we get the land to grow billions of tons of clover? We don't have to; this process should work with leaves, farm waste, and grass clippings. Plus by seeding the reactor with already longish fibers from low grade recycled paper, the useful life of the fibers is extended, and the reaction efficiencies can be increased. Even if it isn't possible to make paper grade cellulose out of soft stemmed plants, these enzymes could used to "upgrade" lower quality short cellulose.
Another possibility is to move away from plant based cellulose and use cellulose produced by microorganisms, via aerobic fermentation. I am not sure how you would market paper made from sewer water, but I am sure someone could do it.
Imagine large ponds filled with sewer water, and bubbled with flue gas, covered with a cm thick layer of cellulose bound microorganisms (biofilm). Every once in a while you skim it off, render the lipids for biodiesel, the protein for animal feed, the soluble carbohydrates for ethanol production, and the rest becomes paper, or the boards in someone’s back deck. Oh and the water comes out cleaner and ready to go into a swamp or river for final purification.
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