Organosolv is an industrial process under development for the processing of wood into pulp used in papermaking manufacture for a variety of consumer needs. The process was invented and patented by Theodore Kleinert in 1971, but was being researched as far back as the beginning of the 20th century. It is a replacement for the Kraft process of pulping, which uses large amounts of water that are polluted with organic chlorine compounds in the process, and subsequently added to the waste-water stream of a pulp mill. Kleinert's method substitutes an organic solvent for water, which can then be recovered through distillation and recycled, making the process much more environmentally friendly. Waste cellulose produced in the organosolv reaction also has value as an ingredient for the production of ethanol fuel, which adds another level of value to it as a pulping technique.
The types of organic solvents most often used in the organosolv process include formic acid and acetic acid mixed with water, but several other acid formulations have also been studied. As of the early 1990s, four chemical methods of organosolv pulping were in production or the testing state. They included the use of methanol, acetic acid, and peroxyformic acid compounds to break down wood lignin into pulp. While each method offered environmental advantages over the Kraft process, they produced pulp that was inferior in strength to that produced by using the Kraft method. The Milox pulping organosolv method improved upon the quality of the pulp produced while using no environmentally-hazardous chlorine or sulphur compounds, yet it proved difficult to recover the solvent in this method.
Kraft pulping remains the chosen pulping technique in industry as of 2011, due to its ability to produce a superior commercial product. This is despite the fact that it is a type of sulfite pulping that also produces air pollution in the form of organic sulphur compounds released into the atmosphere. While organosolv research is ongoing, the drawbacks to the process deal with the efficient chemical recovery of the solvents used, and finding an ideal solvent formula that will produce an end pulp product that is competitive with what the Kraft process makes.
The pulp and paper industry faces several challenges going forward. Increasingly strict environmental legislation as well as the rise in cost for raw materials is making it less economically sound. Alternatives to wood are being sought to remedy this, such as biomass waste that contains wood lignin and cellulose compounds. The current Kraft pulp method also uses much more energy and water than experimental organosolv approaches do, which may give them an industrial edge in the near future as energy costs rise and fresh water resources become increasingly scarce. Several organosolv methods are currently being used in isolated pulp mill production in Canada and elsewhere, but they have yet to attain an industry dominance that the Kraft process has.