Organosolv is an eco-friendly process for converting wood into pulp used in papermaking. It replaces water with organic solvents, which can be recycled. The process also produces waste cellulose that can be used to make ethanol fuel. However, the Kraft pulping process remains the industry standard due to its ability to produce a superior commercial product. The pulp and paper industry faces challenges such as stricter environmental legislation and rising raw material costs, leading to a search for alternatives like biomass waste. Organosolv methods have yet to achieve industry dominance over the Kraft process.
Organosolv is an industrial process under development for converting wood into pulp used in papermaking for a variety of consumer needs. The process was invented and patented by Theodore Kleinert in 1971, but has been researched since the early 20th century. It is a substitute for the Kraft pulping process, which uses large amounts of water that is polluted with organic chlorine compounds in the process and then added to a paper mill’s wastewater stream. Kleinert’s method replaces water with an organic solvent, which can then be recovered via distillation and recycled, making the process much more environmentally friendly. The 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 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 acidic formulations have also been studied. By the early 1990s, four chemical methods of organosolv pulping were in production or in testing. They included the use of methanol, acetic acid, and peroxyformic acid compounds to break down wood lignin into a paste. While each method offered environmental benefits over the Kraft process, they produced pulp with lower strength than that produced using the Kraft method. The Milox organosolv pulping method has improved the quality of the pulp produced without using environmentally harmful chlorine or sulfur compounds, however it has proved difficult to recover the solvent with this method.
Kraft pulping remains the pulping technique of choice in the 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 paste which also produces air pollution in the form of organic sulfur compounds released into the atmosphere. While organosolv research is ongoing, the disadvantages of the process involve the efficient chemical recovery of the solvents used and the search for an ideal solvent formula that will produce a final pulp product that is competitive with what the Kraft process does.
The pulp and paper industry faces several challenges in the future. Ever stricter environmental legislation and rising raw material costs make it less sound from an economic point of view. Alternatives to wood are being sought to remedy this, such as biomass waste which contains wood lignin and cellulose compounds. The current Kraft pulp method also uses significantly more energy and water than experimental organosolv approaches, which could give them an industrial edge in the near future as energy costs rise and freshwater resources become increasingly scarce. Several organosolv methods are currently used in the production of isolated pulp mills in Canada and elsewhere, but have yet to achieve industry dominance that has the Kraft process.
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