At InfoBloom, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.
Chemical pulp refers to a type of paper pulp used in the manufacturing of high-quality paper and paper products, which is produced through a process that chemically breaks down the lignin found in wood fibers. Lignin is the natural glue that holds wood cells together, and its removal is essential for producing strong, durable paper. The most common methods for creating chemical pulp are the Kraft process and the sulfite process. According to the Food and Agriculture Organization of the United Nations, the Kraft process accounts for around 80% of the world's pulp production, making it the predominant method due to its efficiency and the high strength of the resulting paper.
During the Kraft process, wood chips are cooked in a solution of sodium hydroxide and sodium sulfide, which dissolves the lignin without degrading the cellulose fibers. This results in a pulp that is not only strong but also has a reduced tendency to discolor over time. The environmental impact of pulp production is significant, with the pulp and paper industry being one of the largest consumers of water and emitters of greenhouse gases in the manufacturing sector. However, advancements in technology and increased recycling efforts have led to more sustainable practices within the industry. For instance, the Environmental Paper Network reports that recycled paper now accounts for over half of the raw materials used in paper production globally, helping to reduce the demand for virgin wood and the associated environmental footprint.
Pulp is wood fiber that is generally used to make paper. Chemical pulp is created by a method that uses chemicals and heat to convert wood into pulp. This process can be, and generally is, used as an alternative to mechanical pulping, which involves obtaining wood fibers by way of a grinding process.
Chemical pulp tends to be more common than mechanically derived pulp. Chemical pulping generally results in the production of paper with greater sheet strength than the paper produced by mechanical pulping. It is also a process that can be regarded as highly efficient due to the possibility of chemical recovery.
Chemical recovery is part of the process in which the chemicals used to treat the wood are reused for another purpose. In some cases, this used liquid, which is often referred to as liquor, is used to produce other chemicals. In other cases, the chemicals are used to create energy.
There are two widely recognized processes for producing chemical pulp. One is known as sulfate pulping. The other is known as sulfite pulping. The major differences between these are the chemicals used, the quality of paper produced, and the economy of chemical recovery.
Sulfate pulping is a process that was developed in Germany in 1879. It is sometimes called kraft pulping because kraft means strength in German, and the paper produced with this chemical pulp is strong. It can be used to make paper bags, writing paper, or diapers. Chemicals are typically always recovered in this process.
Sulfite pulping is a process that was developed in the United States in 1867. It generally results in a light chemical pulp that is easier to bleach and easier to refine. Paper produced by this method can be used for newspaper, writing paper, or cellophane. With this method, however, there is not always chemical recovery.
Both processes are generally executed in a similar manner. Chemical pulping usually begins with debarking trees to create wood chips. Those chips are then cooked in a chemical mixture, or liquor. The purpose of this is to dissolve the wood’s lignin, a natural component that binds the fibers together, and to break down other elements in the wood. When this part of the process is complete the liquor is generally black.
This black liquor is what is used in the chemical recovery process. It can be used in the production of another chemical, such as tall oil. It can also be combusted to create heat or electrical energy.