Created: 16 April 2015

In Brazil, the two main wood sources used for producing pulp are pinus and eucalyptus planted forests, which account for over 98% of the volume produced. Pulp can also be obtained from other types of non-wood plants such as bamboo, babassu, agave and agricultural waste (sugarcane bagasse).

After the planting, growth and harvesting of planted forests, wood is debarked and chopped into small pieces called chips. Then, the wood chips are sorted for removing wood shavings and sawdust, and afterwards they undergo mechanical and chemical processes to produce pulp.

In the first step of this process, which is called pulping, the wood chips are cooked in a piece of equipment called a digester, using water, chemicals, pressure and temperatures in the order of 150°C (302°F). The purpose of this is to separate cellulose fibers from lignin—the substance that binds these fibers together increasing the rigidity of plant cell walls and which, together with cellulose, comprises the greater part of the wood in trees and shrubs. After the separation, the cellulosic fibers form a brown stock that, in the following step of the process, goes through a series of processes and chemical reactions designed to screen, wash and bleach the pulp to the desired degree of whiteness.

At the end of these steps, pulp may follow one of two basic distinct paths:

1 – It may either be pumped into a paper machine—in the case of integrated mills (which have a forest base and produce pulp and paper).
2 – Or it may go through a drying process and be stored in bales for subsequent sale to paper mills as market pulp.

Lignin is not discarded after being separated from the fibers. Instead, it goes through another process designed to generate power while recovering the chemicals used in pulping.

Types and applications

Two pulp types possessing different physical and chemical characteristics are used in papermaking.

Softwood pulp – Softwood pulp is made of long fibers from coniferous species such as the pinus —which is planted in Brazil—whose length ranges between 2 and 5 millimeters. It is used in the production of papers requiring higher resistance, such as those used in packaging and in the inner layers of cardboard, in addition of newsprint.

Hardwood pulp – Hardwood pulp is made of short fibers ranging between 0.5 and 2 millimeters in length, mainly taken from eucalyptus. These fibers are ideal for producing papers for printing and writing and for tissue products (toilet paper, paper towels and napkins). Eucalyptus fibers are also used in specialty papers, among other uses. They are shorter, very soft and present good absorption.

Sustainable production

Unlike other industries in the domestic economy, the planted trees industry generates the greater part of the energy it requires. In 2015, 65.1 million gigajoules were produced from green energy, accounting for 67% of the industry's energy consumption. Additionally, the more modern pulp projects, as well as being self-sufficient in energy, generate a surplus for the grid, at around 11.9 million gigajoules, equal to a midsize hydropower plant.

The industry’s two main concerns are to increase the energy efficiency in processes and adopt renewable resources of power generation. In that sense, the industries in the sector almost exclusively use the byproducts from their processes to generate thermal and electric power, namely forestry biomass and black liquor (black liquor is a byproduct of the pulp production process).