Papermaking is a highly energy intensive process. A paper mill utilizes biomass and fossil fuel energy to provide steam and electricity for plant operations. Biomass is a renewable energy source that is derived from wood waste during the production of virgin fiber. Fossil fuels are non-renewable resources used to meet the remaining energy demand at the mill. A mill may produce a paper product that contains a certain percentage of recycled fiber and virgin fiber. The type of fiber and paper grade directly impacts the amount and source of energy consumed in a paper mill. There is a correlation between the increase in recycled fiber and the increase in fossil fuel use which contributes to the total carbon dioxide output at the mill.
A model was developed to calculate the energy balance in a paper mill producing unbleached kraft linerboard with a pulp yield of 52 percent. The total carbon dioxide output was determined for the production of 100 % virgin fiber and 100 % recycled fiber. It was then compared with actual data from an undisclosed linerboard mill. This helped determine the accuracy of the results.
This study determined that replacing virgin fiber with recycled fiber increases fossil fuel consumption during linerboard production; however, virgin fiber had the highest total carbon dioxide output for the paper mill. Using the available data from the model, replacing one ton of virgin fiber with one ton of recycled fiber will decrease carbon dioxide output by 1.5 tons.