Producing dissolving pulp from agricultural waste

Abstract

A growing population imposes an increased demand on textile fibres based on cellulose. Forecasts predict a cellulose gap due to the lack of cotton and the need to assess other sustainable cellulose resources for dissolving pulp production. Circular cellulose resources might be agricultural wastes. Here we evaluated oat husks, wheat straw, potato pulp and pressed sugar beet pulp which are available in sufficient amounts in Sweden to produce dissolving pulp using the soda pulping process. Initial pulps from oat and wheat were further refined to achieve the purity of the dissolving pulp while potato and sugar beets were discarded due to processing difficulties. High purity dissolving pulps were obtained including both acid prehydrolysis pretreatment, soda cooking and a bleaching sequence. To evaluate the environmental impact of the production of dissolving pulp from oat husks and wheat straw, the process was scaled-up from lab scale to industrial scale and simulated, using Aspen PLUS. The results of the process simulations were evaluated through life-cycle assessment. Processing wheat straw required a higher chemical and energy demand compared to oat, but wheat pulp had a lower environmental impact. Both wheat and oat pulp had a higher impact than wood due to differences in cultivation. Nevertheless, dissolving pulp from wheat and oat might be a sustainable substitute for cotton or dissolving pulp from wood.