Is Kraft Pulping the Future of Biorefineries? A Perspective on the Sustainability of Lignocellulosic Product Development

Abstract

By reflecting on the history and environmental impact of conventional biorefining, such as kraft pulping, we aim to explore important questions about how natural polymers can be more sustainably sourced to develop bio-products and reduce reliance on plastics. Since the Industrial Revolution, chemical pulping processes have enabled the mass production of cellulosic products from woody biomass. Kraft pulping, which dominates within modern pulp and paper mills, has significantly contributed to environmental pollution and carbon emissions due to sulfurous byproducts and its high water and energy consumption. While chemical pulping technologies have advanced over time, with improvements aimed at enhancing sustainability and economic feasibility, conventional biorefineries still face challenges related to biomass conversion efficiency and environmental impact. For example, efforts to fully utilize wood resources, such as isolating lignin from black liquor, have made limited progress. This perspective provides a thoughtful examination of the growth of chemical pulping, particularly the kraft process, in the production of consumer goods and its environmental consequences. It also presents key insights into the bottlenecks in developing truly sustainable biomass conversion technologies and explores potential alternatives to traditional chemical pulping.

Keywords: biopolymer properties; emerging biorefinery; environmental impact; kraft pulping; lignin; pulp and paper.

Figure 1

Schematic representation of a typical kraft pulping process with emphasis on the advances in woodchip digestion and black liquor treatment. Until the 1950s, woodchips were digested in a batch process, but in the 1980s continuous digesters were introduced, reducing the white liquor requirement. In the 1990s, single-drum recovery boilers were introduced. Since their introduction, these boilers have grown fourfold in capacity (as of 2016) and have significantly reduced NOx and particulate matter emissions. Adapted from [35,36].