Structural and chemical characterization of hop bine fibers and their applications in the paper industry

Abstract The growth in the Humulus lupulus L. or hops industry, a perennial species, driven by demand from brewers has had annual revenue growth of 11.3% since 2015 making it one of the fastest growing agricultural commodities in the Pacific Northwest (PNW). There is currently 85,000 MT per year of hop bine in the PNW available for paper making. The land dedicated to hop agriculture increased by 68% from 2010 to 2019 in the Yakima Valley. The plant Humulus lupulus L. belongs to the same family as Cannabis sativa L., industrial hemp, which has seen practical use in both the paper industry and in the biobased development. The bulk density of the hop bine is low, 0.296 g/cm3 and only 1.5 metric tons of bine is produced per acre each year. However, as crops allocated to production of renewable resources compete for land previously dedicated to food crops, the residual biomass from hop cultivation offers an inexpensive alternative source of renewable lignocellulosic biomass without cannibalizing a food crop. H. lupulus was characterized to evaluate the acceptability for use as a paper making fiber and for hydrolytic conversion to biobased products. The high carbohydrate content, 58%, is similar to other lignocellulosic materials suitable for bioenergy feedstocks. The fiber has morphological characteristics similar to hardwood with length and width centered around 0.85 mm and 16.5 µm, respectively. The tensile strength of the hop-made papers was 61% greater than the industrial hemp made papers at the same refining level. This fiber presents a sustainable multi-use commodity with excellent application in biobased products and paper making which would otherwise be lost.