Quality parameters relevant for densification of bio-materials: Measuring methods and affecting factors - A review

Highlights: • Methods to measure quality parameters of densified bio-materials are discussed. • Factors affecting the quality parameters of bio-materials are discussed. • There is a need for dedicated standards for densified bio-materials. -- Abstract: Densification has been carried out for many years, mostly in biomass processing, animal feed production, and pharmaceutical industries. During the years, researchers and engineers attempted to improve the product quality and minimize the production costs. The most important quality parameters of solid bio-materials are the compressive strength, abrasion resistance, impact resistance, moisture adsorption, and density. Various studies used different standard and non-standard methods to characterize these quality parameters. The objective of this paper is twofold: (1) to investigate the state-of-the-art methods and devices used in the quality assessment of densified bio-materials, including a comparison between non-standard and standard methods. (2) to discuss the effect of different factors on the properties of densified bio-materials using an integrated approach. The results show a lack of standard methods for the quality assessment of bio-materials and therefore, there is an emerging need for development of dedicated standards for bio-materials. Moreover, the use of dissimilar methods and devices in the quality assessment of bio-materials gives risk to uncertainties about the effect of different factors on the product quality.