The comminution of lignocellulosic biomass is a key operation for many applications as bio-based materials, bio-energy or green chemistry. The grinder used can have a significant impact on the properties of the ground powders, of those of the end-products and on the energy consumption. Since several years, the milling of lignocellulosic biomass has been the subject of numerous studies most often focused on specific materials and/or applications but there is still a lack of generic knowledge about the relation between the histological structure of the raw materials, the milling technologies and the physical and chemical properties of the powders. This review aims to point out the main process parameters and plant raw material properties that influence the milling operation and their consequences on the properties of ground powders and on the energy consumption during the comminution.

Lignocellulosic feedstocks present a growing interest in many industrial processes as they are an ecological alternative to petroleum-based products. Generally, the size of plant raw materials needs to be reduced by milling step(s), to increase density, facilitate transport and storage, and to increase reactivity. However, this unit operation can prove to be important in term of investments, functioning costs, and energy consumption if the process is not fully adapted to the histological structure of the plant material, possibly challenging the profitability of the whole chain of the biomass conversion. In this paper, the different technologies that can be used for the milling of lignocellulosic biomass were reviewed and different avenues are suggested to improve the milling performances thanks to thermal pretreatments. Based on examples on wheat straw milling, the main points to take into consideration in the choice of a milling technologies have been highlighted in regards to the specifications of ground powder. A specific focus on the hazards associated to the milling and the manipulation of fine biomass particles is also realized at the end of the paper from the perspective of industrial applications.