Читать книгу High-Performance Materials from Bio-based Feedstocks - Группа авторов - Страница 22

The elements C, O, H, and N generally present the major organic constituents of biomass in the form of polysaccharides, proteins, lipids, or other molecules. In addition to these, biomasses may also contain a significant fraction of inorganic material. The inorganic fraction can be separated from the organic matrix by combustion in the form of ash, of which the amount and elemental composition vary greatly between biomass sources and combustion conditions [20, 21]. Most commonly, inorganic elements consist of Si, Ca, K, P, Al, Mg, Fe, S, Na, and Ti with different proportions depending on the biomass source [20].

Biomasses such as rice husk contain relatively high amounts of Si, which can be extracted and used in various applications from energy storage to construction materials [22]. The successful use of Si derived from biomass is shown as anode material for Li‐ion batteries. A major challenge for Si‐based anodes is the low capacity retention, large volume change during lithium insertion/deinsertion process, and poor electrical conductivity, which can be partly overcome by using nanostructured materials [23]. Chapter 4 provides some critical perspectives on the application of biomass‐derived Si in Li‐ion batteries.

Another potential use of biomass ashes is demonstrated in the production of construction materials. Removal of the organic matrix by controlled combustion produces Si‐rich ash that can be used to produce geopolymer materials as an alternative to traditional Portland cement [24]. These biomass ashes can substitute aluminosilicate sources instead of traditional fly ash from coal burning and leads to lower greenhouse gas production. Although large‐scale application of bio‐based inorganic materials is not available at the present time, the utilization of inorganic materials from biomasses is expected to increase with increasing environmental awareness. Challenges include the reduction of transportation cost of bulky biomass, and the inhomogeneity of ashes needs to be overcome to promote their usage. Various treatment options and applications of biomass ashes for geopolymer applications are discussed and assessed in Chapter 13.