Volume 16 Issue 3

Lignin is one of the most important and widespread carbon sources on Earth. Significant amounts of lignin are delivered to the market by pulp mills and biorefineries, and there have been many efforts to develop routes for its valorization. Over the years, lignin has been used to produce biobased chemicals, materials, and advanced biofuels on the basis of its variable functionalities and physicochemical properties. Today, lignin’s applications are still limited by its heterogeneity, variability, and low reactivity. Thus, modification technologies have been developed to allow lignin to be suitable for a wider range of attractive industrial applications. The most common modifications used for this purpose include amination, methylation, demethylation, phenolation, sulfomethylation, oxyalkylation, acylation or esterification, epoxidation, phosphorylation, nitration, and sulfonation. This article reviews the chemistry involved in these lignin modification technologies, discussing their effect on the finished product while presenting some market perspectives and future outlook to utilize lignin in sustainable biorefineries.

Biochar is highly valuable in various applications due to its unique physicochemical properties such as high thermal efficiency, high surface area, surface functional groups, and crystal structure. The goal of this review is to establish a systematic strategy of biochar production for applications in various fields. First, the characteristics of biomass as feedstock for biochar production and their classification are discussed according to the types present in nature. Second, the technology for biochar production and the production yield are examined. In thermochemical conversion for biochar production, five major types of pyrolysis processes are suggested, and the production yield is evaluated according to pyrolysis parameters (feedstock pretreatment, operating temperature, heating rate, residence time, carrier gas). In addition, biochar production from pyrolysis of mixed feedstock has recently been suggested; thus, the evaluation of the production yield from co-pyrolysis is included. Finally, analytical techniques for biochar characterization are investigated and the application of biochar in various fields is considered, such as in adsorbents, energy storage devices, and catalysts.