Recent advancements in biochar production according to feedstock classification, pyrolysis conditions, and applications: A review

Abstract

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.

Under a Tropical Climate and in Sandy Soils, Bat Guano Mineralises Very Quickly, Behaving More like a Mineral Fertiliser than a Conventional Farmyard Manure

“…Biochar was prepared through an artisanal method of slow pyrolysis, which consists of heating biomass waste (feedstock) into a reactor (made from two metallic drums) for one day. The reader is referred to [27] for more details on this type of slow pyrolysis. Some properties of biochar are shown in Table 2.…”

“…Biochar can persist in soils for hundreds or thousands of years and, by increasing soil pH, porosity, and water availability, can create favourable conditions for the development of plant roots and the growth of microbial communities [25]. Biochar can be produced by simple artisanal processes, using local organic resources from agricultural and forestry activities as feedstock [27], which can be a useful way of recycling those materials and having a positive impact on a smallholder's income.…”

Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions

“…Application of biochar to agricultural soils has shown variable effects on GHG emissions, ranging from decrease, increase, or no change. Beneficial effects of biochar depend on biochar properties that can vary greatly with type of feedstock (Abagandura et al., 2019; Fungo et al., 2014; He et al., 2017) and production process (Chun et al., 2021; Freitas et al., 2020; He et al., 2017). The benefits of biochar also vary with crop (Olszyk et al., 2020; Shakoor, Arif, et al., 2021), soil type (He et al., 2017; Kavitha et al., 2018), application rate (Guo, 2020), and climatic conditions (Blanco‐Canqui, 2021; Lu et al., 2020).…”

Enhanced phosphate adsorption and desorption characteristics of MgO-modified biochars prepared via direct co-pyrolysis of MgO and raw materials

“…However, it is a large anion with a negative charge. Thus, it can adsorb positively charged materials, such as heavy-metal ions, but exhibits a poor adsorption ability for anions (Cha et al 2016 ; Chun et al 2021 ). It has even been reported to it has even been reported to exert a repulsion effect during phosphate and nitrate salt adsorption during PO and nitrate salt adsorption (Pinto et al 2019 ).…”