Abstract
Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar applications include: (1) pollution remediation due to high CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several technological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature promotes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review succinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility.
Highlights
The objective of this review presented is to assess: (1) the physicochemical characteristics of biochar formed at different temperatures and from different biomass, (2) the Pyrolysis temperature (°C)
This paper provides a review of the effects of temperature and type of feedstock on the physicochemical properties of biochar and its potential use as a soil conditioner
Studies show that cation exchange capacity (CEC) and volatile matter decreased with increasing pyrolysis temperature, whereas pH, specific surface area, ash and carbon content, pore volume increased with the increase in pyrolysis temperature
Summary
The products of pyrolysis are an oil (a mixture of hydrocarbons), synthetic gas (mixed hydrocarbon gases) and biochar (Lewandowski et al 2010; Verheijen et al 2010) The proportions of these individual products depend on the temperature range, pressure, residence time, etc. As a result of high heating rates and short residence times, fast pyrolysis tends to yield higher proportions of oils. Soil is a complex material and comprises minerals, soil organic matter, water, and air These fractions greatly influence soil texture, structure, and porosity (Baghdadi and Zribi 2016). The explanation of the main mechanisms of changes in physicochemical properties of biochar during pyrolysis at various temperatures and the types of feedstock is necessary to determine the ability of biochar to remediate various soils, which is useful in future studies
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