Abstract
Recent studies have proposed usage of biochar as a substrate amendment in green infrastructure, such as green roofs and bio-filtration units. However, understanding of the variation in physio-chemical properties of biochar due to the production process and feedstock is still lacking. The present study investigated the effects of pyrolysis temperature and feedstocks on the hygroscopic water content and physio-chemical properties of biochar. Biochars were produced from three feedstock types, invasive vegetation (i.e., water hyacinth), non-invasive vegetation (i.e., wood) and one animal waste (i.e., chicken manure). Biochar was produced at two different pyrolysis temperatures (i.e., 300 °C and 600 °C). Scanning electron microscopy + energy dispersive spectrometry (SEM + EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) were performed on all samples to analyze the surface morphology, pore size, element content, functional groups, and chemical bonds. Relative humidity was adjusted to reflect the biochar’s hygroscopic property by measuring the maximum moisture content at the sample equilibrium state. The characterization reveals that the lowest carbon content (42.78%) was found at 300 °C for water hyacinth biochar (WHB). The highest carbon content (92.14%) was found at 600 °C for wood biochar (WB). As the pyrolysis temperature increased, the mean pore volume (from 0.03 to 0.18 cm3/g) and diameter (from 8.40 to 10.33 nm) of the WHB increased. However, the pore diameter of chicken manure (CB) decreased (from 9.23 nm to 7.53 nm) under an increase in pyrolysis temperature. For a given pyrolysis temperature, the hygroscopicity of WHB was highest among all biochars. With an increase in pyrolysis temperature, the hygroscopicity of biochars changed differently. The hygroscopicity of WHB decreased from 82.41% to 44.33% with an increase of pyrolysis temperature. However, the hygroscopicity of CMB and WB remained unchanged. This study suggests that production process of biochars need to be considered for appropriate selection as substrate material in green infrastructure. Further, it promotes the establishment of commercial production of biochar for usage in green infrastructure.
Highlights
A black high porous material with high carbon content produced by pyrolysis of organic material has been receiving increased attention in the last few decades [1,2,3,4]
Biochar with rich nutrients can be used as soil amendments to improve soil fertility whereas biochar with a highly porous structure can be used as a sorbent [5,19,20,21]
The surface biochar produced from different biomass at diff pacitypyrolysis of soil [50]
Summary
A black high porous material with high carbon content produced by pyrolysis (thermochemical decomposition under a low or no oxygen state) of organic material has been receiving increased attention in the last few decades [1,2,3,4]. Several studies have promoted the use of biochar as an amendment in substrate materials in green infrastructure [6,7,8]. This is mainly due to three factors: firstly, the large specific surface area and porous structure results in enhanced adsorption performance and water retention behavior [9,10,11,12]. The physicochemical properties of biochar are directly dependent on the preparation procedure (highest treatment temperature, holding time, pyrolysis atmosphere, etc.) and feedstock properties (both physical and chemical) [25,26]
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