“…Lehmann et al () suggested two basic approaches for reducing nutrient leachability and boosting their retention rates: (a) biochar may act as a slow‐releasing nutrient agent; and (b) adsorption sites are enhanced as a result of biochar application, which contributes to nutrient retention. Biochar produced at low temperatures possess more carboxylic and hydroxyl functional groups, which act as nutrient binding sites (Glaser et al, ); a pine‐derived biochar, for example, gradually reduced soil N mineralization in the form of NO 3 − to concentrations equal to those of NH 4 + –N (Marks, Mattana, Alcañiz, Pérez‐Herrero, & Domene, ). Similarly, when biochar was applied to loamy‐sand soil, the available N content decreased or remained unchanged because of the adsorption of NH 4 + –N, which resulted in depletion of the available N (Kizito et al, ).…”
This review summarizes the influences of pyrolysis conditions and feedstock types on biochar properties and how biochar properties in turn affect soil properties. Mechanistic evidence of biochar's potential for enhancing crop productivity, carbon sequestration, and nutrient use efficiency are also discussed. The review identifies the knowledge gaps, limitations, and future research directions for large‐scale use of biochar. Both pyrolytic parameters and feedstock types are considered to be the main factors controlling biochar properties such as nutrient content, recalcitrance, and pH. Biochar produced at low temperatures may improve nutrient availability and crop yield in acidic and alkaline soils, whereas high‐temperature biochar may enhance long‐term soil carbon sequestration. Biochar can also improve the efficiency of inorganic and organic fertilizers by enhancing microbial functions and reducing nutrient loss, thereby making nutrients more available to plants. Integration of biochar and chemical or organic fertilizers generally provides for better nutrient management and crop yield in most types of soils. Although biochar can improve degraded soils, it is not a panacea; as such, soil‐ and crop‐specific biochar are needed in order to ensure optimum crop yield and agricultural sustainability.
“…Lehmann et al () suggested two basic approaches for reducing nutrient leachability and boosting their retention rates: (a) biochar may act as a slow‐releasing nutrient agent; and (b) adsorption sites are enhanced as a result of biochar application, which contributes to nutrient retention. Biochar produced at low temperatures possess more carboxylic and hydroxyl functional groups, which act as nutrient binding sites (Glaser et al, ); a pine‐derived biochar, for example, gradually reduced soil N mineralization in the form of NO 3 − to concentrations equal to those of NH 4 + –N (Marks, Mattana, Alcañiz, Pérez‐Herrero, & Domene, ). Similarly, when biochar was applied to loamy‐sand soil, the available N content decreased or remained unchanged because of the adsorption of NH 4 + –N, which resulted in depletion of the available N (Kizito et al, ).…”
This review summarizes the influences of pyrolysis conditions and feedstock types on biochar properties and how biochar properties in turn affect soil properties. Mechanistic evidence of biochar's potential for enhancing crop productivity, carbon sequestration, and nutrient use efficiency are also discussed. The review identifies the knowledge gaps, limitations, and future research directions for large‐scale use of biochar. Both pyrolytic parameters and feedstock types are considered to be the main factors controlling biochar properties such as nutrient content, recalcitrance, and pH. Biochar produced at low temperatures may improve nutrient availability and crop yield in acidic and alkaline soils, whereas high‐temperature biochar may enhance long‐term soil carbon sequestration. Biochar can also improve the efficiency of inorganic and organic fertilizers by enhancing microbial functions and reducing nutrient loss, thereby making nutrients more available to plants. Integration of biochar and chemical or organic fertilizers generally provides for better nutrient management and crop yield in most types of soils. Although biochar can improve degraded soils, it is not a panacea; as such, soil‐ and crop‐specific biochar are needed in order to ensure optimum crop yield and agricultural sustainability.
“…The most recent technology developed to prepare charred material from waste with the intent to mitigate climate change by sequestering carbon when applied to the soil (Lehmann and Joseph, 2015). Likewise, biochar also enhanced other important fertility indicators when applied to the soil including carbon content, reduced nitrate mineralization (Marks et al, 2016) and therefore decreased the leaching losses of C and N from soil (Bass et al, 2016;Haider et al, 2017). Biochar application to soil proved to be beneficial for improving soil fertility and carbon sequestration of degraded soil (Yeboah et al, 2009).…”
The beneficial role of biochar is evident in most of infertile soils, however this is argued that increment in crop yield owing to biochar application does not always achieve in cultivated/fertile soils. The nutrient biochar believed to enhance crop yield and soil fertility than structural biochar that may offset the positive effect of chemical fertilizer on crop performance but improves soil structural properties. Therefore, we investigated the effect of biochars [produced from nutrient rich feedstocks like poultry manure (PMB) and farmyard manure (FMB) and structural feedstocks such as wood chips (WCB) and kitchen waste (KWB)], and chemical fertilizers (CF) when applied alone or in combination on soil chemical properties, wheat growth, yield and nitrogen uptake in a cultivated clay loam soil. Sole biochar treatments increased the total carbon and mineral nitrogen content that were 21 and 106% higher, respectively compared to control after 128days (P<0.001). Contrarily, sole biochars application did not increase wheat biological yield and N uptake compared to control (P>0.05) except PMB, the nutrient biochar (P<0.05). Compared to control, grain yield was 6 and 12% lower in WCB and FMB, respectively but not differed from KWB, PMB or WCB-CF. Conversely, co-application of biochars and CF treatments increased crop biological yield but the increment was the highest in nutrient biochars FMB or PMB (29 or 26%), than structural biochars WCB and KWB (15 and 13%), respectively (P<0.05). For N uptake, this increment varies between 16 and 27% and again nutrient biochar has significantly higher N uptake than structural biochars. Hence, nutrient biochars (i.e. PMB) benefited the soil fertility and crop productivity more than structural biochars. Therefore, for immediate crop benefits, it is recommended to use nutrient biochar alone or in combination with chemical fertilizer. Such practice will improve crop performance and the quality of cultivated soil.
“…Figure 4.van Krevelen diagram [50] shows molar ratios of oxygen and hydrogen relative to carbon in the char. Region assigned to biomass from [1,6,14,30,33,34,51]. Note that for the gasifier chars in [1] there were also three excluded outliers (out of a total of eight samples) with O : C > 0.8, and varying H : C up to 1.3.…”
The correlation between thermochemical provenance and biochar functionality is poorly understood. To this end, operational reactor temperatures (spanning the reduction zone), pressure and product gas composition measurements were obtained from a downdraft gasifier and compared against elemental composition, surface morphology and polyaromatic hydrocarbon content (PAH) of the char produced. Pine feedstock moisture with values of 7% and 17% was the experimental variable. Moderately high steady-state temperatures were observed inside the reactor, with a ca 50°C difference in how the gasifier operated between the two feedstock types. Both chars exhibited surface properties comparable to activated carbon, but the relatively small differences in temperature caused significant variations in biochar surface area and morphology: micropore area 584 against 360 m2 g−1, and micropore volume 0.287 against 0.172 cm3 g−1. Differences in char extractable PAH content were also observed, with higher concentrations (187 µg g−1 ± 18 compared with 89 ± 19 µg g−1 Σ16EPA PAH) when the gasifier was operated with higher moisture content feedstock. It is recommended that greater detail on operational conditions during biochar production should be incorporated to future biochar characterization research as a consequence of these results.
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