Effect of Pyrochar and Hydrochar on Water Evaporation in Clayey Soil under Greenhouse Cultivation

Effect of wood and peanut shell hydrochars on the desiccation cracking characteristics of clayey soils

Soil cracking can significantly alter the water and nutrient migration pathways in the soil, influencing plant growth and development. While biochar usage has effectively addressed soil cracking, the feasibility of using less energy-intensive hydrochars in desiccating soils remains unexplored. This study investigates the impact of wood and peanut shell hydrochars on the desiccation cracking characteristics of clayey soil. A series of controlled environmental laboratory incubations with regular imaging was conducted to determine crack development's dynamic in unamended and hydrochar-amended soils. The results reveal that the addition of wood hydrochar at 2% and 4% dosage reduced the crack intensity factor (CIF) by 22% and 43%, respectively, compared to the unamended control soil. Similarly, the inclusion of peanut shell hydrochar at 2% and 4% lowered the CIF by 22% and 51%, respectively. The presence of hydrophilic groups on the surface of hydrochars, such as O-H, CH, and C-O-C, enhanced the water retention capacity, as confirmed by Fourier-transform infrared analysis. The CIF decrease is attributed to mitigated water evaporation rates, enabled by enhanced water retention within the hydrochar pore spaces. These findings are supported by scanning electron microscopy analyses of the hydrochar morphology. Despite CIF reduction with hydrochar incorporation, the crack length density (CLD) increased across all hydrochar-amended series. In contrast to unamended soil which exhibited pronounced widening of large cracks and extensive inter-pore voids, the incorporation of hydrochar resulted in higher CLD due to the formation of finer interconnecting crack meshes. Consequently, the unamended control soil suffered greater water loss due to heightened evaporation rates. This study sheds new light on the potential of hydrochars in addressing desiccation-induced soil cracking and its implications for water conservation.

Ecological consequences of biochar and hydrochar amendments in soil: assessing environmental impacts and influences

Anthropogenic activities have caused irreversible consequences on our planet, including climate change and environmental pollution. Nevertheless, reducing greenhouse gas (GHG) emissions and capturing carbon can mitigate global warming. Biochar and hydrochar are increasingly used for soil remediation due to their stable adsorption qualities. As soil amendments, these materials improve soil quality and reduce water loss, prevent cracking and shrinkage, and interact with microbial communities, resulting in a promising treatment method for reducing gas emissions from the top layer of soil. However, during long-term studies, contradictory results were found, suggesting that higher biochar application rates led to higher soil CO2 effluxes, biodiversity loss, an increase in invasive species, and changes in nutrient cycling. Hydrochar, generated through hydrothermal carbonization, might be less stable when introduced into the soil, which could lead to heightened GHG emissions due to quicker carbon breakdown and increased microbial activity. On the other hand, biochar, created via pyrolysis, demonstrates stability and can beneficially impact GHG emissions. Biochar could be the preferred red option for carbon sequestration purposes, while hydrochar might be more advantageous for use as a gas adsorbent. This review paper highlights the ecological impact of long-term applications of biochar and hydrochar in soil. In general, using these materials as soil amendments helps establish a sustainable pool of organic carbon, decreasing atmospheric GHG concentration and mitigating the impacts of climate change.

Introduction of a Zn-based metal-organic framework @ biomass porous activated carbon as a high-sensitive coating for a stainless steel SPME fiber: application to the simultaneous analysis of nonsteroidal anti-inflammatory drugs

The present study introduces a high-efficiency nanocomposite material featuring a zinc-based metal-organic framework and a novel porous activated carbon derived from bread waste. The prepared nanocomposite, namely Zn-MOF-5@BHPAC, has been synthesized by a low-temperature hydrothermal process and coated onto the surface of a stainless steel wire with epoxy glue. The fabricated fiber has been employed as an SPME fiber applied in the extraction and pre-concentration of some nonsteroidal anti-inflammatory drugs (NSAIDs) before their high-performance liquid chromatography-ultraviolet (HPLC-UV) studies. The characterization studies were performed utilizing field emission scanning electron microscopy, elemental mapping, energy-dispersive X-ray spectroscopy, elemental analyzer, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller surface area analysis. Under the optimal conditions, the method demonstrated low detection limits (LODs, 0.06-0.15 µg L-1), wide linear ranges (LRs, 0.20-380 µg L-1) with good linearity (R2 > 0.991), good precisions (RSDs < 6.95%), and acceptable relative recoveries (RR > 85%). Using the green and affordable biomass of bread as a novel carbon-rich source is an innovative idea provided in this study. In addition, the hybridization of the obtained carbon-based material with the MOF compound to create a new high-capacity sorbent is another strength of the proposed method. Long service lifetime, economic efficiency, environmental friendliness, and high extraction capability were some of the other advantages of the suggested procedure. Therefore, the method can utilize successfully for the simultaneous determination of NSAIDs (as model analytes) in different matrixes.

Water-washed hydrochar in rice paddy soil reduces N2O and CH4 emissions: A whole growth period investigation

Hydrochar (HC), an environment-friendly material, enhances soil carbon sequestration and mitigate greenhouse gases (GHGs) emissions in croplands. In this study, the water-washed HC (WW-HC) was applied to paddy soil to investigate effects on nitrous oxide (N₂O) and methane (CH₄) emissions during rice growth period. Four treatments, namely control (without N fertilizer and WW-HC), N fertilizer (WW-HC00), N fertilizer with 0.5 wt% WW-HC (WW-HC05) and N fertilizer with 1.5 wt% WW-HC (WW-HC15), were established. Results showed the WW-HC addition reduced N₂O and CH₄ emissions, global warming potential (GWP) and greenhouse gas intensity (GHGI) during the growing season. Moreover, the WW-HC application reduced N₂O cumulative emission (P < 0.05) (by 28.6% and 23.8% for WW-HC05 and WW-HC15, respectively). It was mainly due to the reduced ratio of (nirK + nirS) to nosZ under WW-HC15 (P < 0.05). Compared with WW-HC00, the WW-HC05 reduced CH₄ cumulative emissions by 14.8%, while the WW-HC15 increased by 9.7%. This might be ascribed to the significantly reduced expression of the methanogenic mcrA gene and ratio of mcrA to pmoA by WW-HC (P < 0.05). The WW-HC05 amendment decreased GWP and GHGI by 18.6% and 32.5%, respectively. Furthermore, the WW-HC application greatly improved nitrogen use efficiency by 116-145% compared with the control. Our study indicates the WW-HC application is a promising GHGs mitigation practice in paddy fields.

Comparison of plant growth and remediation potential of pyrochar and thermal desorption for crude oil-contaminated soils

Crude oil contamination is a serious environmental threat for soil and plants growing in it. This study provides the first experimental evidence for comparison of the efficacy of pyrochar (slow pyrolysis biochar), thermal desorption and their combined application for degradation of crude oil contaminated soil (0%, 10%, and 20%), and growth of lettuce under glasshouse conditions. Pyrochar was produced by pyrolysis of sawdust at 350 °C, whereas thermal desorption was done by soil pyrolysis at 500 °C. Soil incubations were done for 120 days. The results of soil analysis showed that the crude oil degradation efficiency for the combined application was highest (40%), whereas pyrochar and thermal desorption was 25% and 19.6%, respectively. The maximum degradation products of crude oil were manifested by the detection of low molecular weight hydrocarbons (ranged between 173 and 422) in the soil with combined application treatment using Gas Chromatography-Mass Spectrometry (GC–MS) analysis. Crude oil contamination significantly reduced the germination and growth of the lettuce plants. Similarly, the combined application also improved plant growth by an increase of 24% in germination percentage, 35.5% in seedling vigor index, and 27% in promptness index under 20% crude oil contamination. Remediation caused a significant increase in fresh and dry biomass (40%), leaf area (30%), total chlorophyll (21%), water potential (23.6%), osmotic potential (27%), and membrane stability index (40%). Moreover, there was an increase in the contents of proline (32%), total amino acids (29%), soluble sugars (37%), proteins (27%), and antioxidant enzymes such as superoxide dismutase (19%), catalase (33%) and peroxidase (38%). This study confirmed the efficacy of pyrochar (slow pyrolysis biochar), thermal desorption, and their combined application for crude oil decontamination of soil at laboratory scale and also in improving soil usability by improved germination and growth of lettuce.

Hydrochar did not reduce rice paddy NH3 volatilization compared to pyrochar in a soil column experiment

Pyrochar (PC) is always with high pH value, and improper application might increase rice paddy ammonia volatilization (PAV), which is the main nitrogen loss through air during rice production. Differently, hydrochar (HC) takes the advantages of high productive rate and always with lower pH value compared with PC. However, effect pattern and mechanism of HC on PAV are still unclear. In the present study, soil column experiments were conducted to investigate the effect of PC and HC application on PAV. In total, treatments with four types of biochar (WPC, SPC, WHC and SHC, i.e., PC and HC prepared with wheat straw and sawdust, respectively) and two application rates (0.5% and 1.5%, w/w) were set up and non-biochar application was used as control. Results showed that, application of HC with low pH value could not reduce PAV compared with PC. Total PAV increased significantly as the increase of HC application rate (especially for WHC). The increment of PAV under high rate HC application might be due to the strong buffer capacity of soil, the aging of biochar, the high nitrogen from HC. The results indicated that HC should be pretreatment before utilization in agricultural environment considering PAV reduction.