Search

Purpose: Humic substances (HSs) and biochar (BC) are carbon-based soil amendments. These amendments improve soil health and fertility, enhance nutrient pools and carbon content, remove soil pollutants, and enhance plant performance. As a result, they contribute to agro-environmental sustainability and the development of a circular bioeconomy. However, there is a lack of research on the effects of HSs-aged BC or the co-application of BC and HSs on the agro-environmental system. Therefore, further studies are needed to understand the impacts of these amendments on the agro-environmental system. Methods: This study utilizes a novel technique based on BC aging with HSs to investigate the BC-aging process, factors influencing it, as well as the impact of BC and HSs on soil physicochemical properties, nutrient pools, microbial communities, immobilization of metal ions in the soil, and plant performance. We gathered original research articles, meta-analysis papers, book chapters, conference proceedings, and technical notes from high-quality peer-reviewed journals and reputable websites. Results and discussion: The extensive literature evaluation revealed that the potential benefits of BC are closely related to variations in the physicochemical composition of the BC and soil because microorganisms do not prefer fresh BC for colonization. In some studies, BC showed a detrimental impact on the soil microbiome. Therefore, the influence of BC on the soil microbiome, nutrient pool, pollutant removal, and plant growth strongly depends on the residence time of BC in the soil and its prior aging with HSs. Aging BC with HSs is more effective than using fresh BC as it enhances nutrient pools, accessibility to plants, pollutant amelioration capacity, microbial activities, and consequently, plant performance due to the presence of surface functional groups and the adsorbed nutrient-rich organic molecules. Conclusions: The soil fertility traits and plant performance were impacted by aging or a combination of BC with HSs. However, detailed characterizations and continuous experiments are required to gain in-depth insights into the interaction mechanisms between the aging of BC with HSs via the liquid soaking technique and soil fertility traits. [ABSTRACT FROM AUTHOR]

The expansion of biofuels produced from cooking oils and vegetal oils is expected to increase, together with the production of exhausted clay used in the refinery process. Clay produced in the process is considered waste as it is not intended for further applications. This study has assessed a sample of clay produced by a vegetal oil refinery plant and tested it for environmental applications with two types of vegetal species. In the experiment, the oily clay was added to a sandy loam soil in different percentages in order to modify the soil texture and assess the effect on the hydrological and chemical properties. The results demonstrated that on the one hand, oily clay does not change the pH in the soil mixture and it enriches the elemental composition (in terms of Mg, Cu and Zn), but, on the other hand, there are counteracting effects. Even if oily clay did not have toxic effects on seed germination, when applied to the soil, the presence of Ni did affect the plants' growth. The results thus suggest the need for phytoremediation prior to any application of such clay in soil. [ABSTRACT FROM AUTHOR]

Abstract The agronomic management of vineyards, aimed at the maximization of grape yields, is intensive and includes repeated tillage, crop residues removal, strict weed and pest control treatments. In viticulture, healthy soils and a suitable climate are the key factors that influence the quality of the produced wine. Even under intensive agronomic practices, typical of conventional viticulture, the choice of appropriate soil management strategies can preserve soil quality in the long term. The use of biochar as soil amendment has been suggested as a potential practice that allows restoration of the functionality of degraded soils in terms of water retention, chemical and biological fertility. In this paper we report the results of a long field trial on biochar amendment of a vineyard, assessing the impact on soil functionality, VOC emission and fertility. Our results show that biochar effects on soil functions and fertility are maintained in the long term (seven years) after a one-time application. Highlights • Biochar application is an effective practice for restoration of the functionality of degraded soils. • Changes in soil fertility after a single application of biochar persist after seven years • Biochar incorporation into soil caused substantial changes in the metabolic pathways of soil microbial activity. • Biochar is an environmentally-friendly solution for soil management in vineyards. [ABSTRACT FROM AUTHOR]

Abstract The effectivity of biochar as soil amendment depends on its physical and chemical characteristics, related to the type and features of the thermal production process, such as peak temperature, heating rate, holding time, as well as on the used feedstock. The textural characteristics of biochar in terms of surface area, pore size and pore volume distribution, important for its physicochemical properties, are critically dependent on the feedstock type, the production process, and possible further activation methods. This study was based on a single biochar type, resulting from slow pyrolysis at the working temperature of 550 °C of raw material from coppiced woodlands, as well as on a single experiment. For the first time, controlled hydrodynamic cavitation was proven as a fast and effective way to enhance the surface area of biochar by as much as 120%, while preserving or improving the respective chemical composition. The introduced technique, while easily applicable and scalable, showed far higher efficiency than the conventional method of increasing the working temperature of the pyrolysis process, with higher process yields by at least an order of magnitude. Moreover, hydrodynamic cavitation processes could be straightforwardly integrated with other consolidated methods, such as hydrothermal carbonization and chemical activation, possibly leading to effective synergism. Graphical abstract Image Highlights • HC processing of biochar downstream of SP is feasible and convenient. • HC shows much higher yield than elevating the working temperature in SP processes. • Biochar maintains original chemical composition and pH within acceptable levels. • Composition of biochar improves nitrogen and ash content for soil applications. • Possible useful synergism with consolidated manufacturing and activation methods. [ABSTRACT FROM AUTHOR]

The effect of biochar addition on the levels of black carbon (BC) and polcyclic aromatic hydrocarbons (PAHs) in a vineyard soil in central Italy was investigated within a two year period. Hydropyrolysis (HyPy) was used to determine the contents of BC (BCHyPy) in the amended and control soils, while the hydrocarbon composition of the semi-labile (non-BCHyPy) fraction released by HyPy was determined by gas chromatography-mass spectrometry, together with the solvent-extractable PAHs. The concentrations of these three polycyclic aromatic carbon reservoirs changed and impacted differently the soil organic carbon over the period of the trial. The addition of biochar (33 ton dry biochar ha-1) gave rise to a sharp increase in soil organic carbon, which could be accounted for by an increase in BCHyPy. Over time, the concentration of BCHyPy decreased significantly from 36 to 23 mg g-1 and as a carbon percentage from 79% to 61%. No clear time trends were observed for the non-BCHyPy PAHs varying from 39 to 34 μg g-1 in treated soils, not significantly different from control soils. However, the concentrations of extractable PAHs increased markedly in the amended soils and decreased with time from 153 to 78 ng g-1 remaining always higher than those in untreated soil. The extent of the BCHyPy loss was more compatible with physical rather than chemical processes. [ABSTRACT FROM AUTHOR]