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In recent years, the simple synthesis of artificial humic substances (A-HS) by alkaline hydrothermal processing of waste biomass was described. This A-HS was shown to support water and mineral binding, to change soil structure, to avoid fertilizer mineralization, and to support plant growth. Many of the observed macroscopic effects could, however,...
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... concept of "anthropogenic soil systems" is not new and, in reduction and simplification, in the form of adding mined peat to otherwise carbon-poor mineral soils a tool of plant breeding in rose gardens, greenhouses, and artificial environments ( Figure 1). In green houses or urban farming industry, most plants do not touch real soil anymore but grow on optimized substrates, where water and fertilizer can be continuously applied, while a porous material (e.g., blown clay) is considered sufficient to give stability. ...
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... green houses or urban farming industry, most plants do not touch real soil anymore but grow on optimized substrates, where water and fertilizer can be continuously applied, while a porous material (e.g., blown clay) is considered sufficient to give stability. Reducing soil to such a matrix medium of course is a brute, but for greenhouses apparently feasible simplification ( Figure 1a). For farmland with its alternating climate, water, and light conditions and based on the above quoted observation that sustained fertility goes strictly with soil carbon content, people can differentiate essentially three anthropogenic approaches: (i) addition of manure and waste biomasses, 27,28 (ii) biochar addition, 29 and (iii) natural and artificial humic substances 30 ( Figure 1b). ...
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... soil to such a matrix medium of course is a brute, but for greenhouses apparently feasible simplification ( Figure 1a). For farmland with its alternating climate, water, and light conditions and based on the above quoted observation that sustained fertility goes strictly with soil carbon content, people can differentiate essentially three anthropogenic approaches: (i) addition of manure and waste biomasses, 27,28 (ii) biochar addition, 29 and (iii) natural and artificial humic substances 30 ( Figure 1b). ...
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... addition, biochar addition develops its positive action on "soil material" properties only at rather high doses of addition, partly well above practical and economic feasibility. 42,43 The candidate discussed the most in the following chapters is artificial humic substance (A-HS) made by hydrothermal humification (HTH) 44 (Figure 1c). HTH is also using wet biomass which is obviously hard to burn, with a carbon efficiency of close to 100%, but is adding base throughout the hot water treatment. ...
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... a role of thumb, the amount of phenolic groups in the final organic condensate for instance goes with the primary phenolics/lignin input, while the number of carboxylic acids can be controlled by the added base, as every base unit can split a carbohydrate into two carboxylic acids. 44 A-HS can be "conjugated" to mineral soils, that is simple dispersion and mixing creates a homogeneous, with increasing amounts of A-HS, more brown-black powder which is difficult to separate again 45 (Figure 1d). This is indeed very different from simple addition of biochar powders, which easily separate by flotation. ...
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... next step of the anthropogenesis of soil as a living matter system is the priming of natural, poor soil with minor amounts of a reinforced artificial soil. The rationale behind such an experiment is that the newly established optimized anthropogenic soil material system contains all relevant chemical molecules, but also all grown microbial species to reorganize after mixing on a larger scale, i.e., the primary living matter system can act as a "primer" and could be "diluted" ( Figure 10). 86 It is clear that the mixing will destroy the former established spatiotemporal organization patterns, but the bacteria provided might be able after "plugging" to reactivate organization in the then diluted state. ...
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... the Veen plot of Figure 10, we indeed can learn that most of the bacterial species, but also fungal species, stay observable. Indeed, many species are, however, rather typical in weak soils and apparently not visible anymore in strong soils, with only a few species being dominant in strong soils. ...
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... experiments interestingly allow to reisolate the carbon from the cultivated samples and follow the altered morphology of at least biochar (note that A-HS are mostly aggregating molecules and can dissolve, change shape, or spread onto surfaces) on the length scales of the diverse microscopies. This is shown in Figure 11. 41 Indeed, one can observe how a carbonized sheet-like plant fragment (here from chopped corn stalks) is peeled of its outer layers already after 90 days in a fulvic acid supported microbiome system. ...
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... observation that they are potentially not the same carbon atoms stored in soil over a thousand years is only a legal problem for a potential accounting of carbon credits, while science is used Figure 10. Veen and species composition diversity of bacteria (a) and fungi (c) of original soil and the artificial soil constructed by the mixture of black soil derived from hydrothermal humification reaction with the original soil in ratios of 0%, 10%, 30%, and 50%, which are noted as CK, SS-10, SS-30, and SS-50, after 30 days postconstruction. ...
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... indices of sequencing were >0.999, indicating that the sequencing results indeed represent the real situation of the species and structure of bacterial community. 86 Figure 11. SEM images of original biochar and aged biochar collected from soil experiencing 90-day, 135-day, and 180-day cultivation. ...
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... this last potential application is more a joint architectural and cultural vision than reality, we want to come back to the starting point of living engineered materials for improving also the technology and life quality in inner cities. Greening skyscrapers and facades or even just planting inner city trees improves air quality, moderate temperature peaks, improves thermal insulation of buildings by an active, responding system. Modern pioneers of this movement are for instance the creators of Bosco Verticale (2014, Milano, Figure 11a), the already half-realized vision of a "Garden City Singapore" (starting in 1967), or the current plannings within Saudi Arabia's Vision 2030 program. Just viewing Figure 12, we can anticipate a necessity of urban soil materials in largest amounts and then even with added future chemical and engineering performance profiles. ...
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... pioneers of this movement are for instance the creators of Bosco Verticale (2014, Milano, Figure 11a), the already half-realized vision of a "Garden City Singapore" (starting in 1967), or the current plannings within Saudi Arabia's Vision 2030 program. Just viewing Figure 12, we can anticipate a necessity of urban soil materials in largest amounts and then even with added future chemical and engineering performance profiles. Vertical faç ade greening for instance depends on a mechanical support structure, e.g., textile fabrics or biofoams, which then support or complement the mineral soil. ...
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From soil composition and structure to nutrient dynamics and microbial interactions, the chapter elucidates the intricate web of factors influencing the fertility of agricultural soils. It examines the impact of human activities, such as agricultural practices and land use changes, on soil quality and sustainability. The chapter also explores advan...
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... The artificial hydrogeochemical technique simulates humification for synthesizing artificial humic matter in a short time and with high carbon recovery rate (close to 1), providing a novel route for sustainable utilization of so called "waste-biomass" for the reconstruction of soil humus layer, and even laid the base Keywords Anthropogenic soil, Artificial black soil, Optimization of soil mechanical structure, Recovery of biological function Graphical Abstract for the chemical retro-design and optimization of "black soils" (Yang et al. 2019b;. Furthermore, the rapid synthesis of environmental materials, namely anthropogenic soil as a "carbon pump", possess multiple functional component-structures and achieves 100% recycling of exogenous organic carbon, as compared to the previous individual components of artificial humic substances reported by our group (Yang et al. 2021a(Yang et al. , 2023. ...
... It has been confirmed that the hydrothermal humification-carbonization process is similar to the natural soil-forming process. This process involves the generation of "carbon sinks" (artificial humic substance-mineral and artificial humic substance-hydrochar) through polymerisation or abiotic self-assembly, as well as the continuous dissociation of soluble humic substances, rather than direct exogenous carbon recharge and carbonaceous pyrolysis processes (Yang et al. , 2019a(Yang et al. , 2023. This is the key to the upgrade of anthropogenic soil properties, especially agronomic properties, with artificial black soil as the functional fraction. ...
Herein, the feasibility of artificial black soil (ABS) derived from hydrothermal humification-hydrothermal carbonization (HTH-HTC) for restructuration of weak soil was verified. This study breaks through the long history of soil formation and evolution, and obtains reconstructed anthropogenic soil (AS) system which only takes one month, for the further application of rice seedlings. HTH-HTC derived by-products are slightly acidic, which facilitates the effective nutrient uptake and prevention of wilt diseases for acid-loving rice seedlings. AS mainly consists of the inherent components retained from weak soil such as SiO 2 and minerals, and exogenous components such as artificial humic substances and hydrochar, as introduced by hydrothermal humification processes. Results exhibit that AS has high contents of ammonium nitrogen, organic matter, organic carbon, and abundant porous structure for nutrient transport and water holding, especially, the community diversity and richness of microbial system gets the expected recovery and new beneficial bacteria (such as Caballeronia calidae ) or fungi (such as Humicola ) appear. Positive effects of AS on agronomic traits in rice seedlings are quantified. As a general result, this study supports the application of AS in sustainable agriculture, and provides a novel strategy to tackle the already-omnipresent land degradation by anthropogenic misuse and larger scale accidents.
... Similar approaches can be applied to manganese, which behaves similarly to iron in nature. Artificial Humic Substances (AHS) are emerging as a sustainable and versatile tool to address the challenges of modern agriculture (Yang and Antonietti, 2020;Yang et al., 2023). These substances, synthesized through the hydrothermal conversion of biomass, mimic the properties and functionalities of natural HS. ...
... In the case of AHS-Mn5, we were not able to analyze the Mn-edge due to the low signal-to-noise ratio on the spectra. The presence of manganese in the 2+ oxidation state can be explained by the redox properties of AHS (Yang et al., 2023). During the synthesis of AHS, electron-rich (i.e., reduced) groups, such as phenolic groups, are formed, and they are able to prevent manganese oxidation. ...
This study presents a new strategy for the production of sustainable manganese fertilizer based on artificial humic substances (AHS). AHS with different manganese concentrations (0‒20%) were synthesized from poplar bark under alkaline conditions via hydrothermal treatment. For the 20% manganese formulation, the interaction of manganese with AHS resulted in reduced solubility (from 25.2% to 12.3% organic carbon) and average molecular weight of humic acids (from 11.6 to 3.9 KDa), indicating preferential binding of the high-molecular-weight fraction. The formulation with 5% of manganese achieved optimal manganese loading without compromising the AHS solubility (19.4%). Structural analyses showed only minor changes in AHS in the presence of manganese, indicating that the main structural fragments of the AHS were preserved. Structural, morphological, and spectroscopic characterizations confirmed the formation of amorphous manganese complexes within the AHS matrix, primarily in the plant-available Mn(II) oxidation state. Plant bioassays showed increased manganese uptake with the application of AHS containing 5% Mn compared to MnCl2 alone (64 mg/kg vs. 40 mg/kg in dry cucumber biomass). Interestingly, unmodified AHS at higher concentrations (50 mg/L) further enhanced manganese (67 mg/kg) and iron (up to 209 mg/kg) uptake, highlighting the potential role of AHS in facilitating metal transport
... Artificial humic acid (A-HA), an emerging EOC derived from biological by-products or waste, has a carbon-negative property [13,14]. Our previous research has identified A-HA as a facilitator for the establishment of interactive microbial systems along mineral particle interfaces and plays an important role in maintaining soil ecosystem services [15,16]. A-HS has been proved to change soil structure, support water and mineral binding, avoid fertilizer mineralization, and furthermore support plant growth [14][15][16][17]. ...
... Our previous research has identified A-HA as a facilitator for the establishment of interactive microbial systems along mineral particle interfaces and plays an important role in maintaining soil ecosystem services [15,16]. A-HS has been proved to change soil structure, support water and mineral binding, avoid fertilizer mineralization, and furthermore support plant growth [14][15][16][17]. We emphasized the role of A-HA as a soil microbial carbon pump based on results that A-HA markedly promotes the growth of Rubbrivivax gelatinosus, which has multiple roles in carbon sequestration, and modulates the microbial community structure, resulting in soil carbon sequestration and reduction of OC loss [17,18]. ...
Fe (hydr)oxides have a substantial impact on the structure and stability of soil organic carbon (SOC) pools and also drive organic carbon turnover processes via reduction–oxidation reactions. Currently, many studies have paid much attention to organic matter–Fe mineral–microbial interactions on SOC turnover, while there is few research on how exogenous carbon addition abiotically regulates the intrinsic mechanisms of Fe-mediated organic carbon conversion. The study investigated the coupling process of artificial humic acid (A-HA) and Fe(hydr)oxide, the mechanism of inner-sphere ligands, and the capacity for carbon sequestration using transmission electron microscopy, thermogravimetric, x-ray photoelectron spectroscopy, and wet-chemical disposal. Furthermore, spherical aberration-corrected scanning transmission electron microscopy–electron energy loss spectroscopy and Mössbauer spectra have been carried out to demonstrate the spatial heterogeneity of A-HA/Fe (hydr)oxides and reveal the relationship between the increase in Fe-phase crystallinity and redox sensitivity and the accumulation of organic carbon. Additionally, the dynamics of soil structures on a microscale, distribution of carbon–iron microdomains, and the cementing-gluing effect can be observed in the constructing nonliving anthropogenic soils, confirming that the formation of stable aggregates is an effective approach to achieving organic carbon indirect protection. We propose that exogenous organic carbon inputs, specifically A-HA, could exert a substantial but hitherto unexplored effect on the geochemistry of iron–carbon turnover and sequestration in anoxic water/solid soils and sediments.
... A-HS, as the organic carbon material produced by hydrothermal humification of biomass waste, has broad application prospects in climate change mitigation, soil improvement, and agricultural productivity. [21][22][23][24] A-HS commonly contains labile carbon components which will be mineralized into carbon dioxide through both biological and abiotic processes. [25][26] Therefore, it is crucial to assess the stability of organic carbon fraction in A-HS to reveal the potential of A-HS in application of long-term carbon sequestration. ...
Hydrothermal humification technology for the preparation of artificial humic matters provides a new strategy, greatly promoting the natural maturation process. Iron, as a common metal, is widely used in the conversion of waste biomass; however, the influence of Fe³⁺ on hydrothermal humification remains unknown. In this study, FeCl3 is used to catalyze the hydrothermal humification of corn straw, and the influence of Fe³⁺ on the hydrothermal humification is explored by a series of characterization techniques. Results show that Fe³⁺ as the catalyst can promote the decomposition of corn straw, shorten the reaction time from 24 h to 6 h, and increase the yield from 6.77 % to 14.08 %. However, artificial humic acid (A‐HA) obtained from Fe³⁺‐catalysis hydrothermal humification contains more unstable carbon and low amount of aromatics, resulting in a significantly decreased stability of the artificial humic acid. These results provide theoretical guidance for regulating the structure and properties of artificial humic acid to meet various maintenance needs.
... Currently, there have been some studies on the application of HHA obtained from biomass waste in agriculture and environmental remediation fields (Pinto et al., 2023； Shen et al., 2022Yang et al., 2023;, which have confirmed the application value of HHA equivalent to commercial humic acid. ...
Hydrothermal humification of biowaste, in comparison to the traditional coal-based humic acid extraction process, better aligns with the goals of carbon neutrality and sustainability. This article provided a comprehensive review on the current advancements in hydrothermal humification of biowaste. Hydrothermal humic acid (HHA) derived from different biowaste sources was compared, exhibiting significant differences in their hydrophobicity, oxygen-containing functional group content, and structural characteristics. The influence of key parameters, including reaction temperature, residence time, pH and the action of catalysts on HHA yield was analyzed. The pathways through which biowaste and its major components transform into HHA were elucidated. Coal-like hydrochar has shown significant potential for producing HHA through hydrothermal treatment, with HHA selectivity exceeding 65%. HHA also exhibits promising performance in agriculture and environmental remediation, offering comparable value to commercial humic acid. Future research should concentrate on establishing the correlation between hydrothermal conditions and the efficiency of biowaste humification, thereby facilitating the development of a predictive model for assessing efficiency. Additionally, exploring the application value of hydrothermal-synthesized HHA with diverse chemical characteristics will guide the optimization of hydrothermal conditions and selection of suitable feedstock.
... Simple sugars, furans, organic acids, and phenols derived from the decomposition of lignocellulose under hydrothermal conditions act as humification precursors of artificial humic acid (AHA) (Yang et al., 2019). Due to the elevated temperature and pressure, hydrothermal technology can quickly convert lignocellulosic waste into HA within hours (Yang et al., 2023). Although the structure and characteristic functional group of AHA obtained in hydrothermal humification are similar to the natural humic acid (NHA), the nutritional value, including nitrogen, phosphorus, potassium, and trace elements, is still relatively low compared with the natural ones . ...
This study investigated hydrothermal humification of corn straw acid hydrolysis residue with biogas slurry impregnation, aiming at producing water-soluble artificial humic acid fertilizer for fertilizer application and soil remediation. Hydrothermal humification parameters, including potassium hydroxide concentration (1-3 mol/L), retention time (2-6 h), and temperature (140-180 °C), were investigated using water as the liquid phase. The selected hydrothermal humification condition was 1.5 mol/L potassium hydroxide at 180 °C for 4 h. Moreover, biogas slurry impregnation (0-30 days) was evaluated to improve humic acid yield without introducing additional chemicals or energy input. Biogas slurry as the liquid phase increased the humic acid production by 73.24% with 5 days of impregnation compared to the control due to the alkalinity. The humic acid concentration was sufficient for China's national standard of water-soluble humic acid fertilizers in such conditions. The organic components in biogas slurry were involved in artificial humification as a precursor, forming C-N bonds with humic acid. The product with fortified nitrogen-containing functional groups enhanced the nutrient slow-release characteristics and water retention capabilities. The pot experiment further confirmed that artificial humic acid prepared in this study not only promoted the growth of plants but also achieved soil remediation.
Transparent soil (TS) presents immense potential for root phenotyping due to its ability to facilitate high-resolution imaging. However, challenges related to transparency, mechanical properties, and cost hinder its development. Herein, we introduce super-transparent soil (s-TS) prepared via the droplet method using low acyl gellan gum and hydroxyethyl cellulose crosslinked with magnesium ions. The refractive index of the hydroxyethyl cellulose solution (1.345) closely aligns with that of water (1.333) and the low acyl gellan gum solution (1.340), thereby significantly enhancing the transmittance of hydrogel-based transparent soil. Optimal transmittance (98.45%) is achieved with polymer concentrations ranging from 0.8 to 1.6 wt.% and ion concentrations between 0.01 and 0.09 mol·L−1. After 60 days of plant cultivation, s-TS maintains a transmittance exceeding 89.5%, enabling the detailed visualization of root growth dynamics. Furthermore, s-TS exhibits remarkable mechanical properties, withstanding a maximum compressive stress of 477 kPa and supporting a maximum load-bearing depth of 186 cm. This innovative approach holds promising implications for advanced root phenotyping studies, fostering the investigation of root heterogeneity and the development of selective expression under controlled conditions.
Hydrothermal carbonization (HTC) solid and liquid products may inhibit seed germination, necessitating post-treatment. The hydrothermal humification (HTH) method addresses this drawback by transforming inhibitory compounds, such as aromatics, into artificial humic acids (AHAs) and artificial fulvic acids (AFAs). This study introduces a novel approach by investigating the substitution of the commonly used alkaline agent in HTH, KOH, with hydrated lime to develop cost-effective hydrothermal fertilizers from sugar beet pulp, enriching them with AHAs. It assesses the effects of lime on AHA production and soluble organic compounds compared to KOH. The results indicate that lime significantly reduces furans (from 560 to 3.15 mg/kg DM in solid and from 344 to 3.86 mg/L in process liquid) and boosts sugars and organic acids, especially lactic acid (from 4.70 to 65.82 g/kg DM in solid and from 4.05 to 22.89 mg/L in process liquid), increasing hydrochar yield (68.8% with lime vs. 27.4% with KOH). Despite the lower AHA production with lime compared to KOH (3.47% vs. 15.50%), lime-treated hydrothermal products are abundant in calcium and magnesium, boasting a pH of 7. This property presents a safer and more efficient alternative to hydrothermal fertilizers. The characterization of AHAs aligns with standard and natural humic substances, while lime-assisted HTH products, applied at a level of 0.01% w/w, could significantly enhance wheat growth and nutrient uptake compared to the control group. Importantly, these products show no toxicity on Daphnia magna, underscoring their potential for sustainable agriculture.
