Organic Feedstock Research Articles

Microbiome assembly and stability during start-up of a full-scale, two-phase anaerobic digester fed cow manure and mixed organic feedstocks

Carbon transformations during anaerobic digestion are mediated by complex microbiomes, but their assembly is poorly understood, especially in full-scale digesters. Gene-centric metagenomics combining functional and taxonomic classification was performed for an on-farm digester during start-up. Cow manure and organic waste pre-treated in a hydrolysis tank were fed to the methane-producing digester and the volatile solids loading rate was slowly increased from 0 to 3.5 kg volatile solids m−3 d−1 over one year. The microbial community in the anaerobic digester exhibited a high ratio of archaea, which were dominated by hydrogenotrophic methanogens. Bacteria in the anaerobic digester had a high abundance of genes for ferredoxin cycling, H2 generation, and more metabolically complex fermentations than in the hydrolysis tank. In total, the results show that a functionally stable microbiome was achieved quickly during start-up and that the microbiome created in the low-pH hydrolysis tank did not persist in the downstream anaerobic digester.

Impacts of Anaerobic Thermophilic Fermentation on Physicochemical Characteristics of Effluents Derived from Diverse Organic Feedstocks

Impacts of Anaerobic Thermophilic Fermentation on Physicochemical Characteristics of Effluents Derived from Diverse Organic Feedstocks

The Effect of Different Biochar Characteristics on Soil Nitrogen Transformation Processes: A Review

For the last 30 years, interest has focused on biochar and its potential to store carbon in soil to mitigate climate change whilst improving soil properties for increased crop production and, therefore, could play a critical role in both agricultural sustainability and broader environmental aims. Biochar, a carbonaceous product, is formed from organic feedstock pyrolysised in the absence of air and, therefore, is a potential means of recycling organic waste. However, different feedstock and pyrolysis conditions result in a biochar with a range of altered characteristics. These characteristics influence nitrogen transformation processes in soil and result in the metabolism of different substrates and the formation of different products, which have different effects on agricultural yield. This paper reviews how the production of biochar, from varying feedstock and pyrolysis conditions, results in different biochar characteristics that influence each stage of the nitrogen cycle, namely processes involved in fixation, assimilation, mineralisation and denitrification. The nitrogen cycle is briefly outlined, providing a structure for the following discussion on influential biochar characteristics including carbon composition (whether recalcitrant or rapidly metabolisable), mineral composition, surface area, porosity, cation exchange capacity, inhibitory substances and pH and so on. Hence, after the addition of biochar to soil, microbial biomass and diversity, soil porosity, bulk density, water-holding capacity, cation exchange capacity, pH and other parameters change, but that change is subject to the type and amount of biochar. Hence, products from soil-based nitrogen transformation processes, which may be beneficial for plant growth, are highly dependent on biochar characteristics. The paper concludes with a diagrammatic summation of the influence of biochar on each phase of the nitrogen cycle, which, it is hoped, will serve as a reference for both students and biochar practitioners.

Carbon Neutral Fuels and Chemicals from Standalone Biomass Refineries

The urgency to eliminate man-made greenhouse gas emissions and achieve energy security/independence by all countries justifies an energy policy that considers the major role of renewable biomass as a source of organic feedstock for producing adequate organic chemicals and biofuels on a sustainable basis and economically. This paper investigates a three-stage thermochemical process to convert wet biomass into a tailored mix of syngas for producing green methanol, hydrogen, and Fischer-Tropsch products. The three-stage thermochemical process involves the torrefaction of wet biomass using hot carbon monoxide gas, pyrolysis of torrefied biomass to produce biochar, and final gasification of the pyrolysis gases by auto thermal reforming up to 1400o C temperature. The proposed process is suitable to utilize a wide variety of biomass materials such as freshly harvested biomass without field drying, agro waste, forest/plantation litter, organic municipal solid wastes, sludge from sewage water treatment plants, solid biomass rejects from anaerobic digesters, bagasse from sugar or first-generation ethanol plants, organic solid rejects from second-generation ethanol plants, waste glycerides from biodiesel plants, industrial organic waste, etc. The proposed process offers valorization of biomass so that the net income of farmers is enhanced a fewfold by selling freshly harvested biomass. The economic analysis found that carbon-neutral hydrogen, methanol, etc can be produced below the prevailing costs of such products derived from fossil crude oil or natural gas without considering carbon credits. It is feasible in a standalone biomass refinery to use any biomass as only one bulk raw material/feedstock without any harmful emissions to water bodies or the atmosphere except carbon neutral carbon dioxide gas if not sequestrated.

The oxygen-tolerant reductive glycine pathway assimilates methanol, formate and CO2 in the yeast Komagataella phaffii

The current climatic change is predominantly driven by excessive anthropogenic CO2 emissions. As industrial bioprocesses primarily depend on food-competing organic feedstocks or fossil raw materials, CO2 co-assimilation or the use of CO2-derived methanol or formate as carbon sources are considered pathbreaking contributions to solving this global problem. The number of industrially-relevant microorganisms that can use these two carbon sources is limited, and even fewer can concurrently co-assimilate CO2. Here, we search for alternative native methanol and formate assimilation pathways that co-assimilate CO2 in the industrially-relevant methylotrophic yeast Komagataella phaffii (Pichia pastoris). Using 13C-tracer-based metabolomic techniques and metabolic engineering approaches, we discover and confirm a growth supporting pathway based on native enzymes that can perform all three assimilations: namely, the oxygen-tolerant reductive glycine pathway. This finding paves the way towards metabolic engineering of formate and CO2 utilisation to produce proteins, biomass, or chemicals in yeast.

The Effect of Reverse Sorption on an Extraction Kinetics Melanin Case

Research into extraction kinetics is one of the crucial factors in a technological process. Extraction is used predominantly when working with organic feedstock. The study of the kinetics of extraction of a substance is a complex process, which is influenced by a large number of factors. This paper presents an analysis of one of these factors, namely the influence of reverse sorption on the process of substance release from the matrix. Sorption can directly affect the intraparticle diffusion constants and, consequently, the rate of release of the substance. Using buckwheat husk as an example, its sorption capacity was assessed to assess the sorption factor on the rate of melanin release. To select the optimal parameters of the chemical process, the experiment was carried out at temperatures of 40, 50, and 60 degrees Celsius. The Axelrud and Baker–Lonsdale equations were used to describe the kinetic models.

Utilization of Organic Waste in a Direct Carbon Fuel Cell for Sustainable Electricity Generation

There is much organic waste that comes from by-products of agriculture and product processing, solid waste from livestock, and municipal waste. Conventional methods that are widely used for the treatment and management of organic fractions of waste are landfilling, composting, anaerobic digestion, incineration, gasification, and pyrolysis. Among the above methods, pyrolysis is a relatively simple, robust, and scalable technology for transforming diverse organic waste feedstock into renewable energy products. Recently, the electrochemical conversion of biochar into electricity in direct carbon fuel cells (DCFC) has also been investigated and shown to be feasible and highly efficient. This paper focuses on the utilization of organic waste as a fuel and the investigation of their characteristics during electrochemical reactions in molten hydroxide direct carbon fuel cells (MH-DCFCs). Organic waste of different origins (the food-processing industry, urban and suburban areas, municipal solid organic waste, sewage sludge) with diversified characteristics was used as the main feedstock. The lowest power density was determined for sewage sludge (5.1 mW cm−2), and the best results were obtained for peanut shells (53.14 mW cm−2). This study concludes that higher elemental carbon, lower ash content and the presence of reactive surface oxygen functional groups in biochar obtained from organic waste might contribute to better cell performance. Moreover, the research establishes the potential of carbonized organic waste as a prospective alternative fuel source for power generation in an MH-DCFC.

Can waste eggshell replace commercial zeolites as catalyst for bio-oil production?

The utilisation of calcium oxide (CaO) from waste chicken eggshells, fishbone, and dolomite as a catalyst in the co-pyrolysis of empty fruit bunch (EFB) and high-density polyethene plastic (HDPE) was investigated and compared with existing commercial zeolite catalysts (HZSM-5, NaY, and FCC). In-situ catalytic co-pyrolysis of EFB-HDPE was performed for each CaO and zeolite-based catalyst. Gas Chromatography-Mass Spectrometry (GC-MS) was used to analyse the hydrocarbon content of the bio-oil produced by pyrolysis. The highest hydrocarbon content (61.62%) was obtained from the calcined eggshell (CES) catalyst and was comparable to that of the commercial zeolite catalyst, HZSM-5, with a hydrocarbon content of 53.53%. Brunauer–Emmett–Teller (BET) analysis, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis, and Particle Size Analysis (PSA) have proven the viability of CaO-based catalysts in the co-pyrolysis process for bio-oil production via fast pyrolysis. The CES achieved the desired pore diameter (175.15 nm) which was exhibited in the morphology analysis (SEM) and exhibited a uniform arrangement of calcium oxide particles and a porous structure. This finding provides fundamental insight into CaO from organic waste as a suitable alternative to zeolite catalysts in the co-pyrolysis of organic and inorganic feedstocks.

Trick of the Trade: Unveiling the Importance of Feedstock Chemistry in Trichoderma-Organic Amendments-Based Bio-Stimulants

We investigated the effect of Trichoderma harzianum in combination with biochar or other organic feedstocks, i.e., fish meal, Medicago, and maize straw, on the growth of Lens culinaris, Zea mays, Oryza sativa, and Glycine max. Biochar and other organic feedstocks were characterized by 13C-CPMAS NMR spectroscopy. Fish and Medicago had low C/N and high N content, while biochar, maize, and AC (Activated Carbon) had high C/N. pH ranged from 9.38 for biochar to 5.67 for AC. 13C-CPMAS NMR showed large chemical changes in organic mixtures leading to aromatic C-type enrichment in the presence of biochar or AC. Biochar and organic feedstocks inoculated with T. harzianum showed different effects, ranging from inhibition to crop stimulation. Overall, out of 88 cases, T. harzianum inoculum had a positive effect on root length in 46 cases (52.2%). The effect of fungal inoculum was particularly positive when combined with AC or biochar and when non-pyrogenic amendments were present. In contrast, a negative effect was observed when T. harzianum was inoculated with N-rich non-stabilized organic amendments. Further research is needed to identify the specific mechanisms underlying the inhibitory and bio-stimulatory effects of Trichoderma mixtures with organic amendment for the right combinations of raw materials that maximize crop productivity.

Suppressing the formation of N-heteroaromatics during hydrothermal liquefaction of proteinaceous model feedstock

Hydrothermal liquefaction was applied to model mixtures containing lard oil (lipid), cellulose (carbohydrate), and bovine serum albumin (protein), representing biogenic organic waste feedstocks. The content of protein was kept constant for every experiment, while the lipid and cellulose content was changed, which is expressed by the lipid to protein (LtoP) or cellulose to protein (CtoP) ratio. The reactions were conducted at 350 °C with a residence time of 20 min in 25 ml micro autoclaves. Afterwards, the lumped recovery of carbon and nitrogen into the different product phases was investigated and representative compounds were identified to get an overview of the composition on a molecular level. A high LtoP ratio results in an increased biocrude yield and eventually higher carbon recovery, while the nitrogen recovery is slightly lowered. The formation of nitrogen containing heteroaromatic species could be suppressed by the addition of lipids from 6.10 to 0.03% for pyrazines and 2.69 to 0.43% for indoles. Consequently, the formation and nitrogen recovery by heteroaliphatic amide species increased from 0.00 to 8.77%. Different reaction pathways for the formation of the different species are proposed. It turned out that reactive amine from protein degradation can be “trapped” in stable amides, preventing the formation of nitrogen heteroaromatics with oxygenated from carbohydrates.Graphical abstract

Biochemical conditions for anaerobic digestion of agricultural feedstocks: A full-scale study linking elements concentration and residual methane potential

Agricultural biogas plants should operate at the highest biological efficiency, with a fast anaerobic conversion of organic feedstocks leading to a low Residual Methane Potential (RMP). Optimal biochemical conditions boost the metabolic activity of microorganisms, providing better process performances. In this study, RMP of 16 full scale agricultural biogas plants operating with different agri-based feedstock categories was used as indicator of biological efficiency and linked to their operational parameters such as Organic Loading Rate (OLR), Hydraulic Retention Time (HRT) and to chemical elements concentration in the digestate. RMP ranged between 1% and 26% of the total biomethane produced revealing a clear relation with HRT. The Principal Component Analysis (PCA) showed how specific trace elements supplementation, in the order Se > Mo > Co, and their concentration ratios (Ni/Co and Ni/Se) lead to RMP reduction in full-scale agricultural biogas plants with low HRT (<48 days) and high OLR (>3.61 kgVS m−3 day−1) mainly fed with manure and agro-industrial by-products.

Deep sea benthic microbial fuel cell split-release landers

The study introduces the benthic microbial fuel cell lander (BMFC Lander)-an newly constructed modification to an untethered instrumented seafloor platform or “ocean lander” for probing deep-sea energy potential at depths exceeding 1000 meters below the sea surface over long timescales (two to five months). The BMFC Lander’s design includes a detachable anode that permits the re-use of its electrical and anode components in subsequent deployments. Six BMFC Landers successfully deployed in the Southern California bight that hosted a variety of water depth and temperature conditions for testing BMFC performance, demonstrating their reliability as platforms for deployment, energy generation and recovery. Four Lander’s BMFC payloads generated a combined total energy density of approximately 30Whrsm−2 from the seafloor. Organic feedstock (chitin) shortened the time to discharge potential and enhanced power production for two BMFCs in deep-sea sediments despite increased depths and lower temperatures. The BMFC Landers, with a low-cost overhead, are adaptable to support a variety of low-power sensors for tracking water parameters.

Preparation, characterization and nitrogen availability of nitrohumic acid as a slow-release nitrogen fertilizer

ABSTRACT Nitrohumic acids (NHAs) are considered as promising slow-release N fertilizers. In this study, NHA was produced from six organic feedstocks, including coal, leonardite, municipal waste compost, sewage sludge, and apple and beech biochars via nitration using nitric acid. The nitration process was conducted in two ways: (i) after humic acid (HA) extraction (NHAD), and (ii) before HA extraction (NHAID). The prepared NHAs were then characterized using FT-IR and CHNS analysis. Additionally, N mineralization of NHAs was investigated in a sandy loam soil sample. The FT-IR spectra showed that both methods of nitration loaded nitro (NO2) groups into the HA structure. However, the CHNS analysis indicated the highest rate of N increase for NHAD (106%) and NHAID (113%) extracted from leonardite. Moreover, on average, the total acidity and carboxylic groups of the HAs increased by 7.5% and 14.5% after the nitration processes, respectively. The highest extraction yields of NHAD (26.1%) and NHAID (42.1%) were also obtained from leonardite. Although the extraction yield of NHAID was on average two times higher than that of NHAD, NHAD indicated a higher soil N availability (1.4 times). We concluded that the NHAD extracted from leonardite could be considered as an alternative slow-release N fertilizer.

Separation of furfuryl alcohol from water using hydrophobic deep eutectic solvents

Furfuryl alcohol (FA) is an important organic chemical feedstock that must be separated from water to upgrade it into high-value-added products. Since FA forms an azeotrope with water, liquid-liquid extraction is a suitable option for separating both compounds. This work evaluates the separation of FA from water using hydrophobic deep eutectic solvents (DES). Three DES were prepared using menthol, thymol, and octanoic acid by combining them in molar ratio as follows: thymol + octanoic acid (1:2), menthol + octanoic acid (1:2), and thymol + menthol (1:1). Experimental liquid-liquid equilibria (LLE) of ternary systems water + FA + DES measured at 313.15 K and 101.13 kPa were used to determine the distribution coefficient and selectivity values for FA when using each DES. The experimental results were compared with molecular dynamics (MD) using Martini 3 force field and modeled using Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) without any adjustable binary parameters. According to the results, selectivities and distribution coefficients using hydrophobic DES have comparable values to traditional volatile organic compounds (VOCs) used to separate FA from water. In general, DES shows better distribution coefficients compared with typical organic solvents. According to the results, a good alternative would be menthol + octanoic acid (1:2) or thymol + menthol (1:1) to replace typical VOCs. MD and PC-SAFT provide accurate estimations for ternary LLE in the range of examined thermodynamic conditions, which confirms the predictive consistency of both approaches. Microscopic properties computed with MD simulations evidence a surface activity or absolute adsorption of FA in the interfacial region, which is correlated with favorable distribution coefficients and selectivities.

A specific H2/CO2 consumption molar ratio of 3 as a signature for the chain elongation of carboxylates from brewer's spent grain acidogenesis.

Brewer's spent grain (BSG) is an undervalorized organic feedstock residue composed of fermentable macromolecules, such as proteins, starch, and residual soluble carbohydrates. It also contains at least 50% (as dry weight) of lignocellulose. Methane-arrested anaerobic digestion is one of the promising microbial technologies to valorize such complex organic feedstock into value-added metabolic intermediates, such as ethanol, H2, and short-chain carboxylates (SCC). Under specific fermentation conditions, these intermediates can be microbially transformed into medium-chain carboxylates through a chain elongation pathway. Medium-chain carboxylates are of great interest as they can be used as bio-based pesticides, food additives, or components of drug formulations. They can also be easily upgraded by classical organic chemistry into bio-based fuels and chemicals. This study investigates the production potential of medium-chain carboxylates driven by a mixed microbial culture in the presence of BSG as an organic substrate. Because the conversion of complex organic feedstock to medium-chain carboxylates is limited by the electron donor content, we assessed the supplementation of H2 in the headspace to improve the chain elongation yield and increase the production of medium-chain carboxylates. The supply of CO2 as a carbon source was tested as well. The additions of H2 alone, CO2 alone, and both H2 and CO2 were compared. The exogenous supply of H2 alone allowed CO2 produced during acidogenesis to be consumed and nearly doubled the medium-chain carboxylate production yield. The exogenous supply of CO2 alone inhibited the whole fermentation. The supplementation of both H2 and CO2 allowed a second elongation phase when the organic feedstock was exhausted, which increased the medium-chain carboxylate production by 285% compared to the N2 reference condition. Carbon- and electron-equivalent balances, and the stoichiometric ratio of 3 observed for the consumed H2/CO2, suggest an H2- and CO2-driven second elongation phase, converting SCC to medium-chain carboxylates without an organic electron donor. The thermodynamic assessment confirmed the feasibility of such elongation.

A Review on Biofuels and Chemicals Production by Co-pyrolysis of Solid Biomass Feedstocks and Non-degradable Plastics

Modern lives have resulted in a substantial rise in the volume of plastic waste in recent years. Throughout, there is a lot of solid biomass that can be used as energy. By co-pyrolysis, these waste plastic and solid biomass feedstock mixes can be transformed to produce synergistic fuels and value-added products. To promote environmentally appropriate pathways for waste management and sustainability, the manufactured products can be used as chemicals and pollutant sorbents. This review's main focus is on the advancement of this method of waste disposal and energy production. The difficulties and potential benefits of developing combinations of solid organic waste and plastic feedstock for co-pyrolysis are also covered. With the introduction of waste biomass for improved synergistic effects in waste disposal as well as the recovery of energy and value-added products, the objective was to provide attractive practicable pathways for clean and efficient disposal of plastic wastes.

Butanol as a major product during ethanol and acetate chain elongation.

Chain elongation is a relevant bioprocess in support of a circular economy as it can use a variety of organic feedstocks for production of valuable short and medium chain carboxylates, such as butyrate (C4), caproate (C6), and caprylate (C8). Alcohols, including the biofuel, butanol (C4), can also be generated in chain elongation but the bioreactor conditions that favor butanol production are mainly unknown. In this study we investigated production of butanol (and its precursor butyrate) during ethanol and acetate chain elongation. We used semi-batch bioreactors (0.16L serum bottles) fed with a range of ethanol concentrations (100-800mM C), a constant concentration of acetate (50mM C), and an initial total gas pressure of ∼112kPa. We showed that the butanol concentration was positively correlated with the ethanol concentration provided (up to 400mM C ethanol) and to chain elongation activity, which produced H2 and further increased the total gas pressure. In bioreactors fed with 400mM C ethanol and 50mM C acetate, a concentration of 114.96 ± 9.26mM C butanol (∼2.13gL-1) was achieved after five semi-batch cycles at a total pressure of ∼170kPa and H2 partial pressure of ∼67kPa. Bioreactors with 400mM C ethanol and 50mM C acetate also yielded a butanol to butyrate molar ratio of 1:1. At the beginning of cycle 8, the total gas pressure was intentionally decreased to ∼112kPa to test the dependency of butanol production on total pressure and H2 partial pressure. The reduction in total pressure decreased the molar ratio of butanol to butyrate to 1:2 and jolted H2 production out of an apparent stall. Clostridium kluyveri (previously shown to produce butyrate and butanol) and Alistipes (previously linked with butyrate production) were abundant amplicon sequence variants in the bioreactors during the experimental phases, suggesting the microbiome was resilient against changes in bioreactor conditions. The results from this study clearly demonstrate the potential of ethanol and acetate-based chain elongation to yield butanol as a major product. This study also supports the dependency of butanol production on limiting acetate and on high total gas and H2 partial pressures.

Challenges for Hybrid Water Electrolysis to Replace the Oxygen Evolution Reaction on an Industrial Scale.

To enable a future society based on sun and wind energy, transformingelectricity into chemical energy in the form of fuels is crucial. This transformation can be achieved in an electrolyzer performing water splitting, where at the anode, water is oxidized tooxygen-oxygen evolution reaction (OER)-to produce protons and electrons that can be combined at the cathode to form hydrogen-hydrogen evolution reaction (HER). While hydrogen is a desired fuel, the obtained oxygen has no economic value. A techno-economically more suitable alternative is hybrid water electrolysis, where value-added oxidation reactions of abundant organic feedstocks replace the OER. However, tremendous challenges remain for the industrial-scale application of hybrid water electrolysis. Herein, these challenges, including the higher kinetic overpotentials of organic oxidation reactions compared to the OER, the small feedstock availably and product demand of these processes compared to the HER (and carbon dioxide reduction), additional purifications costs, and electrocatalytic challenges to meet the industrially required activities, selectivities, and especially long-term stabilities are critically discussed. It is anticipated that this perspective helps the academic research community to identify industrially relevant research questions concerning hybrid water electrolysis.

Carbon content determines the aggregation of biochar colloids from various feedstocks

The aggregation kinetics of biochar colloids (BCs) play a crucial role in the fate and transport of contaminants, as well as the carbon (C) cycle in the environment. However, the colloidal stability of BCs from various feedstocks is very limited. In this study, the critical coagulation concentration (CCC) of twelve standard biochars pyrolyzed from various feedstocks (municipal source, agricultural waste, herbaceous residue, and woody feedstock) at 550 °C and 700 °C were investigated, and the relationship between the physicochemical characteristics of biochar and the colloidal stability of BCs was further analyzed. The CCC of BCs in the NaCl solution followed the trend of municipal source < agricultural waste < herbaceous residue < woody feedstock, which was similar to the order of C content in biochar. The CCC of BCs showed a strong positive correlation with the C content of various biochars, especially pyrolyzed at a higher temperature of 700 °C. The BCs derived from lignin-rich feedstock (e.g., woody feedstock) had the highest colloidal stability, followed by cellulose-rich feedstock (e.g., agricultural waste and herbaceous residue). The BCs derived from organic matter-rich feedstock (municipal source) were easy to aggregate in the aqueous environment. This study quantitatively provides new insights into the relationship between BCs stability and biochar characteristics from various feedstocks, which is critical to assess biochar environmental behavior in aqueous environments.

Evaluating fundamental biochar properties in relation to water holding capacity

Biochar products that hold and release water within a stable carbonised porous structure provide many opportunities for climate mitigation and a range of applications such as for soil amendments. Biochar that are produced from various organic feedstocks by pyrolysis can provide multiple co-benefits to soil including improving soil health and productivity, pH buffering, contaminant control, nutrient storage, and release, however, there are also risks for biochar application in soils. This study evaluated fundamental biochar properties that influence Water Holding Capacity (WHC) of biochar products and provides recommendations for testing and optimising biochar products prior to soil applications. A total of 21 biochar samples (locally sourced, commercially available, and standard biochars) were characterised for particle properties, salinity, pH and ash content, porosity, and surface area (with N2 as adsorbate), surface SEM imaging, and several water testing methods. Biochar products with mixed particle size, irregular shapes, and hydrophilic properties were able to rapidly store relatively large volumes of water (up to 400% wt.). In contrast, relatively less water (as low as 78% wt.) was taken up by small-sized biochar products with smooth surfaces, along with hydrophobic biochars that were identified by the water drop penetration test (rather than contact angle test). Water was stored mostly in interpore spaces (between biochar particles) although intra-pore spaces (meso-pore and micropore scale) were also significant for some biochars. The type of organic feedstock did not appear to directly affect water holding, although further work is needed to evaluate mesopore scale processes and pyrolytic conditions that could influence the biochemical and hydrological behaviour of biochar. Biochars with high salinity, and carbon structures that are not alkaline pose potential risks when used as soil amendments.