Co-hydrothermal carbonization of swine and chicken manure: Influence of cross-interaction on hydrochar and liquid characteristics

Sequential hydrothermal liquefaction of lignocellulose-rich livestock manure: A new perspective on enhancing the production and quality of low-phenolic biocrude

The treatment and valorization of bulk livestock manure rich in lignocellulose demand efficient processing techniques. Hydrothermal liquefaction (HTL) has emerged as a promising approach for waste-to-energy conversion, effectively transforming lignocellulosic biomass into renewable biocrude. However, the advances in the utilization of HTL-derived biocrude have been hindered by its poor oil quality due to several factors including high phenolic compound content. This study focuses on enhancing the production and quality of low-phenolic biocrude via a sequential HTL process. The results revealed that sequential HTL achieved a high biocrude yield of 59.9%, with a concurrent reduction in phenolic content to 4.2%. This represents an 84.2% decrease in phenolic content compared to biocrude derived from direct HTL (280 ℃), achieving a tradeoff between biocrude yield and quality. Notably, GC-MS revealed that the biocrude produced through sequential HTL was enriched with fatty acids and esters accounting for 80.5%, contributing to the production of hydrocarbon fuels. Additionally, FT-ICR MS revealed that sequential HTL enhanced the biocrude quality and encouraged the production of light fuels. The petroleum fractionation analysis further revealed that sequential HTL-derived biocrude was more desirable in the downstream petroleum refining industry. The model compounds experiments revealed that phenols were likely to to be transferred to the oil phase at relatively high temperatures. Overall, it is the first study to elucidate the phenols removal mechanism and quality improvement of biocrude through the sequential HTL, demonstrating its potential for sustainable disposal and valorization of waste lignocellulosic biomass, and contributing to the development of renewable energy.

Optimized hydrothermal carbonization of chicken manure and anaerobic digestion of its process water for better energy management

Modern poultry production is faced with the challenge of properly managing its associated wastes, in particular chicken manure (CM). There is a need to improve the management of CM through conversion processes that allow the production of value-added products, particularly for energy purposes, such as hydrothermal carbonization (HTC) and anaerobic digestion (AD). The objectives of this study were: i) to optimize the CM-HTC, using response surface methodology with simultaneous optimization of mass yield and higher heating value (HHV), and ii) to evaluate the biomethane potential of the process water generated from hydrochar production under the optimized condition. An analysis of the overall energy potential was also performed. The optimal condition for HTC was 234 °C for 30 min, resulting in hydrochar with an HHV of 14.88 ± 0.22 MJ/kg and a mass yield of 50.00 ± 3.13 wt%. The cumulative methane yield was 179.2 ± 13.1 NmL CH₄/g VSadded and 255.5 ± 14.5 NmL CH₄/g VSadded for process water at 180 °C and 234 °C, respectively. The addition of hydrochar improved the methane yield by 49.6 ± 10.8%, indicating that this is a valuable option for energy recovery from CM. Overall, the HTC-AD integration approach achieved an energy recovery potential of more than 79%, offering an efficient strategy for CM valorization.

Influences of temperature and reaction time on nutrient conversion and metal interactions during hydrothermal treatment of pig manure

Pig manure is a renewable source of nutrients, such as phosphorus and nitrogen, that can be used to produce fertilizers. Hydrothermal treatment experiments using real pig manure were conducted to investigate the effect of temperature (107-200 °C) and reaction time (25-95 min) on nutrient conversion and distribution into hydrochar and process water. Sequential extractions were also performed to determine the phosphorus speciation in raw pig manure and hydrochars. The results showed that phosphorus and nitrogen recovery in the hydrochar was consistently above 94 % and 56 %, respectively, for all the experiments. Phosphorus content in the hydrochar increased from 15.4 to 24.6 mg P/g by increasing temperature and/or reaction time. Sequential extractions showed the increase in temperature led to a decrease in non-apatite inorganic phosphorus and organic phosphorus fractions in the hydrochars, while the apatite inorganic phosphorus fraction (Ca phosphates) increased. The concentration of total dissolved nitrogen in process water increased to values higher than 6000 mg N/L, while the ammonium concentration decreased to values lower than 2000 mg N/L by increasing temperature and/or reaction time. These results appear to indicate that the increase in hydrothermal temperature from 107 to 200 °C promoted the extraction and dissolution of organic nitrogen compounds from solid matrices to process water. This study provides valuable insights into P and N transformation during hydrothermal treatment of pig manure, which represent crucial information for developing sustainable treatment processes that aim to minimize waste disposal while enhancing the closure of anthropogenic P and N cycles.

Co-hydrothermal carbonization of lignocellulosic biomass and swine manure: Optimal parameters for enhanced nutrient reclamation, carbon sequestration, and heavy metals passivation

Hydrochar, the primary product of hydrothermal carbonization (HTC) of wet organic waste, is recognized as a versatile, carbon-abundant material with diverse applications. However, optimizing its performance for specific uses remains challenging. Therefore, this study introduced a co-HTC process involving carbon-rich lignocellulosic materials and ash-rich livestock manure [i.e., Zanthoxylum bungeanum branch residue (ZB) and swine manure (SM), respectively]. The impacts of HTC temperature (i.e., 180 °C, 220 °C, and 240 °C) and mass ratios (i.e., 1:0, 7:3, 5:5, 3:7, and 0:1) on hydrochar properties (e.g., pH, EC, nutrient contents, heavy metal content and availability, chemical stability, etc) and the characteristics of process water were evaluated. Results reveal that co-HTC dramatically improved the quality of hydrochars compared with that derived from a single feedstock. Notably, the ZB:SM ratio had a more substantial impact on total nutrient content, carbon stability, and heavy metal accumulation and mobility. Additionally, the synergistic effects of ZB and SM were greatly dependent on the HTC temperature. By adjusting the feedstock mass ratio and HTC temperature, a highly-functionalized hydrochar can be produced. For example, hydrochars produced at 240 °C with a 7:3 ZB to SM ratio (HC240-7) is optimal for degraded soil amendment, enhancing carbon sequestration and nutrient supplementation. Results from this study could provide valuable insights for improving waste management through HTC and expanding the environmental and agricultural application of hydrochar.

Effect of pyrolysis temperature on physicochemical characteristics and toxic elements for grub manure-derived biochar

While traditional solutions for disposing of animal manure are limited by their time-consuming nature and inefficiency, the pyrolysis of animal manure into biochar is considered a promising disposal option, offering high-value benefits. However, there are few research studies on the physicochemical properties and potential utilization pathway of grub manure-derived biochar (GB) prepared at different temperatures. In this study, grub manure (GM) was pyrolyzed at 450, 600 and 750 °C, and the effect of pyrolysis temperature on the characteristics and applications of GB was illustrated. The results showed that increasing pyrolysis temperature promoted the formation of an aromatic structure, enhanced the stability, and improved the surface pore structure of GB. The relationship between pyrolysis temperature and C/N-containing functional groups in GB was quantitatively analyzed. In the process of pyrolysis of GM to GB, carbonates first decomposed, and then, C[double bond, length as m-dash]O broke into C-O and finally condensed to form an aromatic ring structure at elevated pyrolysis temperature. Although GM was rich in organic matter and total N/P/K, the potentially toxic elements (PTEs) (Ni, Cu, Cd, Pb, Zn and As) in GM presented potential risk. The hazard of PTEs in GB was significantly decreased after GM was pyrolyzed. Overall, pyrolysis provided an opportunity for the sustainable management of GM, and GB is a multi-purpose and high-value product that could be applied in soil improvement, environmental remediation, and climate change mitigation for achieving sustainable development.

Hydrochar and Its Dissolved Organic Matter Aged in a 30-Month Rice-Wheat Rotation System: Do Primary Aging Factors Alter at Different Stages?

Hydrochar, recognized as a green and sustainable soil amendment, has garnered significant attention. However, information on the aging process in soil and the temporal variability of hydrochar remains limited. This study delves deeper into the interaction between hydrochar and soil, focusing on primary factors influencing hydrochar aging during a 30-month rice-wheat rotation system. The results showed that the initial aging of hydrochar (0-16 months) is accompanied by the development of specific surface area and leaching of hydrochar-derived dissolved organic matter (HDOM), resulting in a smaller particle size and reduced carbon content. The initial aging also features a mineral shield, while the later aging (16 to 30 months) involves surface oxidation. These processes collectively alter the surface charge, hydrophilicity, and composition of aged hydrochar. Furthermore, this study reveals a dynamic interaction between the HDOM and DOM derived from soil, plants, and microbes at different aging stages. Initially, there is a preference for decomposing labile carbon, whereas later stages involve the formation of components with higher aromaticity and molecular weight. These insights are crucial for understanding the soil aging effects on hydrochar and HDOM as well as evaluating the interfacial behavior of hydrochar as a sustainable soil amendment.

Artificial Humic Substances as Biomimetics of Natural Analogues: Production, Characteristics and Preferences Regarding Their Use

Various processes designed for the humification (HF) of animal husbandry wastes, primarily bird droppings, reduce their volumes, solve environmental problems, and make it possible to obtain products with artificially formed humic substances (HSs) as analogues of natural HSs, usually extracted from fossil sources (coal and peat). This review studies the main characteristics of various biological and physicochemical methods of the HF of animal wastes (composting, anaerobic digestion, pyrolysis, hydrothermal carbonation, acid or alkaline hydrolysis, and subcritical water extraction). A comparative analysis of the HF rates and HS yields in these processes, the characteristics of the resulting artificial HSs (humification index, polymerization index, degree of aromaticity, etc.) was carried out. The main factors (additives, process conditions, waste pretreatment, etc.) that can increase the efficiency of HF and affect the properties of HSs are highlighted. Based on the results of chemical composition analysis, the main trends and preferences with regard to the use of HF products as complex biomimetics are discussed.

Multivariate and multi-interface insights into carbon and energy recovery and conversion characteristics of hydrothermal carbonization of biomass waste from duck farm

High lipid, high nitrogen duck manure (DM) with high lipid, high lignocellulosic litter materials (LM) are the main wet biomass wastes from duck farms and both are naturally abundant carbon resources. The synthesis of duck farming biomass waste into carbon-rich materials for high value utilization by hydrothermal carbonization (HTC), which can directly treat wet biomass, has not been investigated. In this study, the physicochemical properties of hydrochar derived from co-HTC of DM and LM and its carbon and energy recovery patterns were systematically investigated under multivariate conditions of raw materials ratios, solids contents, temperatures and residence times. The application of synchrotron-based near-edge X-ray adsorption fine structure technique (C K-edge NEXAFS) combined with gas chromatography-mass spectrometry (GC-MS) to the hydrochar and hydrothermal liquid, respectively. At multiple interfaces provided an in-depth analysis of the important material transformations of the co-HTC process and the structure of the hydrochar. Extending residence time (180 min) and increasing LM ratio (M@4%) in co-HTC reaction of DM and LM is beneficial to achieve hydrochar containing higher carbon content (44.84%) at lower reaction temperatures (180 °C). The heating value (HHV) of the hydrochar ranges between 17.12 and 25.05 MJ/kg. The carbon recovery rate of the co-HTC of DM and LM all exceeded 55% and was more closely related to the carbon content of the hydrochar than to its yield. Additionally, the model ERR=0.97±0.01CRR+2.40±0.71 (R2 = 0.99, P < 0.01) was developed to predict energy recovery rate (ERR) based on carbon recovery rate (CRR). Esters were an important intermediate during co-HTC of DM and LM, and the derived hydrochar consisted of a wide range of polycyclic aromatic hydrocarbons, alkanes and N-aromatic heterocycles as well as polyfuran, pyrrole and pyridine structures.

Co-hydrothermal carbonization of polyvinyl chloride and lignocellulose biomasses: Influence of biomass feedstock on fuel properties and combustion behaviors

Co-hydrothermal carbonization (co-HTC) of lignocellulose biomass (LB) and chlorinated waste could produce value-added co-hydrochar while simultaneously removing inorganic metal salts and organic chlorine to the liquid phase. However, there is a lack of understanding of the influence of LB feedstocks on the fuel properties and combustion behaviors of co-hydrochars. Therefore, co-hydrochars derived from co-HTC of pine, bamboo, corncob, wheat stalk, and corn stalk with polyvinyl chloride (PVC) at the mass ratio of 9:1 under 260 °C for 30 min were tested. PVC facilitated the hydrolysis, dehydration, and polymerization of LB compositions (hemicellulose, cellulose, soluble lignin, and insoluble lignin). In turn, these LB compositions could prevent PVC aggregation and promote PVC substitution. Hydrochar fragments could coat the PVC surface and hinder its hydrolysis. Interactions between LB compositions and PVC improved the fuel properties and combustion behaviors of co-hydrochars derived from bamboo, corncob, wheat stalk, and corn stalk while decreasing the fuel properties and combustion behaviors of co-hydrochar derived from pine (HC-PPE). Except for HC-PPE, the fuel ratio (fixed carbon/volatile matter) of co-hydrochars increased to 0.90-1.18 and their HHVs reached approximately 17.5-32.45 MJ/kg without an increased risk of chlorine corrosion. The combustion of co-hydrochars was easier and more stable due to their higher ignition and burnout temperatures and lower activation energies. These findings provide comprehensive knowledge of the LB feedstocks influence on fuel properties and combustion behaviors of co-hydrochars, which would contribute to the cost-effective use of LB and chlorinated wastes.

Study on the Effect of Hydrothermal Carbonization Parameters on Fuel Properties of Chicken Manure Hydrochar

Economic development and population growth lead to the increased production of chicken manure, which is a problematic organic waste in terms of its amount, environmental threats, and moisture content. In this study, hydrothermal carbonization, an emerging way of waste disposal, was performed on chicken manure to produce an energy-rich material called hydrochar. The effects of hydrothermal carbonization temperature (180, 240, 300 °C) and process time (30, 90, 180 min) were summarized. Proximate and ultimate analysis, as well as low and high heating values were applied both on raw material and derived hydrochars. Additionally, the performance of the process was examined. The obtained results show that hydrothermal carbonization is a feasible method for chicken manure disposal and valorization. Although the process time did not influence the fuel properties of chicken manure considerably, a higher temperature led to a significantly higher heating value, reaching 23,880.67 ± 34.56 J × g^-1 at 300 °C and 180 min with an improvement of ~8329 J × g^-1 compared with raw chicken manure (15,551.67 J × g^-1). Considering the energy gain value, the hydrochar derived at 240 °C in 30 min had the best result. Moreover, the energy consumption for this process was relatively low (124.34 ± 8.29 kJ × g^-1). With its still feasible fuel properties and high heating value of 20,267.00 ± 617.83 kJ × g^-1, it was concluded that these parameters of chicken manure hydrochar are the most beneficial and present a potential alternative for conventional fuel.

Can Biochar Improve the Sustainability of Animal Production?

Animal production is a significant contributor of organic and inorganic contaminants in air, soil, and water systems. These pollutants are present beginning in animal houses and impacts continue through manure storage, treatment, and land application. As the industry is expected to expand, there is still a lack of affordable, sustainable solutions to many environmental concerns in animal production. Biochar is a low-cost, sustainable biomaterial with many environmental remediation applications. Its physicochemical properties have been proven to provide environmental benefits via the adsorption of organic and inorganic contaminants, promote plant growth, improve soil quality, and provide a form of carbon sequestration. For these reasons, biochar has been researched regarding biochar production, and application methods to biological systems have a significant influence on the moisture content, pH, microbial communities, and carbon and nitrogen retention. There remain unanswered questions about how we can manipulate biochar via physical and chemical activation methods to enhance the performance for specific applications. This review article addresses the positive and negative impacts of biochar addition at various stages in animal production from feed intake to manure land application.

Wet wastes to bioenergy and biochar: A critical review with future perspectives

The ever-increasing rise in the global population coupled with rapid urbanization demands considerable consumption of fossil fuel, food, and water. This in turn leads to energy depletion, greenhouse gas emissions and wet wastes generation (including food waste, animal manure, and sewage sludge). Conversion of the wet wastes to bioenergy and biochar is a promising approach to mitigate wastes, emissions and energy depletion, and simultaneously promotes sustainability and circular economy. In this study, various conversion technologies for transformation of wet wastes to bioenergy and biochar, including anaerobic digestion, gasification, incineration, hydrothermal carbonization, hydrothermal liquefaction, slow and fast pyrolysis, are comprehensively reviewed. The technological challenges impeding the widespread adoption of these wet waste conversion technologies are critically examined. Eventually, the study presents insightful recommendations for the technological advancements and wider acceptance of these processes by establishing a hierarchy of factors dictating their performance. These include: i) life-cycle assessment of these conversion technologies with the consideration of reactor design and catalyst utilization from lab to plant level; ii) process intensification by integrating one or more of the wet waste conversion technologies for improved performance and sustainability; and iii) emerging machine learning modeling is a promising strategy to aid the product characterization and optimization of system design for the specific to the bioenergy or biochar application.

Review on upgrading organic waste to value-added carbon materials for energy and environmental applications

Value-added materials such as biochar and activated carbon that are produced using thermo-chemical conversion of organic waste have gained an emerging interest for the application in the fields of energy and environment because of their low cost and unique physico-chemical properties. Organic waste-derived materials have multifunctional abilities in the field of environment for capturing greenhouse gases and remediation of contaminated soil and water as well as in the field of energy storage and conversion. This review critically evaluates and discusses the current thermo-chemical approaches for upgrading organic waste to value-added carbon materials, performance enhancement of these materials via activation and/or surface modification, and recent research findings related to energy and environmental applications. Moreover, this review provides detailed guidelines for preparing high-performance organic waste-derived materials and insights for their potential applications. Key challenges associated with the sustainable management of organic waste for ecological and socio-economic benefits and potential solutions are also discussed.