Sustainable Bioenergy Production Research Articles

Jerusalem Artichoke: Nitrogen Fertilization Strategy and Energy Balance in the Production Technology of Aerial Biomass

Jerusalem artichoke (Helianthus tuberosus L.) is a plant with considerable potential for energy generation due to its rapid growth, high biomass yield, and resistance to environmental stresses. The aim of this study was to determine the influence of the nitrogen fertilization strategy on the yield and energy balance in the production technology of Jerusalem artichoke (JA) in a perennial cropping system. The article presents the results of a three-year experiment which was conducted in Poland to determine the effect of different N rates (0, 50, 75, and 100 kg ha−1) supplied with mineral fertilizers and liquid digestate on the energy balance in the production of JA aerial biomass. The experiment had a randomized block design with three replications. The demand for energy in JA cultivation reached 16.2–26.3 (year 1) and 2.9–14.6 GJ ha−1 (years 2 and 3). Energy inputs in the cultivation technology were reduced by 17–19% (year 1) and 35–47% (years 2 and 3) when mineral fertilizers were replaced with digestate. Jerusalem artichoke yields were lowest in the technology without fertilization (12.5 Mg ha−1 DM). Dry matter yield increased significantly (by 43–55%) after the application of 75 kg N ha−1, regardless of fertilizer type. The energy output of biomass peaked (230.1 GJ ha−1) in response to a mineral fertilizer rate of 75 kg N ha−1. In turn, the highest energy gain (218.5 GJ ha−1) was noted after the application of digestate at a rate equivalent to 75 kg N ha–1. The energy efficiency ratio was highest in the technology without fertilization (20.1) and after the application of digestate at a rate equivalent to 75 kg N ha−1 (19.7). Regardless of the factors that limit agricultural production, the energy balance of JA biomass production was most favorable when JA was fertilized with digestate at a rate equivalent to 75 kg N ha−1. The results of this study may pave the way for future research on novel agronomic strategies for sustainable bioenergy production, including nutrient recycling.

Machine learning based prediction and iso-conversional assessment of oxidatively torrefied spent coffee grounds pyrolysis

This research focused on developing a predictive model for mass loss during the pyrolysis of oxidatively torrefied spent coffee grounds (SCG) using machine learning techniques. Four algorithms were employed: artificial neural networks (ANN), k-nearest neighbors (k-NN), random forest (RF), and decision tree (DT), with the RF model demonstrating superior performance (R2 > 0.9981, RMSE <1.346) for both training and testing sets. The pyrolysis behavior, kinetics, and thermodynamics of SCG were also investigated using thermogravimetric analysis (TGA) under an inert atmosphere at different heating rates. Higher heating rates in TGA cause Tpeak values to shift to higher temperatures with increased DTGpeak values, while also resulting in lower Tonset and higher Toffset. Kinetic analysis, using the Flynn-Wall-Ozawa (FWO) method, was identified as the most suitable approach for determining activation energy (Ea), with values ranging from 192.66 to 288.13 kJ mol−1, indicating differences in energy requirements for pyrolysis across samples. Thermodynamic analysis further revealed that both raw SCG and oxidatively torrefied SCG pyrolysis were endothermic reactions. These findings contribute valuable insights into the optimization of biomass conversion technologies, highlighting the potential of machine learning in improving predictive accuracy and efficiency in thermal behavior modeling. This research advances sustainable bioenergy production by promoting the use of SCG, an abundant waste material, as a renewable feedstock in pyrolysis-based processes.

Conversion of glycerol into value-added products

Biomass residues and industrial waste are of great interest for their potential to produce a wide range of bioenergy and value-added products. Crude glycerol can be valorized into value added products by several microorganisms through microbial fermentation. Thus, Significant efforts have been made to develop biological methods to convert crude glycerol into various valuable chemicals and fuels, including 1, 3-propanediol, hydrogen and ethanol.In this context, our work have use glycerol medium as source of carbon for investigate bioethanol and 1, 3-propandiol production, using a microbial consortium. All experiments was carried out in sealed bottles, the reaction medium is placed in the shaker incubator at 37°C with stirring at 130 rpm. . Nitrogen gas was injected to create anaerobic conditions. The highest concentration of ethanol and 1,3 – propanediol obtained were 3.47 (g/l) and 4.8 mg/l respectively . These results highlight promising avenues for the valorization of biomass residues and industrial wastes in sustainable bioenergy production.

The interface between research funding and environmental policies in an emergent economy using neural topic modeling: Proposals for a research agenda

AbstractResearchers have been calling for further analysis of the relationships between academia and policy making. Since several studies are conducted with resources from public funding agencies, it is essential to assess whether governments have been supporting research that can contribute to future environmental policies and whether research has been supporting the elaboration of public policies. To fill these gaps, the objective of this study was to evaluate the similarities and gaps between research and environmental policies. A bibliometric analysis of studies funded by Chilean agencies and text analytics techniques were employed to analyze research and environmental policies. We used BERTopic, a topic modeling technique that generates coherent topic representations. Then, topics obtained from the two sets of documents (research and policies) were compared. This study found that sustainability, life‐cycle assessment, climate change, and ecosystem services are central research themes in the country. The topic modeling analysis showed that research has been concentrated on the areas of “Sustainable Fisheries and Aquaculture Management” and “Sustainable Bioenergy Production and Chemical Processes.” The topics most frequently present in the environmental policies were “Environmental Education for Children: Awareness and Care,” “Bird Conservation and Habitat Importance in Chile,” and “National Biodiversity Conservation and Sustainable Use Strategy.” The greatest gaps are observed in the clusters of “Sustainable Bioenergy Production and Chemical Processes” and “Copper Mining and Mineral Processing Techniques” (prevalent in research) and in “Anatomy and Physiology of Aquatic and Terrestrial Organisms” and “Biogeography and Taxonomy of Southern Hemisphere Insects” (prevalent in policy).

Evaluating the performance effectiveness of briquettes made from coconut dreg charcoal (CDC), tea residue (TR), and cocoa pod (CP)

Abstract Environmental pollution, depletion of fossil fuels, and a significant rise in the human population are contributing to an increase in the greenhouse gas in the atmosphere. Addressing these challenges necessitates the production of clean, low-carbon emission, and sustainable bioenergy, such as briquettes, which can significantly contribute to knowledge and innovation. To assess the effectiveness of briquettes, their characteristics need to be tested using proximate analysis. In examining the characteristics of briquettes, the average moisture content of coconut dreg charcoal and tea residue (CDC+TR) measured 4.835%, contrasting with the 5.9% found in the cocoa pod (CP). The average ash content in CDC+TR was 2.351%, while CP recorded 3.2%. The average volatile matter in CDC+TR was 24.993%, while in CP, it was 31.5%. CDC+TR had an average fixed carbon of 67.815%, compared to CP of 59.5%. Furthermore, the average gross calorific value in CDC+TR was 4562.16 cal/g, whereas in CP, it was 4205.2 cal/g. In conclusion, CP briquettes could serve as an alternative energy source due to ease of production, low sulfur content, and favorable calorific value. CDC+TR, on the other hand, enhanced energy efficiency because of their lower moisture content, ash content, and volatile matter. Additionally, CDC+TR briquettes had higher fixed carbon and gross calorific values compared to CP, making them a suitable energy source.

Role of biochar as a greener catalyst in biofuel production: Production, activation, and potential utilization – A review

BackgroundBiochar is an affordable carbonaceous product produced through a combination of thermochemical conversion processes using organic feedstock in the absence or constrained supply of oxygen. Biochar-based catalysts are promising in numerous catalytic applications for sustainable bioenergy production. MethodsHydrothermal carbonization, gasification, and pyrolysis are conventional biochar production techniques. The biochar must be activated to improve its physiochemical characteristics. The activation is generally classified into three types: physical, chemical, and impregnation. The biochar-based catalysts are categorized into different types, such as pristine, heteroatom-doped, metal-loaded, magnetic, and nanometallic oxide/hydroxide biochar. Significant findingsThese biochar-based catalysts effectively catalyze various biochemical reactions and are extensively used in biofuel production. This article extensively explores various biochar production and activation strategies and their applications as a catalyst for biofuel production. Activated biochar with improved surface properties has a high surface area and adaptable surface chemistry, making it a sustainable alternative to conventional catalysts. Biochar from renewable biomass has advantages in waste management, carbon sequestration, and reduced greenhouse gas emissions. Further research and innovation using nanomaterials, artificial intelligence, and machine learning are needed to utilize biochar as a sustainable and potential green catalyst for advanced biofuel production.

Evaluation of biohydrogen production from rice straw hydrolysate via Clostridium sp. YM1: In-lab fermentation and techno-economic study

This study investigates the potential of rice straw (RS) to be used as a feedstock for the production of biohydrogen (BioH2). To simplify the structure of the RS, thermochemical treatment is applied using HNO3 and NaOH at different concentrations. At a concentration of 1% (v/v) nitric acid (HNO3), the highest sugar concentration achieved was 27.73 g/L. This condition was utilized in dark fermentation with Clostridium sp. YM1 at 30 °C in an anaerobic environment, resulting in a biohydrogen production that surpasses the yield of the control sample by 27%. Furthermore, supplementation of 20 mg of ferrous and magnesium ions enhanced the biohydrogen yield (HY), which achieved 1.12 molH₂/molsugar and 1.19 molH₂/molsugar, respectively. This study demonstrated that butyric acid fermentation was the main pathway for Clostridium sp. YM1 to produce BioH2 from HNO3-treated RS. The findings were further evaluated for their economic profitability using SuperPro designer in batch production mode to treat 100 kgRS/batch that demonstrated the feasibility of the project with payback period (PBP), and net present value (NPV) of 3.78 years and USD 4,722,929, respectively. The study herein provides valuable insights and recommendations aimed at enhancing the feasibility of the conversion of RS into BioH2, thereby advancing the potential for sustainable bioenergy production.

Expression of Concern: Agricultural waste biomass for sustainable bioenergy production: Feedstock, characterization and pre-treatment methodologies

Expression of Concern: Agricultural waste biomass for sustainable bioenergy production: Feedstock, characterization and pre-treatment methodologies

Simulating short-term light responses of photosynthesis and water use efficiency in sweet sorghum under varying temperature and CO2 conditions.

Climate change, characterized by rising atmospheric CO2 levels and temperatures, poses significant challenges to global crop production. Sweet sorghum, a prominent C4 cereal extensively grown in arid areas, emerges as a promising candidate for sustainable bioenergy production. This study investigated the responses of photosynthesis and leaf-scale water use efficiency (WUE) to varying light intensity (I) in sweet sorghum under different temperature and CO2 conditions. Comparative analyses were conducted between the A n-I, g s-I, T r-I, WUEi-I, and WUEinst-I models proposed by Ye etal. and the widely utilized the non-rectangular hyperbolic (NRH) model for fitting light response curves. The Ye's models effectively replicated the light response curves of sweet sorghum, accurately capturing the diminishing intrinsic WUE (WUEi) and instantaneous WUE (WUEinst) trends with increasing I. The fitted maximum values of A n, g s, T r, WUEi, and WUEinst and their saturation light intensities closely matched observations, unlike the NRH model. Despite the NRH model demonstrating high R 2 values for A n-I, g s-I, and T r-I modelling, it returned the maximum values significantly deviating from observed values and failed to generate saturation light intensities. It also inadequately represented WUE responses to I, overestimating WUE. Across different leaf temperatures, A n, g s, and T r of sweet sorghum displayed comparable light response patterns. Elevated temperatures increased maximum A n, g s, and T r but consistently declined maximum WUEi and WUEinst. However, WUEinst declined more sharply due to the disproportionate transpiration increase over carbon assimilation. Critically, sweet sorghum A n saturated at current atmospheric CO2 levels, with no significant gains under 550 μmol mol-1. Instead, stomatal closure enhanced WUE under elevated CO2 by coordinated g s and T r reductions rather than improved carbon assimilation. Nonetheless, this response diminished under simultaneously high temperature, suggesting intricate interplay between CO2 and temperature in modulating plant responses. These findings provide valuable insights into photosynthetic dynamics of sweet sorghum, aiding predictions of yield and optimization of cultivation practices. Moreover, our methodology serves as a valuable reference for evaluating leaf photosynthesis and WUE dynamics in diverse plant species.

European Green Deal: Justification of the Relationships between the Functional Indicators of Bioenergy Production Systems Using Organic Residential Waste Based on the Analysis of the State of Theory and Practice

Based on the analysis conducted on the state of theory and practice, the expediency of assessing the relationships between the functional indicators of bioenergy production systems using the organic waste of residential areas is substantiated in the projects of the European Green Deal. It is based on the use of existing results published in scientific works, as well as on the use of methods of system analysis and mathematical modeling. The proposed approach avoids limitations associated with the one-sidedness of sources or subjectivity of data and also ensures complete consideration of various factors affecting the functional indicators of the bioenergy production system from the organic waste of residential areas. Four types of organic waste generated within the territory of residential areas are considered. In our work, we used passive experimental methods to collect data on the functional characteristics of bioenergy production systems, mathematical statistics methods to process and interpret trends in the functional characteristics of bioenergy production systems using municipal organic waste, and mathematical modeling methods to develop mathematical models that reflect the patterns of change in the functional characteristics of bioenergy production systems. The results indicate the presence of dependencies with close correlations. The resulting dependencies can be used to optimize processes and increase the efficiency of bioenergy production. It was found that: (1) yard waste has the highest volume of the total volume of solid organic substances but has a low yield of biogas and low share of methane production; (2) food waste has the highest yield of biogas and, accordingly, the highest share of methane production; (3) mixed organic waste has the lowest volume of the total volume of solid organic substances and the lowest content of volatile organic substances. The amount of electricity and thermal energy production varies by type of organic waste, with mixed organic waste having a higher average amount of electricity production compared to other types of waste. It was established that the production volume of the solid fraction (biofertilizer) is also different for different types of organic waste. Less solid fraction is produced from food waste than from yard waste. The obtained research results are of practical importance for the development of sustainable bioenergy production from organic waste in residential areas during the implementation of the European Green Deal projects. They provide further research on the development of effective models for determining the rational configuration of bioenergy production systems using organic waste for given characteristics of residential areas.

Salt tolerance evaluation and mini-core collection development in Miscanthus sacchariflorus and M. lutarioriparius.

Marginal lands, such as those with saline soils, have potential as alternative resources for cultivating dedicated biomass crops used in the production of renewable energy and chemicals. Optimum utilization of marginal lands can not only alleviate the competition for arable land use with primary food crops, but also contribute to bioenergy products and soil improvement. Miscanthus sacchariflorus and M. lutarioriparius are prominent perennial plants suitable for sustainable bioenergy production in saline soils. However, their responses to salt stress remain largely unexplored. In this study, we utilized 318 genotypes of M. sacchariflorus and M. lutarioriparius to assess their salt tolerance levels under 150 mM NaCl using 14 traits, and subsequently established a mini-core elite collection for salt tolerance. Our results revealed substantial variation in salt tolerance among the evaluated genotypes. Salt-tolerant genotypes exhibited significantly lower Na+ content, and K+ content was positively correlated with Na+ content. Interestingly, a few genotypes with higher Na+ levels in shoots showed improved shoot growth characteristics. This observation suggests that M. sacchariflorus and M. lutarioriparius adapt to salt stress by regulating ion homeostasis, primarily through enhanced K+ uptake, shoot Na+ exclusion, and Na+ sequestration in shoot vacuoles. To evaluate salt tolerance comprehensively, we developed an assessment value (D value) based on the membership function values of the 14 traits. We identified three highly salt-tolerant, 50 salt-tolerant, 127 moderately salt-tolerant, 117 salt-sensitive, and 21 highly salt-sensitive genotypes at the seedling stage by employing the D value. A mathematical evaluation model for salt tolerance was established for M. sacchariflorus and M. lutarioriparius at the seedling stage. Notably, the mini-core collection containing 64 genotypes developed using the Core Hunter algorithm effectively represented the overall variability of the entire collection. This mini-core collection serves as a valuable gene pool for future in-depth investigations of salt tolerance mechanisms in Miscanthus.

Lipid Yields and Fatty Acid Composition if Indigenous Microalgae, Isolated from the Beira, and Diyawanna Urban Lakes, for Sustainable Biofuel Production in Sri Lanka

&#x0D; Biofuels are carbon-neutral combustibles produced from renewable biomass. Third generation biofuels, derived from microalgal biomass, are distinctly superior to their preceding generations, due to higher productivity and resource use efficiency of microalgae compared to conventional energy crops. It is a viable source of sustainable energy for our country due to the availability of water, ambient temperatures and year-round sunlight needed for microalgae cultivation, and most importantly, the abundance of diverse microalgae species. However, these native microalgae are relatively unexplored for their productivities and thereby, greatly underutilized. This research was aimed to investigate the lipid yields and fatty acid compositions of local freshwater microalgae, and to identify their potential for biodiesel production. This was carried out by (1) microalgae isolation and morphological identification (2) microalgae cultivation (3) biomass harvesting, lipid extraction, gravimetric measurement of extracted lipids and (4) acid-catalysed transesterification, followed by GCMS analysis of the biodiesel product. Chlorella sp., Chlorococcum sp. and Chlamydomonas sp. were isolated from Beira/ Diyawanna Lakes using streak plate technique in solid standard BBM media. They were next cultivated under axenic conditions in liquid standard BBM media under 16: 8 (light: dark), at 25°C for 20 days in duplicates. The biomass was then harvested using alum, dried to reach a constant weight and the Bligh and Dyer lipid extraction was done in triplicate. The extracted lipids were trans-esterified with methanol, using sulfuric acid catalyst at 90° C for 60 minutes. The separated product was analysed by GCMS. Chlorella sp., Chlorococcum sp. and Chlamydomonas sp. cultivated under standard conditions gave average lipid yields of 11.34±1.01%, 15.00±1.40% and 2.10±0.50% respectively. Average lipid yield of Chlamydomonas sp. was significantly lower than the other two species at 95% confidence level (Two-sample T test on SPSS Version 21). GCMS analysis of the biodiesel product from Chlorella sp. indicated significant levels of saturated fatty acids including palmitic and stearic acids, monounsaturated fatty acids like cis-11- eicosenoic acid and polyunsaturated fatty acids including linoleic and linolenic acids. The fatty acid ratios were used to calculate the saturation value, cetane number, density, iodine value and pour point of the produced biodiesel. These quality parameters were in accordance with the ASTM D6751- 20a standards. Therefore, with a substantial yield and fatty acid composition of intracellular lipids, this local species of Chlorella can be a prospective candidate for sustainable bioenergy production in Sri Lanka.&#x0D; &#x0D; Keywords: Chlorella, Chlorococcum, Chlamydomonas, Microalgal lipids, Biodiesel

Biochar‐based catalysts derived from biomass waste: production, characterization, and application for liquid biofuel synthesis

AbstractAmong the feasible options for valorizing lignocellulosic biomass into value‐added products, biochar is considered to be extremely appealing and it could be applied easily in several established thermochemical processes. Biochar possesses a large surface area due to its porous nature, which permits easy use in various applications, including catalytic biofuel production. This work summarizes research on biochar generation processes, its critical physicochemical properties, and factors that influence them. Important studies adopting biochar catalysts for liquid biofuel production are critically reviewed, and the reaction mechanisms and biofuel yield are analyzed. Finally, challenges in the use of biochar‐based catalysts for biofuel production are presented, together with possible solutions. In general, this current work aims to provide the critical characteristics of biochar as a potential catalyst to biofuel synthesis toward sustainable bioenergy production.

Comprehensive Characterization of Lignocellulosic Biomass and their effective Delignification for Sustainable Bioenergy

The study provides a thorough examination of the biofuel potential of three unique lignocellulosic crop residues: rice straw (Oryza sativa), corn stalk (Zea mays) and sugarcane bagasse (Saccharum officinarum) of Odisha. In the investigation, we explored the compositional, thermal and structural characteristics of these biomass sources, shedding light on their suitability for sustainable bioenergy production. Proximate analysis indicated variances in critical factors in the range of 5.9-14.8% (moisture content), 1.8-19.4% (ash content), 60-72.4% (volatile matter) and 9.6-14.7% (fixed carbon) which contribute to the various energy generating capacities of these materials. An in-depth investigation of cellulose, hemicellulose and lignin concentration revealed the promise of sugarcane bagasse as a cellulose-rich option for bioethanol synthesis. Thermochemical profiling using thermogravimetric and FTIR analysis revealed information about thermal stability and chemical changes, with pretreatment having an important role in increasing biomass accessibility and crystallinity. The significance of pretreatment-induced crystallinity for effective enzymatic hydrolysis and fermentable sugar generation was highlighted by X-ray diffraction (XRD) . Overall, this study advances our understanding of the intricate relationships between biomass composition, structure and bioenergy potential, offering valuable insights for the development of sustainable biofuel production strategies.

Genomic insights into clostridia in bioenergy production: Comparison of metabolic capabilities and evolutionary relationships.

Bacteria from diverse genera, including Acetivibrio, Bacillus, Cellulosilyticum, Clostridium, Desulfotomaculum, Lachnoclostridium, Moorella, Ruminiclostridium, and Thermoanaerobacterium, have attracted significant attention due to their versatile metabolic capabilities encompassing acetogenic, cellulolytic, and C1-metabolic properties, and acetone-butanol-ethanol fermentation. Despite their biotechnological significance, a comprehensive understanding of clostridial physiology and evolution has remained elusive. This study reports an extensive comparative genomic analysis of 48 fully sequenced bacterial genomes from these genera. Our investigation, encompassing pan-genomic analysis, central carbon metabolism comparison, exploration of general genome features, and in-depth scrutiny of Cluster of Orthologous Groups genes, has established a holistic whole-genome-based phylogenetic framework. We have classified these strains into acetogenic, butanol-producing, cellulolytic, CO2-fixating, chemo(litho/organo)trophic, and heterotrophic categories, often exhibiting overlaps. Key outcomes include the identification of misclassified species and the revelation of insights into metabolic features, energy conservation, substrate utilization, stress responses, and regulatory mechanisms. These findings can provide guidance for the development of efficient microbial systems for sustainable bioenergy production. Furthermore, by addressing fundamental questions regarding genetic relationships, conserved genomic features, pivotal enzymes, and essential genes, this study has also contributed to our comprehension of clostridial biology, evolution, and their shared metabolic potential.

Unraveling the effects of sodium carbonate on hydrothermal liquefaction through individual biomass model component and machine learning-enabled prediction

Despite sodium carbonate (Na2CO3) being commonly utilized as a catalyst in actual biomass hydrothermal liquefaction (HTL), its impact on individual biomass components hasn't been well-examined. This study thus delves into the role of Na2CO3 in HTL of biomass model components (carbohydrate, lignin, protein, and lipid) at varying conditions. Na2CO3 at 5 wt% amplified carbohydrate degradation into biocrude and aqueous-gaseous products (AG), resonating with previous work on carbohydrate-rich feedstocks. While Na2CO3 has a marginal effect on lignin HTL, it negatively influences lipid HTL. Here, 5 wt% and 13.5 wt% Na2CO3 decrease the biocrude yield from 95.6% to less than 10%, simultaneously increasing the AG yield to approximately 90%. This is presumably due to the interaction of lipid decomposition intermediates (fatty acids) with sodium cations, resulting in water-soluble soap. For protein HTL, a low Na2CO3 concentration (5 wt%) has no significant impact on product formation, but excessive Na2CO3 (27 wt%) converts a considerable portion of biocrude into AG. In addition to these explorations that provided insights for actual biomass HTL, we also developed a machine learning model to adequately predict HTL biocrude yield by taking Na2CO3 effect into consideration. The Adaboost machine learning model displayed the most satisfactory prediction performance (training and testing R2: 0.96, 0.8) among the three investigated machine learning models. The feature importance analysis reveals lipid content and Na2CO3 concentration as pivotal factors over HTL process conditions and other biochemical components. This research provides fundamental insights into the Na2CO3 role in HTL product formation pathway and offers an intelligent and precise prediction model for HTL biocrude yield, thereby advancing the development of more efficient and sustainable bioenergy production processes.

Sustainable energy recovery from mixed agri-food waste by hydrothermal carbonisation: Mechanistic evaluation of the evolution of product characteristics

To address aggravating climate concerns and enhance bioenergy production, mixed agri-food waste (MAFW) was upgrade into high quality solid biofuel using hydrothermal carbonisation (HTC), demonstrating the potential to convert low-quality biowaste into valuable bioenergy resource. The influence of reaction temperature (190–230 °C), residence time (1–5 h) and solid loading (5–20 %) on the evolution of hydrochar and process water (PW) characteristics were systematically investigated to gain mechanistic insight into the HTC process of MAFW. In addition, an assessment of the valorisation option(s) for MAFW PW was conducted to guide the development of a conceptual HTC-based biorefinery system for sustainable bioenergy production. Results demonstrated that high HTC reaction severity (increased reaction temperature and residence time) enhanced the fuel characteristics of the hydrochar except for nitrogen content, which increased by ⁓86 % at the most severe HTC operating condition. Furthermore, the concentration of organic compounds in the PW showed a significant decrease as the reaction severity increased, except for total phenol content which showed a consistent increase. Meanwhile, the concentration of organic compounds in the PW increased as the solid loading increased. Overall, MAFW PW is rich in organic matter but relatively low in nutrients. Based on the analysis of the hydrochar and PW characteristics at different HTC operating conditions, it was revealed that dehydration, decarboxylation, aromatisation and Maillard reaction constitute primary reaction mechanisms influencing the HTC conversion of MAFW. Although higher reaction severity yielded a high degree of coalification in MAFW hydrochar, a medium reaction severity was conducive for producing high-quality solid biofuel. Additionally, medium solid loading yielded ample solid yield and a moderate organic matter concentration in the PW. To efficiently valorise the MAFW PW, a multistage process involving the combination of wet oxidation, anaerobic digestion and nutrient recovery was proposed. The findings presented in this study offer valuable referential information for improving the fuel quality of hydrochar obtained from MAFW and guiding the development of a sustainable strategy to harness the energy potential of MAFW via HTC.

Proximate and compositional assessment of pretreatment methods on selected lignocellulose biomass for biogas production

&#x0D; The efficient conversion of lignocellulosic biomass into biogas is a critical avenue in sustainable bioenergy production. Pretreatment enhances the accessibility of lignocellulose components for subsequent enzymatic hydrolysis and biogas production. This study evaluated the proximate and compositional changes induced by various pretreatment techniques on lemon grass and fluted pumpkin stalk, with a focus on optimizing biogas yield. Alkaline, hydrothermal, and combined hydrothermal pretreatment processes were applied on the feedstocks. The biomass surface characteristics were determined through proximate and compositional analysis.The characterization of the untreated biomass showed that lemon grass and fluted pumpkin stalk recorded; dry matter, moisture content, fixed carbon, total kjeldahl nitrogen and ash content in the ranges of 94.49%-94.56%, 5.44%-5.51%, 26.35%-28.95%, 1.33%-1.932% and 6.00%-12.00% respectively. The cellulose values of the untreated biomass ranged from 34.04% for fluted pumpkin stalk to 38.66% for lemon grass. However, the content of the cellulose increased with pretreatment to values ranging from 44.20% to 51.06%. The results of this analysis showed that the selected lignocellulose biomass has properties that are consistent with past literature stating them as suitable substrates for biogas production. Nonetheless, the potential for increased biogas yield from anaerobic digestion is greater when combined hydrothermal and alkaline pretreatment is used.

Hybridization of anaerobic digestion with solar energy: A solution for isolated livestock farms

Intensive farming causes an important amount of greenhouse gas emissions. This scenario can be significantly reduced by the implementation of renewable technologies and transforming farms from energy consumers to energy providers. In the particular case of livestock production, biogas and solar energy reduce greenhouse gas emissions and the energy demand of the installations. However, the implementation of these technologies requires solutions adapted to local scenarios, such as connectivity to the energy grids. In this work, a biogas/biomethane production system, energetically covered with hybrid solar panels is proposed as a solution for isolated areas where biodegradable substrates (manure) are abundant. Thus, the electrical and thermal requirements of the digester are supplied by solar panels, reducing the biogas self-consumption and the energy inputs from the electrical grid. Hybrid solar panels also provide sufficient energy for operation of an upgrading system to obtain biomethane of fuel vehicle quality, increasing the energy self-sufficiency of the agricultural activities. This solution has been simulated in five different climatic regions corresponding to areas of intense pig farming activity. The results demonstrate the sustainable bioenergy production in isolated farms with limited connection to the energy grid and organic matter availability. Furthermore, the economic study showed that the proposed technology is competitive compared to other technologies in the energy sector.

Bioenergy crops, biodiversity and ecosystem services in temperate agricultural landscapes—A review of synergies and trade‐offs

AbstractThe Paris agreement on climate change requires rapid reductions in greenhouse gas emissions. One important mitigation strategy, at least in the intermediate future, is the substitution of fossil fuels with bioenergy. However, using agriculture‐ and forest‐derived biomass for energy has sparked controversy regarding both the climate mitigation potential and conflicts with biodiversity conservation. The urgency of the climate crisis calls for using forests for carbon sequestration and storage rather than for bioenergy, making agricultural biomass an attractive alternative for fossil energy substitution. However, this calls for comprehensive assessments of its sustainability in terms of consequences for biodiversity and ecosystem services. In this review, we provide a first holistic overview of the impacts on ecosystems of land‐use changes from bioenergy crop production in temperate climates, by synthesizing results on both biodiversity and ecosystem service impacts. We found that bioenergy‐related land‐use changes can have both positive and negative effects on ecosystems, with original land use, bioenergy crop type and scale of bioenergy production being important moderators of impacts. Despite the risk of opportunity cost for food production, perennial crop cultivation on arable land had the lowest occurrence of negative impacts on biodiversity and ecosystem services. Growing biomass for bioenergy on surplus land has been suggested as a way to alleviate competition with food production and biodiversity conservation, but our results demonstrate that utilizing marginal or abandoned land for bioenergy crop production cannot fully resolve these trade‐offs. Furthermore, there is a lack of empirical studies of the biodiversity value of marginal and abandoned land, limiting our understanding of the sustainability implications of biomass cultivation on surplus land. We argue that future research and policies for bioenergy production must explicitly consider biodiversity and ecosystem services in combination to avoid potential trade‐offs between the two and to ensure sustainable bioenergy production.