BioEnergy Research最新文献

Biochar production and household energy utilization have garnered considerable attention in developing nations worldwide for over a decade. Gasification-based cookstoves mitigate numerous issues related to conventional cooking methods while effectively producing biochar. The novelty of this work lies in utilizing the gasifier stove for biochar production while simultaneously offering a clean cooking solution that empowers the livelihood of the rural population. The present study is carried out to investigate the effects of primary airflow on the thermal performance and biochar yield of a natural draft gasification technology-based improved cookstove. The inlet area of primary air varies from 25 to 100% in increments of 25%, producing biochar samples BC 25, BC 50, BC 75, and BC 100. The produced biochar is further characterized by performing proximate and ultimate analysis, X-ray diffraction analysis, FTIR analysis, and BET surface area analysis. The developed cookstove exhibits thermal efficiency in the range of 26.96–28.52%, while the biochar yield varies between 15.2 and 20.4%. The emission of carbon monoxide calculated per unit useful energy delivered to the pot ranges from 2.48 to 3.89 g/MJ_D corresponding to various airflow rates of primary air. The calorific value and percentage carbon content in the produced biochar samples range between 7424 and 8329 kcal/kg and 84.42 and 86.82%, respectively. The surface area of the biochar sample is increased three times with the increment in the primary air inlet area from 25 to 100%.

The low temperatures in Northeastern China offer a promising and energy-efficient approach for lignocellulose pretreatment. The effects of freeze-thaw pretreatment on the microstructure of corn stover hydrolysis characteristics and fermentation acid production were investigated using corn stover as the raw material. The experimental results demonstrated that the reducing sugar release and soluble chemical oxygen demand (SCOD) values of corn stover following freeze-thaw pretreatment exhibited increases of 15.8% to 67.0% and 13.9% to 68.9%, respectively, compared to those of the control group. Freeze-thaw pretreatment modifies the microstructure of corn stover by breaking hydrogen bonds in the amorphous region between cellulose and hemicellulose, facilitating lignin removal. The acid yield of the treated corn stover under optimal pretreatment conditions is enhanced by up to 77.9% compared with the control group. The initial pH pronouncedly influenced the acid yield of anaerobic fermentation of corn stover, with the highest acid yield of 3.8 g/L observed at pH values between 7.5 and 8. This study provides theoretical guidance for the industrial development of a low-cost and low-energy consumption pretreatment method in lignocellulose wastes.

Coffee roasting by-products represent a significant, underutilized side-stream globally. This study investigates hydrothermal liquefaction (HTL) as a method to convert these materials into hydrochar, water-rich light oil, and heavy oil. Using HTL at 300 °C for 60 min, we evaluated the energy content and properties of the resulting hydrochars, finding energy values exceeding 33 MJ/kg—significantly higher than the 19–21 MJ/kg of the raw materials. Hydrothermal liquefaction of spent coffee grounds produced more hydrochar (18 g) and heavy oil (1.2 g) than silverskin (12–14 g hydrochar and 0.1–0.5 g heavy oil). In contrast, silverskin generated twice as much light oil (9.7 g) as spent coffee grounds (4.6 g). Silverskin hydrochars exhibited higher gross calorific value (Baqué 33.95 ± 0.06 MJ/kg, Mariposa 33.86 ± 0.07 MJ/kg, Meira 33.22 ± 0.00 MJ/kg), lower ash content (3–5%), and reduced volatile matter (57–61%) than their raw form. Spent coffee grounds produced hydrochar with the highest gross calorific value (34.27 ± 0.01 MJ/kg), lowest ash content (0.8%) and the most significant reduction in volatile matter. Light and heavy oils produced were rich in alkaloids, fatty acids, and phenolic compounds, with potential applications in cosmetics and pharmaceuticals. This work contributes to both bioenergy production and circular economy strategies, valorising the two main side-streams of the coffee industry. With broad implications for sustainable waste management, this study highlights the potential of HTL to advance global bioenergy goals.

The integration of automation, artificial intelligence (AI), and machine learning (ML) is revolutionizing the field of biomass transformation by enabling smarter, more efficient, and scalable processes. AI/ML have shown significant promise in enhancing processes such as biofuel production, anaerobic digestion, and waste-to-energy conversion by enabling predictive analytics, process control, and real-time monitoring. For instance, ML algorithms can predict optimal fermentation conditions for bioethanol production, while deep learning models can enhance enzyme selection for the breakdown of lignocellulosic biomass. Intelligent decision support systems (IDSS) are being applied to improve process efficiency in biogas plants by analyzing large datasets from sensor networks. Despite these advancements, critical challenges remain, including the need for laboratory automation, robust data infrastructure, a skilled workforce, and broader technology adoption. This review uniquely consolidates and analyzes the integration of AI/ML across a wide spectrum of biomass transformation processes, rather than focusing on isolated applications as seen in previous studies. This review presents a comprehensive overview of current developments, identifies existing limitations, and outlines future directions for researchers and practitioners aiming to drive innovation in this interdisciplinary field.

Small sewage treatment plants (STPs) in developing regions often flare the biogas produced in their upflow anaerobic sludge blanket (UASB) reactors, giving away a cost-effective energy source. This study tests whether on-site biogas-to-energy can pay for itself in approximately 2 years, even in plants treating less than 30 l s⁻¹. A small-scale STP in Angra dos Reis, Brazil (25 L/s), was studied, with an average biogas flow of 9.7 m³/h; electricity generation was modeled for an engine generator unit with an efficiency of 30%. The techno-economic results show that the actual system would generate 125 MWh/year at a levelized cost of 0.017–0.023 USD/kWh, covering 47% of the plant’s electricity demand. At a discount rate of 8%, the net present value was + 9.3 k US$, and the simple payback period was 2 years for the initial investment. Additionally, extrapolating the results to account for future expansion of the sewage treatment plant based on the total population in the region served by the system reveals even more promising results, with a suggested payback period of 1 year and 1 month of operation, covering approximately 57% of electricity demand. Scaling this retrofit to the approximately 18,000 comparable UASB-based STPs worldwide at low capital cost could reduce electricity bills by approximately 40% and avoid ~ 450 tons of CO₂-eq. per plant per year through methane capture and displacement of electricity from the grid. These results confirm that decentralized biogas power generation on a small scale is not only technically feasible, but also financially attractive and ecologically beneficial for operators of sewage and wastewater treatment plants and municipalities.

This research explored hydrothermal carbonization to enhance digestate from lignocellulosic biogas power plants as a soil amendment for low-carbon agriculture. Hydrochar was produced from real digestate via hydrothermal carbonization at 225–265 °C, hydrothermal carbonization at 265 °C demonstrating optimal properties for agricultural use. Key benefits include enhanced phosphorus retention, controlled-release nutrient behavior as indicated by Chlorella vulgaris cultivation in its water-soluble fraction, and safe application as a soil amendment, with heavy metal concentrations within regulatory limits and absent in the water-soluble fraction. Based on theoretical calculations, labile carbon—represented by the water-soluble organic carbon fraction in hydrochar—was reduced 15-fold at 265 °C compared to the digestate. This reduction could decrease greenhouse gas emissions from 441 to 29 tons CO₂-equivalent annually in a 1 MW biogas plant scenario, while sequestering 766 tons of carbon in cropland soils. Additionally, theoretical calculations suggest co-digestion with hydrothermal wastewater could enhance nutrient recovery and methane production, contributing to low-carbon emissions. These findings underscore hydrothermal carbonization’s potential for sustainable biogas power plant, agriculture, and climate change mitigation.

Volatile fatty acid accumulation may cause inhibition, or complete cessation of methanogenesis, which was undesirable for large-scale anaerobic digestion (AD) engineering. In this study, it was unexpectedly observed that methanogenesis gradually resumed after a long period of time when gas production had stopped due to acid inhibition in maize straw solid-state (SS)-AD. The results showed SS-AD achieved the cumulative methane production of 9.32 mL/gVS and maintained the acetic acid degradation rate at 70.8%–88.8% within 8 days of methanogenesis recovery. 16S rRNA amplicon sequencing and metagenomic analysis revealed that Thermoclostridium, Defluviitalea, and Hydrogenispora were the key bacteria resisting extreme acidic stress, while Methanosarcina mazei, Methanoculleus thermophilus, and Methanosarcina thermophila were the key archaea promoting methanogenesis recovery. Microorganisms survived under extreme acidic stress mainly by lysine decarboxylation and biosynthesis of cell membranes/walls and flagella. Meanwhile, enhanced tryptophan synthesis and metabolism accelerated carbon supply to TCA cycle, promoting the growth and reproduction of microorganisms under extreme acidic stress. Moreover, the genetic information processing ability and CRISPR-Cas system were enhanced in M. mazei and M. thermophila, which favored their survival and growth in SS-AD. M. thermophilus mainly contributed to the methanogenesis by CO₂ reduction. This study helps in developing SS-AD methodology for overcoming extreme acidic stress.

Graphical Abstract

The high cost of biomass feedstock hinders the growth of the cellulosic ethanol industry, especially in regions like China where biomass is extensively dispersed. To tackle this issue, we devised a biomass supply chain model encompassing collection, pretreatment, storage, and transportation phases. We examined the effects of various collection and pretreatment method combinations on supply-chain costs and CO₂ emissions. The model’s validity was confirmed using Heilongjiang and Zhejiang as representatives of northern and southern regions. Mechanized collection with shredding-baling proved to be the most economical, costing 226.6 y/t in Heilongjiang and 217.7 y/t in Zhejiang within a 60 km collection radius. For CO₂ emissions, mechanized collection with kneading emerged as the optimal choice. With governmental subsidies, mechanized collection with kneading became the preferred option, considering both cost and CO₂ emissions. By incorporating agricultural cooperatives, costs were further reduced by up to 70 y/t in Heilongjiang and 65 y/t in Zhejiang. This model facilitates the cost-effective collection of straw for ethanol production in biomass-scattered China. Biomass decentralization combining collection and pretreatment methods is key to achieving site-specific biomass supply. Furthermore, the model can be adapted for acquiring biomass feedstock in other sectors and offers insights for biomass procurement in diverse regions.

Graphical Abstract

Major challenges in using lignocellulosic residues as biogas substrates arise from their high diversity and their typically low nitrogen content, which may not provide sufficient nitrogen for the microorganisms. To investigate to what extent such substrates can be used in biogas plants without extensive pre-treatment, this study presents a 300-day continuous co-digestion of lignocellulosic substrates (i.e., sugarcane reed, lemon, and grape leaves) and goat manure while continuously monitoring various process parameters. The results suggest a stable and effective biogas production at a carbon-to-nitrogen ratio (C/N ratio) of 33, with a production of 244 ± 15 mL_N g_VS⁻¹ d⁻¹ biogas. At a higher C/N ratio of 43, the process remained stable, but hindrance was encountered. Process failure occurred at a C/N ratio of 52, where a rapid decline in biogas production was observed, accompanied by an increase in the volatile fatty acids to total alkalinity ratio (from < 0.2 to 0.9), a drop in the pH-value (from > 7 to 5.4), and an increased CO₂-content of the provided biogas (from > 50% to 43%). The compositional analysis of the digestate suggests an insufficient N-supply and a failure of the carbonate and ammonium buffer systems inside the reactor. The experiment also served to validate a previously developed model based on the individual substrates’ degradation kinetics. With a relative root mean square error rRMSE of 8%, the model adequately predicted biogas production within defined limits. However, it could not anticipate process breakdown at high C/N ratios, highlighting a strong limitation.

Graphical Abstract