Organic waste recycling application increases N availability and mitigates N2O emission without crop yield penalty in the North China Plain.

Introduction: Agricultural organic waste recycling can supply nutrients for crop production and partially replace chemical nitrogen fertilizers, which is beneficial for waste management and environmental protection. Nevertheless, comprehensive evaluation of the effects of different organic materials applications on crop yield and the environment is limited. Methods: Therefore, in this study, a comprehensive investigation of the synergistic effects of straw, pig manure, and biogas residue recycling on the wheat (Triticum aestivum L.) and maize (Zea mays L.) systems was carried out in the North China Plain. Field experiments were conducted from 2019 to 2021, comprising five treatments: straw (ST), pig manure (PM), and biogas residue (BR) partially replacing chemical nitrogen fertilizer, sole application of chemical nitrogen fertilizer (CF), and a control with no nitrogen application (WN). Results and discussion: The results showed that organic materials significantly increased soil total nitrogen (3.04%-9.10%) and N recovery efficiency (REN; 42.21%-44.99%), but pig manure was more beneficial in increasing crop yields (3.50%), especially wheat yields (8.72%), and REN was significantly higher than that of the other treatments. Organic materials performed differently in wheat and maize seasons, and wheat yield could be improved by organic materials return. Organic materials stimulated N2O emission in wheat season (4.28%-32.20%), while biogas residue inhibited the N2O emission in maize season (47.47%). The negative effect of straw and biogas residue on yield decreased with increasing years of return, and pig manure continued to contribute to yield. In conclusion, pig manure is the optimal alternative that can increase crop yield, soil N content, and REN without stimulating N2O emissions.

The simultaneous addition of chitosan and peat enhanced the removals of antibiotics resistance genes during biogas residues composting.

Direct reuse of biogas residue (BR) has the potential to contribute to the dissemination of antibiotic resistance genes (ARGs). Although high-temperature composting has been demonstrated as an effective method for the harmless treatment of organic waste, there is few researches on the fate of ARGs in high-temperature composting of BR. This research examined the impact of adding 5% chitosan and 15% peat on physicochemical characteristics, microbial communities, and removal of ARGs during BR-straw composting in 12 Biolan 220L composters for 48 days. Our results showed that the simultaneous addition of chitosan and peat extended the high-temperature period, and increased the highest temperature to 74 °C and germination index. These effects could be attributed to the presence of thermophilic cellulose-decomposing genera (Thermomyces and Thermobifida). Although the microbial communities differed compositionally among temperature stages, their dissimilarity drastically reduced at final stage, indicating that the impact of different treatments on microbial community composition decreases at the end of composting. Peat had a greater impact on aerobic genera capable of cellulose degradation at thermophilic stage than chitosan. Surprisingly, despite the total copy number of ARGs significantly decreased during composting, especially in the treatment with both chitosan and peat, intI1 gene abundance significantly increased 2 logs at thermophilic stage and maintained high level in the final compost, suggesting there is still a potential risk of transmission and proliferation of ARGs. Our work shed some lights on the development of waste resource utilization and emerging contaminants removal technology.

Methanotrophic Communities and Cultivation of Methanotrophs from Rice Paddy Fields Fertilized with Pig-livestock Biogas Digestive Effluent and Synthetic Fertilizer in the Vietnamese Mekong Delta.

Biogas digestive effluent (BDE) has been applied to rice fields in the Vietnamese Mekong Delta (VMD). However, limited information is available on the community composition and isolation of methanotrophs in these fields. Therefore, the present study aimed (i) to clarify the responses of the methanotrophic community in paddy fields fertilized with BDE or synthetic fertilizer (SF) and (ii) to isolate methanotrophs from these fields. Methanotrophic communities were detected in rhizospheric soil at the rice ripening stage throughout 2 cropping seasons, winter-spring (dry) and summer-autumn (wet). Methanotrophs were isolated from dry-season soil samples. Although the continued application of BDE markedly reduced net methane oxidation potential and the copy number of pmoA genes, a dissimilarity ordination ana-lysis revealed no significant difference in the methanotrophic community between BDE and SF fields (P=0.167). Eleven methanotrophic genera were identified in the methanotrophic community, and Methylosinus and Methylomicrobium were the most abundant, accounting for 32.3-36.7 and 45.7-47.3%, respectively. Type-I methanotrophs (69.4-73.7%) were more abundant than type-II methanotrophs (26.3-30.6%). Six methanotrophic strains belonging to 3 genera were successfully isolated, which included type I (Methylococcus sp. strain BE1 and Methylococcus sp. strain SF3) and type II (Methylocystis sp. strain BE2, Methylosinus sp. strain SF1, Methylosinus sp. strain SF2, and Methylosinus sp. strain SF4). This is the first study to examine the methanotrophic community structure in and isolate several methanotrophic strains from BDE-fertilized fields in VMD.

Use of carbon-encapsulated zero-valent iron nanoparticles from waste biomass to hydrogen sulphide wet removal.

This study evaluates the use of carbon-encapsulated zero-valent iron nanoparticles for biogas upgrading in wet systems. The nanoparticles were produced by hydrothermal carbonization, using olive mill waste (OMW) or microalgae as carbon sources. The solids were characterized to investigate the specific surface area, total and zero-valent iron content, pHPZC and chemical and crystalline composition. Their adsorption performance towards hydrogen sulphide (H2S) was tested by treating two types of synthetic biogas with and without CO2. In both cases, the starting H2S concentration was approximately 60 ppm and the experiments lasted until the complete saturation of the nanoparticles. Optimal Fe/C ratios of 0.05 for OMW nanoparticles and 0.2 for microalgae nanoparticles demonstrated H2S-specific adsorption capacities of 9.66 and 9.55 mgH2SgCE-nZVI-1, respectively, in a synthetic biogas without CO2. The addition of CO2 in biogas reduced adsorption, possibly due to system acidification. X-ray photoelectron spectroscopy analysis revealed surface compounds on the surface of the spent nanoparticles, including disulphides, polysulphides and sulphate. The saturated adsorbents were effectively regenerated with air, leading to the oxidation of sulphur species and desorption. The regeneration allowed a total adsorption capacity of 53.25 and 34.14 mgH2SgCE-nZVI-1, after 10 consecutive cycles of adsorption/regeneration with a single batch of olive mill and microalgae nanoparticles, respectively.

Impact of thermal hydrolysis on VFA-based carbon source production from fermentation of sludge and digestate for denitrification: experimentation and upscaling implications.

Stricter nutrient discharge limits at wastewater treatment plants (WWTPs) are increasing the demand for external carbon sources for denitrification, especially at cold temperatures. Production of carbon sources at WWTP by fermentation of sewage sludge often results in low yields of soluble carbon and volatile fatty acids (VFA) and high biogas losses, limiting its feasibility for full-scale application. This study investigated the overall impact of thermal hydrolysis pre-treatment (THP) on the production of VFA for denitrification through the fermentation of municipal sludge and digestate. Fermentation products and yields, denitrification efficiency and potential impacts on methane yield in the downstream process after carbon source separation were evaluated. Fermentation of THP substrates resulted in 37-70 % higher soluble chemical oxygen demand (sCOD) concentrations than fermentation of untreated substrates but did not significantly affect VFA yield after fermentation. Nevertheless, THP had a positive impact on the denitrification rates and on the methane yields of the residual solid fraction in all experiments. Among the different carbon sources tested, the one produced from the fermentation of THP-digestate showed an overall better potential as a carbon source than other substrates (e.g. sludge). It obtained a relatively high carbon solubilisation degree (39 %) and higher concentrations of sCOD (19 g sCOD/L) and VFA (9.8 g VFACOD/L), which resulted in a higher denitrification rate (8.77 mg NOx-N/g VSS∙h). After the separation of the carbon source, the solid phase from this sample produced a methane yield of 101 mL CH4/g VS. Furthermore, fermentation of a 50:50 mixture of THP-substrate and raw sludge produced also resulted in a high VFA yield (283 g VFACOD/kg VSin) and denitrification rate of 8.74 mg NOx-N/g VSS∙h, indicating a potential for reduced treatment volumes. Calculations based on a full-scale WWTP (Käppala, Stockholm) demonstrated that the carbon sources produced could replace fossil-based methanol and meet the nitrogen effluent limit (6 mg/L) despite their ammonium content. Fermentation of 50-63 % of the available sludge at Käppala WWTP in 2028 could produce enough carbon source to replace methanol, with only an 8-20 % reduction in methane production, depending on the production process. Additionally, digestate production would be sufficient to generate 81 % of the required carbon source while also increasing methane production by 5 % if a portion of the solid residues were recirculated to the digester.

Different bioaugmentation regimes that mitigate ammonium/salt inhibition in repeated batch anaerobic digestion: Generic converging trend of microbial communities.

Bioaugmentation regimes (i.e., dosage, repetition, and timing) in AD must be optimized to ensure their effectiveness. Although previous studies have investigated these aspects, most have focused exclusively on short-term effects, with some reporting conflicting conclusions. Here, AD experiments of three consecutive repeated batches were conducted to determine the effect of bioaugmentation regimes under ammonium/salt inhibition conditions. A positive correlation between reactor performance and inoculum dosage was confirmed in the first batch, which diminished in subsequent batches for both inhibitors. Moreover, a diminishing marginal effect was observed with repeated inoculum introduction. While the bacterial community largely influenced the reactor performance, the archaeal community exhibited only a minor impact. Prediction of the key enzyme abundances suggested an overall decline in different AD steps. Overall, repeated batch experiments revealed that a homogeneous bacterial community deteriorated the AD process during long-term operation. Thus, a balanced bacterial community is key for efficient methane production.

Enhancing landfill efficiency to drive greenhouse gas reduction: A comprehensive study on best practices and policy recommendations.

This article investigates the pivotal role of non-hazardous waste landfills in achieving greenhouse gas (GHG) reduction objectives within the European Union (EU).1 This study leverages the experience of key stakeholders in the European landfilling, assesses the efficacy of 'best-in-class' landfill installations, evaluates their potential impact on GHG reduction, and offers concrete recommendations for operators and policymakers. 'Best-in-class' landfills exceed the commonly accepted best practices by implementing all the following practices: (1) an anticipated capture system during the operating phase, (2) prompt installation of the final cover and capture system, with use of an impermeable cover, (3) operated as bioreactor, keeping optimal humidity, (4) adequate maintenance and reporting, (5) recovery of captured gas and (6) treatment of residual methane emissions throughout the waste decomposition process. The main finding is that switching from the actual mix of practices to 'best in class' practices would reduce by ~21 MtCO2eq (-36%) the emissions due to the degradation of waste landfilled between 2024 and 2035, compared to the 'business-as-usual scenario', while also providing a renewable energy source, bringing potential avoided emissions and energy sovereignty. The findings underscore that in addition to implementing the organics diversion and waste reduction targets of the EU, adopting 'best-in class' landfill practices has the potential to bolster energy recovery, mitigate emissions and stimulate biomethane production, thereby advancing the EU environmental goals.

Enviro-economic and optimal hybrid energy system: Photovoltaic-biogas-hydro-battery system in rural areas of Pakistan.

To satisfy the electricity needs of a village in Tangi, northwest Pakistan, the present research can design and evaluate the environmental and economical aspects of an optimal hybrid photovoltaic-biogas-hydropower-battery energy sustainable system (PV-BG-HP-BESS). This framework integrates various renewable energy sources, delivering a modern, efficient approach to sustainable energy solutions. The HOMER Pro software is utilized to optimize the most economical and effective hybrid energy system. The results showed that the proposed hybrid system comprising 91.4 kWp PV modules, 19.6 kW hydropower, a 50 kW biogas generator (BG), 36 batteries, and a 60.6 kW converter was the most economical choice. This system, which used the cyclic charging (CC) method, had a cost of energy (COE) of 0.0728 $/kWh and a total net present cost (NPC) of $152,242. The suggested hybrid energy system for rural areas of Pakistan includes photovoltaic (PV), biogas (BG), hydro, and battery components to provide a dependable and sustainable power supply. This system minimizes the need for expensive fossil fuels while simultaneously minimizing environmental impact by lowering pollutants and greenhouse gas emissions. The system's annual electricity production is 294,782 kWh, with PV leads at 59.4%, BG at 6.02%, and hydro at 34.6%, ensuring uninterrupted power generation even in remote areas. The unmet load, extra electricity, and capacity shortage illustrate the reliability of the system and make it possible to address rural electrification challenges while supporting sustainable development and economic growth. Moreover, the outcomes of the proposed hybrid system dominate the previous studies in multiple objectives, including cost and sensitivity analysis, when compared.

Combining thermal model and kinetics: Implications in dynamic simulation of anaerobic digesters.

In this study, ADM1-based kinetics were combined with a thermal model that accounts for various heat transfers inside and through the reactor's boundaries. Computing the energy of bioreactions based on kinetic rates prevented an overestimation of approximately 20% in the heat demand of the heat exchanger, compared to calculations using feedstock degradation heat. This also improved the representation of the digester's thermal and reactional inertia. Simulations across different climates demonstrated the necessity to tailor digester construction. In the North West United Kingdom, biogas auto-consumption was 23% higher than that of the same reactor in South West France. Enhancing the thermal insulation of the digester reduced heat losses by 37% in the United Kingdom. Therefore, coupling the kinetic and thermal models expands the insights that can be extracted from simulations, which can be valuable in optimizing the operation and design of biogas digesters.

Improving the anaerobic digestion of sewage sludge by adding cobalt nanoparticles.

This work evaluated the effects of cobalt nanoparticles (CoNPs) (0.025-7 mg/gVS) on the intensification of sewage sludge anaerobic digestion (AD) using biochemical methane potential (BMP) tests. This study was motivated by the need to improve the efficiency and stability of anaerobic digestion of sewage sludge, a critical process in waste management and renewable energy production. The effects at doses less than 2 mg/gVS were not substantial, but 3-7 mg/gVS improved the performance. The maximum biogas yield was 232 mL/gVS (at a dose of 7 mg/gVS), whereas it was 132 mL/gVS in the control (zero dose). Similarly, the reductions in the volatile solids and methane contents reached maxima of 16 and 74.3%, respectively. The analyses of volatile fatty acids, redox potential, and electron transfer system activity indicated that the addition of CoNPs stimulated the early stages of AD. Finally, acetate consumption and the increase in CH4 content suggested that CoNPs positively affected system stability and acetoclastic methanogenesis. That is, CoNPs effectively intensified the behaviour and stability of the anaerobic process. The novelty of this research lies in the comprehensive evaluation of the effects of CoNPs across a wide range of doses on sewage sludge AD, providing new insights into the optimisation of this process for increased biogas production and organic matter reduction.

Data on the effect of co-fermentation of maize and leguminous crops on biogas production, methane production and methane content in biogas.

The presented set of data brings results of the experimental production of biogas and methane from silages of alternative substrates consisting of maize and three leguminous species with a potential to make the production of biogas more friendly to the environment because the cultivation of legumes is generally considered to be more environment friendly than the cultivation of maize: white sweet clover (Melilotus albus Medik.), fodder vetch (Vicia villosa Roth.) and white lupin (Lupinus albus L.). Obtained data allow to compare the composition of experimental substrates and their important parameters (VS, DM, NDF, ADF, CF, starch, cellulose, hemicellulose, CP, lipids and ADL) as well as the yield of biogas, methane and methane in biogas from silage produced as a monosubstrate from the biomass of maize shreddings on the one side with silages produced from the mixture of biomass from maize and diverse legumes on the other side. This set of data can contribute to awareness about possibilities for reducing environmental risks connected with the cultivation of maize in growers of energy crops and operators of biogas plants. The reason is that a considerable number of farmers do not use new technologies of growing biomass for the production of biogas as they cannot quantify the potential impact on biogas yield and hence on the profitability of biogas plant operation. The measured values demonstrate that silages made from the mixed culture were reaching at least the same production of biogas and its quality as the monocultural maize silage.

Anaerobic digestion of poultry manure to power a poultry farm in Ba: Pilot and techno-economic study.

Although poultry is the largest meat by volume produced in Fiji, there has not been any established study, nor application of the anaerobic digestion (AD) of poultry manure (PM) in the country. This paper aims to determine the techno-economic feasibility of the AD of PM to power a poultry farm in Fiji. A pilot scale study was first conducted with mono-digestion batches of poultry manure, and co-digestions with kitchen waste (KW) and newspaper waste (NPW). Solid state anaerobic digestion (SSAD) was employed in all the batches, and the key operational parameters of AD were studied, along with its influence on biogas production. The pilot study revealed that even slight changes in environmental temperature had the greatest effect on biogas production. The most resilient to the temperature changes were the co-digested feedstocks of KW. Yet, given a substantial AD period, the anaerobes in the mono-digesters were able to eventually acclimatize to the SSAD environment, and produce the overall highest biogas production. The pilot study results were then used to conduct a feasibility study of the full-scale design. The analysis showed that the SSAD system would generate 189.46 MWh of electricity annually, with a levelized cost of energy of FJ$0.17/KWh.

A cyclic shift-temperature operation method to train microbial communities of mesophilic anaerobic digestion.

Temperature is the critical factor affecting the efficiency and cost of anaerobic digestion (AD). The current work develops a shift-temperature AD (STAD) between 35 °C and 55 °C, intending to optimise microbial community and promote substrate conversion. The experimental results showed that severe inhibition of biogas production occurred when the temperature was firstly increased stepwise from 35 °C to 50 °C, whereas no inhibition was observed at the second warming cycle. When the organic load rate was increased to 6.37 g VS/L/d, the biogas yield of the STAD reached about 400 mL/g VS, nearly double that of the constant-temperature AD (CTAD). STAD promoted the proliferation of Methanosarcina (up to 57.32 %), while severely suppressed hydrogenophilic methanogens. However, when the temperature was shifted to 35 °C, most suppressed species recovered quickly and the excess propionic acid was quickly consumed. Metagenomic analysis showed that STAD also promoted gene enrichment related to pathways metabolism, membrane functions, and methyl-based methanogenesis.

Sequential carbonization of pig manure biogas residue into engineered biochar for diethyl phthalate removal toward environmental sustainability.

Manure biogas residue has attracted increasing attention in waste recycling but faces substantial challenges because of its low carbon content, high ash content, and high heavy metal content. A novel sequential carbonization approach was proposed for recycling biogas residue; this approach consisted of pre-pyrolysis, activation with Ca(OH)2, and then activation with KOH. Pig manure-derived biogas residue was upcycled into engineered biochar (EB) with a high yield (26 %) and showed excellent performance in removing a typical plasticizer, diethyl phthalate (DEP). The proportion of carbon content greatly increased from 18 % (biogas residue) to 67 % (EB); however, the ash content decreased from 50 % (biogas residue) to 24 % (EB). The concentration of heavy metals decreased, and Zn had the largest decrease from 713 mg kg-1 to 61 mg kg-1 (p < 0.001). The sorption of DEP onto EB was rapid and reached equilibrium within 20 h. The developed specific surface area of EB was 1247 m2/g and provided abundant sorption sites for DEP; additionally, the sorption quantity reached 309 mg/g. The sorption capacity was dominated by surface adsorption. The oxygen-containing functional groups, graphene structure, porous structure, and hydrophobicity of EB contributed to the pore filling, hydrogen bonding, π-π stacking, and partitioning processes. Furthermore, the EB showed excellent practical application potential and great cycling stability. A sequential carbonization strategy was proposed to upcycle manure biogas residue into the EB for DEP removal; moreover, this strategy can aid in the attainment of environmental sustainability, including sustainable waste management and environmental pollution mitigation.

Pressure-centric regulation for efficient anaerobic digestion: State-of-the-art, challenges and prospects.

Anaerobic digestion (AD) is an environmentally friendly technology that simultaneously stabilizes biowaste and produces biogas. Conventional AD faces challenges such as inadequate substrate degradation and low methane purity. Pressure-centric regulation serves as an AD optimization strategy that can enhance the digestion efficiency and generate higher-energy-value biogas. However, limited reviews have been undertaken to focus on this technology. This review is designed to discuss innovations in ex-situ high-pressure pretreatment and in-situ high-pressure anaerobic digestion (HPAD) processes. Moreover, comprehensive understandings on the intrinsic mechanisms of HPAD are critically examined, including physicochemical reaction principles and microbial responses. The constraints currently curtailing these technologies and potential mitigation strategies are also scrutinized. Additionally, current knowledge gaps and future research directions on mechanisms, model fitting, and engineering practices are presented. Overall, this work highlights the feasibility of pressure-centric regulated AD and provides novel insights to overcome existing technical barriers in its application.

Optimizing trigeneration energy systems: Biogas-centric methanol production via direct CO2 hydrogenation with advanced integration of PEM electrolyzer and LNG cold technology.

Biogas, a sustainable alternative to fossil fuels, addresses issues of non-renewability and accessibility. Its structural similarity to fossil fuels makes it a potent option for energy systems. With this in mind, this paper discusses a novel trigeneration system that utilizes biogas and Liquefied natural gas cooling to produce methanol, electricity, cold water, hot water, oxygen, and natural gas. The system integrates various components such as a biogas burner, Kalina cycle, organic Rankine cycle, liquefied natural gas liquid gasification cycle, proton exchange membrane electrolyzer, and methanol synthesis unit. Simulation via Aspen HYSYS software includes an analysis of energy, exergy, economic, and environmental aspects. Efficiency assessment in single generation, cogeneration, trigeneration, and chemical trigeneration modes concludes chemical trigeneration as most efficient, with the proton exchange membrane electrolyzer being the most efficient subsystem. Key variables like Kalina cycle evaporator temperature, gas flow rate to the methanol reactor, and organic Rankine cycle working fluid pressure are assessed. Predictions on thermodynamic, environmental, and economic behaviors, along with their fluctuations, are made. Using a thermoeconomic approach, the economic analysis determines an exergy unit cost of 59.79 $/GJ and a total cost rate of 2764 $/h. Overall, this work presents a novel and efficient chemical trigeneration system that utilizes biogas and LNG cooling to produce multiple products.

Life cycle assessment of tomato biomass residue anaerobic digestion preceded by ethanol-based organosolv and choline chloride-based deep eutectic solvent.

Anaerobic digestion (AD) of lignocellulosic wastes (LW) has garnered substantial interest because of its notable energy and nutrient recovery, along with its potential for reducing greenhouse gas emissions. However, the LW is resistant to degradation, and its hydrolysis typically requires harsh conditions, hence the need for a pretreatment. Conducting a life cycle assessment (LCA) to evaluate the pretreatment of LW is an effective way to assess the environmental impacts associated with various pretreatment methods. This work evaluates and compares three scenarios for handling lignified tomato green waste (TGW), generated in the Greater of Agadir in Morocco, in terms of their environmental impacts and energy demand, using the LCA approach, performed with OpenLCA software. To achieve this aim, the impact of these scenarios on 11 indicators is studied. The analyzed management options include a base case scenario S0 where TGW undergoes a direct anaerobic digestion (AD), organosolv pretreatment of TGW followed by AD of the free-lignin fraction (S1), and choline chloride-based deep eutectic solvent (DES) delignification followed by AD of the free-lignin fraction (S2). The data used for the analysis comes from the Tamelast landfill, laboratory tests, literature, CML-IA baseline and Monte Carlo simulation calculations. The results obtained showed that the introduction of pretreatments in S1 and S2 mitigates significantly the environmental impact in different categories compared to S0. Scenario S2, with its enhanced recovery processes, shows the highest positive environmental contributions, despite its reliance on additional external electricity. S1 and S0 both respect energy circularity. Through this study, it has been demonstrated that chemical pretreatment of LW is energy, water and solvent-intensive and requires a large investment. It opens up perspectives for further works on pretreatment using natural DES technology, its development and its applications in the delignification of ligneous biomass on an industrial scale.

Pilot-scale in-situ biomethanation of sewage sludge: Effects of gas recirculation method.

The methanation efficiency and operational stability of a 2 m3 pilot-scale in-situ biomethanation reactor were investigated using on-site sewage sludge as the substrate, at a wastewater treatment plant. In parallel, a laboratory-scale study was conducted. Hydrogen conversion efficiencies of 96.7 and 97.5 %, and average methane contents of 84.2 and 83.2 % were obtained, for the laboratory and pilot experiments, respectively. The pilot-scale digester was operated at various conditions for 137 d, of which the last 30 d were stable with a high biomethanation efficiency and an average pH of 8.2. Gas recirculation increased the hydrogen conversion efficiency. When hydrogen injection and gas recirculation were applied separately, a 96 % lower gas recirculation rate was needed to achieve the same hydrogen conversion efficiency, compared to a mixture of hydrogen injection and gas recirculation in the same line. These findings may facilitate the selection of suitable gas recirculation concepts for practical biomethanation applications.

Exergetic investigation of the influence of injector location in HCCI engines utilizing DEE as pilot fuel and biogas as primary fuel.

To address the global demand for sustainable energy, integrating biogas into internal combustion engines is becoming more important. Homogeneous Charge Compression Ignition (HCCI) engines, known for high efficiency and low emissions, offer a promising solution. This study investigates the optimal injector location for using biogas in HCCI engines, with diethyl ether (DEE) as the pilot fuel, evaluating three positions: (i) at the port, (ii) 6 cm away (Manifold 1), and (iii) 10 cm away (Manifold 2). Through experiments and simulations, the impact of injector location on engine performance is analyzed across various parameters, including methane fractions, engine loads, and exhaust gas compositions. Results show that port injection achieves the highest first law and exergy efficiencies but increases emissions of hydrocarbons (HC), carbon monoxide (CO), and smoke. At 15 Nm load, Manifold 1 shows a 27.34 % reduction in exergy efficiency compared to port injection, while Manifold 2 exhibits an 18.49 % decrease at higher loads. Despite lower efficiencies, Manifold 1 effectively reduces harmful emissions. The study also considers exergo-economic and sustainability aspects, highlighting that while port injection is optimal for efficiency, Manifold 1 excels in minimizing HC and CO emissions, with a 50 % reduction in HC and 71.43 % reduction in CO emissions at 15 Nm load compared to port injection. Manifold 2 achieves the lowest smoke emissions across all loads. This investigation provides crucial insights into optimizing HCCI engines for biogas utilization, emphasizing injector location, fuel composition, and operating parameters to enhance performance and reduce environmental impact.