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Three tubular bioreactors with a varied substrate flow rate of (2 mL/min, 5 mL/min, and 8 mL/min) were examined for 75 days. At 8 mL/min flow rate, the biohydrogen evolution was higher (3.88 mL H2/h), while its conversion efficiency was lower compared to 5 and 2 mL/min flow rate. The formation of volatile fatty acids and ammonium was also influenced by substrate flow rates. The volatile fatty acids production was slightly higher at 2 mL/min (12.74 ± 2.42 gCOD/L) and 5 mL/min (18.09 ± 2.01 gCOD/L) while, decreasing at 8 mL/min (11.85 ± 0.78 gCOD/L). Substrate flow rate significantly affected the pattern and composition of volatile fatty acids showing higher acetic acid, butyric and propionic acid production of 4.72 ± 1.46 gCOD/L (2 mL/min) 10.41 ± 0.91 gCOD/L (5 mL/min) and 1.78 ± 0.13 gCOD/L (5 mL/min). Continuous substrate input maintained the pH in the reactor due to replacement with fresh substrate, thereby controlling feedback inhibition and boosting metabolite production. Hydrogen-producing Firmicutes on the biofilm confirmed the pivotal role of the microbial community's significant contribution to converting waste to bioenergy. Overall, the present results support the use of a continuous operation mode for large-scale biohydrogen production. However, to ensure the efficacy of the system using waste or wastewater, low substrate flow rates are recommended., Validerad;2024;Nivå 2;2024-04-05 (marisr);Full text license: CC BY

Large quantities of polyvinyl chloride (PVC) and waste tires generated daily have the disadvantage of high content of harmful elements. They cannot be directly applied to blast furnace ironmaking. In this study, Cl in PVC and Zn in pyrolysis products of waste tires (pyrolysis carbon black, CB) were effectively removed by co-hydrothermal carbonization (co-HTC). The results indicated the dechlorination and dezincification efficiencies of co-HTC were improved by 2.78 % and 64.69 %, respectively, compared to HTC. Compositional analysis shows that the ash content of co-HTC is reduced by at least 7.67 % compared to conventional HTC. The hydrochar produced by co-HTC has an higher heating value (HHV) ranging from 30.67 to 34.13 MJ/kg. Results of physical and chemical characteristics analysis showed increasing the proportion of CB can reduce the C–H and -CHCl- functional groups and improve the carbon orderliness of the hydrochar. Combustion characteristics and kinetic analyses show that the combustibility of hydrochar increases with an increase in the proportion of PVC added to the co-HTC. The thermal stability and activation energy of the hydrochar increase with the addition of CB. Overall, this study has removed major harmful elements from PVC and CB through co-HTC, converting both into high-quality solid fuels that can be utilised in blast furnace ironmaking., QC 20240108

First experiments with biogenic residues and a plastic-rich rejects and woody biomass blend were conducted in an advanced 1 MW dual fluidized bed steam gasification demonstration plant at the Syngas Platform Vienna. Wood chips, bark, forest residues, and the plastic-rich rejects and woody biomass blend were tested and the tar composition was analyzed upstream and downstream of the upper gasification reactor, which is designed as a high-temperature column with countercurrent flow of catalytic material. Each feedstock was gasified with olivine as bed material in demonstration scale and is compared to the gasification of softwood pellets with olivine and limestone in pilot scale. A reduction in tar content was observed after countercurrent column for all feedstocks. However, a shift in tar species occurred. While styrene, phenol, and 1H-indene were predominant upstream, naphthalene and polycyclic aromatic hydrocarbons (PAHs) were the prevailing tar species downstream the countercurrent column. Hence, an increase of i.e. anthracene, fluoranthene, and pyrene from the upstream concentration was observed. For pyrene, up to twice the initial concentration was measured. This recombination to PAHs was observed for all feedstocks in demonstration- and pilot-scale. The only exception occurred with limestone as bed material, characterized by a higher catalytic activity in comparison to the typically used olivine. In the perspective of the integrated product gas cleaning, tar with higher temperature of condensation are separated more efficiently in the installed scrubbing unit. Hence, the recombination facilitates an overall decline of tar content after the gas cleaning.

This study aimed to investigate the potential of converting bio-based residues from industrial production of mushrooms and tomatoes into more valuable chemicals with antifungal properties using hydrothermal liquefaction (HTL). Liquid fractions were obtained from HTL of spent substrate of Agaricus bisporus (Lange) Imbach and Pleurotus ostreatus (jacq.) P. kumm., recomposted Agaricus bisporus spent substrate, and tomato residues. The quantitative 1H NMR spectroscopy analysis revealed that the HTL liquids of all residues contained antifungal constituents like phenols and organic acids. The HTL liquids at dilutions of 10 % were able to inhibit the fungi by over 80 %. Interestingly, the fungus P. ostreatus showed tolerance to these constituents as its growth was promoted at the lowest concentration of all the HTL liquids. The HTL liquids had lower ecotoxicity than the commercial wood preservative. These results suggest that the tested residues could be a promising source of preservative chemical constituents for the wood industry.

Bioenergy with carbon capture and storage (BECCS) can be a useful and cost-effective climate change mitigation tool but it is reliant on economic incentives. With this policy perspective article we question the ongoing discussion about the use of biomass for BECCS with basis in three points: (1) under the enhanced transparency framework under the Paris agreement, all parties to the agreement will use the same guidelines to estimate emissions by sources and removals by sinks, in which the emissions and removals in connection to cultivation of biomass are accounted for in the land-use, land-use change and forestry (LULUCF) sector, (2) adding carbon capture to existing processes may lead to a shift in products from that process rather than an increase in biomass use, and (3) BECCS requires substantial financial incentives. With basis in these points, we argue that a certification framework for BECCS that contradicts the guidelines of the Intergovernmental Panel on Climate Change (IPCC) risks unnecessarily hindering deployment of a potentially cost-effective climate change mitigation tool., QC 20231215

Three tubular bioreactors with a varied substrate flow rate of (2 mL/min, 5 mL/min, and 8 mL/min) were examined for 75 days. At 8 mL/min flow rate, the biohydrogen evolution was higher (3.88 mL H2/h), while its conversion efficiency was lower compared to 5 and 2 mL/min flow rate. The formation of volatile fatty acids and ammonium was also influenced by substrate flow rates. The volatile fatty acids production was slightly higher at 2 mL/min (12.74 ± 2.42 gCOD/L) and 5 mL/min (18.09 ± 2.01 gCOD/L) while, decreasing at 8 mL/min (11.85 ± 0.78 gCOD/L). Substrate flow rate significantly affected the pattern and composition of volatile fatty acids showing higher acetic acid, butyric and propionic acid production of 4.72 ± 1.46 gCOD/L (2 mL/min) 10.41 ± 0.91 gCOD/L (5 mL/min) and 1.78 ± 0.13 gCOD/L (5 mL/min). Continuous substrate input maintained the pH in the reactor due to replacement with fresh substrate, thereby controlling feedback inhibition and boosting metabolite production. Hydrogen-producing Firmicutes on the biofilm confirmed the pivotal role of the microbial community's significant contribution to converting waste to bioenergy. Overall, the present results support the use of a continuous operation mode for large-scale biohydrogen production. However, to ensure the efficacy of the system using waste or wastewater, low substrate flow rates are recommended., Validerad;2024;Nivå 2;2024-04-05 (marisr);Full text license: CC BY

This study aimed to investigate the potential of converting bio-based residues from industrial production of mushrooms and tomatoes into more valuable chemicals with antifungal properties using hydrothermal liquefaction (HTL). Liquid fractions were obtained from HTL of spent substrate of Agaricus bisporus (Lange) Imbach and Pleurotus ostreatus (jacq.) P. kumm., recomposted Agaricus bisporus spent substrate, and tomato residues. The quantitative 1H NMR spectroscopy analysis revealed that the HTL liquids of all residues contained antifungal constituents like phenols and organic acids. The HTL liquids at dilutions of 10 % were able to inhibit the fungi by over 80 %. Interestingly, the fungus P. ostreatus showed tolerance to these constituents as its growth was promoted at the lowest concentration of all the HTL liquids. The HTL liquids had lower ecotoxicity than the commercial wood preservative. These results suggest that the tested residues could be a promising source of preservative chemical constituents for the wood industry.

First experiments with biogenic residues and a plastic-rich rejects and woody biomass blend were conducted in an advanced 1 MW dual fluidized bed steam gasification demonstration plant at the Syngas Platform Vienna. Wood chips, bark, forest residues, and the plastic-rich rejects and woody biomass blend were tested and the tar composition was analyzed upstream and downstream of the upper gasification reactor, which is designed as a high-temperature column with countercurrent flow of catalytic material. Each feedstock was gasified with olivine as bed material in demonstration scale and is compared to the gasification of softwood pellets with olivine and limestone in pilot scale. A reduction in tar content was observed after countercurrent column for all feedstocks. However, a shift in tar species occurred. While styrene, phenol, and 1H-indene were predominant upstream, naphthalene and polycyclic aromatic hydrocarbons (PAHs) were the prevailing tar species downstream the countercurrent column. Hence, an increase of i.e. anthracene, fluoranthene, and pyrene from the upstream concentration was observed. For pyrene, up to twice the initial concentration was measured. This recombination to PAHs was observed for all feedstocks in demonstration- and pilot-scale. The only exception occurred with limestone as bed material, characterized by a higher catalytic activity in comparison to the typically used olivine. In the perspective of the integrated product gas cleaning, tar with higher temperature of condensation are separated more efficiently in the installed scrubbing unit. Hence, the recombination facilitates an overall decline of tar content after the gas cleaning.

Enzymatic saccharification is used to convert polysaccharides in lignocellulosic biomass to sugars which are then converted to ethanol or other bio-based fermentation products. The efficacy of commercial cellulase preparations can potentially increase if lytic polysaccharide monooxygenase (LPMO) is included. However, as LPMO requires both a reductant and an oxidant, such as molecular oxygen, a reevaluation of process configurations and conditions is warranted. Saccharification and fermentation of pretreated softwood was investigated in demonstration-scale experiments with 10 m3 bioreactors using an LPMO-containing cellulase preparation, a xylose-utilizing yeast, and either simultaneous saccharification and fermentation (SSF) or hybrid hydrolysis and fermentation (HHF) with a 24-hour or 48-hour initial phase and with 0.15 vvm aeration before addition of the yeast. The conditions used for HHF, especially with 48 h initial phase, resulted in better glucan conversion, but in poorer ethanol productivity and in poorer initial ethanol yield on consumed sugars than the SSF. In the SSF, hexose sugars such as glucose and mannose were consumed faster than xylose, but, in the end of the fermentation >90% of the xylose had been consumed. Chemical analysis of inhibitory pretreatment by-products indicated that the concentrations of heteroaromatic aldehydes (such as furfural), aromatic aldehydes, and an aromatic ketone decreased as a consequence of the aeration. This was attributed mainly to evaporation caused by the gas flow. The results indicate that further research is needed to fully exploit the advantages of LPMO without compromising fermentation conditions.

Achieving optimal nutrient composition in locally sourced ruminant feeds is important, but can be challenging in resource-limited production systems. For example, improving the composition of available local feed resources is a key obstacle to efficiently mitigating enteric methane (CH4) emissions in ruminants. This study characterized the nutritional content and in vitro methane (CH4) yield of ruminant feedstuffs accessible in Ethiopia. A survey of 60 experienced farmers in two representative districts in Amhara region, Ethiopia, provided 33 feed samples, which were classified into four ruminant feed categories: Grasses (n=10); indigenous plants (trees, shrubs, herbaceous plants) (n=13); crop residues (n=5); and agro-industrial by-products (n=5). Nutritional composition was assessed by proximate and detergent methods. Methane yield (g CH4/kg feed dry matter (DM)) and total gas yield (L/kg DM) were evaluated using a fully automated in vitro gas production system. A colorimetric assay was conducted to measure condensed tannin content (CT, mg/g) in relevant feeds. Lower crude protein (CP) values were observed for the grass (mean 65.2 g/kg DM) and crop residues (mean 54.5 g/kg DM) categories. Agro-industrial by-products had the highest CP (mean 260 g/kg DM), while indigenous plants exhibited intermediate levels (163 g/kg DM). There was significant variation in CH4 yield (P<0.01) between grasses (12.4–24.7 g/kg DM) indigenous plants (1.8–19.3 g/kg DM), and agro-industrial by-products (8.1–26.9 g/kg DM). The indigenous plant Trifolium acaule gave the lowest in vitro CH4 yield (1.8 g/kg DM). A positive relationship was observed between in vitro dry matter digestibility (IVDMD), CH4, and total gas yield. Percentage of CH4 in total gas production varied with feed category (grasses 14.5–19.6%; indigenous plants 3.1–16.9%; crop residues 15.8–20.6%; agro-industrial by-products 12.8–18.7%), and within category, e.g., Trifolium acaule (3.1%), Acacia nilotica L. (7.1%), Ziziph

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for fu

The use of green heterogeneous catalysts that are obtained from waste agricultural biomass can make the production of biodiesel more economical. In this research, three solid base heterogeneous catalysts (Catalyst A, B, and C) were synthesized from kola nut pod husks, and the synergistic effects of the elemental composition on catalytic activities for biodiesel production were studied. The results revealed a high surface area of Catalysts A, B, and C at 419.90 m2/g, 430.54 m2/g, and 432.57 m2/g, respectively. Their corresponding pore diameters are 3.53 nm, 3.48 nm, and 3.32 nm, showing that the catalysts are mesoporous in nature. The X-ray Fluorescence (XRF) results revealed the presence of a variety of alkaline earth metals and their corresponding metal oxides in substantial amounts. Catalyst A was produced with the highest concentration of calcium at 40.84 wt.% and calcium oxide at 68.02 mole%. The substantial concentration of other elements, such as potassium, magnesium, and aluminum, and their corresponding metal oxides are the proof of high catalytic activity of the produced green catalysts. The high CaO contents of all three produced catalysts and their high surface areas indicate their strong potential for good catalytic activities applied to the synthesis of biodiesel.

Samhället har ökade energibehov och krav på minskad miljöpåverkan, vilket gör biobränsle viktigt för hållbar energi. Biovärmeverks anläggningarna måste utvecklas för att bli mer miljövänliga och kunna ersätta fossila bränslen. De utsätts för höga termiska, kemiska och mekaniska påfrestningar, vilket innebär säkerhetsrisker. Således finns det lagar på trycksatta anordningar att fungera utan el genom att säkerhetsställa att överhettning undviks. Därför har biobränslepannor nödkylningssystem som förhindrar överhettning genom att hålla rörtemperaturen under den temperatur som pannan byggs för att klara, i denna studie är pannan dimensionerad för 140–150°C. Systemet, som består av stålrör med kallt vatten, aktiveras vid elavbrott eller temperaturökning, och luftflödet samt bränsletillförseln stoppas. Eftersom det är svårt att fastställa nödkylningseffekten överdimensioneras nödkylaren. Det är vanligt att nödkylaren tillverkas i diskreta storlekar och inte skräddarsys för varje panna. Vilket kan leda till onödig materialanvändning, kostnader och utsläpp. Studien, i samarbete med AKJ Energiteknik AB, syftar till att ge underlag för dimensionering av nödkylningssystemet för att minska kostnader och utsläpp. Målet är att skapa en dynamisk modell i Simulink och MATLAB och verifiera den med mätdata. Studien undersöker nödkylningssystemets funktion, kylbehov samt vatten- och materialåtgång, och utvärderar påverkan på kostnad och miljö genom CO2-ekvivalenter med förslag på åtgärder för systemets dimensioner. Den dynamiska modellen byggdes upp i Simulink och MATLAB Pannan konstruerades i zoner utifrån dimensionsförändringar i pannans rörkanaler där rökgasen flödade igenom samt förenklad beräkning för ugnens temperatur och rökgasflöde. Modellen verifierades mot mätdata från kapaciteter, temperaturer på rökgasen och vattnet samt granskades från företaget. Modellen kontrollerades utifrån känslighetsanalys, litteratur och värmeövergångstal och således skapades en trovärdig modell, Society has increasing energy demands and requirements for reduced environmental impact, making biofuel essential for sustainable energy. Facilities must be developed to become more environmentally friendly and capable of replacing fossil fuels. These facilities are subjected to high thermal, chemical, and mechanical stresses, which pose safety risks. Consequently, regulations exist for pressurized devices that operate without power by ensuring overheating is avoided. Therefore, biofuel boilers are equipped with emergency cooling systems to prevent overheating by maintaining the tube temperature below the design threshold, which in this study is 140–150°C. The system, composed of steel tubes containing cold water, activates in the event of a power outage or temperature increase, and airflow and fuel supply are halted. Since determining the emergency cooling effect is challenging, the emergency cooler is often oversized. It is common for emergency coolers to be manufactured in discrete sizes rather than customized for each boiler, which can lead to unnecessary material usage, costs, and emissions. This study, conducted in collaboration with AKJ Energiteknik AB, aims to provide insights for sizing emergency cooling systems to reduce costs and emissions. The objective is to develop a dynamic model in Simulink and MATLAB, validated with measurement data. The study investigates the emergency cooling system's function, cooling requirements, water and material consumption, and evaluates their impact on costs and the environment through CO2- equivalents, proposing dimensioning measures for the system. The dynamic model was constructed in Simulink and MATLAB. The boiler was segmented into zones based on changes in the boiler's pipe channels where flue gas flows, alongside simplified calculations for furnace temperature and flue gas flow. The model was validated against measurement data for capacities, flue gas and water temperatures, and reviewed by the company. Sensitiv

Bioenergi med avskiljning och lagring av koldioxid (BECCS) håller på att utvecklas till en viktig teknik för negativa utsläpp och planeras spela en avgörande roll för Sveriges mål om noll nettoutsläpp av koldioxid till 2045. Stora BECCS-anläggningar förväntas, till exempel den som planeras i Värtahamnen av Stockholm Exergi. Mindre punktkällor för koldioxidutsläpp, som avloppsreningsverket i Käppala, en biogasproducent, skulle också kunna bidra till negativa utsläpp genom BECCS, dvs. genom att fånga upp biogen koldioxid från anaerob jäsning. Ekonomiska faktorer begränsar dock implementeringen av hela BECCS-värdekedjan i mindre skala. Genom att använda en närliggande större BECCS-anläggning kan dessa kostnadsbarriärer övervinnas genom att skapa nav för BECCS och utnyttja synergier. I detta arbete undersöks de tekniska och ekonomiska utmaningarna med att integrera en CO2-ström från Käppala WWTP med Stockholm Exergis anläggning. Olika scenarier för CO2-integrering identifierades, med beaktande av flera faktorer, inklusive CO2-koncentration och renhetsbegränsningar för kondensering, kortdistanstransport och affärsmodell bakom biogasproducenten. Käppala reningsverk släpper för närvarande ut biogen CO2 i form av en CO2/luftblandning till atmosfären. Detta arbete visade att CO2 kan tas emot av Stockholm Exergi i form av en CO2/luftblandning, CO2-gas eller kondenserad CO2. Käppala reningsverk skulle antingen kunna behålla sin nuvarande vattenreningsprocess, som ger CO2/luftblandningen, eller modernisera sin biogasuppgraderingsprocess för att producera koncentrerad CO2. Vidare konstaterades att en rörledning är det mest ekonomiska alternativet för kortdistanstransport av CO2, antingen i en blandning eller i koncentrerad form, men långa ledtider kräver långsiktig planering. Om transporten istället sker med lastbilar krävs en ombyggnad och ett förvätskningssteg vid Käppalaverket. En litteraturgenomgång av tillgängliga tekniker för Käppala reningsverk identifierade en membran, Bio-energy with carbon capture and storage (BECCS) is emerging as a major negative emission technology and is scheduled to play a crucial role to Sweden’s net-zero goal by 2045. Large BECCS facilities are anticipated, such as the one planned in Värtahamnen by Stockholm Exergi. Smaller CO2 point sources like Käppala wastewater treatment plant (WWTP), a biogas producer, could also contribute to negative emissions through BECCS, i.e., by capturing the biogenic CO2 from anaerobic fermentation. However, economic constraints limit the implementation of the entire BECCS value chain on a smaller scale. Utilizing a nearby larger BECCS facility can help overcome these cost barriers by creating hubs for BECCS, leveraging synergies. This work explores the technical and economic challenges of integrating a CO2 stream from Käppala WWTP with Stockholm Exergi’s facility. Various scenarios for CO2 integration were identified, considering multiple factors, including CO2 concentration and purity constraints for liquefaction, short-distance transport, and business model behind the biogas producer. Käppala WWTP currently releases biogenic CO2 in the form of a CO2/air mixture to the atmosphere. This work found that CO2 can be received by Stockholm Exergi in the form of a CO2/air mixture, CO2 gas, or liquefied CO2. Whereas Käppala WWTP could either keep their current water scrubbing process, yielding the CO2/air mixture, or perform a revamp of their biogas upgrading process to produce concentrated CO2. Moreover, it was found that a pipeline is the most economical option for short-distance transport of CO2, either in a mixture or concentrated form, but long lead times make necessary long-term planning. If instead transport is carried out by trucks, a revamp and a liquefaction stage at Käppala WWTP are necessary. A literature review on the available technologies targeted at Käppala WWTP identified a membrane process as the most appropriate technology for a revamp of the biogas upgrading

The growing need for climate mitigation solutions has contributed so thatbiochar has gained significant interest. Primary for its ability as a carbon sinkbut there is also a growing interest due to several other aspects within industriese.g. substitution effects, increased resource efficiency, an enabler forindustrial symbiosis, and its beneficial properties when put in soil that can increasegrowth. Previous studies of biochar have been dominant within the environmentalperspective of biochar, analyzing detailed characteristics of its propertiesand carbon sink potential. Some studies have a holistic perspective reflectingon countries specific energy mix and the different benefits of producingbiochar. However, previous studies are far too few to determine the value-chainof biochar. Hence previous studies have knowledge gaps within the holistic lifecycle approach from a provider or customer perspective of biochar, not reflectingon demand for quality requirements in different utilization areas and markets.The need for validation of the environmental and the economic performanceof biochar has to be established, and the economic perspective of biochar hasmajor knowledge gaps since previous studies are scarce. The study aims to establish the value-chain of biochar by evaluating theenvironmental, economic, and social perspectives through life cycle thinking.The core of the study is to distinguish value, which first has to reflect thebiochar quality requirements from providers and customers, captured throughinterviews and literature research. The quality requirements enable a goal forproducing biochar and determine what processes and biomass are needed fordifferent markets. This is evaluated through a case development which considersthe different quality requirements. Life cycle assessment (LCA) with acradle-to-grave perspective and life cycle costing (LCC) with a cradle-to-gatewere then used to distinguish biochar´s environmental and economic performance. The interviews and

The use of green heterogeneous catalysts that are obtained from waste agricultural biomass can make the production of biodiesel more economical. In this research, three solid base heterogeneous catalysts (Catalyst A, B, and C) were synthesized from kola nut pod husks, and the synergistic effects of the elemental composition on catalytic activities for biodiesel production were studied. The results revealed a high surface area of Catalysts A, B, and C at 419.90 m2/g, 430.54 m2/g, and 432.57 m2/g, respectively. Their corresponding pore diameters are 3.53 nm, 3.48 nm, and 3.32 nm, showing that the catalysts are mesoporous in nature. The X-ray Fluorescence (XRF) results revealed the presence of a variety of alkaline earth metals and their corresponding metal oxides in substantial amounts. Catalyst A was produced with the highest concentration of calcium at 40.84 wt.% and calcium oxide at 68.02 mole%. The substantial concentration of other elements, such as potassium, magnesium, and aluminum, and their corresponding metal oxides are the proof of high catalytic activity of the produced green catalysts. The high CaO contents of all three produced catalysts and their high surface areas indicate their strong potential for good catalytic activities applied to the synthesis of biodiesel.

Enzymatic saccharification is used to convert polysaccharides in lignocellulosic biomass to sugars which are then converted to ethanol or other bio-based fermentation products. The efficacy of commercial cellulase preparations can potentially increase if lytic polysaccharide monooxygenase (LPMO) is included. However, as LPMO requires both a reductant and an oxidant, such as molecular oxygen, a reevaluation of process configurations and conditions is warranted. Saccharification and fermentation of pretreated softwood was investigated in demonstration-scale experiments with 10 m3 bioreactors using an LPMO-containing cellulase preparation, a xylose-utilizing yeast, and either simultaneous saccharification and fermentation (SSF) or hybrid hydrolysis and fermentation (HHF) with a 24-hour or 48-hour initial phase and with 0.15 vvm aeration before addition of the yeast. The conditions used for HHF, especially with 48 h initial phase, resulted in better glucan conversion, but in poorer ethanol productivity and in poorer initial ethanol yield on consumed sugars than the SSF. In the SSF, hexose sugars such as glucose and mannose were consumed faster than xylose, but, in the end of the fermentation >90% of the xylose had been consumed. Chemical analysis of inhibitory pretreatment by-products indicated that the concentrations of heteroaromatic aldehydes (such as furfural), aromatic aldehydes, and an aromatic ketone decreased as a consequence of the aeration. This was attributed mainly to evaporation caused by the gas flow. The results indicate that further research is needed to fully exploit the advantages of LPMO without compromising fermentation conditions.

The use of green heterogeneous catalysts that are obtained from waste agricultural biomass can make the production of biodiesel more economical. In this research, three solid base heterogeneous catalysts (Catalyst A, B, and C) were synthesized from kola nut pod husks, and the synergistic effects of the elemental composition on catalytic activities for biodiesel production were studied. The results revealed a high surface area of Catalysts A, B, and C at 419.90 m2/g, 430.54 m2/g, and 432.57 m2/g, respectively. Their corresponding pore diameters are 3.53 nm, 3.48 nm, and 3.32 nm, showing that the catalysts are mesoporous in nature. The X-ray Fluorescence (XRF) results revealed the presence of a variety of alkaline earth metals and their corresponding metal oxides in substantial amounts. Catalyst A was produced with the highest concentration of calcium at 40.84 wt.% and calcium oxide at 68.02 mole%. The substantial concentration of other elements, such as potassium, magnesium, and aluminum, and their corresponding metal oxides are the proof of high catalytic activity of the produced green catalysts. The high CaO contents of all three produced catalysts and their high surface areas indicate their strong potential for good catalytic activities applied to the synthesis of biodiesel.

Anaerobic digestion (AD) technology can potentially address the gap between energy demand and supply playing a crucial role in the production of sustainable energy from utilization of biogenic waste materials as feedstock. The biogas production from anaerobic digestion is primarily influenced by the chemical compositions and biodegradability of the feedstock. Organosolv-steam explosion offers a constructive approach as a promising pretreatment method for the fractionation of lignocellulosic biomasses delivering high cellulose content.This study showed how synergetic co-digestion serves to overcome the challenges of mono-digestion's low efficiency. Particularly, the study evaluated the digestibility of organosolv-steam pretreated wheat straw (WSOSOL) in mono as well as co-digesting substrate with cheese whey (CW) and brewery spent grains (BSG). The highest methane yield was attained with co-digestion of WSOSOL + CW (338 mL/gVS) representing an enhanced biogas output of 1–1.15 times greater than its mono digestion. An ammonium production was favored under co-digestion strategy accounting for 921 mg/L from WSOSOL + BSG. Metagenomic study was conducted to determine the predominant bacteria and archaea, as well as its variations in their populations and their functional contributions during the AD process. The Firmicutes have been identified as playing a significant role in the hydrolysis process and the initial stages of AD. An enrichment of the most prevalent archaea genera enriched were Methanobacterium, Methanothrix, and Methanosarsina. Reactors digesting simpler substrate CW followed the acetoclastic, while digesting more complex substrates like BSG and WSOSOL followed the hydrogenotrophic pathway for biomethane production. To regulate the process for an enhanced AD process to maximize CH4, a comprehensive understanding of microbial communities is beneficial., Full text license: CC BY 4.0

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for fu

Biogas has long been used as a household cooking fuel in many tropical counties, and it has the potential to be a significant energy source beyond household cooking fuel. In this study, we describe the use of low electrical energy input in an anaerobic digestion process using a microbial electrochemical cell (MEC) to promote methane content in biogas at 18, 28, and 37 °C. Although the maximum amount of biogas production was at 37 °C (25 cm3), biogas could be effectively produced at lower temperatures, i.e., 18 (13 cm3) and 28 °C (19 cm3), with an external 2 V power input. The biogas production of 13 cm3 obtained at 18 °C was ~65-fold higher than the biogas produced without an external power supply (0.2 cm3). This was further enhanced by 23% using carbon-nanotubes-treated (CNT) graphite electrodes. This suggests that the MEC can be operated at as low as 18 °C and still produce significant amounts of biogas. The share of CH4 in biogas produced in the controls was 30%, whereas the biogas produced in an MEC had 80% CH4. The MEC effectively reduced COD to 42%, whereas it consumed 98% of reducing sugars. Accordingly, it is a suitable method for waste/manure treatment. Molecular characterization using 16s rRNA sequencing confirmed the presence of methanogenic bacteria, viz., Serratia liquefaciens and Zoballella taiwanensis, in the inoculum used for the fermentation. Consistent with recent studies, we believe that electromethanogenesis will play a significant role in the production of value-added products and improve the management of waste by converting it to energy., Godkänd;2024;Nivå 0;2024-06-14 (joosat);Funder: Tribhuvan University under National Priority Area Research Project (TU-NPAR-077/78-ERG-07);Full text license: CC BY

Achieving optimal nutrient composition in locally sourced ruminant feeds is important, but can be challenging in resource-limited production systems. For example, improving the composition of available local feed resources is a key obstacle to efficiently mitigating enteric methane (CH4) emissions in ruminants. This study characterized the nutritional content and in vitro methane (CH4) yield of ruminant feedstuffs accessible in Ethiopia. A survey of 60 experienced farmers in two representative districts in Amhara region, Ethiopia, provided 33 feed samples, which were classified into four ruminant feed categories: Grasses (n=10); indigenous plants (trees, shrubs, herbaceous plants) (n=13); crop residues (n=5); and agro-industrial by-products (n=5). Nutritional composition was assessed by proximate and detergent methods. Methane yield (g CH4/kg feed dry matter (DM)) and total gas yield (L/kg DM) were evaluated using a fully automated in vitro gas production system. A colorimetric assay was conducted to measure condensed tannin content (CT, mg/g) in relevant feeds. Lower crude protein (CP) values were observed for the grass (mean 65.2 g/kg DM) and crop residues (mean 54.5 g/kg DM) categories. Agro-industrial by-products had the highest CP (mean 260 g/kg DM), while indigenous plants exhibited intermediate levels (163 g/kg DM). There was significant variation in CH4 yield (P<0.01) between grasses (12.4–24.7 g/kg DM) indigenous plants (1.8–19.3 g/kg DM), and agro-industrial by-products (8.1–26.9 g/kg DM). The indigenous plant Trifolium acaule gave the lowest in vitro CH4 yield (1.8 g/kg DM). A positive relationship was observed between in vitro dry matter digestibility (IVDMD), CH4, and total gas yield. Percentage of CH4 in total gas production varied with feed category (grasses 14.5–19.6%; indigenous plants 3.1–16.9%; crop residues 15.8–20.6%; agro-industrial by-products 12.8–18.7%), and within category, e.g., Trifolium acaule (3.1%), Acacia nilotica L. (7.1%), Ziziph

In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture., Funding: Kamprad Family Foundation [20200041], Värdeskapande av koldioxid från biogasproduktion

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for fu

The use of green heterogeneous catalysts that are obtained from waste agricultural biomass can make the production of biodiesel more economical. In this research, three solid base heterogeneous catalysts (Catalyst A, B, and C) were synthesized from kola nut pod husks, and the synergistic effects of the elemental composition on catalytic activities for biodiesel production were studied. The results revealed a high surface area of Catalysts A, B, and C at 419.90 m2/g, 430.54 m2/g, and 432.57 m2/g, respectively. Their corresponding pore diameters are 3.53 nm, 3.48 nm, and 3.32 nm, showing that the catalysts are mesoporous in nature. The X-ray Fluorescence (XRF) results revealed the presence of a variety of alkaline earth metals and their corresponding metal oxides in substantial amounts. Catalyst A was produced with the highest concentration of calcium at 40.84 wt.% and calcium oxide at 68.02 mole%. The substantial concentration of other elements, such as potassium, magnesium, and aluminum, and their corresponding metal oxides are the proof of high catalytic activity of the produced green catalysts. The high CaO contents of all three produced catalysts and their high surface areas indicate their strong potential for good catalytic activities applied to the synthesis of biodiesel.

Enzymatic saccharification is used to convert polysaccharides in lignocellulosic biomass to sugars which are then converted to ethanol or other bio-based fermentation products. The efficacy of commercial cellulase preparations can potentially increase if lytic polysaccharide monooxygenase (LPMO) is included. However, as LPMO requires both a reductant and an oxidant, such as molecular oxygen, a reevaluation of process configurations and conditions is warranted. Saccharification and fermentation of pretreated softwood was investigated in demonstration-scale experiments with 10 m3 bioreactors using an LPMO-containing cellulase preparation, a xylose-utilizing yeast, and either simultaneous saccharification and fermentation (SSF) or hybrid hydrolysis and fermentation (HHF) with a 24-hour or 48-hour initial phase and with 0.15 vvm aeration before addition of the yeast. The conditions used for HHF, especially with 48 h initial phase, resulted in better glucan conversion, but in poorer ethanol productivity and in poorer initial ethanol yield on consumed sugars than the SSF. In the SSF, hexose sugars such as glucose and mannose were consumed faster than xylose, but, in the end of the fermentation >90% of the xylose had been consumed. Chemical analysis of inhibitory pretreatment by-products indicated that the concentrations of heteroaromatic aldehydes (such as furfural), aromatic aldehydes, and an aromatic ketone decreased as a consequence of the aeration. This was attributed mainly to evaporation caused by the gas flow. The results indicate that further research is needed to fully exploit the advantages of LPMO without compromising fermentation conditions.

Anaerobic digestion (AD) technology can potentially address the gap between energy demand and supply playing a crucial role in the production of sustainable energy from utilization of biogenic waste materials as feedstock. The biogas production from anaerobic digestion is primarily influenced by the chemical compositions and biodegradability of the feedstock. Organosolv-steam explosion offers a constructive approach as a promising pretreatment method for the fractionation of lignocellulosic biomasses delivering high cellulose content.This study showed how synergetic co-digestion serves to overcome the challenges of mono-digestion's low efficiency. Particularly, the study evaluated the digestibility of organosolv-steam pretreated wheat straw (WSOSOL) in mono as well as co-digesting substrate with cheese whey (CW) and brewery spent grains (BSG). The highest methane yield was attained with co-digestion of WSOSOL + CW (338 mL/gVS) representing an enhanced biogas output of 1–1.15 times greater than its mono digestion. An ammonium production was favored under co-digestion strategy accounting for 921 mg/L from WSOSOL + BSG. Metagenomic study was conducted to determine the predominant bacteria and archaea, as well as its variations in their populations and their functional contributions during the AD process. The Firmicutes have been identified as playing a significant role in the hydrolysis process and the initial stages of AD. An enrichment of the most prevalent archaea genera enriched were Methanobacterium, Methanothrix, and Methanosarsina. Reactors digesting simpler substrate CW followed the acetoclastic, while digesting more complex substrates like BSG and WSOSOL followed the hydrogenotrophic pathway for biomethane production. To regulate the process for an enhanced AD process to maximize CH4, a comprehensive understanding of microbial communities is beneficial., Full text license: CC BY 4.0

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for fu

Biogas has long been used as a household cooking fuel in many tropical counties, and it has the potential to be a significant energy source beyond household cooking fuel. In this study, we describe the use of low electrical energy input in an anaerobic digestion process using a microbial electrochemical cell (MEC) to promote methane content in biogas at 18, 28, and 37 °C. Although the maximum amount of biogas production was at 37 °C (25 cm3), biogas could be effectively produced at lower temperatures, i.e., 18 (13 cm3) and 28 °C (19 cm3), with an external 2 V power input. The biogas production of 13 cm3 obtained at 18 °C was ~65-fold higher than the biogas produced without an external power supply (0.2 cm3). This was further enhanced by 23% using carbon-nanotubes-treated (CNT) graphite electrodes. This suggests that the MEC can be operated at as low as 18 °C and still produce significant amounts of biogas. The share of CH4 in biogas produced in the controls was 30%, whereas the biogas produced in an MEC had 80% CH4. The MEC effectively reduced COD to 42%, whereas it consumed 98% of reducing sugars. Accordingly, it is a suitable method for waste/manure treatment. Molecular characterization using 16s rRNA sequencing confirmed the presence of methanogenic bacteria, viz., Serratia liquefaciens and Zoballella taiwanensis, in the inoculum used for the fermentation. Consistent with recent studies, we believe that electromethanogenesis will play a significant role in the production of value-added products and improve the management of waste by converting it to energy., Godkänd;2024;Nivå 0;2024-06-14 (joosat);Funder: Tribhuvan University under National Priority Area Research Project (TU-NPAR-077/78-ERG-07);Full text license: CC BY

Achieving optimal nutrient composition in locally sourced ruminant feeds is important, but can be challenging in resource-limited production systems. For example, improving the composition of available local feed resources is a key obstacle to efficiently mitigating enteric methane (CH4) emissions in ruminants. This study characterized the nutritional content and in vitro methane (CH4) yield of ruminant feedstuffs accessible in Ethiopia. A survey of 60 experienced farmers in two representative districts in Amhara region, Ethiopia, provided 33 feed samples, which were classified into four ruminant feed categories: Grasses (n=10); indigenous plants (trees, shrubs, herbaceous plants) (n=13); crop residues (n=5); and agro-industrial by-products (n=5). Nutritional composition was assessed by proximate and detergent methods. Methane yield (g CH4/kg feed dry matter (DM)) and total gas yield (L/kg DM) were evaluated using a fully automated in vitro gas production system. A colorimetric assay was conducted to measure condensed tannin content (CT, mg/g) in relevant feeds. Lower crude protein (CP) values were observed for the grass (mean 65.2 g/kg DM) and crop residues (mean 54.5 g/kg DM) categories. Agro-industrial by-products had the highest CP (mean 260 g/kg DM), while indigenous plants exhibited intermediate levels (163 g/kg DM). There was significant variation in CH4 yield (P<0.01) between grasses (12.4–24.7 g/kg DM) indigenous plants (1.8–19.3 g/kg DM), and agro-industrial by-products (8.1–26.9 g/kg DM). The indigenous plant Trifolium acaule gave the lowest in vitro CH4 yield (1.8 g/kg DM). A positive relationship was observed between in vitro dry matter digestibility (IVDMD), CH4, and total gas yield. Percentage of CH4 in total gas production varied with feed category (grasses 14.5–19.6%; indigenous plants 3.1–16.9%; crop residues 15.8–20.6%; agro-industrial by-products 12.8–18.7%), and within category, e.g., Trifolium acaule (3.1%), Acacia nilotica L. (7.1%), Ziziph

In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture., Funding: Kamprad Family Foundation [20200041], Värdeskapande av koldioxid från biogasproduktion

In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture., Funding: Kamprad Family Foundation [20200041], Värdeskapande av koldioxid från biogasproduktion

Samhället har ökade energibehov och krav på minskad miljöpåverkan, vilket gör biobränsle viktigt för hållbar energi. Biovärmeverks anläggningarna måste utvecklas för att bli mer miljövänliga och kunna ersätta fossila bränslen. De utsätts för höga termiska, kemiska och mekaniska påfrestningar, vilket innebär säkerhetsrisker. Således finns det lagar på trycksatta anordningar att fungera utan el genom att säkerhetsställa att överhettning undviks. Därför har biobränslepannor nödkylningssystem som förhindrar överhettning genom att hålla rörtemperaturen under den temperatur som pannan byggs för att klara, i denna studie är pannan dimensionerad för 140–150°C. Systemet, som består av stålrör med kallt vatten, aktiveras vid elavbrott eller temperaturökning, och luftflödet samt bränsletillförseln stoppas. Eftersom det är svårt att fastställa nödkylningseffekten överdimensioneras nödkylaren. Det är vanligt att nödkylaren tillverkas i diskreta storlekar och inte skräddarsys för varje panna. Vilket kan leda till onödig materialanvändning, kostnader och utsläpp. Studien, i samarbete med AKJ Energiteknik AB, syftar till att ge underlag för dimensionering av nödkylningssystemet för att minska kostnader och utsläpp. Målet är att skapa en dynamisk modell i Simulink och MATLAB och verifiera den med mätdata. Studien undersöker nödkylningssystemets funktion, kylbehov samt vatten- och materialåtgång, och utvärderar påverkan på kostnad och miljö genom CO2-ekvivalenter med förslag på åtgärder för systemets dimensioner. Den dynamiska modellen byggdes upp i Simulink och MATLAB Pannan konstruerades i zoner utifrån dimensionsförändringar i pannans rörkanaler där rökgasen flödade igenom samt förenklad beräkning för ugnens temperatur och rökgasflöde. Modellen verifierades mot mätdata från kapaciteter, temperaturer på rökgasen och vattnet samt granskades från företaget. Modellen kontrollerades utifrån känslighetsanalys, litteratur och värmeövergångstal och således skapades en trovärdig modell, Society has increasing energy demands and requirements for reduced environmental impact, making biofuel essential for sustainable energy. Facilities must be developed to become more environmentally friendly and capable of replacing fossil fuels. These facilities are subjected to high thermal, chemical, and mechanical stresses, which pose safety risks. Consequently, regulations exist for pressurized devices that operate without power by ensuring overheating is avoided. Therefore, biofuel boilers are equipped with emergency cooling systems to prevent overheating by maintaining the tube temperature below the design threshold, which in this study is 140–150°C. The system, composed of steel tubes containing cold water, activates in the event of a power outage or temperature increase, and airflow and fuel supply are halted. Since determining the emergency cooling effect is challenging, the emergency cooler is often oversized. It is common for emergency coolers to be manufactured in discrete sizes rather than customized for each boiler, which can lead to unnecessary material usage, costs, and emissions. This study, conducted in collaboration with AKJ Energiteknik AB, aims to provide insights for sizing emergency cooling systems to reduce costs and emissions. The objective is to develop a dynamic model in Simulink and MATLAB, validated with measurement data. The study investigates the emergency cooling system's function, cooling requirements, water and material consumption, and evaluates their impact on costs and the environment through CO2- equivalents, proposing dimensioning measures for the system. The dynamic model was constructed in Simulink and MATLAB. The boiler was segmented into zones based on changes in the boiler's pipe channels where flue gas flows, alongside simplified calculations for furnace temperature and flue gas flow. The model was validated against measurement data for capacities, flue gas and water temperatures, and reviewed by the company. Sensitiv

Bioenergi med avskiljning och lagring av koldioxid (BECCS) håller på att utvecklas till en viktig teknik för negativa utsläpp och planeras spela en avgörande roll för Sveriges mål om noll nettoutsläpp av koldioxid till 2045. Stora BECCS-anläggningar förväntas, till exempel den som planeras i Värtahamnen av Stockholm Exergi. Mindre punktkällor för koldioxidutsläpp, som avloppsreningsverket i Käppala, en biogasproducent, skulle också kunna bidra till negativa utsläpp genom BECCS, dvs. genom att fånga upp biogen koldioxid från anaerob jäsning. Ekonomiska faktorer begränsar dock implementeringen av hela BECCS-värdekedjan i mindre skala. Genom att använda en närliggande större BECCS-anläggning kan dessa kostnadsbarriärer övervinnas genom att skapa nav för BECCS och utnyttja synergier. I detta arbete undersöks de tekniska och ekonomiska utmaningarna med att integrera en CO2-ström från Käppala WWTP med Stockholm Exergis anläggning. Olika scenarier för CO2-integrering identifierades, med beaktande av flera faktorer, inklusive CO2-koncentration och renhetsbegränsningar för kondensering, kortdistanstransport och affärsmodell bakom biogasproducenten. Käppala reningsverk släpper för närvarande ut biogen CO2 i form av en CO2/luftblandning till atmosfären. Detta arbete visade att CO2 kan tas emot av Stockholm Exergi i form av en CO2/luftblandning, CO2-gas eller kondenserad CO2. Käppala reningsverk skulle antingen kunna behålla sin nuvarande vattenreningsprocess, som ger CO2/luftblandningen, eller modernisera sin biogasuppgraderingsprocess för att producera koncentrerad CO2. Vidare konstaterades att en rörledning är det mest ekonomiska alternativet för kortdistanstransport av CO2, antingen i en blandning eller i koncentrerad form, men långa ledtider kräver långsiktig planering. Om transporten istället sker med lastbilar krävs en ombyggnad och ett förvätskningssteg vid Käppalaverket. En litteraturgenomgång av tillgängliga tekniker för Käppala reningsverk identifierade en membran, Bio-energy with carbon capture and storage (BECCS) is emerging as a major negative emission technology and is scheduled to play a crucial role to Sweden’s net-zero goal by 2045. Large BECCS facilities are anticipated, such as the one planned in Värtahamnen by Stockholm Exergi. Smaller CO2 point sources like Käppala wastewater treatment plant (WWTP), a biogas producer, could also contribute to negative emissions through BECCS, i.e., by capturing the biogenic CO2 from anaerobic fermentation. However, economic constraints limit the implementation of the entire BECCS value chain on a smaller scale. Utilizing a nearby larger BECCS facility can help overcome these cost barriers by creating hubs for BECCS, leveraging synergies. This work explores the technical and economic challenges of integrating a CO2 stream from Käppala WWTP with Stockholm Exergi’s facility. Various scenarios for CO2 integration were identified, considering multiple factors, including CO2 concentration and purity constraints for liquefaction, short-distance transport, and business model behind the biogas producer. Käppala WWTP currently releases biogenic CO2 in the form of a CO2/air mixture to the atmosphere. This work found that CO2 can be received by Stockholm Exergi in the form of a CO2/air mixture, CO2 gas, or liquefied CO2. Whereas Käppala WWTP could either keep their current water scrubbing process, yielding the CO2/air mixture, or perform a revamp of their biogas upgrading process to produce concentrated CO2. Moreover, it was found that a pipeline is the most economical option for short-distance transport of CO2, either in a mixture or concentrated form, but long lead times make necessary long-term planning. If instead transport is carried out by trucks, a revamp and a liquefaction stage at Käppala WWTP are necessary. A literature review on the available technologies targeted at Käppala WWTP identified a membrane process as the most appropriate technology for a revamp of the biogas upgrading

The growing need for climate mitigation solutions has contributed so thatbiochar has gained significant interest. Primary for its ability as a carbon sinkbut there is also a growing interest due to several other aspects within industriese.g. substitution effects, increased resource efficiency, an enabler forindustrial symbiosis, and its beneficial properties when put in soil that can increasegrowth. Previous studies of biochar have been dominant within the environmentalperspective of biochar, analyzing detailed characteristics of its propertiesand carbon sink potential. Some studies have a holistic perspective reflectingon countries specific energy mix and the different benefits of producingbiochar. However, previous studies are far too few to determine the value-chainof biochar. Hence previous studies have knowledge gaps within the holistic lifecycle approach from a provider or customer perspective of biochar, not reflectingon demand for quality requirements in different utilization areas and markets.The need for validation of the environmental and the economic performanceof biochar has to be established, and the economic perspective of biochar hasmajor knowledge gaps since previous studies are scarce. The study aims to establish the value-chain of biochar by evaluating theenvironmental, economic, and social perspectives through life cycle thinking.The core of the study is to distinguish value, which first has to reflect thebiochar quality requirements from providers and customers, captured throughinterviews and literature research. The quality requirements enable a goal forproducing biochar and determine what processes and biomass are needed fordifferent markets. This is evaluated through a case development which considersthe different quality requirements. Life cycle assessment (LCA) with acradle-to-grave perspective and life cycle costing (LCC) with a cradle-to-gatewere then used to distinguish biochar´s environmental and economic performance. The interviews and

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for fu

First experiments with biogenic residues and a plastic-rich rejects and woody biomass blend were conducted in an advanced 1 MW dual fluidized bed steam gasification demonstration plant at the Syngas Platform Vienna. Wood chips, bark, forest residues, and the plastic-rich rejects and woody biomass blend were tested and the tar composition was analyzed upstream and downstream of the upper gasification reactor, which is designed as a high-temperature column with countercurrent flow of catalytic material. Each feedstock was gasified with olivine as bed material in demonstration scale and is compared to the gasification of softwood pellets with olivine and limestone in pilot scale. A reduction in tar content was observed after countercurrent column for all feedstocks. However, a shift in tar species occurred. While styrene, phenol, and 1H-indene were predominant upstream, naphthalene and polycyclic aromatic hydrocarbons (PAHs) were the prevailing tar species downstream the countercurrent column. Hence, an increase of i.e. anthracene, fluoranthene, and pyrene from the upstream concentration was observed. For pyrene, up to twice the initial concentration was measured. This recombination to PAHs was observed for all feedstocks in demonstration- and pilot-scale. The only exception occurred with limestone as bed material, characterized by a higher catalytic activity in comparison to the typically used olivine. In the perspective of the integrated product gas cleaning, tar with higher temperature of condensation are separated more efficiently in the installed scrubbing unit. Hence, the recombination facilitates an overall decline of tar content after the gas cleaning.

This study aimed to investigate the potential of converting bio-based residues from industrial production of mushrooms and tomatoes into more valuable chemicals with antifungal properties using hydrothermal liquefaction (HTL). Liquid fractions were obtained from HTL of spent substrate of Agaricus bisporus (Lange) Imbach and Pleurotus ostreatus (jacq.) P. kumm., recomposted Agaricus bisporus spent substrate, and tomato residues. The quantitative 1H NMR spectroscopy analysis revealed that the HTL liquids of all residues contained antifungal constituents like phenols and organic acids. The HTL liquids at dilutions of 10 % were able to inhibit the fungi by over 80 %. Interestingly, the fungus P. ostreatus showed tolerance to these constituents as its growth was promoted at the lowest concentration of all the HTL liquids. The HTL liquids had lower ecotoxicity than the commercial wood preservative. These results suggest that the tested residues could be a promising source of preservative chemical constituents for the wood industry.

Waste management in the northern latitudes is often more challenging than in the more central regions. Under the Arctic climate conditions with large distances between settlements and to the recycling facilities, and relatively smaller markets and volume of produced waste, there are special needs for developing new innovative solutions for waste management. WANO focuses on cross-border business and innovation cooperation in the field of waste management, including municipal and industrial waste, in the regions of Troms, Finnmark and Nordland (Norway), Lapland and North Ostrobothnia (Finland) and Norrbotten (Sweden). The project identifies key actors, technologies, innovation trends, and cross-border collaboration possibilities in the Arctic waste sector. Among the lessons learned so far which are highlighted in this policy brief are that waste management in Norway has already taken important steps to promote innovation and cooperation but that there is a demand for additional knowledge-based expertise among the waste management actors in north Norway. Cross-border initiatives are welcomed in north Norway by the actors. The big hindrance seems to be “know-who”: the Norwegian actors need more information about the actors across the border in north Finland and north Sweden.

The depletion of finite fossil fuel reserves and the severe environmental degradation resulting from human activities have compelled the expeditious development and application of sustainable waste to energy technologies. To encapsulate energy and environment in sustainability paradigm, bio waste based energy production is need to be forged in organic bio refinery setup. According to world bioenergy association, biomass can cover 50 % of the primary energy demand of the world. Therefore, the present study focuses on reforming the energy mix for a clean energy generation, where, sample composition of cotton stalk was acidified in dilute (5% wt.) hydrochloric acid (HCL) for analyzing material burnout patterns in biomass conversion systems utilized in organic bio refinery sector. Advanced thermochemical burning technique, which includes pyrolysis and combustion was applied at four different leaching times from 0 to 180 min under nitrogen environment from 0 degrees C to 500 degrees C and air from 500 degrees C to 900 degrees C, respectively. Different analyses including proximate, ultimate, gross calorific value (GCV), thermos-gravimetric, kinetic, XRD, FTIR, SEM-EDS were used for analyzing the degradation of demineralized cotton stalk at different treatment rates. Proximate study demonstrated that cotton stalk leaching for 180 min has efficiently infused HCL, leading in a significant increase in fixed carbon and higher heating value of 20.23 % and 12.48%, respectively, as well as a reduction in carbon footprint of around 54.80%. The findings of proximate was validated by GCV analysis and CHNS analysis as value of carbon and hydrogen has shown increasing behavior with the time delay in demineralization Thermo-gravimetric and derivative thermo-gravimetric data analyses shows an increasing trend of conversion efficiency, with the maximum increase of 98 % reported for sample 3H. TT.DEM. XRD characterization has reported 23 degrees to 25 degrees angle for all the observed p

The use of green heterogeneous catalysts that are obtained from waste agricultural biomass can make the production of biodiesel more economical. In this research, three solid base heterogeneous catalysts (Catalyst A, B, and C) were synthesized from kola nut pod husks, and the synergistic effects of the elemental composition on catalytic activities for biodiesel production were studied. The results revealed a high surface area of Catalysts A, B, and C at 419.90 m2/g, 430.54 m2/g, and 432.57 m2/g, respectively. Their corresponding pore diameters are 3.53 nm, 3.48 nm, and 3.32 nm, showing that the catalysts are mesoporous in nature. The X-ray Fluorescence (XRF) results revealed the presence of a variety of alkaline earth metals and their corresponding metal oxides in substantial amounts. Catalyst A was produced with the highest concentration of calcium at 40.84 wt.% and calcium oxide at 68.02 mole%. The substantial concentration of other elements, such as potassium, magnesium, and aluminum, and their corresponding metal oxides are the proof of high catalytic activity of the produced green catalysts. The high CaO contents of all three produced catalysts and their high surface areas indicate their strong potential for good catalytic activities applied to the synthesis of biodiesel.

The study evaluated removal of industrial CO2 from cement flue gas using algal cultivation. Local polycultures were grown in an up-scaled outdoor photobioreactor over 5 years in northern Europe. Algal biomass was harvested 2–3 times per week and the closed panel system was re-filled with seawater amended with nutrients. Flue gas was fed to the photobioreactor circulatory system in one direction or re-circulated. Removal efficiency of CO2 averaged 9 % in non-recirculation and 17 % in re-circulation modes and reached 20–60 % under best cultivation conditions. Recovery of carbon into algal biomass reached up to 10 g m2d−1 in non-recirculation mode. Biomass performance was explained by circulation mode and shift of polyculture traits. Stability of biomass quality was shown over seasons, with higher relative content of protein in autumn. Toxic elements in biomass were below legal thresholds for upcycling. The study shows feasibility of algal solutions for conversion of waste, applied in temperate climate. © 2023 The Authors

Scarcity in fossil fuel reserves and their environmental impacts has forced the world towards the production of clean and environment-friendly fuels called biofuels. This review focuses on the importance of different machine learning models and optimization techniques to simulate and optimize process conditions, yield and parameters in the fermentation of cellulosic biomass from fifty recent studies. The superiority of ML models, especially ANN dominance in 70 % of studies with highest coefficient of regression over conventional techniques in the production of bioethanol and biohydrogen is comprehensively reviewed. Research gaps and studies directed toward the usage of most optimum ML models in future are directed after the sensitivity analysis with 5 % variation that suggest the stability of ML models. It is intended to spur further investigation into the development and use of ML models combined with optimization methods and CFD in the fermentation process to produce bioethanol and biohydrogen.

This study aimed to investigate the potential of converting bio-based residues from industrial production of mushrooms and tomatoes into more valuable chemicals with antifungal properties using hydrothermal liquefaction (HTL). Liquid fractions were obtained from HTL of spent substrate of Agaricus bisporus (Lange) Imbach and Pleurotus ostreatus (jacq.) P. kumm., recomposted Agaricus bisporus spent substrate, and tomato residues. The quantitative 1H NMR spectroscopy analysis revealed that the HTL liquids of all residues contained antifungal constituents like phenols and organic acids. The HTL liquids at dilutions of 10 % were able to inhibit the fungi by over 80 %. Interestingly, the fungus P. ostreatus showed tolerance to these constituents as its growth was promoted at the lowest concentration of all the HTL liquids. The HTL liquids had lower ecotoxicity than the commercial wood preservative. These results suggest that the tested residues could be a promising source of preservative chemical constituents for the wood industry.

Waste management in the northern latitudes is often more challenging than in the more central regions. Under the Arctic climate conditions with large distances between settlements and to the recycling facilities, and relatively smaller markets and volume of produced waste, there are special needs for developing new innovative solutions for waste management. WANO focuses on cross-border business and innovation cooperation in the field of waste management, including municipal and industrial waste, in the regions of Troms, Finnmark and Nordland (Norway), Lapland and North Ostrobothnia (Finland) and Norrbotten (Sweden). The project identifies key actors, technologies, innovation trends, and cross-border collaboration possibilities in the Arctic waste sector. Among the lessons learned so far which are highlighted in this policy brief are that waste management in Norway has already taken important steps to promote innovation and cooperation but that there is a demand for additional knowledge-based expertise among the waste management actors in north Norway. Cross-border initiatives are welcomed in north Norway by the actors. The big hindrance seems to be “know-who”: the Norwegian actors need more information about the actors across the border in north Finland and north Sweden.

This study aimed to investigate the potential of converting bio-based residues from industrial production of mushrooms and tomatoes into more valuable chemicals with antifungal properties using hydrothermal liquefaction (HTL). Liquid fractions were obtained from HTL of spent substrate of Agaricus bisporus (Lange) Imbach and Pleurotus ostreatus (jacq.) P. kumm., recomposted Agaricus bisporus spent substrate, and tomato residues. The quantitative 1H NMR spectroscopy analysis revealed that the HTL liquids of all residues contained antifungal constituents like phenols and organic acids. The HTL liquids at dilutions of 10 % were able to inhibit the fungi by over 80 %. Interestingly, the fungus P. ostreatus showed tolerance to these constituents as its growth was promoted at the lowest concentration of all the HTL liquids. The HTL liquids had lower ecotoxicity than the commercial wood preservative. These results suggest that the tested residues could be a promising source of preservative chemical constituents for the wood industry.

In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture., Funding: Kamprad Family Foundation [20200041], Värdeskapande av koldioxid från biogasproduktion

First experiments with biogenic residues and a plastic-rich rejects and woody biomass blend were conducted in an advanced 1 MW dual fluidized bed steam gasification demonstration plant at the Syngas Platform Vienna. Wood chips, bark, forest residues, and the plastic-rich rejects and woody biomass blend were tested and the tar composition was analyzed upstream and downstream of the upper gasification reactor, which is designed as a high-temperature column with countercurrent flow of catalytic material. Each feedstock was gasified with olivine as bed material in demonstration scale and is compared to the gasification of softwood pellets with olivine and limestone in pilot scale. A reduction in tar content was observed after countercurrent column for all feedstocks. However, a shift in tar species occurred. While styrene, phenol, and 1H-indene were predominant upstream, naphthalene and polycyclic aromatic hydrocarbons (PAHs) were the prevailing tar species downstream the countercurrent column. Hence, an increase of i.e. anthracene, fluoranthene, and pyrene from the upstream concentration was observed. For pyrene, up to twice the initial concentration was measured. This recombination to PAHs was observed for all feedstocks in demonstration- and pilot-scale. The only exception occurred with limestone as bed material, characterized by a higher catalytic activity in comparison to the typically used olivine. In the perspective of the integrated product gas cleaning, tar with higher temperature of condensation are separated more efficiently in the installed scrubbing unit. Hence, the recombination facilitates an overall decline of tar content after the gas cleaning.