ARTICLE | doi:10.20944/preprints202306.0383.v1
Subject: Environmental And Earth Sciences, Other Keywords: anaerobic digestion; hydrolytic bacteria; biogas additives; evogen biogas additive; supplements
Online: 6 June 2023 (05:32:29 CEST)
Biogas production from organic waste is a promising renewable energy source, but achieving optimal production and digester stability can be challenging. This study investigated the impact of the Evogen microbial additive on biogas production and digester quality through microbial abundance and physicochemical parameter analysis. Two biogas plants, BG01 and BG02, were examined using 16S rRNA profiling to assess microbial abundance. Simultaneously, physicochemical parameters, including FOS/TAC ratio, total solids, volatile solids, biogas production, and VFA profile, were measured to evaluate digester performance. Results revealed distinct microbial community shifts in Evogen-treated digesters. Increased abundance of methanogenic archaea and hydrolytic bacteria indicated improved anaerobic digestion. Evogen supplementation also positively affected digester performance, with higher FOS/TAC ratios indicating enhanced acidification and methanogenesis. Reductions in total solids and volatile solids demonstrated improved organic matter degradation. Significantly higher biogas production was observed in Evogen-treated digesters, highlighting its potential as a microbial additive. Furthermore, VFA profiling demonstrated improved process stability and reduced substrate inhibition in Evogen-treated digesters. In summary, Evogen microbial additive positively influenced microbial dynamics, improving biogas production and digester quality. These findings contribute to optimizing biogas production systems and understanding the complex microbial interactions within anaerobic digesters.
REVIEW | doi:10.20944/preprints202308.0397.v1
Subject: Engineering, Energy And Fuel Technology Keywords: biodiesel; glycerol; biogas; biohydrogen; bioethanol
Online: 4 August 2023 (10:46:03 CEST)
Biodiesel is seen as a successor to diesel of petrochemical origin, as it can be used in cycle engines and stationary engines, and be obtained from renewable raw materials. Currently, the biodiesel production process on an industrial scale is mostly carried out through the transesterification reaction, also forming glycerol as a product. Pure glycerol is used in the pharmaceutical, cosmetic, cleaning, food and other industries. Even presenting numerous applications, studies indicate that there is a saturation of glycerol in the market which is directly related to the production of biodiesel. This increase causes a commercial devaluation of pure glycerol; making the separation and purification processes unfeasible from an economic point of view. Despite the economic unfeasibility of the aforementioned processes, they continue to be carried out due to environmental issues. Faced with the problem presented, this work aims at a bibliographical review of works that aimed to use glycerol as a raw material for the production process of biofuels, these processes being carried out mostly via fermentation.
COMMUNICATION | doi:10.20944/preprints202205.0278.v1
Subject: Engineering, Energy And Fuel Technology Keywords: sulfur; biogas; biochar; methane fermentation
Online: 20 May 2022 (12:19:17 CEST)
Methane fermentation of organic waste is one way to minimize organic waste, which accounts for 77% of the global municipal waste stream. The use of biowaste treatment technologies helps to improve the energy independence of the regions. Improving the efficiency of the methane fermentation process by using additives from waste may be an attractive alternative to the original technology. The use of biochar as an additive for methane fermentation has been shown to increase the production potential of biogas. The reasons for the improvement in efficiency are complex among others, it is assumed that the specific surface area of biochar may increase the population of anaerobic organisms. Up to date, there are many researches on the effect of biochar additions on methane fermentation, but there is no research on the effect of sulfur-biochar composite. The composite product in the form of a mixture of biochar and molten sulfur is an interesting area of research. In this experiment additions of the sulfur-biochar composite were tested to improve the fermentation process. The composite consisted of 40% biochar and 60% of sulfur and was added to the process. As results the addition of 1% of the composite increased the biogas potential by 4%.
ARTICLE | doi:10.20944/preprints202112.0059.v1
Subject: Engineering, Chemical Engineering Keywords: Methane fermentation; biogas; biomethane; biochar; pyrolysis; hydrothermal carbonization; biochemical methane potential; biogas production kinetics
Online: 6 December 2021 (11:16:52 CET)
The proof-of-the-concept of application of low-temperature food waste biochars for the anaerobic digestion (AD) of food waste (the same substrate) was tested. The concept assumes that residual heat from biogas utilization may be reused for biochar production. Four low-temperature biochars produced under two pyrolytic temperatures 300 °C and 400 °C and under atmospheric and 15 bars pressure with 60 minutes retention time were used. Additionally, the biochar produced during hydrothermal carbonization (HTC) was tested. The work studied the effect of a low biochar dose (0.05 gBC x gTSsubstrate-1, or 0.65 gBC x L-1) on AD batch reactors’ performance. The biochemical methane potential test took 21 days and the process kinetics using the first-order model were determined. The results showed that biochars obtained under 400°C with atmospheric pressure and under HTC conditions improve methane yield by 3.6%. It has been revealed that thermochemical pressure influences the electrical conductivity of biochars. The biomethane was produced with a rate (k) of 0.24 d-1, and the most effective biochars increased the biodegradability of FW to 81% in comparison to variants without biochars (75%).
ARTICLE | doi:10.20944/preprints202306.0589.v1
Subject: Environmental And Earth Sciences, Other Keywords: activated carbon; hydrogen sulfide; biogas; physical adsorption; micropores; biogas; solid fibrous digestate; carbon dioxide; mesopores
Online: 8 June 2023 (04:31:16 CEST)
The goal of this work is to develop a sustainable value chain of carbonaceous adsorbents that can be produced from the solid fibrous digestate (SFD) of biogas plants and further applied in integrated desulphurisation-upgrading (CO2/CH4 separation) processes of biogas to yield high purity biomethane. On this purpose, physical and chemical activation of the SFD derived biochar was optimised to afford micro-mesoporous activated carbons (ACs) of high BET surface area (590-2300 m2g−1) and enhanced pore volume (0.57-1.0 cm3g−1). Gas breakthrough experiments from fixed bed columns of the obtained ACs, using real biogas mixture as feedstock, unveiled that the physical and chemical activation conclude to different types of ACs which are sufficient for biogas upgrade and biogas desulphurisation respectively. Performing breakthrough experiments at three temperatures close to ambient it was possible to define the optimum conditions for enhanced H2S/CO2 separation. It was also concluded that the H2S adsorption capacity is significantly affected by restriction to gas diffusion. Hence, the best performance was obtained at 50 oC and the maximum observed in the H2S adsorption capacity vs the temperature is attributed to the counterbalance between adsorption and diffusion processes.
ARTICLE | doi:10.20944/preprints202107.0586.v1
Online: 26 July 2021 (14:49:51 CEST)
Potential of co-digestion mixing thickened secondary sludge (TS) from extended aeration wastewater treatment plant and locally available substrates (whey, grease and septage) has been studied using three steps. The first step was a batch test to determine biological methane potential (BMP) of different mixtures of the three co-substrates with TS. The second step has been carried out with lab-scale reactors (20 L) simulating anaerobic continuous stirred tank reactors fed by three mixtures of co-substrates determined according to previous step results. Modelling using ADM1 as a mechanistic model was applied in the third step to help understanding the co-digestion process. According to BMP step, septage used as co-substrate has a negative effect on performance and addition of 10 to 30% grease or 10% whey would lead to a higher production of biogas and with an increase of the methane content. The results from the reactor showed less evi-dence of the positive effects observed with the BMP assay. Protein and lipid fractions of particu-late biodegradable COD are important variables for digester stability and methane production as predicted by modelling. Results of simulations with ADM1 model adapted to co-digestion confirmed that this model is a powerful tool to optimize the process of biogas production.
ARTICLE | doi:10.20944/preprints202001.0127.v1
Subject: Business, Economics And Management, Business And Management Keywords: biogas; Brazilian agribusiness; business model; energy
Online: 12 January 2020 (16:20:18 CET)
The present article discusses the institutional model adopted in Brazil regarding energy production through biomass. The theoretical-empirical method is used to conclude that the model's difficulties can be overcome by adopting a network of contracts capable of subjecting renewable energy generation to an energy compensation model.
Subject: Engineering, Energy And Fuel Technology Keywords: biogas; chemical kinetics; anaerobic digestion; modelling
Online: 1 November 2019 (11:18:40 CET)
The kinetics of biogas production from biomass depends on several factors such as: carbon to nitrogen ratio (C/N), reactor temperature (T), and retention time (RT). The purpose of this study was to obtain a new model for predicting biogas production. Spent Mushroom Compost (SMC) was used to produce biogas in a batch type reactor. The experiments were carried out with different C/N ratios (12.1, 20, 30 and 40) and in both mesophilic (35°C) and thermophilic (55°C) temperatures. The results showed that the Maximum biogas production at 35°C, C/N=20 was equal to 41.9 mL/gVS and 55°C, C/N=30 was equal to 51.6 mL/gVS. By using experimental data, a new kinetic model was proposed to predict biogas production. Comparing the values of the results indicate that the total values of RMSE for Logistics, Gampartz and new kinetic models was 0.1906, 0.1830 and 0.1617, respectively. Therefore, the process of anaerobic digestion of biomass can be assumed to be just a chemical reaction, and the new kinetic model is an appropriate alternative to microbial growth models.
ARTICLE | doi:10.20944/preprints202309.0661.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: biogas; cattle manure; energy potential; macroalgae; methane
Online: 11 September 2023 (11:19:41 CEST)
The decline of fossil fuels, the increase of greenhouse gases and the global demand for energy are driving the search for alternative energy sources. Anaerobic digestion is a promising technology because it can convert organic biomass into biogas. As the climate warms, there is an increase in biomass of plant origin in water bodies, and ecosystems are unable to clean themselves. This work aims to show that macroalgae and aquatic plants can be an excellent raw material for biogas production. By mixing them with co-substrates such as cattle manure, higher biogas and methane yields can be obtained. When Cladophora glomerata and Zostera marina macroalgae are mixed with cattle manure, the biogas yield is up to 458.8 mL/gVS and 397.9 mL/gVS, respectively. Methane concentration remained high and reached 62.4%–64.1%. The obtained research results show the high energy value of biogas and the energy potential of biomass. Macroalgae increased the energy potential of biogas to 22.9 MJ/m3, and the energy potential of biomass reached 2.40 MJ/Kg. Due to its high energy value, biogas produced from the considered substrates can be an excellent alter-native to fossil fuels. Integrating aquatic macroalgae into anaerobic digestion is a promising approach for a waste-free marine and freshwater system.
REVIEW | doi:10.20944/preprints202201.0026.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Anaerobic digestion; iron additives; biogas; catalyst; bioenergy
Online: 5 January 2022 (10:23:53 CET)
The world is facing a serious energy crisis and environmental pollution problems due to a sharp increase in the world population. Bioenergy is an eminent solution to these problems. Anaerobic digestion is a green energy technology used worldwide for the conversion of organic waste to biogas. It is reported that organic wastes are hard to digest and need some technical improvement in the anaerobic digestion process to improve biogas yield. Iron-based additives, due to their electron acceptance and donation capabilities, have been emphasized as being exceptional in improving anaerobic digestion process efficiency amongst all other enhancement options. This study reviews the major available types of iron-based additives, their characteristics, and their preparation methods. The preferred iron-based additive that has a significant effect on the enhancement of biogas yield is also discussed. The use of iron-based additives in the anaerobic digestion process with varying dosages and their impact on the biogas generation rate is also being studied. Substrates, operating parameters, and types of anaerobic digesters used in recent studies while researching the effects of iron-based additives are also part of this review. Lastly, this study also confirms that iron-based additives have a significant effect on the reduction rate of the volatile suspended solids, methane content, biogas yield, and volatile fatty acids.
ARTICLE | doi:10.20944/preprints201907.0259.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Biogas; Agricultural Wastes; Maize Silage; Gas Production
Online: 23 July 2019 (11:40:15 CEST)
The aim of the study was to examine the biogas and methane yield of maize silage, a wastes in agricultural point of view and compare it to the biogas productivity of commonly used mixture of maize silage and mixed fodder with water. The experimental study was carried out into 2 parts. Firstly, the batch experiment was conducted in Mesophilic conditions (35°C), at five different hydraulic retention times (HRT): 6 DAT, 11 DAT 20 DAT 29 DAT and 41 DAT. The results revealed that maize silage was generated the highest biogas yield of 537 mL /241 mL at the HRT of 6days /41 days. Mixed fodder produced the highest biogas yield of 421 mL at the HRT of 6th days and the lowest one was 252 mL at the HRT of 20th days. Finally, the methane, carbon dioxide and hydrogen sulphide of biogas produced from maize silage and mixed fodder were analyzed using a gas chromatography. The results shown that biogas from maize silage precedes the gas less than the mixed fodder. In the field level experiment proved that from mixed fodder produced gas which would be enough for 7 member’s family used 3 months for the purpose of their cooking.
ARTICLE | doi:10.20944/preprints201808.0541.v1
Subject: Engineering, Chemical Engineering Keywords: anaerobic process; biogas; coffee wastewater; digester construction
Online: 31 August 2018 (05:47:42 CEST)
Wet coffee processing methods will produce wastewater containing organic matter. The high content of organic matter can be utilized as biogas through the anaerobic process. Anaerobic digesters construction can affect removal process of wastewater pollution and biogas quantity. The purpose of this study is to determine the effect of digester construction between conventional digester, CSTR and UASB producing biogas from coffee wastewater. The conventional digester worked without temperature control system as control, a UASB digester, and CSTR digester worked with temperature control system. Biomass volume was about 5 L with 35 days incubation time. Temperature and pH for UASB and CSTR were set within the range 30 – 35oC and pH 6.0 – 8.0. Based on the feeding variations, UASB has a stable performance with 83.57 ml/day of average biogas production. It has also highest remediation efficiency of COD, BOD and C/N with 85.00±0.34 %, 84.40%± 5.66 and 97.78± 0.57.
REVIEW | doi:10.20944/preprints202210.0149.v1
Subject: Biology And Life Sciences, Biology And Biotechnology Keywords: Biogas; anaerobic digestion; gene mutation; bioengineering; lignocellulose biomass
Online: 11 October 2022 (10:33:29 CEST)
The demand for an efficient utilization of abundant biomasses is growing for the production of biogas and valuable bioproducts. Lignocellulose biomass is a cheap and most abundant carbon source for the production of biofuels such as bioethanol, biobutanediol, and other bio-based chemicals. Due to its complex heterogeneity, its hydrolysis gives rise to a mixture of sugars, mainly glucose; a hexose and xylose; a pentose. Glucose is the most abundant carbohydrate monomer. Most microorganisms have evolved the ability to utilize it preferably due to carbon catabolite repression regulatory mechanism at the detriment of the pentoses. Some microbes even lack the ability to utilize them. This has led to the sequential use of these sugars and accompanying reduced productivity due to inadequate utilization of the pentoses. Also, this sequential utilization of the sugars takes time and makes the overall processes economically costly. Since lignocellulose hydrolysates comprise both hexoses and pentoses, the catabolism of these sugar mixtures to biofuels will require an efficient microbial strain capable of simultaneous utilization. The use of CCR negative mutants can achieve this. CCR negative mutants simultaneously utilize pentoses and hexoses, ensuring an improved fermentation efficacy and greater productivity, thus, making the overall bioprocess economically feasible. This article reviewed several approaches employed in creating these mutant microorganisms. A brief insight on carbon catabolite repression and phosphostransferase system were made. It also highlighted the biogas production processes, factors affecting anaerobic digestion, lignocellulosic biomass structure, challenges with their use and solutions to overcoming the challenges.
REVIEW | doi:10.20944/preprints202110.0424.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Cassava peels; valorisation; thermal; thermo-chemical; biochemical; biogas
Online: 28 October 2021 (07:27:14 CEST)
The large-scale processing of Cassava (Manihot esculenta Crantz.) generates significant quantities of solid wastes annually. Cassava peels (CP) account for 5 wt.% - 30 wt.% of wastes from the processing of cassava tubers. The poor disposal and management of CP pose risks to human health, safety and the environment. Therefore, there is an urgent need to identify and examine low cost, socially acceptable and environmentally friendly strategies to mitigate the immediate and long terms disposal and management challenges. Lack of such measures results in the accumulation of CP wastes, which are currently buried, combusted, or dumped in open fields. Therefore, this paper reviewed the potential routes for the biochemical, thermochemical, and plasma valorisation of CP. The literature reviewed revealed that biochemical technologies such as anaerobic digestion (AD) and fermentation are the most widely utilised approaches currently adopted for CP valorisation. AD produces biogas (methane 50-72 vol. % and carbon dioxide 25-45 vol. %), whereas fermentation yields bioethanol. However, the numerous challenges such as substrate-induced inhibition, associated with the biochemical processes hamper microbial degradation, methane formation, and process efficiency. Furthermore, the processes generate secondary wastes or digestate/sludge, which requires additional processing before disposal. Therefore, innovative thermal, thermochemical, and plasma technologies were proposed to valorise CP into syngas, biofuels, bioenergy, biochemicals, and fertilizers, among others. However, the waste products of fermentation cannot be effectively utilised as bio-fertilizers, whereas bioethanol causes corrosion in engines. Overall, the biochemical, thermal, thermochemical and plasma technologies can effectively valorise CP for effective net energy generation.
Subject: Engineering, Automotive Engineering Keywords: biogas digestion; hydrogen sulfide; ferric oxide; waterworks sludge)
Online: 25 May 2021 (14:15:53 CEST)
Ferric oxide containing waterworks sludge can be used to reduce formation of hydrogen sulfide during anaerobic digestion. The ferric compound is reduced biochemically in the digester and forms insoluble pyrite in digester sludge. Often virgin ferric chloride is used to solve the hydrogen sulfide problem. Since 2013, Sydvatten AB has supplied a growing number of digestion plants in Sweden with ferric containing dewatered waterworks sludge from the drinking water treatment plant Ringsjöverket to limit the formation of hydrogen sulfide. At the waterworks, ferric chloride is added to enhance coagulation of organic matter from the source water. The sludge formed in this process is dewatered and landfilled, but also recycled in the biogas production in order to reduce the hydrogen sulfide concentration. In this study, the use of sludge, for hydrogen sulfide removal in digesters, was technically and economically evaluated from cases studies from 13 full-scale digesters in Sweden. Compared with use of fresh ferric chloride, the operational costs are reduced up to 50 % by using sludge. The quality of the sludge is high and its content on metals is low or very low, especially when compared with requirements from different certification standards on biosolid reuse applied in Sweden. An addition of waterworks sludge containing iron to a digester for removal of dissolved hydrogen sulfide is a technically and economic good alternative when producing biogas. It is also one step closer to a circular economy, when replacing use of virgin chemicals with the by-product waterworks sludge which saves energy, material and reduces the carbon foot-print of the waterworks.
REVIEW | doi:10.20944/preprints202301.0391.v2
Subject: Engineering, Energy And Fuel Technology Keywords: agrivoltaics; photovoltaics; biogas; renewable energy; agriculture; livestock; horticulture; aquaculture
Online: 16 March 2023 (04:13:23 CET)
Agrivoltaics (Agri-PV, AV) – the joint use of land for the production of agricultural products and energy – has recently been rapidly gaining popularity, as it can significantly increase income per unit of land area. In a broad sense, AV systems can include converters of not only solar, but also energy from any other local renewable source, including bioenergy. Current approach to AV represents an evolutionary development of agroecology and integrated PV power supply to the grid. That results in nearly doubled income per unit area. While AV could provide a basis for revolution in large-scale unmanned precision agriculture and smart farming which is impossible without on-site power supply, chemical fertilisation and pesticides reduction, and yield processing on-site. These approaches could change the logistics and the added value production chain in agriculture dramatically, and so, reduce its carbon footprint. Utilisation of decommissioned solar panels in AV could make the technology twice cheaper and postpone the need for bulk PV recycling. Unlike the mainstream discourse on the topic, this review feature is in focusing on the possibilities for AV to be stronger integrated into agriculture that could also help in relevant legal collisions (considered as neither rather than both components) resolution.
REVIEW | doi:10.20944/preprints202108.0463.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Power-to-X; Biomass; Biogas; renewable energy; energy storage
Online: 24 August 2021 (10:33:03 CEST)
This review reports the available technologies for the flexible utilization of biomass towards negative CO2 emissions and addresses the possibility to couple biogas production plants with the electrical grid converting excess electrical energy into storable chemical molecules. This changed mind-set towards biomass utilization can lead readily to the implementation of negative CO2 emission along the entire bioenergy supply chain without limiting the potential for Power-to-X applications. First, the technologies for direct conversion of waste and wood into gaseous energy carriers are screened, to highlight the potential for the production of renewable fuels. Second, the processes for the removal of CO2 from biogenic gas streams are analysed in terms of technological performance, cost and further potential for the CO2 recovered. These technologies are the key to pre-combustion CO2 capture and negative emissions. Third, the possibility of coupling biomass conversion and synthetic fuels production is explored, providing an overview on the technical maturity of the various energy storage processes. The flexible use of biomass can be an essential part of the future CO2-free energy systems, as it can directly provide energy carriers all around the year and also large quantities of climate-neutral carbon for the production of synthetic fuels with renewable energy. In turn, when no additional renewable electricity is available, the CO2 by-product from biofuel synthesis can be used for the negative emissions. This opens the way to an efficient strategy for the seasonal storage of electrical energy, realizing a carbon-neutral energy system coupled with the development of carbon-negative energy strategy.
ARTICLE | doi:10.20944/preprints202102.0142.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: Anaerobic digestion; circular economy; biogas; fish waste; anchovy; limonene
Online: 4 February 2021 (15:03:46 CET)
Anchovies are amid the largest fish catch worldwide. The anchovy fillet industry generates a huge amount of biowaste (e.g. fish heads, bones, tails) that can be used for the extraction of several potentially valuable bioproducts including omega-3 lipids. Following the extraction of valued fish oil rich in omega-3, vitamin D3 and zeaxanthin from anchovy fillet leftovers using biobased limonene in a fully circular process, the solid residue was used as starting substrate for the production of biogas by anaerobic digestion. The results first reported in this study demonstrate good potential energy recovery of the anchovy sludge of about 280 mLCH4∙gVS-1. Due to unbalanced C/N ratio typical of marine biowaste, co-digestion with a carbon rich substrate is recommended.
REVIEW | doi:10.20944/preprints201811.0441.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: biogas; renewable energy; anaerobic digestion; waste activated sludge; disintegration
Online: 19 November 2018 (09:57:56 CET)
Due to rapid urbanization, the quantity of wastewater treatment plants (WWTP) has increased, and with it the amount of waste generated by them. Sustainable management of this waste can lead to the creation of energy-rich biogas through the fermentation process. This review presents recent advances in the anaerobic digestion process resulting in greater biogas production. Disintegration techniques for enhancing waste activated sludge fermentation can be generally partitioned into biological, physical and chemical, each of which are covered in this review. These disintegration techniques were compared mainly in terms of their biogas yield. It was found that ultrasonic and microwave disintegration provides the highest biogas yield (>500%); however, they are also the most energy demanding (>10,000 kJ kg-1 total solids).
ARTICLE | doi:10.20944/preprints202311.0895.v1
Subject: Environmental And Earth Sciences, Sustainable Science And Technology Keywords: biogas plans; anaerobic digestion; feedstock sustainable energy; prospects and barriers
Online: 14 November 2023 (09:38:05 CET)
As the global demand for renewable energy continues to rise, biogas technology has emerged as a promising solution for sustainable energy generation. This review article presents the advantages of biogas technologies and extensively discusses the main principles of biogas production in the methane fermentation process. In this respect, the main parameters of the process, which require monitoring and are at the same time decisive for its course and efficiency are described, the principles of substrate selection are discussed and the necessity and advantages of the use of organic waste according to the model of a circular economy and the concept of sustainable development, are indicated. The part on biogas production is summarised with an explanation of the necessity to treat and purify biogas, taking into account the share of methane extracted. A special place in this paper is devoted to the design, construction, functioning and operation of biogas plants, based on both scientific and practical aspects. In conclusion of this chapter, the economic aspects and profitability of operating biogas plants are discussed, taking into account, in a theoretical balance sheet – in addition to investment and operating costs and the availability and cost of raw materials – the possibilities of producing and using electricity and heat, as well as environmental and social benefits. The article concludes with a discussion of opportunities and barriers to the development of biogas plants, pointing to: financial issues, access to feedstock, political regulations, public awareness and the geopolitical situation as key factors issues related to biogas plants – in different regions of the world.
ARTICLE | doi:10.20944/preprints202306.1755.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Biogas slurry; Drip; Nutrigation; Spinach; Phenology; Nutrient uptake; Microbial properties
Online: 26 June 2023 (07:06:06 CEST)
To achieve higher crop yields and maintain environmental conservation, it becomes imperative to adopt novel agricultural methods that improve both the quantity and quality of produce. The above study focused on investigating the effectiveness of integrated use of biogas slurry (BS) and inorganic nutrigation on spinach growth and nutrient uptake through drip irrigation. Under field conditions and using a split plot design, spinach was cultivated with seven different treatments: biogas slurry nutrigation (BSN) (T1), integrated inorganic + organic nutrigation: 40% Recommended dose of fertilizer (RDF) +BSN (T2), 60% RDF +BSN (T3), 80% RDF +BSN(T4), 100% RDF(T5), slurry broadcasting (SB) (T6), and control(T7). The results showed that spinach grown with T4 80% RDF +BSN exhibited optimum plant height and leaf count compared to spinach under other treatments and was at par with T5 100% RDF for crop parameters. T5 treated plants demonstrated the longest roots, followed by T4 treated plants. The biomass produced by T4 was at par with T5 in the first (T4= 4.60 tonha-1, T5 =4.67 tonha-1) and second harvesting(T4= 6.69 tonha-1, T5 =6.89 tonha-1).In terms of macronutrient content in spinach leaves, significant differences were found only for nitrogen (N),potassium (K), while the phosphorus contents were not significantly influenced. Incorporating biogas slurry into the soil modifies microbial enzyme activities, specifically dehydrogenase and phosphatase. Normally, alkaline phosphatase shows greater activity than acidic phosphatase, but the addition of biogas slurry equalized the enzymatic activity of both, establishing a harmonized enzymatic profile. Fertilizing spinach with integrated Biogas slurry nutrigation + inorganic nutrigation not only improves growth and development to a similar extent as inorganic fertilizer but also enhances the nutrient content of the spinach, contributes to environmental preservation, and reduces production costs.
REVIEW | doi:10.20944/preprints202008.0233.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: lignocellulosic substrate; pre-treatment; microalgae/cyanobacteria; biogas; problems; animal feed
Online: 10 August 2020 (03:46:14 CEST)
Modern day civilization is dependent on energy generation by fossil fuels. But the major drawback of using fossil fuels is environmental pollution. Microalgae are potential candidate for production of various products of interest, such as proteins, mini food, pigments and triglycerides that can be converted into biofuels. Lignocellulosic feedstocks are the most abundantly available raw material of plants that can serve as a promising feedstock for cultivating bacteria, fungi, yeasts and microalgae to produce biofuels and other value-added products. Owing to the abundant availability of these low/no cost substrates, can be utilized as feedstocks for cultivating microalgae to generate biogas/biodiesel. Likewise, there is much room to exploit defatted algal biomass to be used as animal/fish feed and oil producing/accumulating genes knowledge in future to produce high and good quality biodiesel and biogas.
ARTICLE | doi:10.20944/preprints202002.0266.v1
Subject: Chemistry And Materials Science, Chemical Engineering Keywords: deep eutectic solvents; absorption; biogas; dimethyl disulfide; green solvents; desulfurization
Online: 18 February 2020 (11:10:40 CET)
The paper presents a synthesis of deep eutectic solvents (DESs) based on choline chloride (ChCl) as hydrogen bond acceptor and phenol (Ph), glycol ethylene (EG), and levulinic acid (Lev) as hydrogen bond donors in 1:2 molar ratio. DESs were successfully used as absorption solvents for removal of dimethyl disulfide from (DMDS) from model biogas steam. Several parameters affecting the absorption capacity and absorption rate has been optimized including kind of DES, temperature, the volume of absorbent, model biogas flow rate, and initial concentration of DMDS. Furthermore, reusability and regeneration of DESs by means of adsorption and nitrogen barbotage followed by the mechanism of absorptive desulfurization by means of density functional theory (DFT) as well as FT-IR analysis were investigated. Experimental results indicate that the most promising DES for biogas purification is ChCl:Ph, due to high absorption capacity, relatively long absorption rate, and easy regeneration. The research on the absorption mechanism revealed that van der Waal interaction is the main driving force for DMDS removal from model biogas.
ARTICLE | doi:10.20944/preprints201905.0183.v1
Subject: Biology And Life Sciences, Biology And Biotechnology Keywords: Anaerobic digestion; biogas; green energy; municipal solid waste; organic waste
Online: 15 May 2019 (10:33:58 CEST)
Global waste generation keeps increasing over the year and requires innovative solutions to minimize their impacts on environmental quality and public health. Predicted 2.2 billion tonnes per year of global municipal waste generation in the year 2025 which 1.6 fold is higher than in 2012. Hence, a strategic plan must be ascertained to overcome the future challenges of MSW locally and globally. Universiti Putra Malaysia (UPM) coined an initiative to demonstrate a showcase pilot plant for green energy production from MSW. Therefore, the data was obtained from the survey and actual sampling within the UPM compound to estimate the MSW generated and it's potentially used for green energy production. It is estimated that 5.0 – 7.0 tonne per day of MSW generated which about 30 - 35% is an organic fraction. Upon separation, the organic fractions were digested into biogas through anaerobic. At the maximum conversion of organic fraction, about 775 kWh of electricity may able to generate from the waste. In this study, the complete biorefinery setup and utilize organic components from the MSW generated in UPM was proposed that the biogas subsequently will be used to produce green energy in the form of electricity or cooking fuel.
ARTICLE | doi:10.20944/preprints202309.1455.v1
Subject: Environmental And Earth Sciences, Waste Management And Disposal Keywords: calorific value; biomass conversion; biogas production; chemical energy; energy efficiency; cogeneration
Online: 21 September 2023 (07:26:41 CEST)
Using a wide range of organic substrates in the methane fermentation process enables efficient biogas production. Nonetheless, in many cases, the efficiency of electricity generation in biogas plant cogeneration systems is much lower than expected, close to the calorific value of the applied feedstock. This paper analyses energy conversion efficiency in a 1 MWel agricultural biogas plant fed with corn silage or vegetable waste and pig slurry as a feedstock dilution agent, depending on the season and availability. Biomass conversion studies were carried out for 12 months, during which substrate samples were taken once a month. The total primary energy in substrates was estimated in laboratory conditions by measuring the heat of combustion in a ballistic bomb calorimeter (17,760 MWh·year-1), and in the case of pig slurry, biochemical methane potential (BMP, (201.88±3.21 m3·Mg VS-1). Further, the substrates were analysed in terms of their chemical composition — from protein, sugar and fat content to mineral matter determination, among other things. The results obtained during the study were averaged. Based on such things as the amount of biogas produced at the plant, the amount of chemical (secondary) energy contained in methane as a product of biomass conversion (10,633 MWh·year-1) was calculated. Considering the results obtained from the analyses, as well as the calculated values of the relevant parameters, biomass conversion efficiency was determined as a ratio of chemical energy in methane to (primary) energy in substrates, which was 59.87%, as well as electricity production efficiency, as a ratio of electricity produced (4,913 MWh·year-1) to primary energy, with a 35% cogeneration system efficiency. Full energy conversion efficiency, related to electricity production, reached a low value of 27.66%. This article provides an insightful, unique analysis of energy conversion in an active biogas plant as an open thermodynamic system.
REVIEW | doi:10.20944/preprints202309.1329.v1
Subject: Engineering, Chemical Engineering Keywords: Biogas; Dye-containing wastewater; Resource recovery; Sludge; UASB reactors; Water reuse
Online: 20 September 2023 (03:27:04 CEST)
Dye-containing effluent generated in textile industries is polluting and complex wastewater. It should be managed adequately before the final destination. The up-flow anaerobic blanket (UASB) reactor application is an eco-friendly and cost-competitive treatment. The present study briefly reviews the UASB application for dye wastewater valorization. Bioenergy and clean water production potential during dye-containing wastewater treatment are emphasized to promote resource recovery in textile industries. Efficiencies of color and chemical oxygen demand of 50–97% and 60–90% are reported in bench-scale UASB studies. A biogas yield of 0.36–36.04 L d-1 in UASB, which treats dye-containing effluents, is documented. Bioenergy production and water reuse allow environmental and economic benefits. However, data on full-scale UASB treating dye wastewater are missing. Besides, studies on combined systems integrating membrane processes, such as ultrafiltration and nanofiltration, and pretreatment of wastewater and sludge for improvements in biogas production might realize the complete potential for resource recovery of UASB technology.
ARTICLE | doi:10.20944/preprints202008.0650.v1
Subject: Engineering, Energy And Fuel Technology Keywords: power to gas; CO2 methanation; Ni catalyst; biogas utilization; CO2 hydrogenation
Online: 30 August 2020 (10:34:53 CEST)
Biogas contains more than 40% CO2 that can be removed to produce high quality CH4. Recently, CH4 production from CO2 methanation has been reported in several studies. In this study, CO2 methanation of biogas was performed over a 20 wt% Ni-Mg-Al catalyst, and the effects of CO2 conversion rate and CH4 selectivity were investigated as a function of CH4, O2, H2O, and N2 compositions of the biogas. At a gas hourly space velocity (GHSV) of 30,000/h, the CO2 conversion rate was ~79.3% with a CH4 selectivity of 95%. In addition, the effects of the reaction temperature (200–450 °C), GHSV (21,000–50,000/h), and H2/CO2 molar ratio (3–5) on the CO2 conversion rate and CH4 selectivity over the 20 wt% Ni-Mg-Al catalyst were evaluated. The characteristics of the catalyst were analyzed using Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The catalyst was stable for approximately 200 h at a GHSV of 30,000/h and a reaction temperature of 350 °C. CO2 conversion and CH4 selectivity were maintained at 75% and 93%, respectively, and the catalyst was therefore concluded to exhibit stable activity.
ARTICLE | doi:10.20944/preprints202307.0237.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: Anaerobic co-codigestion; Biochemical methane potential; slaughterhouse waste; Kinetic model; biogas; methane
Online: 5 July 2023 (08:42:33 CEST)
The anaerobic digestion (AD) of rumen residues and wheat straw in different proportions of inoculum (66.67, 50, 33.33 %V/V) to substrate and their co-digestion potential have been exhaustively studied in this research. It explores variation of feedstock characteristics such as biodegradability and methane potential during AD and anaerobic co-digestion (ACoD) of rumen residues (RR) with wheat straw (WS), under mesophilic conditions. Comparative performance was made with a organic load rate of 18 gVS/L (with 2:1, 1:1 and 1:2 g/g VS of inoculum to substrate). Among different kinetic models studied (modified Gompertz model, transfer model and logistic function), the AD and ACoD of substrates showed better fit to Gompertz model (R2: 0.977–0.997) indicating variation in lag phase and methane production rate depending on the substrate characteristics. During AD, the methane yield improved as the inoculum ratio increased, however, there was no significant difference in ACoD yield from RR to WS for the inoculum to substrate ratios studied, due to the synergistic effect as a result. of greater biodegradability and optimal conditions (such as the C/N ratio). A comparison of methane generation means indicated that maximum methane production can be achieved by mixing rumen residue (75 %) and wheat straw (25 %) with a C/N ratio of (38.15).
ARTICLE | doi:10.20944/preprints202104.0594.v1
Subject: Engineering, Automotive Engineering Keywords: lignocellulosic biomass; wheat straw; anaerobic digestion; chemical pretreatment; ultrasound pretreatment; biogas enhancement.
Online: 22 April 2021 (09:10:33 CEST)
Biomass is an attractive energy source that can be used for production of heat, power, and transport fuels, and when produced and used on a sustainable basis, can make a large contribution to reducing greenhouse gas (GHG) emissions. Anaerobic digestion (AD) is a suitable technology for reducing organic matter and generating bioenergy in the form of biogas. This study investigates the factors allowing the optimization of the process of biogas production from the co-digestion of wheat straw (WS) and bovine manure. The statistical analysis of the experiments carried out show that ultrasonic processing plays a fundamental role by sonication density and solids concentration leading to improved characteristics of WS by reducing particle size and increasing concentration of soluble chemical oxygen demand. The higher the sonicating power used, the more the waste particles are disrupted. The optimality obtained under mesophilic conditions for WS pretreated with 4% w/w (weight by weight) H2O2 at temperature 36 °C under 10 minutes of ultrasonication at 25 kHz improves the methane yield by 64%.
REVIEW | doi:10.20944/preprints202009.0068.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Bio-energy; Artiﬁcial intelligence; Industry 4.0; Biodiesel; Biogas; Renewable energy; Supply Chain
Online: 3 September 2020 (09:32:40 CEST)
Machine learning (ML) is penetrating in all walks of life and is one of the major driving forces behind the fourth industrial revolution, typically known as Industry 4.0. This study reviews the state-of-the-art ML applications in the biofuels’ life cycle stages, i.e., soil, feedstock, production, consumption, and emissions. A keyword search is performed to retrieve relevant articles from the databases of the Web of Science and Google Scholar. ML applications in the soil stage were mostly based on the use of satellite images of land for estimation of biofuels yield or suitability analysis of agricultural land. In the second stage of the life cycle, assessment of rheological properties of the feedstocks and their effect on the quality of biofuels were dominant studies reported in the literature. The production stage included estimation and optimization of quality, quantity, and process conditions. The fuel consumption and emissions stage included analysis of engine performance and estimation of emissions temperature and composition, such as NOx, CO, and CO2. This study identiﬁed the following trends: dominant ML method, the stage of life cycle getting more usage of ML, the type of data used for the development of the ML-based models, and the stage-wise frequently used input and output variables. The ﬁndings of this article are beneﬁcial for academia and industry-related people involved in model development in different stages of biofuel’s life cycle.
REVIEW | doi:10.20944/preprints202009.0033.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Bio-energy; Artificial intelligence; Industry 4.0; Biodiesel; Biogas; Renewable energy; Supply Chain
Online: 2 September 2020 (07:56:48 CEST)
Machine learning (ML) is penetrating in all walks of life and is one of the major driving forces behind the fourth industrial revolution, typically known as Industry 4.0. The purpose of the present study is to review the state-of-the-art ML applications in the biofuels' life cycle stages, i.e., soil, feedstock, production, consumption, and emissions. A keyword search is performed to retrieve relevant articles from the databases of the Web of Science and Google Scholar. ML applications in the soil stage were mostly based on the use of satellite images of land for estimation of biofuels yield or suitability analysis of agricultural land. In the second stage of the life cycle, assessment of rheological properties of the feedstocks and their effect on the quality of biofuels were dominant studies reported in the literature. The production stage included estimation and optimization of quality, quantity, and process conditions. The fuel consumption and emissions stage included analysis of engine performance and estimation of emissions temperature and composition, such as NOx CO, and CO2. This study identified the following trends: dominant ML method, the stage of life cycle getting more usage of ML, the type of data used for the development of the ML-based models, and the stage-wise frequently used input and output variables. The findings of this article are beneficial for academia and industry-related people involved in model development in different stages of biofuel’s life cycle.
ARTICLE | doi:10.20944/preprints201812.0354.v1
Subject: Biology And Life Sciences, Animal Science, Veterinary Science And Zoology Keywords: biogas; black soldier fly; dairy cattle manure; digestate; solid-state anaerobic digestion
Online: 29 December 2018 (05:20:37 CET)
This study was conducted to evaluate the feasibility of applying a two-step biological treatment process, solid-state anaerobic digestion (SSAD) and black soldier fly larvae (BSFL) composting, for treating dairy cattle manure. Biogas from SSAD of dairy cattle manure, and the digestate of SSAD was fed to BSFL. In turn, BSFL can be fed to animals as a protein supplement. Adjustment of pH and 30% inoculation ratio (IR30) during SSAD produced the highest theoretical methane yield, 626.1±28.7 L CH4/kg VSdes, with an ultimate methane yield of 96.81±2.0 L CH4/kg VSload. For BSFL composting, the groups with a feeding rate of 75 and 100 mg/day/larvae had the highest body weight change, which was 969.6±28.4 and 984.1±177.6%, respectively. The combination process of SSAD and BSFL composting increases the incentive for dairy cattle manure treatment enabled higher waste removal efficiency, and produced more valuable products.
ARTICLE | doi:10.20944/preprints201806.0128.v1
Subject: Engineering, Chemical Engineering Keywords: biogas purification; coconut shells; biomass valorization; textural characterization; adsorption isotherms; breakthrough curves.
Online: 7 June 2018 (16:27:12 CEST)
Biomass is a widely distributed and renewable source of carbon. The main objective of this work is to produce an activated carbon from coconut shells with suitable characteristics to separate CO2 from biogas. The textural characterization of the adsorbent has been determined. Pure component adsorption isotherms of CO2 and CH4 at 30, 50 and 70 °C have been measured. Moreover, the performance of the produced activated carbon, as potential adsorbent for CO2 capture from a CO2/CH4 gas mixture has been evaluated under dynamic conditions in a purpose-built fixed-bed setup.
ARTICLE | doi:10.20944/preprints201803.0024.v1
Subject: Engineering, Energy And Fuel Technology Keywords: by-products; biogas; Biogasdoneright; citrus pulp; olive pomace; GIS; indicators; biomass availability
Online: 2 March 2018 (13:11:14 CET)
The necessity to investigate suitable alternatives to conventional fossil fuels has developed the interests in many renewable energy alternatives, especially biomass resources which are widely available and allow to reach both environmental and socio-economic improvements. Among the bioenergy solutions the anaerobic digestion technology makes it possible to produce biogas by reusing and valorising agricultural residues and by-products. In Southern Italy, to date, the development of biogas sector is still very limited, despite the importance of the agricultural sector, especially of citrus and olive cultivation. For this reason, in previous studies the availability of two by-products, i.e., citrus pulp and olive pomace, was analysed in order to choose the most suitable area for a sustainable development of new biogas plants according to the new Biogasdoneright concept. In this paper, after a resume of the multi-step methodology which allowed the computation of biogas production, it was demonstrated that 15.9 GWh-e electricity and 24.5 GWh-e heat per year could be generate by reusing only these two kind of by-products, and could satisfy approximate 17% of the total electricity demand of the agricultural sector (90.2 GWh-e/year) in Catania.
ARTICLE | doi:10.20944/preprints201809.0087.v1
Subject: Engineering, Civil Engineering Keywords: solid waste management; environmental pollution; agricultural waste; cassava waste; biogas generation; sustainable technology
Online: 5 September 2018 (05:32:59 CEST)
Agricultural product like cassava produces huge amounts of waste when processed to consumable goods. The waste generated is generally considered to contribute largely to environmental pollution. This study therefore investigates the waste management practice that is adopted by cassava processors in Ogun State, Nigeria. Five (5) Local Government Areas (LGAs) dominant in processing cassava were selected for the study on the basis of spatial location distribution; landmass and population. The survey involved the use of structured questionnaires administered to cassava processors of the selected LGAs. The Statistical Package for Social Sciences (SPSS) software application and descriptive statistics were used for data analysis. Results of the analysis show that majority (70%) of the cassava processors are females. Cassava peel constitutes 10% of the waste produced, of which 91% are heaped at refuse dump in most communities. Results also reveal that 86.3% of cassava residues are used for animal feeds. Other findings show that the peels when dried are used as bio-fuel for cooking and there is a significant potential for biogas production. From the data captured from respondent during the study, most processors are willing to pay for an improved waste management system. The study therefore suggests proper waste management of cassava waste to minimize environmental pollution.
ARTICLE | doi:10.20944/preprints202305.2236.v1
Subject: Engineering, Chemical Engineering Keywords: Circular economy; greenhouse gas; carbon capture; endogenous striping agents; biogas upgrading; slow-release fertilizer
Online: 31 May 2023 (11:27:31 CEST)
With the current increase in the demand from animal and agricultural products, management of agrowaste has become critical to avoid greenhouse gas emissions. The present article investigates the applicability of ammonium bicarbonate synthesis via flash distillation to valorize and stabilize several types of anaerobic digestate produced from individual fermentations of amino acids. Prior to the development of the model in Aspen Plus v12, the description of the system aqua-ammonia-carbon dioxide provided by the electrolyte non-random two-liquid property method was validated with empirical data available in the literature. The content of CO2 in the digestate was found to be responsible of the OH alkalinity (0.4 equivalents of acid/kg digestate), while the partial and total alkalinities (0.8 eq/kg digestate) were essentially derived from the content of NH3. The most suitable conditions for the flash distillation were 95 ⁰C and 1 bar with the condensation occurring at 25 ⁰C. However, in order to attain the precipitation of NH4HCO3 in the distillate, it was necessary to consider digestates with a moisture content of 50 wt.%, since the minimum levels of inorganic nitrogen and inorganic carbon were not attained otherwise. Even under these conditions, few amino acids (i.e. arginine, glycine, and histidine) were able to provide an anaerobic digestate, upon fermentation, that would be suitable for NH4HCO3 stabilization. Despite alanine digestate and glutamine digestate presented sufficient concentrations of inorganic nitrogen and inorganic carbon, the NH4HCO3-stabilization was not feasible due to the limited volatilization of NH3. The process of stabilization with a capacity of a tonne of digestate per hour was improved by adding hydrochloric acid or sodium hydroxide at rates 44 kg/h, leading to production of 34 kg NH4HCO3/h. The economic viability of this process needs to be investigated considering not only the market value of the isolated inorganic fertilizer but the carbon credits saved, resulting from handling a more stabilized organic manure. Furthermore, given the role of the volatile elements of the biogas as endogenous stripping agents, it is recommended to use a fresh and saturated digestate as feed for the flash distillation.
ARTICLE | doi:10.20944/preprints202305.1341.v1
Subject: Environmental And Earth Sciences, Sustainable Science And Technology Keywords: Biological methanation; trickle-bed reactor; biogas upgrading; high pressure; biomethane; optimization of thermodynamic parameters
Online: 18 May 2023 (11:08:13 CEST)
The increased demand for resources and energy that is developing with rising global consumption represents a key challenge for our generation. Biogas production can contribute to sustainable energy production and closing nutrient cycles using organic residues or as part of a utilization cascade in the case of energy crops. Compared to hydrogen (H2), biogas with a high methane (CH4) content can be fed into the gas grid without restrictions. For this purpose, the CH4 content of the biogas must be increased from 52 to 60 % after anaerobic digestion to more than 96 %. In this study, biological hydrogen methanation (BHM) in trickling-bed reactors (TBR) is used to upgrade biogas. Design of experiments (DoE) is used to determine the optimal process parameters. The performance of the reactors is stable under all given conditions, reaching a “low” gas grid quality of over 90 %. The highest CH4 content of 95.626 ± 0.563 % is achieved at 55 °C and 4 bar, with a methane formation rate (MFR) of 5.111 ± 0.167 m³/(m³·d). The process performance is highly dependent on the H2:CO2 ratio in the educts, which should be as close as possible to the stochiometric ratio of 4. In conclusion, BHM is a viable approach to upgrade biogas to biomethane quality and can contribute to a sustainable energy grid.
ARTICLE | doi:10.20944/preprints202107.0276.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: life cycle assessment; sisal production; circular economy; nutrient depletion; anaerobic digestion; waste management; bioenergy; biogas.
Online: 12 July 2021 (23:02:10 CEST)
Nutrient depletion in Tanzanian sisal production has led to yield decreases over time. We use nutrient mass balances embedded within a life cycle assessment to quantify the extent of nutrient depletion for different production systems, then used circular economy principles to identify potential cosubstrates from within the Tanzanian economy to anaerobically digest with sisal wastes. The biogas produced is then used to generate bioelectricity and the digestate residual can be used as a fertilizer to address the nutrient depletion. If no current beneficial use of the cosubstrate was assumed, then beef manure and marine fish processing waste were the best cosubstrates. If agricultural wastes were assumed to have a current beneficial use as fertilizer, then marine fish processing waste and human urine were the best cosubstrates. The largest reduction in environmental impacts resulted from bioelectricity replacing electricity from fossil fuels in the national electricity grid and improved onsite waste management practices. There is significant potential to revitalize Tanzanian sisal production by applying circular economy principles to sisal waste management and bioenergy production.
ARTICLE | doi:10.20944/preprints202303.0216.v1
Subject: Engineering, Chemical Engineering Keywords: Waste valorization; stabilization; nutrient recovery; closed-loop; modelling; circular economy; ammonium carbonate; organic fertilizer; bioenergy; biogas upgrading
Online: 13 March 2023 (04:42:38 CET)
The use of the commercial simulator Aspen Plus® could bring an amelioration in the accuracy of the predictions of the chemical species composition in the output streams of the anaerobic digestion process, due to availability of a broad library of thermodynamic and phenomena transport properties in this commercial package. In the present investigation, the process simulation model for anaerobic digestion, which was originally developed by Rajendran et al. , has been modified by including a stoichiometric-equilibria reactor to calculate the extent of the ionization of the molecules present in the anaerobic digestate. The refined model offers a more accurate prediction of the composition of the biogas because it delves on the chemical equilibrium of the gaseous stream and the anaerobic digestate. Additionally, the refined model allows to assess the possibility of upgrading the gaseous stream to biomethane degree via manufacturing of ammonium bicarbonate. This processing pathway relies on the stabilization of the anaerobic digestate by means of biomass ash-based treatment. First of all, the titration of the manure digestate with the hydrochloric acid showed that a dose of 3.18 mEq/g would be required to attain the targeted pH of zero-point charge, upon addition of the sewage sludge ash in a ratio to the manure digestate of 0.6 ± 0.2 %. Secondly, the profiles of ammonia, carbon dioxide, and methane found in the biogas agree with both the pH of the treated digestate and the processes described in for the simultaneously upgrading the biogas and the production of ammonium bicarbonate. The refined Aspen Plus® model presented in this article needs to be further developed to ensure the standards are attained in all output streams of stabilized anaerobic digestate, biomethane, and isolated added-value chemical fertilizers.
BRIEF REPORT | doi:10.20944/preprints202308.1024.v1
Subject: Engineering, Chemical Engineering Keywords: anaerobic co-digestion; kinetics of biomethane accumulation; kinetic modeling; biogas; sugar-cane molasses; whey; agro-industrial residues valorization
Online: 14 August 2023 (11:15:17 CEST)
The biomethane accumulation of several combinations of whey and sugarcane molasses, inoculated with sludge from a treatment facility of one of the dairy enterprises of Imbabura, was assessed in the current experiment at a concentration of 0.5 g/l COD. The whey: molasses (W: M) ratios for each treatment were 0:100, 25:75, 50:50, 75:25, and 100:0, with a constant temperature of 37°C and an initial pH adjustment of 7.5. Half a litre of total mixes was used for each treatment in duplicate. Six kinetic models were evaluated to account biomethane accumulation in anaerobic co-digestion processes in batch of whey and sugarcane molasses. Five of these have been tested by other researchers, and one was developed by modifying a first-order model to consider changes in the biomethane accumulation profile. This proposed model, along with the modified two-phase Gompertz model, resulted in the ones that were best able to adjust the experimental data, obtaining in all cases an R² ≥ 0.949, indicating the accuracy of both models. In addition, the proposed here model has five parameters, one less than the modified two-phase Gompertz model, making it more straightforward and robust.
REVIEW | doi:10.20944/preprints202312.0067.v1
Subject: Environmental And Earth Sciences, Sustainable Science And Technology Keywords: anaerobic digestion; Trichoderma sp.; biogas, biomethane; lignocellulosic biomass; waste plant biomass; pretreatment methods; biological pretreatment methods; digestate; organic carrier
Online: 1 December 2023 (10:08:42 CET)
Plant waste biomass is the most abundant renewable energy resource on Earth. The main problem of utilising this biomass in anaerobic digestion is the long and costly stage of degrading its complex structure into simple compounds. A promising solution to this problem are fungi of the Trichoderma genus, which show a high capacity to produce hydrolytic enzymes capable of degrading lignocellulosic biomass. This article discusses the structure of plant waste biomass and the problems resulting from its structure in the digestion process. It presents the methods of pre-treatment of lignocellulose with a particular focus on biological solutions. Based on the latest research findings, key parameters related to the application of Trichoderma sp. as a pre-treatment method are discussed. In addition, the possibility of using the digestate from agricultural biogas plants as a carrier for the multiplication of the Trichoderma sp. fungi, which are widely used in many industries, was discussed.
ARTICLE | doi:10.20944/preprints202306.1043.v1
Subject: Engineering, Other Keywords: brewers’ spent grain; biomethane production kinetics; methane fermentation; biogas; anaerobic digestion; iron powder; Fe; lime; Ca(OH)2; porous ceramic.
Online: 14 June 2023 (10:13:34 CEST)
The process of anaerobic digestion used for methane production can be enhanced by incorporating stimulating materials. The effects of these materials are dependent on various factors including the processed substrate, process conditions, and the type and amount of the stimulating material used. As part of the study, three different stimulating materials - iron powder, lime, and milled porous ceramic - were added to the 30-day anaerobic digestion of the brewer's spent grain to improve its performance. Different doses ranging from 0.2 to 2.3 gTS×L-1 were tested, and methane production kinetics were determined using the first-order model. The results showed that the methane yield ranged from 281.4±8.0 to 326.1±9.3 ml×gVS-1, while substrate biodegradation ranged from 56.0±1.6 to 68.1±0.7%. The addition of lime reduced methane yield at almost all doses by -6.7% to -3.3%, while the addition of iron powder increased methane yield from 0.8% to 9.8%. The addition of ceramic powder resulted in a methane yield change ranging from -2.6% to 4.6%. These findings suggest that the use of stimulating materials should be approached with caution, as even slight changes in the amount used can impact methane production.
ARTICLE | doi:10.20944/preprints202305.1457.v1
Subject: Engineering, Mechanical Engineering Keywords: Efficiency analysis; biogas-powered cooling system; energy and exergy analysis; small-scale plant; absorption cooling system; triple-effect; ECOP; animal species; methane content
Online: 22 May 2023 (03:43:46 CEST)
This study investigates the efficiency of a biogas-powered cooling system through the utilization of energy and exergy calculations. Biogas, which can be generated and stored in small-scale plants as needed, serves as a viable fuel source for absorption cooling systems. The present research focuses on the biogas consumption of a triple-effect absorption cooling system, specifically designed to supply a fixed cooling load of 100 kW under varying operational conditions. The study highlights the COP (Coefficient of Performance) and ECOP (Exergetic Coefficient of Performance) values of the system, along with the exergy destruction rates of its individual components, at the optimal temperatures of operation. Furthermore, to determine the necessary biogas consumption, the study explores the establishment of dedicated farms for various animal species, ensuring an adequate number of animals for biogas production. The findings reveal a COP of 1.78 and an ECOP of 35.4% at the optimized operating temperatures. The minimum mass flow rate of biogas is determined to be 0.0034 kg/s, facilitating the operation of the boiler with a methane content of 65%. The study concludes that a total of 290 head of cattle is required to generate the annual biogas consumption necessary for the cooling system. Also, number of the cattle is enough to establish 284 biogas plants in Bursa province in Türkiye.