Content uploaded by Ayoub Haouas
Author content
All content in this area was uploaded by Ayoub Haouas on Feb 18, 2020
Content may be subject to copyright.
A preview of the PDF is not available
Review on Cow Manure as Renewable Energy
Abstract
The world now is looking for alternative resources of energy instead of using fossil fuels that contribute to the greenhouse gases and that are in depletion. This energy must be renewable and environment eco-friendly. The huge amounts of organic waste produced every year imposes to seek for a new approach and new methods to manage these tremendous quantities of organic waste dumped illegally into natural resources. Cow manure is considered one of the most abundant organic waste threating our world, especially that it produces greenhouse gases, malodours and destroy water and agricultural resources. From the other side, cow manure presents many properties that can be useful as renewable energy and soil organic natural amendment. Regarding the amount of cow manure produced, there is a significant possibility and opportunity for all researchers to work on this organic waste. One of the best biochemical methods used to manage cow manure is an-aerobic digestion. It is considered an attractive approach especially in terms of renewable energy (producing biogas and bio-fertilizers). This review article presents an overview of cow manure used as substrate and co-substrate in the anaerobic digestion process from different perspectives.
... Water hyacinth is a nutrient-rich substrate and contains easily biodegradable organic matter, which makes it excellent for biogas production. It has a comparatively high C/N ratio , high cellulose (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30).65%) and hemicellulose content (23.2-33.4%), and a low lignin content (5.6-16%), suggesting that it could be used as a feedstock in biogas generation [17]. ...
... Collected materials were kept in a plastic bag and transported to the Addis Ababa Institute of Technology. The anaerobically digested cow dung was selected as an inoculum to initiate the AD process based on its accessibility, nutrient content, stability, microbial activity, and compatibility with different waste materials [27]. The inoculum was obtained from cow dung that had been fermented in a mesophilic anaerobic environment before this study began [28]. ...
Considering the difficulty of digesting coffee husk (CH) and water hyacinth (WH) due to the lignin content, the present study investigated the influence of feedstock mixing ratios on the co-digestion performance of CH and WH with food waste (FW) at 38 ± 1 °C and its kinetics. Food waste was considered as co-substrate due to its ease of digestion. Batch experiments were conducted using CH/WH/FW ratios (100:0:0, 0:100:0, 35:35:30, 30:30:40, 25:25:50, 20:20:60, and 0:0:100 w/w) with total solids (TS) content of about 9.5% (w/v). The results indicated that the addition of FW significantly enhanced WH and CH digestion performance, with the maximum biogas yield of 572.60 ±\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document} 2.30 mL/gVS, best synergistic effect of 1.5, highest biodegradability of 89.22%, and a biodegradation rate of 57.82% obtained at a mix ratio of 25:25:50, which was improved by 179.71% compared to CH mono-digestion. In addition, the organic conversion efficiency of TS and volatile solids reached 69.86 and 81.48%, respectively. Conversely, CH mono-digestion yielded the lowest biogas yield of 204.71 ± 10.74 mL/g VS, highlighting its unfeasibility. The modified logistic equation showed the best fit to the experimental data. The optimum CH/WH/FW ratio of 25:25:50 demonstrated the highest biogas yield and methane content at 66.30 ± 0.76%.
Graphical Abstract
... Collected materials were kept in a plastic bag and transported to the Addis Ababa Institute of Technology. The anaerobically digested cow dung was selected as an inoculum to initiate the AD process based on its accessibility, nutrient content, stability, microbial activity, and compatibility with different waste materials [29]. The inoculum was obtained from cow dung that had been fermented in a mesophilic anaerobic environment before this study began [30]. ...
Coffee husk (CH) and water hyacinth (WH) are seen as environmental challenges causing eutrophication of water streams and infestation of water bodies. These biomass resources, available in plenty with high organic content can be considered for anaerobic digestion. However, their high lignin content poses a challenge to their biodegradability in which case co-digestion with easily degradable food waste (FW) could alleviate this problem. Thus, the synergistic effect with co-digestion of CH and WH employing increasing FW levels on biogas yield, biodegradability (BD fpc ), and biodegradation rate (η BD ) were investigated in this work. Experimental studies were conducted with a varied mixtures of CH/WH/FW (100:0:0, 0:100:0, 35:35:30, 30:30:40, 25:25:50, 20:20:60 and 0:0:100) at constant temperature (38 ± 1°C). The results indicated that addition of FW significantly enhanced WH and CH digestion performance, with the maximum biogas yield of 572.60 ml/gVS, highest BD fpc of 89.22% and η BD of 57.82% obtained at a mix ratio of 25:25:50, which was improved by 194.98% compared to CH mono-digestion. The co-digestion tests exhibited strong synergy due to their nutritional balance and other interactive effects promoting stability. Maximum synergy was 1.72 for a mix of 20:20:60. The modified Gompertz, logistic, and first-order kinetic models were used to simulate the experimental data to portray the biodegradation and kinetics involved. The modified logistic equation was seen to be the best fit to elucidate biogas production. The current findings highlighted the importance of increasing the easily biodegradable waste fractions in the co-digestion of lignocellulosic biomass for enhanced biodegradability.
... When manure is not properly processed, livestock farming activities negatively impact the environment (Velthof et al., 2014). On the other hand, manure (from animals) is an attractive natural resource for production of renewable energy and significantly improves soil fertility (Tallou et al., 2020). The low C/N ratio found in manure, the high nitrogen content, the low volatile solids (VS) content, and, in some cases, the high proportion of lignocellulosic biomass are significant limitations to the use of manure in fermentation (Tsapekos et al., 2016;Issah et al., 2020). ...
The content of heavy metals in soil should be continuously monitored, especially in organic crops. Exceeding the permissible concentrations of these elements may lead not only to inhibition of plant growth but also to ingestion into the organisms of animals that feed on these plants.
Heavy metals usually enter the soil via precipitation or manure. There is a noticeable increase in interest in digestate for fields fertilization. Therefore, the authors decided to test the heavy metal content in substrates (slurry and solid input) and digestate. The 15x3 samples tested showed that only trace amounts of heavy metals were present. The study shows that the content of these elements in the digestate is not the sum of the elements supplied to the digester with the substrates. In most of the samples tested, lead concentrations did not exceed 5 mg‧kg ⁻¹ . The lowest amounts of cadmium (an average of 0.28 mg‧kg ⁻¹ ) were observed in the slurry, and the highest (an average of 0.34 mg‧kg ⁻¹ ) in the solid substrate fed to the digester. Slurry had the lowest mercury and cadmium contents (average 0.012 mg‧kg ⁻¹ and 5.8 mg‧kg ⁻¹ ). The highest concentration of chromium was registered in the digestate (average 3 mg‧kg ⁻¹ ) and this was on average 0.3 mg‧kg ⁻¹ higher than the feedstock and 0.5 mg‧kg ⁻¹ than the slurry
... Livestock activities have an environmental impact when manure is not effectively managed [8,9]. On the other hand, animal manure is considered an attractive natural resource for renewable energy production, and can also replace industrial fertilizers and improve soil fertility [10,11]. ...
This study presents the improved biogas production by determining the optimum pH and insulation reactor from cow, sheep, and poultry manure (which are the most available in our location). The experiment was carried out in 2000 mL digester put in the water bath at 37 ˚C. The mixing ratio of animal manure and water used was 1:1 in 12 days of Hydraulic Retention Time (HRT). Produced gas was measured by the volumetric water replacement method. The optimum pH will be chosen in the experimental test with different pH ranges in the first phase. Three set-ups were prepared with different pHs (6.5, 7, 7.5).The results showed that the pH had significant effects on biogas yield, where pH7 had the highest biogas production and pH 6.5 is the lowest. The second phase, investigated the effect of the insulation of the reactor on the biogas yield. The biogas was produced from an insulated reactor higher than the photoreactor because of the growth of algae which produces oxygen in the photoreactor. Therefore, it is given that the study which gave a maximum yield of biogas from the batch digestion process might be met the future energy demand.
... A su vez, el incremento de los desechos de estas producciones de animales, específicamente las heces, se pueden convertir en contaminantes del medio ambiente (Godfray et al., 2018). Existen tecnologías para el aprovechamiento de estos residuos en función de la digestión anaerobia mediante los biodigestores (Chibás et al., 2017;Tallou et al., 2020), o una alternativa aeróbica que puede tener un fuerte impacto en la alimentación del futuro, el uso de insectos para su degradación con sus múltiples beneficios, tanto ambientales como nutricionales (Rumpold & Schlüter, 2013). ...
RESUMEN Con el objetivo de evaluar en diferentes sustratos en condiciones abióticas semicontroladas el rendimiento de la acción de larvas de díp-teros saprófagos, sobre varios tipos de residuos: salvado de trigo, cerdaza, germen de maíz, cáscara de arroz, gallinaza, borra de café y cachaza, cinco experimentos fueron realizados con diferentes combinaciones de los mismos. Por la mañana y la tarde, fueron registradas las temperaturas dentro de los sustratos, y la temperatura ambiente máxima, mínima, media, y la humedad relativa. Las temperaturas y la humedad relativa en los sustratos siempre estuvieron por encima de la ambiental. La producción de proteínas, y por tanto la producción de larvas (la cantidad de larvas y no su peso), en la cáscara de arroz no se logró altos rendimientos y en la borra de café no hubo desarro-llo de larvas. Los sustratos que produjeron mayor producción de larvas fueron las combinaciones de heces fecales de cerdo con salvado de trigo a los seis días (50%) y a los ocho días (20%), con 2869,11 g m2-1y 991,33 g m2-1, respectivamente. No se encontraron agentes patógenos (Salmonella spp. Escherichia coli y Coccidia spp) en los sustratos o larvas. Palabras clave: producción larval, diptera, proteínas alternativas, inocuidad, temperatura ABSTRACT With the aim to evaluate the performance of the action of saprophagous dipteran larvae on different substrates under semi-controlled abio-tic conditions on various types of waste: wheat bran, pig manure, corn germ, rice husk, chicken manure, coffee grounds and filter cake, five experiments were carried out with different combinations of these. In the morning and afternoon, the temperatures inside the substrates were recorded, as well as the maximum, minimum, average and average ambient maximum, minimum, average and relative humidity were recorded. The temperatures and relative humidity in the substrates were always above the ambient temperature. Protein production, and therefore larval production (the number of larvae and not their weight), high yields were not achieved on rice husk and there was no larval development on coffee grounds. The substrates that produced the highest larval production were the combinations of pig manure with wheat bran at six days (50%) and at eight days (20%), with 2869.11 g m 2-1 and 991.33 g m 2-1, respectively. No pathogens (Salmonella spp. Escherichia coli and Coccidia spp) were not found on the substrates or larvae.
... Livestock activities have an environmental impact when manure is not effectively managed [8,9]. On the other hand, animal manure is considered an attractive natural resource for renewable energy production, and can also replace industrial fertilizers and improve soil fertility [10,11]. ...
This study presents the improved biogas production by determining the
optimum pH and insulation reactor from cow, sheep, and poultry manure (which are the most available in our location). The experiment was carried out in 2000 mL digester put in the water bath at 37 ˚C. The mixing ratio of animal manure and water used was 1:1 in 12 days of Hydraulic Retention Time (HRT). Produced gas was measured by the volumetric water replacement method. The optimum pH will be chosen in the experimental test with different pH ranges in the first phase. Three set-ups were prepared with different pHs (6.5, 7, 7.5). The results showed that the pH had significant effects on biogas yield, where pH7 had the highest biogas production and pH 6.5 is the lowest. The second phase, investigated the effect
of the insulation of the reactor on the biogas yield. The biogas was produced from an insulated
reactor higher than the photoreactor because of the growth of algae which produces oxygen in
the photoreactor. Therefore, it is given that the study which gave a maximum yield of biogas
from the batch digestion process might be met the future energy demand.
... The anerobic digestion of waste is a clean, simple, and low-cost form of non-conventional renewable energy (NCRE), in relation to other technologies of this type [55]. In addition, it provides the ability to use a great variety of animal manure, agricultural residues, and waste from the food industry, generating various agricultural and socioeconomic benefits through the reduction of odors, the inactivation of pathogens, and the generation of a renewable and clean fuel for use in multiple applications [56][57][58][59][60][61][62]. In Europe, livestock waste is considered to have high biogas potential; e.g., Sweden has the potential to generate an average of 3-6 TWh per year [63,64]. ...
Anaerobic digestion is a system that can have a high environmental impact through the use of different wastes to obtain biogas and its consequent use for the generation of renewable energy. The objective of this study was to implement a polyethylene biodigester, using polystyrene for thermal insulation in a dog kennel, using canine feces collected in the same place during a period of 5 months to obtain biogas and energy. The results indicated that biogas production started on day 30 and stopped during the winter period with low temperatures; therefore, from day 54 onwards, equine manure was added to continue producing biogas. Although biogas was obtained, the biodigester did not function optimally, due to the fact that the materials used in its construction did not provide efficient insulation from the low external temperatures; the low C/N ratio of the canine feces, which led to a reduction in the processing of the methanogenic bacteria; and the low amount of feces collected for use. In general, the use of a biodigester can provide a tool for the biological processing and management of organic waste, yielding a cumulative source of renewable energy and ensuring environmental safety.
... Another biomass of interest-DP-comes from the date fruits used to generate many products, including juice concentrates, and fermented products generating date fruit wastes, including pits with high nutritional value [16]. The third and key waste feed-cow manure-is produced in huge amounts, and is one of the biggest threats in the world due to its associated greenhouse gas emissions [17].On a national scale, Qatar produces around 210,000 tons every year [18]; assuming about 60-80% of this is volatiles generated, about 150,000 tons of products could be produced every year. Pyrolysis has recently emerged as an alternative to biogas plants, as the processing time is limited to a few minutes, compared to anaerobic digestion which requires 30-40 days on average [19,20]. ...
Background: Bioenergy attracts much attention due to the global demand for renewable and sustainable energy resources. Waste biomass feedstocks—date pits, coffee waste, and cow dung—require efficient and environmentally friendly waste-management technologies such as pyrolysis. Fast pyrolysis occurs at fast heating rates (10–100 °C/s), generates high bio-oil yields, and is the most widely used process for biofuel generation. The aim of the study is to compare the effect of pyrolysis between single, binary, and ternary feeds on thermal degradation behavior and bio-oil composition. Methods: Thermogravimetric analysis (TGA) was conducted at 30 °C/min from room temperature to 850 °C to understand the thermal degradation behavior of the biomasses. A Pyroprobe® reactor—a micro-scale pyrolyzer—was used to conduct the fast pyrolysis at 500 °C with a heating rate of 10 °C/s, and the volatile contents were quantified using a gas chromatograph–mass spectrometer (GC/MS). Results: The (TGA) showed three main stages of decomposition following dehydration, devolatilization, and char degradation for the different single and multiple feeds. According to the identified compounds, the bio-oil components are broadly identified as aldehydes, amines, aliphatic, aromatics, alcohols, furans, ketones, and acids. The three single-biomass pyrolysis products have four compounds in common, acetic acid and ketone groups (acetic acid, 2-propanone, 1-hydroxy-, benzyl methyl ketone, and 1,2-cyclopentanedione). Conclusion: The bio-oil generated from the feeds comprises great potential for volatiles, diesel, and gasoline production with carbon atoms ranging from C2–C33. Future studies should focus on understanding the effect of procedural parameters, including blending ratio, temperature, and heating rates, on bio-oil composition. Additional molecular techniques should be employed to understand biomass components’ reaction mechanisms to produce useful bio-oil products.
Agricultural biogas plants are among the renewable energy sources. While they have many advantages, they are less common than photovoltaic or wind power plants. One of the reasons for the lack of support for the construction of new agricultural biogas plants is the belief that biogas plants will affect the operation of consumers connected in its immediate vicinity through interference introduced into the grid. This article presents the possibilities a biogas plant built on a farm offers. The impact of an on-farm biogas plant on the voltage parameters of a farm specializing in barnless cattle rearing is analyzed in detail. As demonstrated by the authors’ research in one of the agricultural biogas plants (with an electrical capacity of 40 kW), these plants do not introduce significant disturbances to the power quality into the grid. The most significant changes in the parameters of the voltage supplying the farm under study were caused by the operation of the digester mixer installed in the fermenter. Thanks to the research, it was also possible to identify a problem with the effect of the digester mixer on the energy parameters produced in the biogas plant. This problem has so far not been noticed or corrected by biogas plant manufacturers.
Vermicomposting is an economical and environmentally friendly process. However, related knowledge of vermicomposting aquatic plant residues (APRs), earthworm quality, and mechanisms for metal removal from water is still lacking. Nelumbo and Oenanthe javanica residues and their mixture were treated with Eisenia foetida and cattle manure for 45 days. Compared with the control comprising only cattle manure, addition of the APR mixture improved earthworm quality, mainly for low crude ash, high alkaloid compounds and different fat compositions in the Nelumbo residue and the balanced protein proportion of the APR mixture. All the vermicompost especial O. javanica residue added (VO) played efficient roles in removing metals from water initially containing 2.0 mg Cu L⁻¹ and 8.0 mg Zn L⁻¹. There were higher removal efficiencies (Ers) at the dosage of 4 g L⁻¹ with a small microbial contribution. VO significantly increased Ers, which could be from the decrease of phylum Firmicutes (especial Bacteroides) abundance, stronger CH2, C = O, and CH, the addition of COOH groups, and higher organic matter and total phosphorus contents. The combination of VO and Hippuris vulgaris was optimized as an ecological and economical method for treating complex-metal polluted water. Moreover, our study widened the route for APR reuse.
The work aimed in developing new design of plants and helps improving the efficiency of the plants. This study represents a complete analysis of energy and cost of selected biogas plants and solar PV systems. Data were collected from 20 small scale biogas plants and 20 solar PV systems from 3 sub-Districts of Tangail Districts and 1 sub-District of Rajshahi, Bangladesh. Often three sizes of biogas plants- small (2.4 m3), medium (3.2 m3) and large (4.8 m3) were found and five capacities of 40, 50, 65, 75 and 85 watt-peak solar PV systems were found in the sampled areas. It was found that the energy payback time of biogas plants were 2 years for 2.4m3, 1.66 years for 3.2 m3 and 2.33 years for 4.2 m3 plant. While the energy payback time for solar PV systems were found 6.53 to 7.57 years depending on system capacity. Cost payback period of biogas plants were 3.4 years for 2.4 m3, 2 years for 3.2 m3 and 2.5 years for 4.2 m3 while cost payback period for solar PV systems were found 2.55 to 4.03 years. The cost per unit biogas was found 9.8 BDT (Bangladeshi Taka) for cow dung based plants and 6.9 BDT for poultry waste based plants while the cost of per unit solar electricity was found average 8.2 BDT.
Spent tea waste (STW) is an organic waste that is disposed in open land after preparation of tea. Generally, it is disposed in an open land which increases anthropogenic gases. Converting it into useful energy or value added product may reduce disposal problem and anthropogenic activity. In this study, STW was co-digested with cow manure (CM) for obtaining biogas by anaerobic digestion. For this purpose, STW was mixed with CM at different proportions, namely 50:50, 40:60, 30:70, 20:80, and 0:100 percentages on a mass basis, were used in five different anaerobic digesters. The samples were kept in different anaerobic digesters for the study. The effect of important input parameters like pH, Carbon to Nitrogen (C/N), and digestion time on the biogas production were studied. Further, the collected biogas from the digesters were characterised to ensure the suitability for use as a renewable fuel. Furthermore, the digested slurry was also analysed for its use in agriculture sector. The results are presented in this paper.
With the increase of energy consumption and wastes generation due to human activities, anaerobic digestion (AD), a technology which turns wastes into bio-energy, is receiving more and more attention in the world. It is well known that there are at least three stages involved in anaerobic digestion, i.e., hydrolysis, acidification, and methanogenesis. Until now, however, the advances in enhancing acidification and methanogenesis have not been reviewed. This review provides a comprehensive overview of the methods reported to enhance each step involved in anaerobic digestion. More important, enzymes are the key to anaerobic digestion, and the strategies for improving enzyme activity are summarized. As electron transfer has been reported to play an important role in anaerobic digestion, the research progress of the approaches for the acceleration of direct interspecies electron transfer in methane production is also introduced. In addition, the recent advances in increasing the reduction of carbon dioxide to methane, which has been widely observed in methanogenesis step, are reviewed. Furthermore, the techno-economic assessment of anaerobic digestion is made, and the key points for future studies are proposed.
The quest for improved living conditions in rapidly growing Indian communities puts pressure on natural resources and produces emissions which harm the environment, society and the economy. Current municipal solid waste (MSW) practices are an important example, as most waste remains untreated and is often deposited on unsafe dumpsites or burned on open fires. Anaerobic digestion (AD) is an option to treat the large biodegradable fraction ('biowaste'). In rural parts of India, the technology to supply energy from biogas has been promoted for 30 years. Biowaste treatment in urban MSW management and organic fertilizer ('digestate') production for agriculture via AD have more recently gained attention but with limited success so far. Recent environmental policies in waste, energy, agricultural and other sectors have, however, set important cornerstones for a broader diffusion in the coming years. On the basis of peer-reviewed literature and governmental reports, we identify barriers and enabling factors along the AD chain (biowaste to technology to product utilization), and analyse relevant boundary conditions for the new multi-sector policies. We show that AD implementation has repeatedly failed due to unrealistic assumptions on biowaste quantity and quality, underestimation of the complex biowaste supply chain, unsuitable AD designs and overestimation of economic returns from biogas and digestate. Local knowledge and capacities for planning and process control are lacking in many places and resources required for operation and maintenance in the long run have often been ignored. We found that the multi-facetted value propositions of AD - including biowaste treatment, energy and fertilizer products - have only been partially tapped due to the exclusive focus on biogas. The new sector policies provide important enabling factors for change. Decentralized AD plants operating on a few tons biowaste per day from reliable and manageable sources (e.g. fruit and vegetable markets) could be a more promising step forward than large-scale investments which rely on large biowaste volumes from various sources. The parallel development of biowaste management, planning tools for municipalities, standardized digestate monitoring protocols and studies on simple, low-cost optimization measures for methane recovery from a wide range of biowastes and innovative high-solid AD digester designs will be prerequisites for the long-term future of AD projects.
Follow this link for 50 days' free access: https://authors.elsevier.com/c/1YXMl14Z6tX63v
Impacts of adding different amounts of cow manure (CM) on the anaerobic digestion (AD) of oat straw (OS) with total solids content (TS) values of 4%, 6%, 8% and 10% was assessed over 50 days using batch experiments. A modified Gompertz model was introduced to predict the methane yield and determine the kinetic parameters. The optimum addition was a 1:2 ratio of CM to the OS added, which resulted in a suitable C/N ratio of 27 and a higher degradation rate of lignocellulose. The best cumulative methane yield of 841.77 mL/g volatile solids added (VSadded) was 26.64% greater than that of digesting OS alone. In addition, the amount of CM added produced larger effects than that of changes in the TS. However, higher CM concentrations were found to be inhibitory. Clustering analysis could provide significant guidance for demonstrating project process and combining farming and animal husbandry.
The world is now seeking sources of renewable energy that are both economical and environmentally friendly. Purified biogas is one essential source of renewable energy that can act as a substitute for fossil fuels. Anaerobic digestion has been recognised as a biochemical method of biogas generation that can convert organic compounds into a sustainable source of energy. Anaerobic co-digestion, AcoD is considered a pragmatic method to resolve the difficulties related to substrate properties and system optimisation in single-substrate digestion processes. The present manuscript studied the research prospects and challenges of anaerobic co-digestion, and the contributions of different methods in biogas generation studies. With the increased use of anaerobic co-digestion, the complexity of the process also increases. Several mathematical models had been established to optimise the anaerobic co-digestion technique. The biological methane potential test is a preferred technique for measuring the biodegradability and decomposition rate of organic substances. Furthermore, various additives are now used to maximise methane production. The improvement and optimisation processes of biogas production still need to be investigated in greater detail. In developing countries like Malaysia, biogas production may be more economically feasible if the latest simulation and characterisation methods are used at the industrial scale. Finally, this review describes a design and development framework to incorporate various aspects to enhance biogas production.
Livestock farming generates animal manure as a by-product. In comparison to in some countries, manure is hardly used for energy production in Switzerland. A growing awareness of renewable energy needs, resource depletion, and climate challenges make the huge untapped potential of livestock manure very attractive, particularly regarding biogas technology. Here, we assessed the energy and greenhouse gas (GHG) emissions benefits of using manure for biogas, considering its spatial distribution in Switzerland. First, laboratory measurements were conducted to compare the composition of fresh manure with values from literature. Then, detailed assessments of manure availability for biogas production were performed. Finally, the mitigation potential regarding GHG emissions was estimated for three scenarios. The new lab-scale values confirmed early storage as an important phase that is still not considered in practice. Under current farming practice, Swiss manure could produce 430 million m3 biogas or 15 PJ gross biogas yearly, mostly from cattle. However, only 6% of this manure is currently being used for anaerobic digestion. The manure is widely spread across the country in relatively small farms. Considering the spatial distribution of manure and Swiss agricultural structures, there is considerable potential for small-scale individual installations, with a peak of approximately 250 GJ gross biogas yearly, as well as for joint-farm installations. If the currently exploitable amount of manure were used for energy, the emission of 159 kt of CO2 equivalent could be prevented compared to emissions under current management practices. Thus, manure digestion could be promoted for its wide environmental and energetic benefits.
This paper investigates the environmental and economic performance of the power production from biogas using Life Cycle Assessment, Life Cycle Costing and Cost Benefit Analysis methodologies. The analysis is based on a commercial thermophilic biogas plant located in Spain where is installed a Combined Heat and Power system that produces electricity that is sold to the grid. Power generation has been assumed as the only function of the biogas system, expanding the system boundaries to include the additional function related to the end-of-life management of the biowastes. Thus environmental burdens from the conventional management of residues were calculated separately and subtracted. The base scenario involves using agri-food waste, sewage sludge and pig/cow manure as substrates. This situation is compared against an alternative scenario where the production of synthetic fertilizer is surrogated by the digestate.
The results have shown that the most impacting activities in all impacts categories of power production are primarily attributable to the operation and maintenance of the biogas plant except for water resource depletion and climate change. The avoided emissions associated with the conventional management of pig/cow manure more than offset GHG emissions of the biogas system resulting in a negative impact value of −73.9 g CO2 eq/kWh in the base case scenario. The normalized results show that local impact categories such as primarily human toxicity, fresh water ecotoxicity and particulate matter are the most significantly affected by the biogas system while global impact categories as climate change and ozone depletion are less severely affected.
The operation and maintenance phase is also shown to be the largest contributor after the life cycle cost analysis, followed by the construction and dismantling of the biogas plant and the profitability of the project is primarily related to the income obtained from the management of the biowastes used as substrates.
The aim of this study was to evaluate the enhancement of biogas production from cattle manure (CM) at pilot-plant scale using: a) ultrasound pretreatment (US) (520 kJ/kg Total Solids (TS); 409.59 kJ), b) co-digestion with crude glycerine (Gly) from the biodiesel industry (6% w/w), and c) US pretreatment (520 kJ/kg TS; 340.84 kJ), applied to the aforementioned mixture of both substrates prior to anaerobic co-digestion. The reactor used for this purpose was an Induced Bed Reactor (IBR), with a useful volume of 1250 L. Methane production from CM was enhanced by the application of low-energy ultrasound pretreatment (520 kJ/kg TS) (from 0.29 to 0.46 m³ CH4/kg Volatile Solids (VSadded)), and by co-digestion with Gly (from 0.29 to 0.44 m³ CH4/kg VSadded). The best results were obtained when the mixture of CM + Gly was pretreated by US (up to 0.59 m³ CH4/kg VSadded). Observation by Scanning Electron Microscopy (SEM) of the microstructural changes the CM underwent after pretreatment and/or co-digestion with crude glycerine enabled the discussion and justification of the results obtained in the present study.