Recent Updates on the Use of Agro-Food Waste for Biogas Production

Effects of ciprofloxacin on biogas production and microbial community composition in anaerobic digestion of swine wastewater in ASBR type reactor

In swine farming, antibiotics are often used to reduce disease and promote animal growth. Part of these compounds is not absorbed by the swine body, being excreted and later reaching the treatment systems, soil, and nearby waterbodies. This research sought to investigate the influence of adding ciprofloxacin (CIP) on the anaerobic digestion of swine wastewater. For that, a bench-scale anaerobic sequential batch reactor (ASBR) was used, with 5 L of working volume in six different phases, with volumetric organic loading rate (VOLR) and CIP dosage variation. According to the results, the optimal VOLR for the reactor was 0.60 ± 0.11 gSV L-1 d-1, resulting in biogas productivity of 0.51 ± 0.03 Lbiogas L-1 d-1. After initial stability, adding substrate with 0.5 mgCIP L-1 resulted in an abrupt drop of 82% in the productivity from the 7th to 11th day of addition, coinciding with volatile acids accumulation. Afterward, the reactor recovered and reached apparent stability, with productivity similar to the previous step without the drug. For 2.5 mgCIP L-1 in the substrate, the biogas productivity at equilibrium was 11.8% lower than in the phases with the same VOLR and 0.0 and 0.5 mgCIP L-1. Organic matter removals near 80% were achieved for both dosages. The 16S rRNA metagenomic analyses showed an increase in the relative abundance of most of the phyla found, indicating that the dosages used allowed the acclimatization of microorganisms and possibly the compound biodegradation.

From feedstock to digestion: Unraveling the impact of humic acid composition on anaerobic digestion

In the anaerobic digestion (AD) process, the effects of humic acid (HA) derived from different feedstocks on AD are influenced by the variations in their structural composition and oxygen-containing functional groups. Thus, clarifying the structural differences of HA obtained from different feedstocks is crucial for understanding their impact on AD. In this study, the structure of five humic acids (HAs) derived from liquid digestate, food waste, silage corn straw, lignite and commercial HA, and their effects on AD were investigated. The study found that HA from food waste had more carboxyl groups, while straw-derived HA had more phenolic hydroxyl groups. Both types of HA had higher aromaticity and humification degree and showed significant inhibition effect on AD. HA from food waste had an average methanogenic inhibition rate of 43.5 % with 1 g/L HA added. In addition, commercial HA and HA derived from lignite had similar functional group types and aromaticity, with an average methanogenic inhibition rate of about 20 %. The study revealed that HAs with more carboxyl groups exhibited greater effectiveness in inhibiting AD, thereby confirming the influence of HA structures derived from different feedstocks on AD. In conclusion, this study provides valuable insights into the mechanism of HA effect on AD and offers guidance for future research focused on enhancing AD efficiency.

Subcritical Water Pretreatment for Anaerobic Digestion Enhancement: A Review

This work reviews hydrothermal subcritical water pretreatment to enhance biogas production through anaerobic digestion. The complexity of the lignocellulosic structure has been the main limitation contributing to unsatisfactory biogas production throughout the anaerobic digestion. The high resistance of the structure to biological hydrolysis has increased the interest in applying pretreatment prior to anaerobic digestion to facilitate hydrolysis. Hydrothermal subcritical water technology, an environmentally friendly pretreatment that uses water as the main medium, is gaining prominence in biogas enhancement. However, the subcritical water pretreatment influence on structural properties, biogas production, and the production of anaerobic process inhibitors signifies a knowledge gap and needs an evaluation. This review presents the need for pretreatment reaction and properties in the subcritical water region, biogas production from subcritical water pre-treated waste, production of inhibitors, and its challenges are discussed. This pretreatment could be a promising option and further enhance biogas production throughout the anaerobic digestion process.

The Preparation Processes and Influencing Factors of Biofuel Production from Kitchen Waste

Kitchen waste is an important component of domestic waste, and it is both harmful and rich in resources. Approximately 1.3 billion tons of kitchen waste are produced every year worldwide. Kitchen waste is high in moisture, is readily decayed, and has an unpleasant smell. Environmental pollution can be caused if this waste is treated improperly. Conventional treatments of kitchen waste (e.g., landfilling, incineration and pulverization discharge) cause environmental, economic, and social problems. Therefore, the development of a harmless and resource-based treatment technology is urgently needed. Profits can be generated from kitchen waste by converting it into biofuels. This review intends to highlight the latest technological progress in the preparation of gaseous fuels, such as biogas, biohythane and biohydrogen, and liquid fuels, such as biodiesel, bioethanol, biobutanol and bio-oil, from kitchen waste. Additionally, the pretreatment methods, preparation processes, influencing factors and improvement strategies of biofuel production from kitchen waste are summarized. Problems that are encountered in the preparation of biofuels from kitchen waste are discussed to provide a reference for its use in energy utilization. Optimizing the preparation process of biofuels, increasing the efficiency and service life of catalysts for reaction, reasonably treating and utilizing the by-products and reaction residues to eliminate secondary pollution, improving the yield of biofuels, and reducing the cost of biofuels, are the future directions in the biofuel conversion of kitchen waste.

Recent advances in biogas production using Agro-Industrial Waste: A comprehensive review outlook of Techno-Economic analysis

Agrowaste sources can be utilized to produce biogas by anaerobic digestion reaction. Fossil fuels have damaged the environment, while the biogas rectifies the issues related to the environment and climate change problems. Techno-economic analysis of biogas production is followed by nutrient recycling, reducing the greenhouse gas level, biorefinery purpose, and global warming effect. In addition, biogas production is mediated by different metabolic reactions, the usage of different microorganisms, purification process, upgrading process and removal of CO₂ from the gas mixture techniques. This review focuses on pre-treatment, usage of waste, production methods and application besides summarizing recent advancements in biogas production. Economical, technical, environmental properties and factors affecting biogas production as well as the future perspective of bioenergy are highlighted in the review. Among all agro-industrial wastes, sugarcane straw produced 94% of the biogas. In the future, to overcome all the problems related to biogas production and modify the production process.

Integrated system of anaerobic digestion and pyrolysis for valorization of agricultural and food waste towards circular bioeconomy: Review

Agricultural and food waste have become major issue affecting the environment and climate owing to growing population. However, such wastes have potential to produce renewable fuels which will help to meet energy demands. Numerous valorization pathways like anaerobic digestion, pyrolysis, composting and landfilling have been employed for treating such wastes. However, it requires integrated system that could utilize waste and promote circular bioeconomy. This review explores integration of anaerobic digestion and pyrolysis for treating agricultural and food waste. Proposed system examines the production of biochar and pyro-oil by pyrolysis of digestate. The use of this biochar for stabilizing anaerobic digestion process, biogas purification and soil amendment will promote the circular bioeconomy. Kinetic models and framework of techno-economic analysis of system were discussed and knowledge gaps have been identified for future research. This system will provide sustainable approach and offer carbon capture and storage in form of biochar in soil.

Organic Waste Substrates for Bioenergy Production via Microbial Fuel Cells: A Key Point Review

High-energy consumption globally has raised questions about the low environmentally friendly and high-cost processes used until now for energy production. Microbial fuel cells (MFCs) may support alternative more economically and environmentally favorable ways of bioenergy production based on their advantage of using waste. MFCs work as bio-electrochemical devices that consume organic substrates in order for the electrogenic bacteria and/or enzyme cultures to produce electricity and simultaneously lower the environmental hazardous value of waste such as COD. The utilization of organic waste as fuels in MFCs has opened a new research path for testing a variety of by-products from several industry sectors. This review presents several organic waste substrates that can be employed as fuels in MFCs for bioenergy generation and the effect of their usage on power density, COD (chemical oxygen demand) removal, and Coulombic efficiency enhancement. Moreover, a demonstration and comparison of the different types of mixed waste regarding their efficiency for energy generation via MFCs are presented. Future perspectives for manufacturing and cost analysis plans can support scale-up processes fulfilling waste-treatment efficiency and energy-output densities.

Economic Conditions of Using Biodegradable Waste for Biogas Production, Using the Example of Poland and Germany

Biogas production is a process with great potential. It uses the biodegradable raw materials of animal, vegetable and municipal waste. The amount of municipal as well as agricultural waste is increasing every year. This waste is an unmanaged and nuisance waste, and using it in biogas plants reduces the amount of waste. Biogas production is part of the EU’s policy to reduce dependence on fossil fuels and use energy from renewable sources (diversification of energy sources). Its importance is certain to increase in the future as energy demand increases. This article deals with the economical use of biodegradable waste for biogas production in Poland and Germany. Both countries have a similar agricultural and municipal waste structure. An agricultural biogas plant is one way of obtaining energy based on renewable energy sources (RES). Energy production from agricultural biogas will allow Poland to meet the 32% obligation imposed by the EU and Germany to continue to be the market leader in biogas plants. The biogas market in Poland is growing, while in Germany, there is a decline in biogas installations. The article indicates what changes need to take place in agriculture and the use of municipal waste in these countries to sustain the development of biogas plants. Both countries should maintain animal husbandry to ensure continuous access to substrate and use waste for production rather than growing maize or other mixtures only for biogas plants. Due to the high price of chemical fertilisers, pulp from biogas plants should be an alternative to chemical fertilisers in both countries, which will contribute to greener crops. The governments of both countries should support such measures.

Novel Approaches in the Valorization of Agricultural Wastes and Their Applications

Worldwide, a huge amount of agricultural food wastes and byproducts containing valuable bioactive compounds are generated, especially throughout the entire supply chain. Minimizing food wastes and byproducts is the first option to avoid environmental problems, and to help the economy and the society. Although many countries implement policies to reduce food wastes and byproducts, and different management methods are available to utilize agricultural food wastes, they are still produced annually. Nanotechnological and biotechnological approaches are recently used as novel and green applications to valorize agricultural food wastes and improve their stability and applicability. In this Review, these approaches are covered in detail with given examples. Another valorization way of consumable food waste is using it for functional food production. This Review focuses on specific examples of functional foods with food waste as an ingredient. In addition, the problems and limitations of waste management and valorization methods are investigated, considering future perspectives.

Processing of Distillery Stillage to Recover Phenolic Compounds with Ultrasound-Assisted and Microwave-Assisted Extractions

This study investigated the effect of ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) conditions (extraction time, acetone concentration, solid-to-solvent ratio) on the efficiency of polyphenol recovery from distillery stillage and antioxidant activity of the extracts. The highest total polyphenol content, flavonoid content, and phenolic acid content were obtained with 10-min UAE and 5-min MAE at a solid-to-acetone ratio of 1:15 (w:v). Recovery yield was the highest with an aqueous solution of 60% acetone, confirming the results of Hansen Solubility Parameter analysis. Although UAE resulted in approximately 1.2 times higher extraction yield, MAE showed a better balance between extraction yield and energy consumption exhibited by its 3-fold higher extraction rate than that of UAE. Content of total polyphenols and phenolic acids strongly correlated with antioxidant activity, indicating that these compounds provide a substantial contribution to the bioactive properties of the extracts. Six phenolic acids were extracted, predominately ferulic and p-coumaric acids, and free forms of these acids constituted 91% of their total content, which opens various possibilities for their application in the food, cosmetics, and pharmaceutical industries.

Recovery of Household Waste by Generation of Biogas as Energy and Compost as Bio-Fertilizer—A Review

Nowadays, organic waste and especially household waste represents a significant global issue due to population growth. The anaerobic digestion (AD) process is an essential operation contributing powerfully to the valorization of organic waste including food waste in terms of renewable energy generation (biogas) and the rich-nutrient residue that can be utilized as bio-fertilizer. Thus, this process (AD) allows for good recovery of household waste by generating biogas and compost. However, the AD operation has been affected by several key factors. In this paper, we aim to involve different critical parameters influencing the AD process, including temperature, pH, organic loading rate (OLR), carbon to nitrogen ratio (C/N), and total solid content (TS(%)). Further, the paper highlights the inhibition caused by the excessive accumulation of volatile fatty acids (VFAs) and ammoniac, which exhibits the positive effects of co-digestion, pretreatment methods, and mixing techniques for maintaining process stability and enhancing biogas production. We analyze some current mathematical models explored in the literature, such as distinct generic, non-structural, combined, and kinetic first-order models. Finally, the study discusses challenges, provides some possible solutions, and a future perspective that promises to be a highly useful resource for researchers working in the field of household waste recovery for the generation of biogas.

Monitoring of Food Waste Anaerobic Digestion Performance: Conventional Co-Substrates vs. Unmarketable Biochar Additions

This study proposed the selection of cost-effective additives generated from different activity sectors to enhance and stabilize the start-up, as well as the transitional phases, of semi-continuous food waste (FW) anaerobic digestion. The results showed that combining agricultural waste mixtures including wheat straw (WS) and cattle manure (CM) boosted the process performance and generated up to 95% higher methane yield compared to the control reactors (mono-digested FW) under an organic loading rate (OLR) range of 2 to 3 kg VS/m³·d. Whereas R3 amended with unmarketable biochar (UBc), to around 10% of the initial fresh mass inserted, showed a significant process enhancement during the transitional phase, and more particularly at an OLR of 4 kg VS/m³·d, it was revealed that under these experimental conditions, FW reactors including UBc showed an increase of 144% in terms of specific biogas yield (SBY) compared to FW reactors fed with agricultural residue. Hence, both agricultural and industrial waste were efficacious when it came to boosting either FW anaerobic performance or AD effluent quality. Although each co-substrate performed under specific experimental conditions, this feature provides decision makers with diverse alternatives to implement a sustainable organic waste management system, conveying sufficient technical details to draw up appropriate designs for the recovery of various types of organic residue.

Agricultural Waste-Based Biochar for Agronomic Applications

Agricultural activities face several challenges due to the intensive increase in population growth and environmental issues. It has been established that biochar can be assigned a useful role in agriculture. Its agronomic application has therefore received increasing attention recently. The literature shows different applications, e.g., biochar serves as a soil ameliorant to optimize soil structure and composition, and it increases the availability of nutrients and the water retention capacity in the soil. If the biochar is buried in the soil, it decomposes very slowly and thus serves as a long-term store of carbon. Limiting the availability of pesticides and heavy metals increases soil health. Biochar addition also affects soil microbiology and enzyme activity and contributes to the improvement of plant growth and crop production. Biochar can be used as a compost additive and animal feed and simultaneously provides a contribution to minimizing greenhouse gas emissions. Several parameters, including biochar origin, pyrolysis temperature, soil type when biochar is used as soil amendment, and application rate, control biochar’s efficiency in different agricultural applications. Thus, special care should be given when using a specific biochar for a specific application to prevent any negative effects on the agricultural environment.

Anaerobic Mineralization of Recirculating Aquaculture Drum Screen Effluent for Use as a Naturally-Derived Nutrient Solution in Hydroponic Cropping Systems

Operation and effluent treatment costs are limiting factors for the success of recirculating aquaculture systems (RAS) in meeting seafood demand in the United States. Adopting a capture-and-reuse waste management model similar to terrestrial agriculture farmers would allow RAS farmers to monetize effluent and offset production costs. The moisture content and nutrient profile of RAS effluent makes it a potential option for use as a hydroponic fertilizer. Treatment of RAS waste is needed to mineralize particulate-bound nutrients before becoming a viable hydroponic nutrient solution. Anaerobic treatment (AT), a method used by municipal and agricultural waste treatment facilities to reduce total solids, has been shown to successfully mineralize particulate-bound nutrients from RAS effluent. Continuously mixed anaerobic batch bioreactors were used to evaluate the degree to which AT may mineralize particulate-bound nutrients in solid RAS waste. Concentrations of twelve different macro- and micro-nutrients were analyzed in the waste before and after treatment. Effluent samples were analyzed to determine the fraction of each nutrient in the solid and aqueous forms. This study showed that AT is an effective method to mineralize particulate-bound nutrients in RAS effluent and the mineralization rate data may be used to design a pilot-scaled flow-through RAS effluent treatment system.

Comparison of microbial community structures between mesophilic and thermophilic anaerobic digestion of vegetable waste

The anaerobic digestion performance correlates with the functional microbial community. Mesophilic and thermophilic digestions of vegetable waste were conducted, and dynamics of the microbial community were investigated. The mesophilic and thermophilic collapsed stages occurred at organic loading rates of 1.5 and 2.0 g VS/(L d) due to the accumulation of volatile fatty acids with final concentrations of 2276 and 6476 mg/L, respectively. A high concentration of volatile fatty acids caused the severe inhibition of methanogens, which finally led to the imbalance between acetogenesis and methanogenesis. The mesophilic digestion exhibited a higher microbial diversity and richness than the thermophilic digestion. Syntrophic acetate-oxidizing coupled with hydrogenotrophic methanogenesis was the dominant pathway in the thermophilic stable system, and acetoclastic methanogenesis in the mesophilic stable system. The dominant acidogens, syntrophus, and methanogens were unclassified_f__Anaerolineaceae (8.68%), Candidatus_Cloacamonas (19.70%), Methanosaeta (6.10%), and Methanosarcina (4.08%) in the mesophilic stable stage, and Anaerobaculum (12.59%), Syntrophaceticus (4.84%), Methanosarcina (30.58%), and Methanothermobacter (3.17%) in thermophilic stable stage. Spirochaetae and Thermotogae phyla were the characteristic microorganisms in the mesophilic and thermophilic collapsed stages, respectively. These findings provided valuable information for the deep understanding of the difference of the microbial community and methane-producing mechanism between mesophilic and thermophilic digestion of vegetable waste.

Water-Energy-Nutrients Synergies in the Agrifood Sector: A Circular Economy Framework

Circular economy is emerging as a regenerative concept that minimizes emissions, relies on renewable energy, and eliminates waste based on the design of closed-loop systems and the reuse of materials and resources. The implementation of circular economy practices in resource-consuming agricultural systems is essential for reducing the environmental ramifications of the currently linear systems. As the renewable segment of circular economy, bioeconomy facilitates the production of renewable biological resources (i.e., biomass) that transform into nutrients, bio-based products, and bioenergy. The use of recycled agro-industrial wastewater in agricultural activities (e.g., irrigation) can further foster the circularity of the bio-based systems. In this context, this paper aims to provide a literature review in the field of circular economy for the agrifood sector to enhance resource efficiency by: (i) minimizing the use of natural resources (e.g., water, energy), (ii) decreasing the use of chemical fertilizers, (iii) utilizing bio-based materials (e.g., agricultural/livestock residues), and (iv) reusing wastewater from agrifood operations. The final objective is to investigate any direct or indirect interactions within the water-energy-nutrients nexus. The derived framework of synergetic circular economy interventions in agriculture can act as a basis for developing circular bio-based business models and creating value-added agrifood products.

Enhanced Cadmium Accumulation and Tolerance in Transgenic Hairy Roots of Solanum nigrum L. Expressing Iron-Regulated Transporter Gene IRT1

Solanum nigrum L., a hyperaccumulator of cadmium (Cd), is regarded as a promising candidate for phytoremediation of heavy metal pollution. In the present study, the hairy roots of Solanum nigrum L. were selected as a model plant system to study the potential application of Iron-regulated Transporter Gene (IRT1) for the efficient phytoremediation of Cd pollution. The transgenic hairy roots of Solanum nigrum L. expressing the IRT1 gene from Arabidopsis thaliana were successfully obtained via the Agrobacterium tumegaciens-mediated method. Expression of IRT1 reduced Cd stress-induced phytotoxic effects. Significantly superior root growth, increased antioxidant enzyme activities, decreased reactive oxygen species (ROS) levels, and less cell apoptosis were observed in the transgenic hairy roots of Solanum nigrum L. compared to the wild-type lines under Cd stress. Enhanced Cd accumulation was also carried out in the transgenic hairy roots compared to the control (886.8 μg/g vs. 745.0 μg/g). These results provide an important understanding of the Cd tolerance mechanism of transgenic IRT1 hairy roots of Solanum nigrum L., and are of particular importance to the development of a transgenic candidate for efficient phytoremediation process.

Waste to Energy: A Focus on the Impact of Substrate Type in Biogas Production

Anaerobic digestion is an efficient technology for a sustainable conversion of various organic wastes such as animal manure, municipal solid waste, agricultural residues and industrial waste into biogas. This technology offers a unique set of benefits, some of which include a good waste management technique, enhancement in the ecology of rural areas, improvement in health through a decrease of pathogens and optimization of the energy consumption of communities. The biogas produced through anaerobic digestion varies in composition, but it consists mainly of carbon dioxide methane together with a low quantity of trace gases. The variation in biogas composition are dependent on some factors namely the substrate type being digested, pH, operating temperature, organic loading rate, hydraulic retention time and digester design. However, the type of substrate used is of greater interest due to the direct dependency of microorganism activities on the nutritional composition of the substrate. Therefore, the aim of this review study is to provide a detailed analysis of the various types of organic wastes that have been used as a substrate for the sustainable production of biogas. Biogas formation from various substrates reported in the literature were investigated, an analysis and characterization of these substrates provided the pro and cons associated with each substrate. The findings obtained showed that the methane yield for all animal manure varied from 157 to 500 mL/gVS with goat and pig manure superseding the other animal manure whereas lignocellulose biomass varied from 160 to 212 mL/gVS. In addition, organic municipal solid waste and industrial waste showed methane yield in the ranges of 143–516 mL/gVS and 25–429 mL/gVS respectively. These variations in methane yield are primarily attributed to the nutritional composition of the various substrates.

Circular Economy and Economic Development in the European Union: A Review and Bibliometric Analysis

Increased changes in the climate and ecosystems call for a sustainable economic development, where economic growth should be compatible with the environment goals. In order to do this, it is urgent to find new ways of life and new production systems that make our ecological footprint compatible with global sustainability. The concept of the circular economy has brought relevant contributions to this problem. The central objective of the study presented here is to highlight the main insights presented through scientific literature about the concept of the circular economy within the European Union. In practice, the intention is to show what has already been done about this topic and what can/should be implemented in the future. To achieve these objectives, 144 articles were considered from the Web of Science (Core Collection) for the topics “circular economy” and “European Union”. These documents were, firstly, analysed through a proper literature review and later explored through bibliometric analysis, considering bibliographic data and the VOSviewer software. As the main findings have revealed, the increased importance of this concept within the European Union is recognized. However, this paper also identifies several challenges in the literature, namely the concentration of the identified publications in certain countries, organizations, and authors.

Distillery Stillage: Characteristics, Treatment, and Valorization

Distilleries are among the most polluting industries because ethanol fermentation results in the discharge of large quantities of high-strength liquid effluents with high concentrations of organic matter and nitrogen compounds, low pH, high temperature, dark brown color, and high salinity. The most common method of managing this wastewater (distillery stillage) is to use it for soil conditioning, but this requires thickening the wastewater and may cause soil pollution due to its high nitrogen content. Therefore, treatment of distillery stillage is preferable. This review discusses individual biological and physico-chemical treatment methods and combined technologies. In addition, special attention is paid to valorization of distillery stillage, which is a valuable source of polysaccharides and volatile fatty acids (VFAs), as well as natural antioxidants, including polyphenols and other bioactive compounds of interest to the pharmaceutical, cosmetic, and food industries. New directions in improvement of valorization technologies are highlighted, including the search for new eutectic solvents for extracting these compounds. Such technologies are essential for sustainable development, which requires the use of management and valorization strategies for recovery of valuable compounds with minimal disposal of waste streams.

Polyphenolic Profile and Varied Bioactivities of Processed Taiwanese Grown Broccoli: A Comparative Study of Edible and Non-Edible Parts

Broccoli contains a substantial amount of bioactive compounds such as glucosinolates, phenolics, and essential nutrients, which are positively linked to health-promoting effects. This work aimed to evaluate whether both edible and non-edible parts of broccoli could be effective by examining in vitro antioxidant, cytotoxic, apoptotic, and antibacterial properties of its floret, leaf, and seed extracts (FE, LE, and SE, correspondingly). High-performance liquid chromatography (HPLC) and various assays exhibited strong antioxidant activities of all samples. LE obtained the highest capacity, correlated to its polyphenolic contents. SE exerted significant cytotoxicity against A549, Caco-2, and HepG2 cancer cell lines at low inhibitory concentration (IC)₅₀ values (0.134, 0.209, and 0.238 mg/mL, respectively), as tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry confirmed apoptosis induction of extracts in Caco-2 cells by revealing an increased subG1 population and a decreased mitochondrial membrane potential. The considerable antibacterial efficacy was observed in either LE and SE against Bacillus subtilis and Salmonella typhimurium (0.39-0.78 mg/mL) using well-agar diffusion and minimum inhibitory concentration (MIC) techniques, along with the weak activity against Staphylococcus aureus and Escherichia coli (1.56-3.13 mg/mL). The findings suggest that broccoli and its byproducts might serve as a promising source for further development of food or pharmaceutical products.

A Benefit–Cost Analysis of Food and Biodegradable Waste Treatment Alternatives: The Case of Oita City, Japan

As the generation of food scrap, kitchen, and biodegradable wastes increases, the proper handling of these wastes is becoming an increasingly significant concern for most cities in Japan. A substantial fraction of food and biodegradable waste (FBW) ends up in the incinerator. Therefore, an analytic hierarchy process (AHP) benefit–cost analysis technique was employed in this study to compare different FBW treatment technologies and select the most appropriate FBW disposal technology for Oita City. The four FBW treatment options considered were those recommended by the Japanese Food Waste Recycling Law: anaerobic digestion, compost, landfill, and incineration, which is currently in use. The fundamental AHP was separated into two hierarchy structures for benefit analysis and cost analysis. The criteria used in these two analyses were value added, safety, efficiency, and social benefits for benefit analysis, and cost of energy, cost of operation and maintenance, environmental constraints, and disamenity for cost analysis. The results showed that anaerobic digestion had the highest overall benefit while composting had the least cost overall. The benefit–cost ratio result showed that anaerobic digestion is the most suitable treatment alternative, followed by composting and incineration, with landfill being the least favored. The study recommends that composting could be combined with anaerobic digestion as an optimal FBW management option in Oita City.

One-Step or Two-Step Acid/Alkaline Pretreatments to Improve Enzymatic Hydrolysis and Sugar Recovery from Arundo Donax L

Energy crops are not easily converted by microorganisms because of their recalcitrance. This necessitates a pretreatment to improve their biodigestibility. The effects of different pretreatments, as well as their combination on the enzymatic digestibility of Arundo donax L. were systematically investigated to evaluate its potential for bioconversion. Dilute alkaline pretreatment (ALP) using 1.2% NaOH at 120 °C for 30 min resulted in the highest reducing sugar yield in the enzymatic hydrolysis process because of its strong delignification and morphological modification, while ferric chloride pretreatment (FP) was effective in removing hemicellulose and recovering soluble sugars in the pretreatment stage. Furthermore, an efficient two-step ferric chloride-alkaline pretreatment (FALP) was successfully developed. In the first FP step, easily degradable cellulosic components, especially hemicellulose, were dissolved and then effectively recovered as soluble sugars. Subsequently, the FP sample was further treated in the second ALP step to remove lignin to enhance the enzymatic hydrolysis of the hardly degradable cellulose. As a result, the integrated two-step process obtained the highest total sugar yield of 420.4 mg/g raw stalk in the whole pretreatment and enzymatic hydrolysis process; hence, the process is a valuable candidate for biofuel production.

The Review of Biomass Potential for Agricultural Biogas Production in Poland

Adequate management of biomass residues generated by agricultural and food industry can reduce their negative impacts on the environment. The alternative use for agricultural waste is production of biogas. Biomass feedstock intended as a substrate for the agricultural biogas plants may include energy crops, bio-waste, products of animal and plant origin and organic residues from food production. This study reviews the potential of selected biomass residues from the agri-food industry in terms of use for agricultural biogas production in Poland. The most common agri-food residues used as substrates for biogas plants in Poland are maize silage, slurry, and distillery waste. It is important that the input for the agricultural biogas installations can be based on local wastes and co-products that require appropriate disposal or storage conditions and might be burdensome for the environment. The study also discusses several limitations that might have an unfavourable impact regarding biogas plants development in Poland. Given the estimated biomass potential, the assumptions defining the scope of use of agricultural biogas and the undeniable benefits provided by biogas production, agricultural biogas plants should be considered as a promising branch of sustainable electricity and thermal energy production in Poland, especially in rural areas.

Aspectos estructurales y funcionales de la N-Succinil-L, L-diaminopimelato desuccinilasa, una enzima clave para el crecimiento bacteriano y un blanco para el control antimicrobiano

La N-Succinil-L, L-diaminopimelato desuccinilasa (DapE) es una amidohidrolasa dependiente de iones de zinc, homodimérica estricta, que cataliza la descomposición del N-succinil-L, L-2,6-diaminopimelato (NSDAP), en succinato y diaminopimelato (DAP). Reacción que constituye la única fuente de meso-diaminopimelato (mDAP) y L-Lys en la mayoría de las bacterias. DapE es esencial para el crecimiento bacteriano y un blanco farmacológico antimicrobiano. El desarrollo de los inhibidores anti-DapE debe tener en cuenta las propiedades dinámicas de la enzima. Se buscan compuestos que interfieran con la formación del agujero del oxianión, en donde participan grupos de ambas subunidades del dímero, que se acomoda en posición catalítica mediante el cambio conformacional de la enzima de un estado abierto a uno cerrado, después de la unión del sustrato; estabilizando a los intermediarios de reacción y produciendo un descenso en la energía de activación. Con base en el análisis cristalográfico y el acoplamiento del sustrato en DapE que se presenta en este trabajo, se discute el papel de la flexibilidad conformacional de la enzima en la hidrólisis del sustrato. Se observa que tanto el grupo carbonilo del sustrato es susceptible al ataque como una molécula de agua ubicada en el sitio activo y se encuentran cercanos a la trayectoria de ataque, en el ángulo de Bürgi-Dunitz.

A System Dynamics-Based Approach to Help Understand the Role of Food and Biodegradable Waste Management in Respect of Municipal Waste Management Systems

The long-term plan of any city in Japan is to become a material recycling society. The use of all types of municipal waste is essential in maximizing the full potential of material recovery. As such, municipalities are responsible for managing their waste, including food and biodegradable waste (FBW), and this results in some complex schemes. This study uses the system dynamics approach to illustrate and investigate the benefits of separate treatment of FBW. At the same time, to understand the dynamic interactions between all aspects and elements of the current municipal solid waste management system in Oita City. The developed model includes total environmental benefit, motivation to manage waste and resources, and yield from treatment facilities. The result shows that with the introduction of an anaerobic digester (AD) plant for FBW increases the efficiency of incineration. Furthermore, the result indicates that strengthening the regulation of waste sorted and the reduction in the amount of FBW treated in incineration will improve the current system. This study concludes that any policy or regulation less than the proposed result will yield less benefit. Thus, strengthening regulation is a crucial part of the sustainability of FBW management in the long run.

Sustainable Italian Cities: The Added Value of Biomethane from Organic Waste

This work focuses on the profitability of biomethane plants and the environmental benefits obtained recovering the organic fraction of municipal solid waste in Italy. The economic model is based on the calculations of the net present value, considering multiple capacities of biomethane production (ranging from 50 to 500 m3/h) and alternative scenarios based on the variation in subsidies, the selling price of biomethane, and the net revenues from the treatment of organic waste. The environmental analysis quantifies the reduction in greenhouse gas emissions obtained by natural gas vehicles fueled by biomethane. The economic and environmental results encourage energy change that can be achieved by municipalities that support the transformation of natural resources into green fuels. Across 15 Italian municipalities, the potential biomethane production varies from 80.4 million m3/year to 102.8 million m3/year, with an overall net present value ranging from 135 to 187 million €. In addition, the reduction in greenhouse gas emissions varies from 127 to 162 thousand-ton CO2eq/year. Both the economic and environmental results demonstrate that biomethane is a renewable resource with added value for municipalities.

Enhanced Enzymatic Hydrolysis of Pennisetum alopecuroides by Dilute Acid, Alkaline and Ferric Chloride Pretreatments

In this study, effects of different pretreatment methods on the enzymatic digestibility of Pennisetum alopecuroides, a ubiquitous wild grass in China, were investigated to evaluate its potential as a feedstock for biofuel production. The stalk samples were separately pretreated with H₂SO₄, NaOH and FeCl₃ solutions of different concentrations at 120 °C for 30 min, after which enzymatic hydrolysis was conducted to measure the digestibility of pretreated samples. Results demonstrated that different pretreatments were effective at removing hemicellulose, among which ferric chloride pretreatment (FCP) gave the highest soluble sugar recovery (200.2 mg/g raw stalk) from the pretreatment stage. In comparison with FCP and dilute acid pretreatment (DAP), dilute alkaline pretreatment (DALP) induced much higher delignification and stronger morphological changes of the biomass, making it more accessible to hydrolysis enzymes. As a result, DALP using 1.2% NaOH showed the highest total soluble sugar yield through the whole process from pretreatment to enzymatic hydrolysis (508.5 mg/g raw stalk). The present work indicates that DALP and FCP have the potential to enhance the effective bioconversion of lignocellulosic biomass like P. alopecuroides, hence making this material a valuable and promising energy plant.