Anaerobic digestion of sugarcane bagasse for biogas production and digestate valorization

Bio-physical pre-treatments in anaerobic digestion of organic fraction of municipal solid waste to optimize biogas production and digestate quality for agricultural use

This study optimized the anaerobic digestion (AD) of separated collected organic fractions of municipal solid waste (OFMSW) to produce energy and digestate as biofertilizer. Due to OFMSW's partial recalcitrance to degradation, enzymatic (UPP2, MCPS, USC4, USE2, A. niger) and physical (mechanical blending, heating, hydrodynamic cavitation) pre-treatments were tested. Experimental and modeling approaches were used to compare AD performance regarding energy sustainability and digestate quality. Digestate was separated into solid and liquid fractions, and then chemically and physically characterized by investigating the nutrient release mechanisms. Principal Component Analysis was applied, equally weighing energy and digestate productions. Unlike previous studies focusing only on biogas, this study evaluated the effects of pre-treatments on both biogas and digestate production, viewing AD as a biorefinery process for urban waste valorization. Results showed that all pre-treatments were energetically sustainable, but enzymatic pre-treatments yielded digestates richer in nutrients (increase of 80% N, 200% P and 150% K as compared to OFMSW) and with greater organic matter degradation compared to physical pre-treatments. The liquid fraction of digestate from enzymatic pre-treatments had higher nutrient concentrations, while those from physical pre-treatments had more balanced nutrient content, making them more suitable for fertigation.

A comprehensive review on anaerobic digestion with focus on potential feedstocks, limitations associated and recent advances for biogas production

With the escalating energy demand to accommodate the growing population and its needs along with the responsibility to mitigate climate change and its consequences, anaerobic digestion (AD) has become the potential approach to sustainably fulfil our demands and tackle environmental issues. Notably, a lot of attention has been drawn in recent years towards the production of biogas around the world in waste-to-energy perspective. Nevertheless, the progress of AD is hindered by several factors such as operating parameters, designing and the performance of AD reactors. Furthermore, the full potential of this approach is not fully realised yet due the dependence on people's acceptance and government policies. This article focuses on the different types of feedstocks and their biogas production potential. The feedstock selection is the basic and most important step for accessing the biogas yield. Furthermore, different stages of the AD process, design and the configuration of the biogas digester/reactors have been discussed to get better insight into process. The important aspect to talk about this process is its limitations associated which have been focused upon in detail. Biogas is considered to attain the sustainable development goals (SDG) proposed by United Nations. Therefore, the huge focus should be drawn towards its improvements to counter the limitation and makes it available to all the rural communities in developing countries and set-up the pilot scale AD plants in both developing and developed countries. In this regard, this article talks about the improvements and futures perspective related to the AD process and biogas enhancement.

Pyrolysis kinetics and potential utilization analysis of cereal biomass by-products; an experimental analysis for cleaner energy productions in India

The optimal utilization of biomass relies heavily on the specific material and individual needs. Cereal biomass by-products can potentially be employed in thermochemical processes such as pyrolysis and gasification. To compare biomass sources, ultimate analysis, biochar potential, proximate analysis, thermal gravimetric analysis, price per megajoule generated heat, surface texture, and availability are used. A global survey of biomass wastes and opportunities for heat generation is presented in the current article. Here, nine different cereal-based agricultural waste products (barley, wheat, millet, oats, rice, rye straw, sorghum straw/stalk, and maize cob) are studied. Cereal wastes are compared based on calorific value, water content, volatile matter, ash content and ash chemical composition, bulk density, charring properties, availability, and transportation. According to the estimate, 156 million metric tonnes per year, or 6% of India's total emissions, could be eliminated by rice husk alone. Wheat straws, on the other hand, can cut emissions by 2%. Additionally, processing these nine feedstocks might result in the production of 40 GW of electrical energy, which would increase the installed capacity of India's national electric grid by 9%.

Label-free comparative proteomic analysis of Pleurotus eryngii grown on sawdust, bagasse, and peanut shell substrates

The white rot fungi Pleurotus eryngii are environmental microorganisms that can effectively break down lignocellulosic biomass. However, understanding of the mechanisms by which P. eryngii is effective in degrading lignocellulose is still limited. This work aimed to examine the extracellular secretory proteins implicated in the breakdown of lignocellulose in P. eryngii and identify degradation tactics across various cultivation substrates. Thus, a comparative analysis of the secretory proteins based on Nanoliquid chromatography combined with tandem mass spectrometry was conducted among P. eryngii cultivated on sawdusts, bagasse, peanut shells, and glucose. In total, 647, 616, 604, and 511 proteins were identified from the four samples, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of protein expression differences identified pathways (hydrolytic enzymes, catalytic activity, metabolic processes, cellular processes, and response to stimuli) significantly enriched in proteins associated with lignocellulose degradation in P. eryngii. An integrated analysis of proteome data revealed specifically or differentially expressed genes secreted by P. eryngii in different cultivation substrates. The most prevalent carbohydrate-active enzymes involved in lignocellulose degradation in the secretome of the four samples were laccase (Lac), manganese peroxidase (MnP), aryl alcohol oxidase (AaO), and copper radical oxidase (CRO). Among them, Lac 2 mainly involved in the lignin degradation of sawdust peanut shells, and bagasse by P. eryngii, and Mnp 3 was mainly involved in the degradation of peanut shells. AaO and Lac 4 were mainly involved in glucose substrate defense and oxidative stress. It was found that exogenous addition of sawdust and peanut shells significantly increased lignolytic enzyme abundance. These findings provide insight and guidance for improving agricultural waste resource recovery. In this study, the secretomes of P. eryngii grown on four different carbon sources were compared. The findings revealed the extracellular enzymes implicated in the degradation of lignocellulose, offering avenues for further investigation into the biotransformation mechanisms of P. eryngii biomass and the potential utilization of agricultural wastes. SIGNIFICANCE: The cost of the substrate for mushroom cultivation has increased as the production of edible fungus has risen year after year. Therefore, the use of these locally available lignocellulosic wastes as substrates offers a cost-cutting option. Further, the overuse of wood for the cultivation of edible mushrooms is also detrimental to the conservation of forest resources or the ecological environment. Consequently, the use of other agricultural wastes as an alternative to sawdust or other woody substrates is a viable approach for cultivating P. eryngii. The distribution of extracellular lignocellulosic degrading enzymes, inferred in the present study could help improve the cultivation efficiency of P. eryngii vis-à-vis managing agricultural waste.

Gene cloning, expression, and characterization of two endo-xylanases from Bacillus velezensis and Streptomyces rochei, and their application in xylooligosaccharide production

Endo-xylanase hydrolyzing xylan in cellulosic residues releasing xylobiose as the major product at neutral pH are desirable in the substitute sweeteners industry. In this study, two endo-xylanases were obtained from Streptomyces rochei and Bacillus velezensis. SrocXyn10 showed the highest identity of 77.22%, with a reported endo-xylanase. The optimum reaction temperature and pH of rSrocXyn10-Ec were pH 7.0 and 60°C, with remarkable stability at 45°C or pHs ranging from 4.5 to 11.0. rBvelXyn11-Ec was most active at pH 6.0 and 50°C, and was stable at 35°C or pH 3.5 to 10.5. Both rSrocXyn10-Ec and rBvelXyn11-Ec showed specific enzyme activities on wheat arabinoxylan (685.83 ± 13.82 and 2809.89 ± 21.26 U/mg, respectively), with no enzyme activity on non-xylan substrates. The Vmax of rSrocXyn10-Ec and rBvelXyn11-Ec were 467.86 U mg-1 and 3067.68 U mg-1, respectively. The determined Km values of rSrocXyn10-Ec and rBvelXyn11-Ec were 3.08 g L-1 and 1.45 g L-1, respectively. The predominant product of the hydrolysis of alkaline extracts from bagasse, corncob, and bamboo by rSrocXyn10-Ec and rBvelXyn11-Ec were xylooligosaccharides. Interestingly, the xylobiose content in hydrolysates by rSrocXyn10-Ec was approximately 80%, which is higher than most reported endo-xylanases. rSrocXyn10-Ec and rBvelXyn11-Ec could be excellent candidates to produce xylooligosaccharides at neutral/near-neutral pHs. rSrocXyn10-Ec also has potential value in the production of xylobiose as a substitute sweetener.

Biogas production from malt bagasse from craft beer industry: kinetic modeling and process simulation

In this work, biogas was synthesized from malt enriched-craft beer bagasse with the objective to generate clean energy. Thus, a kinetic model based on thermodynamic parameters was proposed to represent the process with coefficient determination (R2) of 0.82. A bench-top biodigester of 2.0 × 10-3 m3 was built in glass, and equipped with sensors to measure pressure, temperature, and methane concentration. The inoculum selected for the anaerobic digestion was the granular sludge, and malt bagasse was used as substrate. Data were fitted to a pseudo-first-order model for the formation of methane gas using the Arrehnius equation as basis. For the simulations of biogas production, the Aspen Plus™ software was used. Results from 23 factorial design experiments evidenced that equipment was efficient, and the craft beer bagasse showed great biogas production, with nearly 95% of methane yield. The temperature was the variable that showed most influence in the process. Moreover, the system has a potential for the generation of 10.1 kWh of clean energy. Kinetic constant rate for methane production was 5.42 × 10-7 s-1 and activation energy 8.25 kJ mol-1. A statistical analysis using a math software was performed and evidenced that the temperature played a major role in the biomethane conversion.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10163-023-01715-7.

Effect of physical and thermal pretreatment of lignocellulosic biomass on biohydrogen production by thermochemical route: A critical review

Energy demands and immense environmental degradation have extorted for production of low-carbon and carbon-neutral fuels. Abundantly available lignocellulosic biomass is second-generation feedstock which has potential to produce biofuels. Among all biofuels, biohydrogen is carbon neutral and sustainable biofuel which can be produced by thermochemical conversion routes mainly gasification. However, there are still numerous unsolved challenges related to physicochemical properties of lignocellulosic biomass. To tackle these issues, physical, chemical and thermal pretreatment methods can be employed to improve these properties and further strengthen usability of biomass for biohydrogen production. Pelletization, torrefaction and hydrothermal carbonization pretreatment have shown significant results for treating biomass and biohydrogen enhancement. This study reviews physical and thermal pretreatment and its effect on biohydrogen yield. Framework of techno-economic analysis of processes is provided for examining feasibility of required pretreatments. This sustainable approach will help to reduce emissions and promote concept of bioenergy with carbon capture and storage.

A review on biological methodologies in municipal solid waste management and landfilling: Resource and energy recovery

Rapid industrialization and urbanization growth combined with increased population has aggravated the issue of municipal solid waste generation. MSW has been accounted for contributing tremendously to the improvement of sustainable sources and safe environment. Biological processing of MSW followed by biogas and biomethane generation is one of the innumerable sustainable energy source choices. In the treatment of MSW, biological treatment has some attractive benefits such as reduced volume in the waste material, adjustment of the waste, economic aspects, obliteration of microorganisms in the waste material, and creation of biogas for energy use. In the anaerobic process the utilizable product is energy recovery. The current review discusses about the system for approaching conversion of MSW to energy and waste derived circular bioeconomy to address the zero waste society and sustainable development goals. Biological treatment process adopted with aerobic and anaerobic processes. In the aerobic process the utilizable product is compost. These techniques are used to convert MSW into a reasonable hotspot for resource and energy recovery that produces biogas, biofuel and bioelectricity and different results in without risk and harmless to the ecosystem. This review examines the suitability of biological treatment technologies for energy production, giving modern data about it. It likewise covers difficulties and points of view in this field of exploration.

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.

Valorization of sugarcane bagasse for sugar extraction and residue as an adsorbent for pollutant removal

Following juice crushing for sugar or bioethanol production from sugarcane, bagasse (SCB) is generated as the main lignocellulosic by-product. This study utilized SCB generated by a hydraulic press as feedstock to evaluate sugar extraction as well as adsorption potential. Total soluble sugar (sucrose, glucose, and fructose) of 0.4 g/g SCB was recovered with H2O extraction in this case. Insoluble sugar, that is, cellulose in SCB, was further hydrolyzed into glucose (2%–31%) with cellulase enzyme, generating a new bagasse residue (SCBE). Persulfate pretreatment of SCB slightly enhanced saccharification. Both SCB and SCBE showed great potential as adsorbents with 98% of methylene blue (MB) removed by SCB or SCBE and 75% of Cu2+ by SCBE and 80% by SCB in 60 min. The maximum adsorption amount (qm) was 85.8 mg/g (MB by SCB), 77.5 mg/g (MB by SCBE), 3.4 mg/g (Cu2+ by SCB), and 1.2 mg/g (Cu2+ by SCBE). The thermodynamics indicated that the adsorption process is spontaneous, endothermic, and more random in nature. The experimental results offer an alternative to better reutilize SCB.

Food Additives from Fruit and Vegetable By-Products and Bio-Residues: A Comprehensive Review Focused on Sustainability

Food waste is one of the fundamental issues when it comes to environmental impacts, and this type of waste results in the food’s loss itself, but also that of water, energy, fertilizers, and other resources used for its production. Many vegetable parts are removed from the final product before reaching retail (peels, roots, and seeds), and these raw materials are rich sources of highly valuable molecules such as phytochemicals, minerals, vitamins, and other compounds with health benefits (prevention of several diseases, improvement of the immune system, regulating gastrointestinal transit, and others). Therefore, substantial efforts have been made to find technological solutions to avoid food waste, namely through its reuse in the food chain, thus promoting the circular economy and sustainability. This review focuses on the biggest wastes generated by the food industry, the most common destinations, and case studies applying these by-products or biowaste in the food industry.