Fungus-based bioherbicides on circular economy.

This review aimed to show that bioherbicides are possible in organic agriculture as natural compounds from fungi and metabolites produced by them. It is discussed that new formulations must be developed to improve field stability and enable the commercialization of microbial herbicides. Due to these bottlenecks, it is crucial to advance the bioprocesses behind the formulation and fermentation of bio-based herbicides, scaling up, strategies for field application, and the potential of bioherbicides in the global market. In this sense, it proposed insights for modern agriculture based on sustainable development and circular economy, precisely the formulation, scale-up, and field application of microbial bioherbicides.

The potential of animal manure management pathways toward a circular economy: a bibliometric analysis.

Improper disposal of animal waste is responsible for several environmental problems, causing eutrophication of lakes and rivers, nutrient overload in the soil, and the spread of pathogenic organisms. Despite the potential to cause adverse ecological damage, animal waste can be a valuable source of resources if incorporated into a circular concept. In this sense, new approaches focused on recovery and reuse as substitutes for traditional processes based on removing contaminants in animal manure have gained attention from the scientific community. Based on this, the present work reviewed the literature on the subject, performing a bibliometric and scientometric analysis of articles published in peer-reviewed journals between 1991 and 2021. Of the articles analyzed, the main issues addressed were nitrogen and phosphorus recovery, energy generation, high-value-added products, and water reuse. The energy use of livestock waste stands out since it is characterized as a consolidated solution, unlike other routes still being developed, presenting the economic barrier as the main limiting factor. Analyzing the trend of technological development through the S curve, it was possible to verify that the circular economy in the management of animal waste will enter the maturation phase as of 2036 and decline in 2056, which demonstrates opportunities for the sector's development, where animal waste can be an economic agent, promoting a cleaner and more viable product for a sustainable future.

Estimation of greenhouse gases emission from domestic wastewater in Nepal: A scenario-based analysis applicable for developing countries.

Domestic wastewater and wastewater treatment plants (WWTPs) are key emitters of greenhouse gases (GHGs). Quantifying these emissions in the present and future is crucial to tackle global climate change issues. As a developing country with few rural and urban wastewater treatment facilities, Nepal may have a unique opportunity to reduce future GHGs emissions by a proper selection of wastewater treatment technology. In this paper, the authors used Python programming to estimate the GHGs emissions from the domestic wastewater sector in Nepal under various technological development scenarios for 2020 to 2040 using the refined 2019 estimation methodology developed by Inter-governmental Panel on Climate Change (IPCC). Results show total equivalent CO2 emission of 3829.43 and 4523.65 Gigagrams in 2020 and 2040, respectively. The 2020 value is seven times greater than Nepal's 2017 national estimates because this study considered rural population and updated methodology. Comparing the technology development scenarios with the Business as Usual scenario, the highest GHGs reduction could be achieved by hybrid constructed wetlands (69.20%) followed by a combined anaerobic and aerobic system with biogas recovery for energy generation (61.72%). Further accuracy may be attained only through the actual measurement of WWTPs emissions and country-specific emission factors. Thus, this paper proposes GHGs estimation of future scenarios portraying urban and rural populations may be invaluable to policymakers of GHGs mitigation for selection of feasible WWTPs, especially in developing countries with limited wastewater treatment facilities and wastewater activity data.

Nutritional, Energy and Sanitary Aspects of Swine Manure and Carcass Co-digestion.

Renewable energy can assist the management of the effects of population growth and rapid economic development on the sustainability of animal husbandry. The primary aim of renewable energy is to minimize the use of fossil fuels via the creation of environmentally friendly energy products from depleted fossil fuels. Digesters that treat swine manure are extensively used in treatment systems; and inclusion of swine carcasses can increase the organic loading rate (OLR) thereby improving biogas yield and productivity on farms. However, the characteristics of the components including animal residues, proteins, lipids, remains of undigested feed items, antimicrobial drug residues, pathogenic microorganisms and nutrient contents, are complex and diverse. It is therefore necessary to manage the anaerobic process stability and digestate purification for subsequent use as fertilizer. Efficient methane recovery from residues rich in lipids is difficult because such residues are only slowly biodegradable. Pretreatment can promote solubilization of lipids and accelerate anaerobic digestion, and pretreatments can process the swine carcass before its introduction onto biodigesters. This review presents an overview of the anaerobic digestion of swine manure and carcasses. We analyze the characteristics of these residues, and we identify strategies to enhance biogas yield and process stability. We consider energy potential, co-digestion of swine manure and carcasses, physical, chemical, and biological pretreatment of biomass, sanitary aspects of swine manure and co-digestates and their recycling as fertilizers.

Cellulolytic enzyme production from agricultural residues for biofuel purpose on circular economy approach.

This study evaluated the production of cellulolytic enzymes from different agricultural residues. The crude enzyme extract produced was characterized and applied for saccharification of some agricultural residues. Maximum cellulolytic activities were obtained using soybean hulls. All enzymatic activities were highly stable at 40 °C at a pH range of 4.5-5.5. For stability at low temperatures, the enzyme extract was stored at freezing temperature and cooling for about 290 days without major loss of activity. The Km values found for total cellulase (FPase), endoglucanase (CMCase), and xylanase were 19.73 mg ml-1, 0.65 mg ml-1, and 22.64 mg ml-1, respectively, and Vmax values were 0.82 mol min-1 mg-1, 0.62 mol min-1 mg-1, and 104.17 mol min-1 mg-1 to cellulose, carboxymethyl cellulose, and xylan, respectively. In the saccharification tests, the total amount of total reducing sugars (TRS) released from 1 g of soybean hulls catalyzed by the enzymes present in the crude enzyme extract was 0.16 g g-1 dry substrate.

Efficient and low-cost alternative of lipase concentration aiming at the application in the treatment of waste cooking oils.

In this study, we evaluated the concentration of lipases from Aspergillus niger using efficient and low-cost methods aiming at application in the treatment of waste cooking oils. The change in ionic strength of the medium by the addition of salt and precipitation with ethanol increased the specific activity from 2.90 to 28.50 U/mg, resulting in a purification factor of 9.82-fold. The use of acetone resulted in a specific activity of 33.63 U/mg, resulting in a purification factor of 11.60-fold. After that, the concentrated lipase was used in the hydrolysis of waste cooking oil and 753.07 and 421.60 µmol/mL of free fatty acids were obtained for the enzyme precipitated with ethanol and acetone, respectively. The hydrolysis of waste cooking oil catalyzed by homemade purified lipase in ultrasonic media can be considered a pretreatment of oil by converting a significant amount of triglycerides into free fatty acids.

Assessment of two immobilized lipases activity and stability to low temperatures in organic solvents under ultrasound-assisted irradiation.

Both stability and catalytic activity of two commercial immobilized lipases were investigated in the presence of different organic solvents in ultrasound-assisted system. In a general way, for Novozym 435, the use of ethanol as solvent led to a loss of activity of 35% after 10 h of contact. The use of iso-octane conducted to a gradual increase in lipase activity in relation to the contact time, reaching a maximum value of relative activity of 126%. For Lipozyme RM IM, after 5 h of exposure, the enzyme presented no residual activity when ethanol was used as solvent. The solvents tert-butanol and iso-octane showed an enhancement of about 20 and 17% in the enzyme activity in 6 h of exposure, respectively. Novozym 435 and Lipozyme IM presented high stability to storage after treatment under ultrasound-assisted system using n-hexane and tert-butanol as solvents.

Assessment of process variables on 2-ethylhexyl palmitate production using Novozym 435 as catalyst in a solvent-free system.

This work reports the optimization of 2-ethylhexyl palmitate production by esterification reaction in a solvent-free system using a commercial lipase as catalyst. For this, a sequential strategy was performed applying three experimental designs. An empirical model was built so as to assess the effects of process variables on the reaction conversion. Afterward, the operating conditions that optimized 2-ethylhexyl palmitate production were determined to be acid to alcohol molar ratio of 1:5.5, 70 degrees C, 150 rpm and 10.5 wt% of enzyme, leading to a reaction conversion as high as 93%. From this point, a kinetic study was carried out evaluating the influence of acid to alcohol molar ratio, enzyme concentration and temperature on product yield. Results obtained in this step allow to conclude that an excess of alcohol (acid to alcohol molar ratio of 1:6), relatively low enzyme concentration (10 wt%) and temperature of 70 degrees C led to nearly complete reaction conversion.