Livestock waste management for energy recovery in Brazil: a life cycle assessment approach.

Livestock farming has exerted intense environmental pressure on our planet. The high emissions to the environment and the high demands of resources for the production process have encouraged the search for decarbonization and circularity in the livestock sector. In this context, the objective of this study was to evaluate and compare the environmental performance of two different uses for biogas generated in the anaerobic digestion of animal waste, either for electricity generation or biomethane. For this purpose, a life cycle assessment approach was applied to evaluate the potential of anaerobic digestion as a management technology for three different livestock wastes, related to beef cattle, dairy, and sheep in the Brazilian animal production context. The results suggest that the treatment scenarios focusing on biomethane generation were able to mitigate the highest percentage of damages (77 to 108%) in the global warming category when compared to the scenarios without the use of anaerobic digestion (3.00·102 to 3.71·103 kgCO2 eq) or in the perspective of electricity generation (mitigation of 74 to 96%). In terms of freshwater eutrophication, the generation of electricity (- 2.17·10-2 to 2.31·10-3 kg P eq) is more favorable than the purification of biogas to biomethane (- 1.73·10-2 to 2.44·10-3 kg P eq), due to the loss of methane in the upgrading process. In terms of terrestrial ecotoxicity, all scenarios are very similar, with negative values (- 1.19·101 to - 7.17·102 kg 1,4-DCB) due to the benefit of nutrient recovery, especially nitrogen, associated with the use of digestate as fertilizer, which was one of the critical points in all scenarios. Based on these results, it is evident that proper management of all stages of the treatment life cycle is the key to decarbonization and circularity in livestock waste management. The biogas use does not present different effects on the environmental performance of the scenarios studied, demonstrating that the purpose should be chosen according to the needs of each plant or management system.

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.

Integration of swine manure anaerobic digestion and digestate nutrients removal/recovery under a circular economy concept.

The application of the circular economy concept should utilize the cycles of nature to preserve materials, energy and nutrients for economic use. A full-scale pig farm plant was developed and validated, showing how it is possible to integrate a circular economy concept into a wastewater treatment system capable of recovering energy, nutrients and enabling water reuse. A low-cost swine wastewater treatment system consisting of several treatment modules such as solid-liquid separation, anaerobic digestion, biological nitrogen removal by nitrification/denitrification and physicochemical phosphorus removal and recovery was able to generate 1880.6 ± 1858.5 kWh d-1 of energy, remove 98.6% of nitrogen and 89.7% of phosphorus present in the swine manure. In addition, it was possible to produce enough fertilizer to fertilize 350 ha per year, considering phosphorus and potassium. In addition, the effluent after the chemical phosphorus removal can be safely used in farm cleaning processes or disposed of in water bodies. Thus, the proposed process has proven to be an environmentally superior swine waste management technology, with a positive impact on water quality and ensuring environmental sustainability in intensive swine production.

Phycoremediation and biomass production from high strong swine wastewater for biogas generation improvement: An integrated bioprocess.

This study investigated the phycoremediation process from swine digestate integrated with photosynthetic biomass and biogas production in the context of circular economy. Effects of total ammonia nitrogen (TAN) and pH on biomass productivity and nutrients removal, using a central rotational composite design, were evaluated. pH showed a significant effect on biomass productivity and phosphate removal. The strain Chlorella sorokiniana (LBA#39) was able to tolerate up to 1300 mg TAN L-1 at neutral pH, with maximum biomass productivity of 198 mg DW L-1 d-1 and removal of 90 and 70 (%) of phosphate and nitrogen, respectively. The biomass harvested after phycoremediation from digestate showed high content of volatile solids (95.4%) and proteins (59.5%). Biochemical methane potential (BMP) from microalgae monodigestion was 292 ± 10 mLNCH4 gVSadd-1. The use microalgae biomass addition in the biodigestion process increased up to 32.1% in biogas production. It is an attractive approach to integrating raw materials into existing agro-industrial facilities and improving biogas production, adopting the concept of circular economy and mitigating greenhouse gas emissions.

Pre-treatment Strategies for Value Addition in Poultry Litter.

We studied different pre-treatments of poultry litter aiming to add economic value to this residue. Strategies were applied to extract ammonium nitrogen with the aim of allowing its further use as fertilizer, and to promote the hydrolysis and solubilization of lignocellulosic components with the aim of facilitating its subsequent conversion to biogas. Ammonia extraction was performed by solubilization in water in a one-step process and by successive extraction steps (3 times 60 min). Successive extractions presented greater removal of total ammonia nitrogen than did one-step extraction, solubilizing about 36% of the ammonia in water. In parallel pre-treatment using ultrasound was performed to increase carbon bioavailability for anaerobic digestion. Using this tool, 24.7 g kg-1 of total organic carbon and 13.0 g kg-1 of total reducing sugars were solubilized, employing 10% dry mass sample amount, 100% amplitude ultrasound at frequency of 20 kHz amplitude and 2.5 min of treatment (energy input of 299 ± 7 kJ L-1; 3,822 ± 95 kJ kg-1). Anaerobic digestion of ultrassound pre-treated biomass was evaluated using a biological biogas production assay, and an increase of 10% of biogas production was obtained compared to untreated samples (147.9 and 163.0 mL g-1 for crude and pre-treated PL, respectively). The findings suggest that these are environmentally friendly and sustainable strategies to add economic value to poultry litter, reducing the environmental impacts of improper disposal.

Sanitary effectiveness and biogas yield by anaerobic co-digestion of swine carcasses and manure.

The present study evaluated anaerobic co-digestion of swine manure and swine carcasses for biogas yield and inactivation/behaviour of pathogens purpose. Biochemical Methane Production tests were performed with samples containing ratios of 3, 7.5 and 15 kgcarcass m-3 manure. For pathogens inactivation experiments known amounts of model microrganisms (sensitive and resistant) were artificially inoculated in anaerobic reactors at 24°C and 37°C. The addition of carcass resulted in an increase until 119% of biogas yield compared to swine manure mono-digestion. Salmonella enterica, Escherichia coli and PCV2 were reduced >3log10 (24°C or 37°C) during 30 days. At 37°C, MS2 and PhiX-174 were reduced 3log10 and 1.8log10, respectively. At 24°C, MS2 reduced 1.5 log10 and PhiX-174 did not present any decay over 30 days. Considering the most resistant biomarkers pathogens, as bacteriophage, we recommend the swine carcasses pre-treatment, such as high temperatures, for sanitary security.

Bioethanol from Spirulina platensis biomass and the use of residuals to produce biomethane: An energy efficient approach.

This study aimed to produce bioethanol using Spirulina platensis biomass and the use of saccharification and fermentation wastes of bioethanol production to produce biomethane. The potential for energy generation in each technological route was quantified. Both, the enzymatic hydrolysis of the microalgae polysaccharides and the fermentation process, presented efficiencies above 80%. The fermentation of the hydrolyzate into ethanol was possible without the addition of synthetic nutrients to the must. The direct conversion of Spirulina biomass to biomethane had an energy potential of 16,770 kJ.kg-1, while bioethanol production from the hydrolysed biomass presented 4,664 kJ.kg-1. However, the sum of the energy potential obtained by producing bioethanol followed by the production of biomethane with the saccharification and fermentation residues was 13,945 kJ.kg-1. Despite this, the same raw material was able to produce both biofuels, demonstrating that Spirulina microalgae is a promising alternative to contribute in the field of renewable energies.

Chemical phosphorus removal: a clean strategy for piggery wastewater management in Brazil.

The intensive production of animal protein is known to be an environmental polluting activity, especially if the wastewater produced is not managed properly. Swine production in Brazil is growing, and technologies to manage all pollutants present in the wastewater effluent are needed. This work presents a case of study of phosphorus (P) removal from piggery wastewater using Ca(OH)2, and demonstrates the feasibility of this strategy for P management. The effluent of a swine manure treatment plant was treated with Ca(OH)2. According to the addition of Ca(OH)2 the pH of the effluent ranged from 8.0 to 10.0. Different conditions of sludge dewatering were evaluated, and the chemical composition of sludge was investigated. Ion chromatography analysis of effluent samples showed that 92% of total P (TP) was present as soluble P (SP) whereas 75% of SP species were present as phosphate. The efficiency of P removal was typically 90% at pH 8.5 and higher than 98% at pH 10.5. The sludge was separated by sedimentation, centrifugation or filtration and dried. The TP content of dried sludge was 9.3% (w/w). X-ray diffraction analysis of the dry sludge showed the presence of amorphous compounds of Ca and P, which is an indication that the sludge obtained from the swine manure treatment has a potential for application as biofertilizer.