Swine manure treatment technologies as drivers for circular economy in agribusiness: A techno-economic and life cycle assessment approach.

Anaerobic digestion has been employed as a technology capable of adding value to waste coupled with environmental impact mitigation. However, many issues need to be elucidated to ensure the systems viability based on this technology. In this sense, the present study evaluated technically, environmentally, and economically, four configurations of swine waste treatment systems focused on the promotion of decarbonization and circularity of the swine chain. For this, a reference plant, based on a compact treatment process named SISTRATES® (Portuguese acronym for swine effluent treatment system) was adopted to serve as a model for comparison and validation. The results showed the importance of prioritization of the energy recuperation routes through anaerobic digestion, providing increased economic benefits and minimizing environmental damage. Thus, the SISTRATES® configuration was the one that presented the best designs in a circular context, maximizing the recovery of energy and nutrients, along with the reduction of greenhouse gas emissions, ensuring the sustainability of the pig production chain.

Assessment of a tannin-based organic polymer to harvest Chlorella vulgaris biomass from swine wastewater digestate phycoremediation.

This study investigated the efficiency of an organic tannin polymer alone or amended with polyacrylamide to harvest Chlorella vulgaris biomass grown in a laboratory-scale photobioreactor treating swine wastewater digestate. The effect of biomass concentration, tannin (TAN) dosages and changes in pH were evaluated in jar test experiments. Among the TAN concentrations tested (11, 22, 44, 89, 178 mg L(-1)), 11 mg L(-1) showed the highest biomass recovery (97%). The highest coagulation/ flocculation efficiencies were obtained at pH 5 to 7. Flocculation efficiency improved from 50 to 97% concomitant with the increasing biomass concentrations from 45 to 165 mg L(-1), respectively. Recovery efficiencies above 95% were achieved with the same TAN dosage (11 mg L(-1)) irrespective of the concentration of organic carbon present (75 to 300 mg TOC L(-1)). Overall, the results suggest that TAN could become an interesting alternative choice of non-toxic organic polymer for harvesting Chlorella sp. from organic-rich wastewater.

Performance of two swine manure treatment systems on chemical composition and on the reduction of pathogens.

Swine effluents must be correctly handled to avoid negative environmental impacts. In this study, the profiles of two swine manure treatment systems were evaluated: a solid-liquid separation step, followed by an anaerobic reactor, and an aerobic step (System 1); and a biodigester followed by serial lagoons (System 2). Both systems were described by the assessment of chemical, bacterial and viral parameters. The results showed that in System 1, there was reduction of chemicals (COD, phosphorus, total Kjeldhal nitrogen - TKN - and NH(3)), total coliforms and Escherichia coli; however, the same reduction was not observed for Salmonella sp. Viral particles were significantly reduced but not totally eliminated from the effluent. In System 2, there was a reduction of chemicals, bacteria and viruses with no detection of Salmonella sp., circovirus, parvovirus, and torque teno virus in the effluent. The chemical results indicate that the treated effluent can be reused for cleaning swine facilities. However, the microbiological results show a need of additional treatment to achieve a complete inactivation for cases when direct contact with animals is required.

Advanced swine manure treatment and utilization in Brazil.

Animal production has changed from subsistence to an industrial model, lowering production costs but giving rise to higher potential environmental impact. When the effluents are not correctly managed, serious pollution events can occur. In Brazil liquid manure is commonly stored in reception pits or covered lagoons (biodigestors), followed by land application as a biofertilizer. In some regions there is an excess of manure due to low soil support capacities, and in these cases new technologies have to be adopted to export or treat the excess effluent. Manure storage time in pits/covered lagoons and new polymers to separate the solid fraction have been studied in Brazil. Treatment technologies, like swine manure treatment systems (SMTS), have been developed from a technical and economical point of view to optimize the processes and give a technological alternative to pork producers increasing production while reducing environmental impact.

Effect of storage time on swine manure solid separation efficiency by screening.

Confined animal feeding operations (CAFOs) have suffered considerable transformations since the last decade in Brazil, because of increasing of their production scale. Swine production is following this same trend, and the volume of manure produced and the form that is managed has a direct impact on houses air quality and efficiency of treatment systems. The objective of this work was to study the manure solid-liquid separation efficiency by screening, subject to different screen opening sizes and pit disposal time under tropical climate conditions. An ammoniacal nitrogen producing rate of 24 mg/L per storage day was observed and a decrease in screen separation efficiency in the first eight days of storage, obtained by solid group analysis. The storage time influenced directly the degradation of organic fraction indicated by the chemical oxygen demand increase overtime. The results suggest that the efficiency of solid-liquid separation is increased when carried out with the shortest storage time.