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.

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.

Culturing and molecular methods to assess the infectivity of porcine circovirus from treated effluent of swine manure.

Samples were collected at the effluent of two swine manure treatment systems and were analyzed by qPCR to determine the presence and amounts of porcine circovirus (PCV2) genetic material. ST cells were inoculated with the positive samples to evaluate virus viability and for viral genotyping. Twenty-five water samples were collected monthly from treated effluent (March 2009 to December 2010). The PCV2 genome was identified by qPCR in 60% of the samples, and all of the positive samples were able to infect ST cells in vitro. Positive samples were genotyped and 60% of them were positive for both PCV2a and PCV2b, 20% were positive for genotype 2a, and 20% were positive for genotype 2b. Our results suggest that these viruses were able to resist the regular wastewater treatment, and this finding demonstrates the necessity of adding a virus inactivation step to the treatment system to guarantee the safety of water reuse.

Detection of circoviruses and porcine adenoviruses in water samples collected from swine manure treatment systems.

Samples collected from two swine manure treatment systems including: swine manure treatment system and demonstrative unit (SMTS and DU), were analyzed by qPCR to quantify the amount of porcine adenovirus (PAdV) and porcine circovirus (PCV2) present. Positive samples were tested for virus integrity using DNase assay. Fifty-six water samples were collected monthly from March 2009 to May 2010. PAdV genome was found 66% of the samples in the SMTS and in 78% of the samples in the DU system. PCV2 was detected in 96% of samples collected from the SMTS system and in 86% of samples from DU. DNase assay revealed that there were undamaged virus particles of both PAdV and PCV2 in all sampling sites in the SMTS. However, undamaged particles of both viruses were detected in samples from the DU system in the affluent and middle sites, though undamaged PCV2 was absent in the effluent samples.

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.