Integral approach for the evaluation of poultry manure, compost, and digestate: Amendment characterization, mineralization, and effects on soil and intensive crops.

The egg industry has increased its production worldwide during the last decades. Several waste management strategies have been proposed to treat large volumes of poultry manure. Composting and anaerobic digestion are the main stabilization processes used. However, there are disagreements on the criteria for applying raw and treated poultry manure to the soil. We studied the relationship between physicochemical, toxicological, microbiological, parasitological, and metabarcoding parameters of raw and treated poultry manure (compost and digestate). Subsequently, we evaluated the mineralization of C, N and P, and the effects of amended soil on horticultural and ornamental crops. Compost and digestate presented better general conditions than poultry manure for use as organic soil amendments. The highest pathogenic microorganism content (total and fecal coliforms, Escherichia coli, and Salmonella spp.) was recorded for poultry manure. Multivariate analyses allowed associating a lower phytotoxicity with compost and a higher microbial diversity with digestate. Therefore, only compost presented stability and maturity conditions. We found high released CO2-C, N loss, and P accumulation in soil amended with a high dose of poultry manure during mineralization. However, high doses of poultry manure and digestate increased the biomass production in the valorization assay. We recommend the soil application of stabilized and mature poultry manure-derived amendments, which reduce the negative impacts on the environment and promote more sustainable practices in agricultural systems.

Performance of semi-continuous anaerobic co-digestion of poultry manure with fruit and vegetable waste and analysis of digestate quality: A bench scale study.

Poultry manure (PM) can contain ammonium and ammonia nitrogen, which may inhibit the anaerobic process. The aim of this work was to evaluate the performance of anaerobic digestion of PM co-digested with fruit and vegetable waste. Two semi-continuous bench scale (19L) stirred tank reactors were used. The operating conditions were: 34.5 °C, 2 gVS/L.d (organic load rate), 28 d of hydraulic retention time and 100 revolutions per m (1 h × 3 times by day) for the agitation. The reactors were fed PM and a mixture of PM and fruit and vegetable waste (FVW) at equal proportions (based on wet weight). The performance of the anaerobic process was assessed through biogas and methane yields, reduction of organic matter, release of nitrogen compounds and the monitoring of stability indicators (pH, volatile fatty acids (VFA), total (TA) and partial (PA) alkalinity). Moreover, the digestate quality was evaluated to determine potential risk and benefits from its application as biofertilizer. Toxicity was assessed using Daphnia magna immobilization tests. Results showed that biogas and methane yields from PM-FVW were 31% and 32% higher than PM alone, respectively. Values of organic matter, pH, alpha (PA/TA) and VFA revealed that stability was approached in PM and PM-FVW. The co-digestion of PM with FVW led to the highest methane and biogas yields, lower FAN and TAN concentrations, and a better digestate quality compared to mono-digestion of this manure.

Toxicity of the effluent from an anaerobic bioreactor treating cereal residues on Lactuca sativa.

Effluents generated during the process of anaerobic digestion should be treated before their disposal into the environment. The aim of this study was evaluating the effectiveness of the effluent treatment system from an anaerobic bioreactor, assessing the toxicity reduction with the Lactuca sativa seed germination and root elongation inhibition test. Three sampling points were selected along the effluent treatment system: inflow into the first treatment pond, outflow from the third pond and recirculated flow to the bioreactor. Effluent dilutions tested for each sampling point were 25% and 50% (v/v), undiluted sample and controls. The pH, conductivity, temperature, dissolved oxygen, BOD5 and COD were measured. The decrease in the organic and inorganic loads was correlated with a reduction in the phytotoxicity. The use of the seed toxicity test allows evaluating the quality and effectiveness of the studied effluent treatment system.