Alice Watte Schwingel

Addition of lipolytic enzyme in anaerobic co-digestion of swine manure and inclusion levels of waste vegetable oil

*Corresponding Author: E-mail: anaorrico@ufgd.edu.br Studies that aim the reusing of agro-industrial wastes have become very important due to the high production of this sector and environmental preservation. The objective of this work was to evaluate the performance of digesters loaded with swine manure, increasing inclusion levels of waste oil and lipolytic enzyme, through the potential of biogas and methane production, as well as reductions in levels of total solids (TS) and volatile solids (VS). Batch digesters were loaded with substrates containing 4% TS, composed of pig manure, waste oil (ratios of 8, 10 and 12% in relation to levels of TS in the substrate) and lipolytic enzyme (0.05, 0.10, 0.15, 0.20 and 0.25% in relation to levels of TS in the substrate), water and inoculum. Maximum reduction of TS and VS were 56.13 and 64.49% respectively and occurred in inclusion levels of 0.15 and 0.13% lipase and 12% oil. The greatest potential for methane for the amounts of TS and VS added (0.23 and 0.29L) were achieved by inclusion of 12% oil and levels of 0.12 and 0.11% lipase, and these values were up to 29.7% higher than yields observed for the lowest inclusion level of enzyme. The inclusion of 12% oil and 0.15% lipase in the composition of substrates containing pig manure improves the yields of methane and reductions in pollutant constituents.

Co-digestion of swine excreta associated with increasing levels of crude glycerin

The objective of this research was to evaluate the performance of anaerobic co-digestion of swine excreta associated with increasing doses of crude glycerin and different hydraulic retention times (HRT). A completely randomized design was adopted in a 3 × 4 factorial arrangement composed of three HRT (10, 17, and 24 days) and four crude glycerin doses (0, 5, 10, and 15 g/100 g of total solids [TS]), with four replications per treatment. The assessed parameters were: biogas production potential, reductions of volatile solids (VS), chemical oxygen demand (COD), and most probable number of total and thermotolerant coliforms. The biogas production per added VS presented quadratic effect at 17 and 24 days of HRT, with ideal doses of 5.5 and 5.9 g of crude glycerin/100 g TS, respectively. There was no difference among glycerin doses at 10-day HRT for VS reductions; however, at HRT of 17 and 24 days, there were differences, with greater reduction of 61.1% for 5 g of crude glycerin/100 g TS at 24-day HRT. The COD reduction values showed an effect among retention times, in which the 24-day HRT provided the best results. Reductions in coliforms were greater than 99%, with no difference among treatments. Addition of 5 to 6 g of crude glycerin/100 g TS with a 24-day HRT is more effective in biogas production and reduction of VS, COD, and coliforms from co-digestion of swine excreta.

Biogas production: litter from broilers receiving direct-fed microbials and an enzyme blend

The effect of additives used in the feed of broilers on anaerobic bio-digestion of poultry litter was evaluated. Four diets were used: NC: negative control; DFM: NC + 500 ppm direct-fed microbials (DFM) containing Bacillus subtilis and Bacillus licheniformis; ENZ: diet formulated with an enzyme blend (20 ppm phytase, 200 ppm protease and 200 ppm xylanase); DFM+E: ENZ + DFM. Substrates for the anaerobic bio-digestion were prepared with litter from each treatment, containing 4 % total solids (TS). These were used in 16 continuous bio-digesters with a 2 kg d−1 load, to determine the production and potential biogas production and composition during an 85-day period. Influent and effluent samples were collected for the amounts of TS and volatile solids (VS), fiber fraction (neutral detergent fiber [NDF], acid detergent fiber [ADF] and lignin), nutrients (N, P and K), and total and thermotolerant coliforms to be determined. For all treatments a reduction in the following effluents was observed as follows: TS (49, 48, 48 and 50 %) VS (70, 54, 55 and 62 %) NDF (91, 90, 95 and 96 %) ADF (89, 88, 93 and 94 %) and lignin (80, 76, 89 and 88 %). The efficiency of the treatment for coliforms in bio-digesters was higher than 90 % in the 85-day period in all treatment groups. There was a reduction in biogas and methane production when DFM (5500 and 4000 mL) and DFM + E (5800 and 4100 mL) were used, compared to treatments NC (6300 mL and 4400) and ENZ (6400 and 4500 mL). The potential production of reduced TS and VS was higher in ENZ (1:00 and 1.74 106 mL kg−1) when compared to NC (0.88 and 1:02 106 mL kg−1), DFM (0.80 and 1:40 106 mL kg−1) and DFM + E (0.88 1:25 and 106 mL kg−1). The additives did not affect the percentage of methane production, and all treatments showed values higher than 70 %. Adding enzymes to the diet of broilers influences the litter characteristics and, as a consequence, increases biogas production. The addition of DFM and DFM + E to broiler diets reduced biogas and methane production.

Desempenho da co-digestão anaeróbia de dejetos suínos com inclusão de glicerina bruta

O objetivo foi avaliar o desempenho da co-digestao anaerobia de dejetos de suinos associados com crescentes doses de glicerina bruta, adotando-se diferentes tempos de retencao hidraulica (TRH). O delineamento utilizado foi inteiramente casualizado em esquema fatorial 3x4, tres TRH (10; 17 e 24 dias) e quatro doses de glicerina bruta (0; 5; 10 e 15% dos solidos totais), com quatro repeticoes por tratamento. Os parâmetros avaliados foram producao e potencial de producao de biogas, reducoes de solidos totais (ST), fibra em detergente neutro (FDN) e fibra em detergente acido (FDA). A producao de biogas e potencial de producao apresentaram efeito quadratico nos TRH de 17 e 24 dias, evidenciando como doses ideais 4,09 e 5,63% de glicerina bruta, respectivamente, para producao e 4,52 e 5,42% de glicerina bruta para potencial de producao. Nao houve diferenca entre as doses de glicerina bruta dentro do TRH de 10 dias para as reducoes de ST. No entanto, foi observado diferenca entre as doses nos TRH 17 e 24, com a maior reducao observada de 54,9% ao incluir 5% de glicerina bruta no maior TRH. As reducoes de FDN e FDA aumentaram de acordo com a adicao de glicerina bruta nos TRHs de 10 e 17 dias. A inclusao de 4 a 6% de glicerina bruta no TRH 24 mostrou-se mais eficiente na producao de biogas e reducoes de ST e FDN. Ja visando maior reducao de FDA pode-se utilizar doses mais altas de glicerina a partir da co-digestao com dejetos suinos.