RESUMO: A co-digestão dos dejetos suínos associados a resíduos vegetais é uma alternativa que pode elevar as produções de biogás e metano alcançadas pela digestão isolada do dejeto. No entanto, recomendações que se baseiem na melhor proporção entre dejeto e forragem, assim como na idade de colheita ainda são escassas na literatura. O objetivo do trabalho foi avaliar inclusões crescentes (0, 25, 50, 75 e 100% dos sólidos totais (ST) de capim elefante (Pennisetum purpureum Schum.) colhido em duas idades de corte mediana (MA) aos 45 dias de crescimento e avançada (AA) aos 90 dias, empregado em co-digestão com o dejeto suíno, adotando-se delineamento inteiramente ao acaso, em esquema fatorial 5x2. Foram utilizados biodigestores batelada de bancada, sendo as produções de biogás acompanhadas durante 12 semanas. Houve influência da idade da forragem (P<0,05) na degradação de sólidos e fibra em detergente neutro, com maiores valores para os substratos que continham a forragem MA. Os maiores rendimentos de CH4 foram alcançados pelos substratos que continham forragem MA na inclusão de 27,7 e 31,6 %, sendo de 253,7 e 222,2 L de CH4 por Kg de ST ou sólido volátil adicionado. A idade das forragens influenciou o início e a persistência das produções de biogás ao longo do período de digestão, sendo vantajosa apenas na inclusão de 25% de forragem com MA.

ABSTRACT: The co-digestion of swine manure with vegetable waste is an alternative that can increase the production of biogas and methane generated by the isolated digestion of manure. However, recommendations that are based on the best ratio between manure and forage, as well as the age of harvest, are still scarce in the literature. This study was conducted to evaluate inclusions (0, 25, 50, 75 and 100%) of the total solids (TS) of Elephant grass (Pennisetum purpureum Schum) harvested at two ages medium age (MA) at 45 days of growth and advanced age (AA) at 90 days in co-digestion with swine manure, using an entirely randomized design in a 5x2 factorial scheme. Batch digesters were used and biogas production was monitored for 12 weeks. There was influence of forage age (P <0.05) on the degradation of solids and neutral detergent fiber, with higher values for the substrates containing MA forage. The highest CH4 yields were obtained by the substrates containing MA forage in the inclusion of 27.7 and 31.6%, being 253.7 and 222.2 L of CH4 per Kg of total or volatile solids. The age of the forages influenced the onset and persistence of biogas production, being advantageous only in the inclusion of 25% of MA forage. The AA forage inclusion is not recommended for co-digestion with swine manure.

ABSTRACT We aimed to evaluate the effects of crude glycerine purity and levels of glycerol on the fermentative profile, microorganisms counting, and nutritional value of Piatã grass silage. The experiment was carried out in a 3×3+1 completely randomized factorial design using three different types of crude glycerine [low purity (40% of glycerol), medium purity (60% glycerol), and high purity (80% glycerol)], three doses of glycerol (20, 40, and 60 g/kg DM), and a control (no crude glycerine added) as an additional treatment, which were stored for 80 days. Statistical differences were not observed on fermentative losses of the treatments tested. The increase of glycerol doses resulted in higher levels of non-fibrous carbohydrates and lower levels of fibre components. The addition of low-purity crude glycerine increased the levels of fat and in vitro digestibility of silages. The highest levels of lactic acid and acetic acid occurred in the treatments with 60 g/kg of glycerol when using crude glycerine with a low purity. The lowest lactic acid content was observed in the control treatment and in the lowest dose of glycerol. The highest glycerol dose (60 g/kg), associated with the lowest degree of crude glycerine purity (40%) resulted in the greatest nutritional value and provided the best silage conservation.

ABSTRACT: The composting of laying hen manure is an efficient way of treating waste and producing an organic fertilizer with excellent characteristics; however, the high N losses reduce its concentration in the resulting fertilizer. Associating this residue with crude glycerin (CG) promotes a better C:N ratio and contributes to higher N retention during composting, with improvements in solids reduction and production of organic fertilizer with higher concentration of this nutrient. We carried out this research considering the hypothesis that adding CG – a byproduct of biodiesel production – to laying hen waste composting provides better N retention in the fertilizer generated. Increasing CG doses (0, 3, 6, 9, and 12 % in relation to the fresh mass in the windrows) were added to the laying hen manure with windrows composted for 70 days. A reduction by 100 % in total and thermotolerant coliforms occurred at all levels of CG addition. The maximum reductions in total (TS) and volatile (VS) solids were 64 and 76 %, respectively, and occurred with the addition of 6 % CG. The windrows that did not receive CG had higher N losses during the process (32 %) while the highest N concentration in the compost was 5 % at 6 % CG. We identified that adding 6 % CG to the laying hen manure in co-composting increases the reductions in TS and VS and provides higher N retention, which improves the quality of the organic fertilizer.

RESUMO: Objetivou-se encontrar a melhor dose de inclusão de óleo residual durante a co-digestão de substratos preparados com dejetos de bovinos leiteiros e suínos, com o intuito de maximizar as reduções de sólidos e as produções de biogás. Foram realizadas no abastecimento e desabastecimento dos biodigestores as análises de sólidos totais (ST), sólidos voláteis (SV) e fibra em detergente neutro (FDN), enquanto as mensurações de biogás duas vezes por semana. A máxima redução de SV (51,4%) foi possibilitada pela inclusão de até 54,6g de óleo de descarte kg dejetos-1, já as máximas degradações de FDN ocorreram com adições de até 69,4g de óleo de descarte kg dejetos-1. As inclusões de até 64g de óleo de descarte kg dejetos-1 possibilitaram produções específicas de biogás de 291,4 e 251,0 L de biogás.kg SV-1 adicionado, para substratos contendo dejetos de suínos e bovinos respectivamente. A adição de óleo em doses entre 45,1 e 69,4g.kg-1 a substratos contendo dejetos de bovinos ou suínos maximiza as reduções dos constituintes sólidos e fibrosos bem como potencializa as produções específicas de biogás, sendo que o dejeto de suíno ainda suporta maiores doses de inclusão de óleo residual.

ABSTRACT: This study aimed to obtain the best dose of waste cooking oil inclusion for the co-digestion of substrates prepared with dairy cattle and swine manure in order to maximize solids reductions and biogas yield. Analyses of total solids (TS), volatile solids (VS), and neutral detergent fiber (NDF) were performed during the loading and unloading of digesters, while biogas yield was measured twice a week. The maximum reduction in VS (51.4%) was reached with the inclusion of up to 54.6g waste cooking oil.kg manure-1. Maximum NDF degradation occurred with inclusions of up to 69.4g waste cooking oil.kg manure-1. Inclusions of up to 64g of waste cooking oil.kg manure-1 provided specific biogas yield of 291.4 and 251.0L biogas.kg VS-1 added to substrates with swine and cattle manure, respectively. Adding oil at doses between 45.1 and 69.4g waste cooking oil kg manure-1 to substrates composed of cattle or swine manure maximizes reductions of solids and fibrous constituents and enhances specific biogas yield. Furthermore, swine manure supports higher doses of waste cooking oil.

ABSTRACT The objective of this study was to evaluate fermentation losses and the nutritional value of silage of Brachiaria brizantha cv BRS Piatã ensiled with different levels of crude glycerin. The experiment followed a 4 × 2 completely randomized factorial design with four doses of crude glycerin (0, 100, 200, and 300 g kg–1 of DM silage) and two cutting ages (45 and 60 days) with four replicates per treatment (silos). The parameters of dry matter losses, effluents losses, gas losses, pH, microbial population, and nutritional value of the silage were evaluated. There was no difference in pH among the tested doses of crude glycerin. However, reductions in dry matter and gas losses were observed as a function of crude glycerin doses. Bacterial populations of lactic acid and facultative mesophilic anaerobes also increased as a function of crude glycerin inclusion. Crude glycerin increased ether extract levels and reduced neutral detergent fiber and acid detergent fiber concentrations (dilution effect), improving chemical composition of the silage. Crude glycerin can be used in the ensiling of Piatã grass and the dose of 300 g kg–1 of DM yields the best results.

ABSTRACT Anaerobic digestion of crude glycerin (CG) along with animal waste has been an excellent option for increasing the production of biogas and methane to achieve efficiency in the treatment of both residues. This study aimed to evaluate improvements in specific productions of biogas and methane, reductions in solid and fibrous components in substrates prepared with dairy cattle manure and CG (containing 14 % glycerol). With these residues, experimental substrates were prepared and placed in 25 batch digesters. Initial content of the TS in the influent was 4 % and CG was added in increasing doses (0, 5, 10, 15 and 20 % relative to total solids (TS) of the influent). Results were submitted to ANOVA and orthogonal contrasts to assess the effects of linear and quadratic order and thereby estimate the optimal CG doses through the adjusted models. The highest values for specific production of methane (0.19 and 0.26 L g−1 of TS and volatile solids (VS) added, respectively) were reached with the CG inclusions of 6 and 8 %, respectively. Total production of biogas with the inclusion of 6 % CG was 11 % higher when compared to the control treatment. The largest reduction in VS (48 %) was achieved with the addition of 4 % CG. Addition of CG at levels between 3 and 8 % improved the efficiency of the process of anaerobic digestion with dairy cattle manure.

RESUMO O objetivo foi avaliar o desempenho da co-digestão anaeróbia de dejetos de suínos associados com crescentes doses de glicerina bruta, adotando-se diferentes tempos de retenção hidráulica (TRH). O delineamento utilizado foi inteiramente casualizado em esquema fatorial 3x4, três TRH (10; 17 e 24 dias) e quatro doses de glicerina bruta (0; 5; 10 e 15% dos sólidos totais), com quatro repetições por tratamento. Os parâmetros avaliados foram produção e potencial de produção de biogás, reduções de sólidos totais (ST), fibra em detergente neutro (FDN) e fibra em detergente ácido (FDA). A produção de biogás e potencial de produção apresentaram efeito quadrático nos TRH de 17 e 24 dias, evidenciando como doses ideais 4,09 e 5,63% de glicerina bruta, respectivamente, para produção e 4,52 e 5,42% de glicerina bruta para potencial de produção. Não houve diferença entre as doses de glicerina bruta dentro do TRH de 10 dias para as reduções de ST. No entanto, foi observado diferença entre as doses nos TRH 17 e 24, com a maior redução observada de 54,9% ao incluir 5% de glicerina bruta no maior TRH. As reduções de FDN e FDA aumentaram de acordo com a adição de glicerina bruta nos TRHs de 10 e 17 dias. A inclusão de 4 a 6% de glicerina bruta no TRH 24 mostrou-se mais eficiente na produção de biogás e reduções de ST e FDN. Já visando maior redução de FDA pode-se utilizar doses mais altas de glicerina a partir da co-digestão com dejetos suínos.

ABSTRACT The aim of this study was to evaluate the performance of the anaerobic co-digestion of pig manure associated with increasing doses of crude glycerine, adopting different periods of hydraulic retention time (HRT). A completely randomised design was used in a 3 x 4 factorial scheme, three HRT (10, 17 and 24 days) and four doses of crude glycerine (0, 5, 10 and 15% of the total solids), with four replications per treatment. The parameters to be evaluated were biogas production and potential production, reduction in total solids (TS), neutral detergent fibre (NDF) and acid detergent fibre (ADF). Biogas production and potential production displayed a quadratic effect for an HRT of 17 and 24 days, showing the doses of 4.09% and 5.63% crude glycerine to be respectively optimal for production, and 4.52% and 5.42% crude glycerine for production potential. There was no difference between the doses of crude glycerine at the HRT of 10 days for reductions in TS. However, a difference was seen between doses at HRT 17 and 24, with the greatest reduction of 54.9% being found when including 5% of crude glycerine at the greatest HRT. The reductions in NDF and ADF were greater with the addition of crude glycerine for an HRT of 10 and 17 days. The inclusion of 4% - 6% crude glycerine at HRT 24 was more efficient in the production of biogas and reducing TS and NDF. With a view to a greater reduction in ADF, higher doses of glycerine can be used in the co-digestion of pig manure.

ABSTRACT 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.

ABSTRACT 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.