Diluation and separation physical of solids and liquids of broiler litter for evaluation of anaerobic digester

ABSTRACT:The solid separation techniques indicate that it can promote a support in anaerobic biological process. This trial was realized in FCAV-UNESP, Jaboticabal, Brazil, in Rural Engineering Department. For this trial two tests were developed, using broiler litter water diluted and separated in a 3mm mesh screen: the treatments consisted in (1kg) broiler litter diluted in (2kg) of water, (1kg) broiler litter and (4kg) water, (1kg) broiler litter diluted in (6kg) of water, (1kg) broiler litter and (8kg) of water, (1kg) broiler litter diluted in (10kg) of water, (1kg) broiler litter and (12kg) water and (1kg) broiler litter diluted in (14kg) of water. Total solids (TS), solid and liquid fraction and biogas production were estimated. There were no significant differences related to solid fraction retained in screen. As the broiler litter became more diluted, a raise in the liquid fractions quantities was observed, ranging from 20.9 to 89.4% of the total diluted waste. Biogas production potentials ranged from 0.2364 to 0.4666 m³ of biogas by 100kg of liquid fraction. Organic carbon numbers ranged from 0.21 to 0.47kg by 100kg of liquid fraction and 5.36 to 6.18kg by 100kg of solid fraction. The highest values obtained for this element in liquid fractions dilutions were 2:1 and 6:1 with 0.46 and 0.47kg by 100kg respectively. The separation of liquid and solid fraction of broiler litter was viable in the smaller dilutions, because those guarantee a reduction in the anaerobic digester implementation costs and dilution water economy. Solid fraction has potential for composting, mainly in a great scale production.

KEYWORDS: anaerobic digestion, animal manure, broiler litter, sludge

With the improvement on the food's production, the livestock is increasing the participation on the environment impacts, thereby it is necessary the developing of sustainability system production (AMORIM et al, 2004). Therefore, today the utilization of the animal manure as energy is must important on the livestock and many companies are investing money on this field (animal manure - recycle nutrients), thinking about the environment impacts too.

The improvement of the production broiler litter is the must worry, cause of this solids waste has a higher pollution power, mainly by higher nitrogen and carbon organic concentration. The solids manure has power combustion of 14.8 x 1012 Kcal (JONES JR. & OGDEN, 1984) and can to be use in associating with coal mineral too. Other option of manage is the separation of solids and liquids fractions, with different goals for each waste.

The liquid fraction can be used in anaerobic digestion and the solids fraction for composting for crop fertilizer or cow bedding. However for a good optimization of anaerobic digestion, this substrate waste, liquid fraction, can to need of accounts on the characteristic of total solids with dilutions for a better performance of the digester. The apparent performance of a separation system will depend on the volume of the solids fraction produced as percentage of the feed stream.

A simple mass balance can show that this will rapidly increase as the feed concentration approaches that of the final solids stream (MARTINEZ et al., 1995). The total solids content of a liquid manure or slurry is divided, in general terms, between that dissolved and that present as suspended matter. Beyond this, a useful fractionation of the suspended matter can be made to reflect the performance of the main groups of separating equipment available, these fractions are dissolved solids, colloidal particle, fine solids, coarse solids and fibre (BURTON, 2007). These technical of separation indicated that it is can to promote a support aerobic biological processes in removing relatively indigestible material from the feed stream; enhance anaerobic digestion performance by producing a concentrated feed from a dilute effluent; produce a compostable solid fraction from liquid manures. Thereby, the aim of this trial was to value the dilution and separation of solids and liquids of broiler litter for supply of digester on the estimate potential biogas' production of liquid fraction of broiler litter.

This trial was realized in FCAV-UNESP, Jaboticabal, Brazil, in Rural Engineering Department. The campus is located at the following geographical coordinates 21015'22'' S; 48018'58'' W and an altitude of 575 meters.

For this trial two test were developed, using reused broiler litter obtained from one commercial producer in the city of São Carlos, 93Km away from Jaboticabal, Brazil, the litter used was made of peanut shell, water diluted and separated in a 3mm mesh screen: the treatments consisted in (1kg) broiler litter diluted in (2kg) of water, (1kg) broiler litter and (4kg) water, (1kg) broiler litter diluted in (6kg) of water, (1kg) broiler litter and (8kg) of water, (1kg) broiler litter diluted in (10kg) of water, (1kg) broiler litter and (12kg) water and (1kg) broiler litter diluted in (14kg) of water.

Solid and liquid fractions were weighted to calculate the percentage of liquid dilution that accessed by static screen and the holding material on screen. Then were analyzed total solids (TS%) at 65°C and 105ºC for humidity correction, organic carbon (C%), to identify organic matter content, organic matter compostable content and organic matter resistant content. The medium values were analyzed by Tukey's Test (p<0.05) by statistic program (FERREIRA, 2000).

The means values by separation of solids fraction (SF) and liquid fraction (LF) of broiler litter in different dilution, total solids (TS) of liquid fraction (LF) and estimative of biogas' production (EBP) were present in Table 1. Did not observed difference significant (p>0.05) in amount of solids fraction held on screen.

 

TABLE 1 - Mean values by separation of solids fraction (SF) and liquid fraction (LF) of broiler litter in different dilution, total solids (TS) of liquid fraction (LF) and estimative of biogas' production (EBP)

Biogas' production of TS added in batch-load digesters with broiler litter on dilution 4:1 (water:broiler litter) of the 0.228m³ of biogas/kg of TS add.

The most diluting of the broiler litter with water, the volume of the liquid fractions would increase, varying from 20.9 to 89.4% of the total manure diluted. There was difference significant (p<0.05) in amount of liquid fraction.

The most diluting of the broiler litter, the total solids decreased, because the screen held the same amounts of the material for the different dilutions and the treatments with higher dilutions, most amounts of the water were used for the same amount of TS.

The contents of the TS were varying on liquid fraction from 1.4 to 5.0%. These parameters are most important to supply of anaerobic digesters because this is have relation with biogas production (ITODO & AWULU, 1999). If the contents of the TS are very higher or very lower, the process can to inhibit (YADVIKA et al. 2004).

Besides, substrates more diluted with low contents of TS and, as a result of this, low potential biogas production, increase the costs in building of the digesters. The potential biogas production varied from 0.2364 to 0.4666 m3 of biogas per 100 kg of liquid fraction. The low values were on the 2:1 dilution and the high values were on the 6:1 dilution. If the results obtained these two dilution were utilized for dimension of the digesters, can to observed (for this 6:1 dilution) that would be necessary a volume with three time more capacity for it obtain the double of biogas production, then increase the costs of this system.

The other factor necessary to value is the TS content, because on the low dilution approached of the values recommend by LUCAS JR. (1996), that was 8% TS of broiler litter manure. Therefore, the TS contents can to influence on the choice of the better model and size digester. The carbon contents of the solids and liquids fractions are presented in Figure 1.

 

FIGURE 1 - The carbon contents in kg per 100 kg of the solids and liquids fractions, by dilutions of the broiler litter with water.

The amounts of organic carbon varied from de 0.21 to 0.47 kg per 100 kg of the liquid fraction and from 5.36 to 6.18 kg per 100 kg of the solids fraction. The high values by liquid fraction were obtained in dilution 2:1 and 6:1 with 0.46 and 0.47 kg per 100 kg, respectively. This is show that the same amount carbon can to entry in the anaerobic digester by both dilutions using the same unit of broiler liter. The solids fraction can to be a potential for composting, mainly if were obtained in a great scale production. However, the analyses of relation between carbon:nitrogen of each dilution were not realized.

The liquid and solid broiler litter fractions are possible in the lower dilutions, because those guarantee a reduction in the anaerobic digester implementation costs and in the economy of water dilution. Solid fraction has potential for composting, mainly in a great scale production.

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