Abstract
ABSTRACT This research aimed to evaluate the biogas production during the anaerobic biodigestion process of dairy cattle manure, with and without solids separation. Sixteen biodigesters of the batch type were used, each one with 2L of capacity, supplied with manure in four different conditions: (1) pure manure, after washing the floors of the free stall system; (2) manure after the solids separator; (3) manure after the solids separator and sand decanter and (4) manure with the solid retained in separator solids, dissolved in water. The hydraulic retention time was of 196 days. The highest reductions of volatile solids (VS) were obtained for the biodigesters supplied with manure that went through some process of solids separation. The highest potential of methane production(CH4) obtained was of 0.2686 m³ CH4 kg −1 of added VS, supplied to digesters with manure after solids separator. The best potential for biogas and methane production was observed when there was a reduction of the solids concentration in the manure and, in this case, the hydraulic retention time can be reduced, which reduces the volume of the biodigester and the cost of implementation and maintenance, but the highest biogas production occurred in the biodigesters without solids separation.
Highlights
The increased demand for animal products causes the intensive exploitation of animals, which are grouped in large numbers, producing large volumes of manure in small areas, generating problems both for their treatment and disposal, as well as for environmental pollution.The possibility of biogas recovery in the treatment of manure has highlighted Bovine farming as one of the main activities for producing large amounts of manure
Biogas recovery is possible with the use of biodigesters and, according to BARBOSA & LANGER (2011); the biodigester represents an excellent alternative for the treatment of generated manure, since it is the producer responsibility, who must provide an appropriate destination to them.Batch type biodigesters are loaded at one time, fermenting for a suitable period, and the material is discharged after the end of the actual biogas production period (BONTURI & VAN DIJK, 2012)
The manure, when collected to enter the biodigester, may contain fractions that may be considered non-biodegradable or slowly biodegradable, arising from food parts not degraded by the animal, such as fibers, or from the washing process as sand, for example.These fractions can affect the process of anaerobic digestion and some authors recommend that the separation of this fraction occurs so that the process becomes more efficient, fast and more economical because it requires reactors with smaller size for the same number of animals (MOLLER et al, 2004)
Summary
Brazil presents as a major cattle producer and in 2012, it had a herd of more than 212 million cattle and, according to the IBGE (2012), the total number of milked cows accounted for approximately 10.9% of the actual cattle, with approximately 23 million cows being milked.The increased demand for animal products causes the intensive exploitation of animals, which are grouped in large numbers, producing large volumes of manure in small areas, generating problems both for their treatment and disposal, as well as for environmental pollution.The possibility of biogas recovery in the treatment of manure has highlighted Bovine farming as one of the main activities for producing large amounts of manure.In practice, biogas recovery is possible with the use of biodigesters and, according to BARBOSA & LANGER (2011); the biodigester represents an excellent alternative for the treatment of generated manure, since it is the producer responsibility, who must provide an appropriate destination to them.Batch type biodigesters are loaded at one time, fermenting for a suitable period, and the material is discharged after the end of the actual biogas production period (BONTURI & VAN DIJK, 2012).The manure, when collected to enter the biodigester, may contain fractions that may be considered non-biodegradable or slowly biodegradable, arising from food parts not degraded by the animal, such as fibers, or from the washing process as sand, for example.These fractions can affect the process of anaerobic digestion and some authors recommend that the separation of this fraction occurs so that the process becomes more efficient (greater production of biogas / kg of solid), fast (less hydraulic retention time) and more economical because it requires reactors with smaller size for the same number of animals (MOLLER et al, 2004).Eng. The increased demand for animal products causes the intensive exploitation of animals, which are grouped in large numbers, producing large volumes of manure in small areas, generating problems both for their treatment and disposal, as well as for environmental pollution.The possibility of biogas recovery in the treatment of manure has highlighted Bovine farming as one of the main activities for producing large amounts of manure. Biogas recovery is possible with the use of biodigesters and, according to BARBOSA & LANGER (2011); the biodigester represents an excellent alternative for the treatment of generated manure, since it is the producer responsibility, who must provide an appropriate destination to them.Batch type biodigesters are loaded at one time, fermenting for a suitable period, and the material is discharged after the end of the actual biogas production period (BONTURI & VAN DIJK, 2012). Agríc., Jaboticabal, v.37, n.3, p.426-432, maio/jun. 2017
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