Anaerobic digestion of poultry litter: technical aspects to improve process performance and water saving

In order to mitigate the significant electricity consumption in poultry farming the anaerobic digestion (AD) has been adopted. This study aimed to obtain information about the dilution, solid/liquid separation, mass balance, and reuse of the biofertilizer (recycle) to dilute poultry litter and to promote water saving while generating an organic fertilizer richer in nutrients. Five dilutions (1:4, 1:6, 1:8, 1:10, and 1:12) were submitted to mass balance test followed or not by solid/liquid separation on a sieve. The fractions of the dilutions 1:6 to 1:10 (poultry litter:water, w:v) were subjected to a test to determine the biochemical methane potential, according to the VDI-4630 standards. The highest potential biogas production was obtained in the liquid fraction of the dilution 1:6, reaching 179.4 L CH4 kg−1 VSadded. This condition was subjected to a semi-continuous feeding to evaluate the biofertilizer to replace water to dilute poultry litter (recycle). The results showed that the replacement of 40% of the dilution water by the biofertilizer had no inhibitory effect on the anaerobic digestion process, reaching values of 236 and 226 L CH4 kg−1 VSadded without and with the recycle, respectively. The decrease in the use of water and an increase in nutrients contained in the effluent (biofertilizer) is reflected in a 66% larger area for corn production. A detailed study of economic feasibility is essential for decision-making on investment and its recovery (payback).Thus, the liquid fraction of the dilution 1:6 with the recycle allowed a 40% saving in the use of clean water for poultry litter dilution, providing a biofertilizer with higher amounts of nitrogen, one of the nutrients most demanded by most crops.