Anaerobic Digestion of Broiler Litter to Produce Biogas Under Laboratory Conditions.

Various technologies have been developed to convert animal waste into renewable energy that could reduce the World dependence on fossil fuels. Nevertheless, these technologies are out of reach of resource-limited farmers. Alabama produces considerable amount of broiler litter that is added to cropland and/or pasture land. However, before the broiler litter is added to soil, biogas can be produced from the litter to add value and to reduce environmental pollution. A laboratory scale experiment was conducted to produce methane (CH₄) under anaerobic conditions. Broiler litter and goat manures were obtained from local farms, mixed with tape water (1:4), and sieved (to pass through a 125-µm sieve). The pH of the slurry in a plastic bottle (355 mL) was adjusted to 6.5, 7.0, and 7.5 with acetic acid (vinegar). The treatments studied were broiler litter (BL) alone, goat (GT) alone, and a mixture of BL + GT (1:1). The top and the bottom of the bottle were perforated and Tygon tubing was inserted permanently for replenishing and removing an aliquot of the slurry daily for analysis. The capped bottle was inverted and kept on a vertical position on a test tube rack with an air headspace of 30% for biogas accumulation. The bottle was incubated at room temperature for 51 days. Each day 40 ml of slurry was removed (and replenished with new slurry) through the tubing from the bottle and the pH was recorded. The gas, hydrogen sulfite (H₂S) and CH₄ generated were measured (Ibrid MX6, Industrial Scientific, Oakdale, PA). The slurry pH significant (P <0.001) affected the biogas released; the H₂S released varied from 0 to 500 ppm and the methane released varied from 0 to 30% with the highest in the BL treatment.