Poultry Litter Solid State Anaerobic Digestion: Effect of Digestate Recirculation Intervals and Substrate/Inoculum Ratios on Process Efficiency

Abstract

This study evaluated the effect of the substrate:inoculum ratio and digestate recirculation conditions on the biogas and methane yield, free ammonia concentration and solid phase agronomic quality (after treatment) of poultry litter solid state anaerobic digestion (SSAD). Experimental tests were conducted using a central composite design (2²), with four trials at the factorial points and three at the central points, using poultry litter as substrate that was collected after 12 cycles of broiler production [TS 76% (w.w −1 )]. Three laboratory-scale reactors containing 3 kg of poultry litter each were operated at mesophilic conditions (37 • C) and seven experimental runs were performed at retention time of 30 days each. There were three substrate:inoculum ratios (1:1; 1:1.66, and 1:3) and three daily recirculation intervals (2, 3, and 4 times per day), and each recirculation event lasted 15 min. The highest biogas and methane yields were183 L Nbiogas .kg VSadd , respectively, and they were obtained at the substrate:inoculum ratio of 1:3 with a digestate recirculation frequency of four times a day. Digestate recirculation was the variable that influenced the concentration of free ammonia; the most frequently recirculated tests had lower concentrations (below 60 mgNH 3 .L −1 ). After the SSAD process, we identified a transfer of nutrients (N, P, K) from the solid phase to the liquid phase. The nutrient concentrations in the solid phase (N out = 11 g.kg −1 , K out = 5 g.kg −1 , and P out = 7 g.kg −1 ) indicated that the digested poultry litter still has potential for use in fertilization. In this study, it was estimated that 90 m 3 biogas .tons −1 poultrylitter was generated using SSAD. Whereas 100 tons of poultry litter are produced after 12 production cycles, the biogas generation capacity reaches 9,000 m 3 /year. In this scenario, farmers can use biogas from poultry litter SSAD as an additional source of energy.

Nitrogen Mineralization in a Sandy Soil Amended with Treated Low-Phosphorus Broiler Litter

“…These environmental risks are leading to the development of technologies to manage nutrient-rich broiler litter that allow the recycling of nutrients as organic soil amendments or plant fertilizer materials. Several management programs and technologies have been developed to solve the problem of surplus N and P from spent broiler litter including: (1) Transfer of broiler litter to nutrient-deficient agricultural lands as compost [6], as fine particles [7] or in pelletized form [8]; (2) improved manure application methods, such as subsurface soil placement of broiler litter, to prevent ammonia emissions or nutrient runoff [9,10]; (3) energy generation by thermal conversion such as incineration [11] or biological anaerobic digestion [12]; and (4) acidification with addition of chemicals to retain N in Environments 2019, 6, 96 2 of 13 the broiler litter [13,14]. As an alternative, the U.S. Department of Agriculture developed a patented process, called "Quick Wash" (QW), to manage the surplus of N and P prior to soil application of broiler litter or animal manure [15].…”

Broiler house litter processing by anaerobic digestion using enzymes

“…There are many studies in the literature on biogas production from poultry manure and litter [3,4,5,6,7,8,9,10,11,12,13,14], but only a few [ 15,16] when biogas was produced in a mixture with sawdust. Miah [16 ] evaluated a mixture of rice hulls, sawdust and chicken excreta of broilers mixed with the cosubstrate cow dung and poultry droppings for the production of biogas.…”

“…An Iranian research study [3] "evaluated codigestion of poultry litters and straw and found highest gas yield (0.12 m 3 CH 4 /kg VS ) and highest methane content (70.2%) at loading rates of 3.0 kg VS /m 3 -d, HRT of 15 days and operating temperatures of 35°C (95°F) (Baebee, 2013) [3], but that yield and quality dropped off significantly at higher loading rates and at lower temperatures.'' The removal of ammonia from anaerobically digested manure was evaluated in this study [13]. "Firstly, the hydrolysis experiments were performed and the effects of temperature, total solids (TS) content and retention time were investigated.…”

“…"Firstly, the hydrolysis experiments were performed and the effects of temperature, total solids (TS) content and retention time were investigated. The results showed that 90% of the organic nitrogen in chicken manure (CM) can be converted into ammonia via biological hydrolysis within 3.6 days at 35 °C and 10-12.5% TS content'' [13]. It is unclear whether dry fermentation AD of poultry litter offers more yield and quality potential than more traditional wet AD.…”

Improving Biomethanation of Chicken Manure by Co-Digestion with Ethanol Plant Effluent

“…However, mono-digestion of CM as a sole feedstock often fails to achieve and maintain stable AD performance due to nutrient imbalance, particularly between carbon (C) and nitrogen (N) [7]. The low C/N ratio of CM, ranging from 7-10 [8], is inhibitory to microbial growth and can lead to significant deterioration of methanogenic performance [9]. Ammonia is released from the degradation of nitrogen-containing compounds, such as protein and urea, and accumulates in the form of free ammonia or ammonium ions, according to pH and temperature, in AD environments.…”