The manures from beef cattle feedlots (or barns that do not use water to flush the animal manure) and poultry barns have relatively low water contents. They are often applied to farmland as fertilizer and thus have not been commonly subjected to AD. However, these two types of manures can be digested using dry AD pro­cesses [37] such as the dry anaerobic combustion (DRANCO) process, ECOCORP process, BEKON process, Kompogas process, and Linde process. These dry AD processes have several advantages over wet AD technologies and are described later in this chapter. Although not demonstrated on either type of manures [27], anaero­bic leaching bed reactors may be suitable for the AD of these manures without any dilution.

Both types of manures can be diluted to slurry and digested in conventional wet AD reactors. For beef cattle manure, a slurry containing 12% TS can be digested, but for poultry litter, a higher dilution (TS <3%) is needed to minimize inhibition by ammonia [44]. Inevitably, such dilutions create the need for large reactor volumes and high capital and operating cost. Pretreatment may be needed to remove the un­ingested diet (e. g., hay in beef cattle manure) or course materials (e. g., bedding materials and feather in poultry litter) prior to AD. Because of the presence of high solid contents, only CSTR, CMCR, and mixed plug-flow loop reactor (MPFLR) are suitable for AD of diluted beef cattle manure and poultry litter [20]. However, in a pilot study [9], upflow anaerobic sludge blanket (UASB) reactors were shown to be suitable and more efficient for the AD of diluted poultry feces. Co-digestion and thermophilic AD are also shown to improve digestion of poultry litter [16]. Thermophilic AD of poultry litter can be difficult due to the resultant high ammonia concentrations that render the AD process unstable [16]. The future will probably see more application of AD to both beef cattle manure and poultry litter, either alone or in co-digestion with other feedstocks, to both harvest bioenergy and produce fertilizer.