Animal waste such as fecal material from swine, chicken, turkey, and cattle is converted into useful forms such as 
fertilizer, other types of soil builders, and even 
nutrient feed additives. Devices, systems, and methods are provided that allow economical conversion and in many instances, alleviate the production and release of undesirable gases such as 
sulfide and 
ammonia. In one embodiment, undesirable anaerobic and 
facultative anaerobic bacteria are killed at a greater rate than desirable soil compatible 
aerobic bacteria. The use of low temperature killing diminishes off gassing commonly associated with other techniques, and the use of gas 
trapping additives such as zeolites provides enhanced soil building qualities such as slow release of 
nitrogen and slow release of 
moisture to soil. The methods allow convenient adjustment of composition, allowing conversion of waste into tailored designer 
fertilizer suited for particular soils. Other embodiments provide other soil building qualities as well as 
nutrient qualities for feedstock used in 
animal husbandry such as 
aquaculture.