# Thermo-Chemical Treatment for Carass Disposal and the Application of Treated Carcass as Compost
## 1 Introduction
In order to treat the undecomposed carcass in burial sites, several techniques including compost, rendering, incineration, and alkaline hydrolysis have been applied [3]. Composing of animal carcasses has advantages including the production of valuable by-products, versatility, ease of handling, and the destruction of pathogens by heat during the production process [16], but major disadvantages of carcass composting methods include the long processing time before the compost is mature, production of nuisance odors and greenhouse gases such as CO\({}_{2}\), and insects such as flies may invade the composting area [7]. Rendering of animal carcasses involves their conversion into three end products using mechanical processes (e.g., grinding, mixing, pressing, decanting, and separating), thermal processes (e.g., cooking, evaporating, and drying), and sometimes chemical processes (e.g., solvent extraction). The end products are carcass meal (proteinaceous solids), melted fat or tallow, and water [17]. The benefits of rendering are that it provides a source of proteins for use in animal feed formulations and provides a hygienic means of disposing of fallen and condemned animals. However, a shortcoming of the technique includes the need for animal carcasses to be transported from the farm to a rendering plant. Because the carcasses will be removed from the infected premises, there are significant biosecurity risks with adverse effects being the by-product wastewater production [18]. Large amounts of energy are consumed to generate the required high temperatures and pressure. This also necessitates the use of specialized equipment and personnel [7]. Incineration is the process where animal carcass or by-products are turned to inorganic ash by being burnt at high temperatures (>850 \({}^{\circ}\)C) which enables to kill the pathogens in the animal carcass [19]. The production of gaseous emissions from burning of wood or fossil fuels is the principal concern. Metal concentrations in the flue gas have also been found to be higher in animal carcass incinerators than in medical incinerators [20]. Other health issues arising from incineration include the release of dioxins and furans from flue gas and fly ash; these can enter the food chain through grazing animals and can also be ingested by humans through the consumption of contaminated crops [9]. In addition to negative impacts on air quality and composition, incineration can also be relatively expensive. Alkaline hydrolysis uses sodium hydroxide or potassium hydroxide under heat and pressure to catalyze the hydrolysis of biological material. This process is carried out in a tissue digester consisting of an insulated, steam-jacketed, stainless-steel pressure vessel with a lid that is manually or automatically clamped [21]. Advantages of this technique of carcass disposal include simultaneous sterilization and digestion of the carcass, as well as the destruction of pathogens including prions. It further reduces waste by weight and volume by up to 97%, and radioactive contaminants are eliminated [21]. However, alkaline hydrolysis is practiced offsite and presents biosecurity problems arising from the transport of infected animal carcass from one area to a process plant [22]. A shortcoming of the process is the generation of large volumes of water as a by-product resulting from the use of alkali, high temperatures, and pressure to catalyze the hydrolysis of biological materials [23]. Therefore, research effort to develop more sustainable and environmentally friendly alternatives to carcass burial is required. In this study, a mechanized thermo-chemical treatment system was developed to remediate burial sites by treating carcasses that had been buried. Dioxins and volatile organic compounds in the exhaust gas generated from the thermo-chemical treatment process were analyzed, and the chemical and biological properties of the thermo-chemically treated animal carcasses were analyzed.