Waste disposal in the meat industry.
According to the requirements of current environmental regulations, meat-processing enterprises are obliged to recycle waste generated in the production of the main products. Biological waste is disposed of by recycling at sanitary-veterinary recycling plants in accordance with applicable rules, disinfected in biothermal holes, destroyed by combustion or, in exceptional cases, landfilled in specially designated areas.
Traditionally, waste is stored at landfills. The disadvantages of waste storage force to seek alternative methods of disposal. There are technologies of complex processing of waste to produce byproducts. However, not all waste of meat processing plants can be subject to secondary use. In addition, the established practice of organic waste recycling with further use of its residues to feed cattle is increasingly suppressed in Europe at the legislative level, as there is an expert opinion that the epizooty of mad cow disease (bovine spongiform encephalopathy (BSE)) and other diseases are caused by the use of meat and bone meal infected by prions due to insufficient processing. Instead, the more widespread is the use of waste as a fuel to generate heat and electricity.
Disposal of solid waste.
In world practice four methods of processing municipal solid waste have found industrial application:
– heat treatment (mainly combustion);
– biothermal aerobic composting (generating fertilizer or biofuel);
– anaerobic fermentation (generating biogas);
Each method has its advantages and disadvantages, its optimal areas of application depending mainly on the morphological composition of MSW and regional conditions. One of the most common and technically developed methods of MSW industrial treatment prior to its disposal in landfills is incineration (often with heat recovery). In European countries 20-25% of municipal waste are processed by incineration, in Japan — about 65%, in the US — about 15% (in the U.S. incineration is considered as one of the main ways of extending the life of landfills). According to foreign reports, the technology of direct MSW combustion is an environmental hazard due to toxic emissions (heavy metals, dibenzodioxins, dibenzofurans, etc.).
Technique and technology of MSW incineration have been continuously improved.
In the 30s, the furnaces for continuous MSW grate combustion have been designed to carry out incineration on the grate installed in the bottom of a furnace (to date MSW grate combustion at a temperature of 850-1000 oC is used most often in the world). In the early 80s, boilers with fluidized bed combustion systems (“solid- gas”) began to appear, they complied more to environmental requirements.
In the early 90s, promising research on the use of Vanyukov metallurgical furnaces was conducted, in these furnaces combustion is implemented at a temperature of 1350 0C in a fluidized bed of bubbling molten slag (generated from CHP ash and slag loaded with municipal solid waste into the furnace); bubbling is carried out by oxidative oxygen-air blast supplied through the lance at the bottom of the side walls of the furnace (lower than the melt / and the temperature achieved provides the decomposition of hazardous organic compounds to simple neutral). In the mid 80’s – early 90-ies, the Institute for high temperatures of the USSR Academy of Sciences developed the scientific foundations of the technology of high-temperature (2000 oC) heat treatment of municipal solid waste in shaft furnaces (identical to blast furnaces by design) which were continuously supplied by air preheated to 1000-1100 0C (air was heated in hot blast stoves which were lined metal reservoirs with ceramic elements in the form of zirconia or aluminium balls).
More than secular practice allows to determine precisely enough the advantages and disadvantages of incineration.
Advantages of this method: reduction of waste volume by 10 times; decrease of risk of soil and water contamination by waste; the possibility of recovery of heat generated.
Disadvantages of the original MSW incineration: the danger of atmospheric pollution; destruction of valuable components; large volume of ash and slag produced (approximately 30% by weight); low efficiency of the recovery of ferrous metals from slag; the complexity of stabilization of the combustion process.