Meat and bones are difficult to compost at home because they are dense, decompose slowly, and contain high levels of protein and fat. These materials are unsuitable for standard backyard piles because they easily create anaerobic conditions, resulting in foul odors. The high organic content also attracts pests like rodents and raccoons, posing a health risk. Successfully processing meat and bones requires specialized methods that manage temperature, aeration, and containment.
Specialized Composting Systems
Processing animal byproducts safely requires systems engineered to handle the unique properties of meat and bone waste. These methods circumvent the issues of pest attraction and pathogen survival common in conventional cold composting.
High-Heat Aerobic Composting
High-Heat Aerobic Composting uses a large, well-managed pile to generate and maintain temperatures high enough to destroy pathogens and accelerate decomposition. The pile needs a minimum size, such as 3x3x3 feet, to provide enough mass for insulation and heat retention. The internal temperature must consistently reach 140°F to 160°F (60°C to 71°C) to effectively kill harmful bacteria. Frequent turning is necessary to introduce oxygen and move cooler outer material into the hot center, ensuring all organic matter reaches pasteurization temperature.
Bokashi Fermentation
Bokashi Fermentation is an anaerobic, two-step process that chemically alters food waste, including meat and bones, before composting. This method uses a sealed container and specialized bran inoculated with beneficial microorganisms to ferment the waste. The fermentation process is quick, eliminates putrid odors that attract pests, and converts proteins and fats into more stable forms. Since Bokashi is fermentation, not true composting, the material must still be buried or incorporated into a hot aerobic pile afterward for final breakdown.
In-Ground Digesters and Burial
In-Ground Digesters and Burial methods rely on the soil’s microbial activity and physical barriers for containment. For a basic trench method, meat and bone scraps are buried deep, ideally at least 18 inches below the soil surface, to prevent animals from digging them up. Specialized digesters are partially buried containers that use the surrounding soil and sun’s heat to accelerate waste digestion while containing the material and its odors.
Pre-Treatment and Material Incorporation
Preparing meat and bone scraps before introducing them to any system is essential for maximizing microbial access and speeding up the decomposition rate. Size reduction is the most immediate way to accelerate the process, as smaller pieces have a greater surface area for microbes to colonize. Grinding or crushing bones and meat scraps into tiny fragments is recommended, sometimes requiring a heavy-duty blender or a hammer mill for larger bones.
Fat Reduction
Fat reduction is an important pretreatment step because large quantities of animal fat can repel water, create hydrophobic clumps, and promote anaerobic conditions. Trimming off excessive fat before adding the scraps prevents the material from becoming greasy and slowing the entire process.
Carbon-to-Nitrogen Ratio
Achieving the correct Carbon-to-Nitrogen (C:N) ratio is necessary for successful breakdown, as meat is a high-nitrogen material that must be balanced with carbon-rich material. The ideal ratio for rapid composting is approximately 30 parts carbon to 1 part nitrogen by weight. For every volume of meat, a larger volume of dry, carbon-rich materials like sawdust, wood chips, or shredded cardboard must be added. This carbon cover absorbs moisture, minimizes odor, and provides the necessary energy source for the microbial population.
Placement Strategy
The placement strategy is the final step in pretreatment and incorporation. In a high-heat pile, pre-treated material must be buried deep inside the center, where core temperatures are highest and most stable. For Bokashi, the fermented material should be thoroughly mixed with the final compost pile or buried deep into a soil trench, ensuring it is completely covered to continue decomposition safely away from pests.
Managing Safety and Environmental Risks
Safe management during composting is necessary to prevent pest attraction and ensure the final product is safe for garden use. Pest exclusion begins with securing the composting system, requiring bins to have tight-fitting lids and no gaps larger than a quarter-inch. Immediate burial and complete covering of all meat and bone material with a thick layer of carbon material or soil prevents odors from attracting scavengers.
Pathogen Monitoring
Pathogen monitoring is important in high-heat aerobic systems, requiring a long-stem compost thermometer to verify internal temperatures. Maintaining the pile at 140°F to 160°F for several days helps eliminate pathogens, and the pile should be turned to ensure all material is exposed to this heat. If a pile fails to reach these temperatures, the finished product should not be applied to food crops for at least 150 days.
Odor Control
Odor control indicates proper aerobic decomposition and is managed by ensuring the correct C:N ratio and adequate aeration. Foul, putrid smells indicate anaerobic conditions, which can be corrected by turning the pile for oxygenation and adding more dry carbon material. The final product check confirms that the finished compost is dark, crumbly, and smells earthy, with no recognizable fragments of meat or bone remaining.