The major technologies for food waste treatment currently include aerobic composting, anaerobic digestion, dewatering and co-incineration, and biological transformation using organisms such as black soldier flies and houseflies. Statistics show that anaerobic digestion accounts for approximately 87.5% of all processes globally, with the remaining methods making up only 12.5%.
Furthermore, the integration of kitchen waste disposers can significantly enhance the efficiency of these processes by reducing the size of organic waste, thus facilitating easier transport and more effective treatment.
(1) Anaerobic Digestion
Anaerobic digestion involves the metabolic activities of various anaerobic microorganisms, including non-methanogenic anaerobes and methanogens, to break down materials into methane, carbon dioxide, and residual by-products (digestate and biogas liquid). Depending on the solid content of the feed materials, anaerobic digestion is categorized into wet and dry processes. Wet anaerobic digestion generally involves feedstocks with less than 15% solids, whereas dry anaerobic digestion handles materials with more than 18% solids. Despite similar processing flows involving "pre-treatment systems + dry/wet anaerobic systems," the different solid content leads to variations in reactor structures, retention times, operating temperatures, and biogas output. In practice, wet anaerobic technology is more mature and widely implemented in domestic food waste treatment facilities. However, with the advancement of waste sorting and technological improvements, there is a growing trend towards adopting dry anaerobic digestion.
(2) Composting
Composting is another common method for the valorization of food waste. The principle involves controlled microbial decomposition, transforming food waste into water, humic substances, and gases such as CO2. Composting can be conducted using open-air pile methods or enclosed equipment (biodegraders). In practical applications, many processes use enclosed equipment for the primary fermentation stage and open-air piles for secondary fermentation. Currently, the utilization of composted products from food waste in landscaping and agriculture/forestry is in its nascent stages. The lack of a robust quality evaluation system poses challenges for subsequent commercial applications. Kitchen waste disposers can streamline this process by breaking down food waste into smaller, more manageable particles, making it easier to handle and compost.
(3) Biological Transformation
Biological transformation uses insects like black soldier flies and maggots to convert food waste, preserving the intrinsic protein content and avoiding the "source contamination effect" of feed-based processing, thus ensuring safety. Post-harvest, the larvae are dried and can be used to extract insect protein and oil. Black soldier fly technology is particularly popular for treating food waste. However, large-scale engineering and optimization of this live organism-based process are still under extensive research.
Current and Future Developments
Current advancements in food waste treatment primarily focus on addressing the shortcomings of anaerobic digestion and aerobic composting. Biological transformation technologies are also gaining attention and have developed rapidly in recent years. However, challenges remain in automation, process stability, and high-value product utilization. Emerging technologies aim for high-value extraction and utilization of food waste components, often leaning towards chemical product manufacturing, such as producing acetic acid, lactic acid, higher fatty acids, and polymeric materials like hydrogels. These processes often involve fermentation but target non-methane products.
Research is also ongoing on the reuse of by-products from mainstream processes, such as using digestate as fertilizer, combining digestate with fly ash to produce concrete, converting digestate into ethanol and particle boards, and gasifying pyrolyzed digestate to synthesize gas, bio-oil, and biochar. Additionally, the resource utilization of biogas liquid includes applications like ethanol production, struvite, and liquid fertilizers.
Conclusion
Overall, while significant strides have been made in food waste treatment technologies, ongoing research and development are crucial for optimizing processes, improving automation and stability, and enhancing the commercial viability and value of end-products. The integration of kitchen waste disposers into these treatment systems can further streamline waste processing, reduce logistical challenges, and enhance the overall efficiency and effectiveness of food waste management strategies.
