Currently, approximately 19 million tons of food waste are generated annually in this country.

Currently, approximately 19 million tons of food waste are generated annually in this country. Among this, the volume of food waste generated by supermarkets, convenience stores, hotels, and the restaurant industry has been particularly notable recently; however, most of it is sent to landfills or incinerated, with the recycling rate remaining below 1%. To address this situation, the government approved the “Bill to Promote the Reuse of Food Circular Resources” in a cabinet meeting at the end of last month and submitted it to the Diet with the aim of recycling the large volumes of food waste generated by food businesses and others. Furthermore, companies outside the food industry, as well as hotels and convenience stores, are increasingly working to recycle food waste generated on their premises as part of their efforts to obtain ISO 14001 certification. In response to these trends, nearly 200 to 300 companies have entered the market for food waste processing equipment, which is essential for handling food waste. This article introduces the current status and challenges of such processing equipment. ● Features and Challenges by Type Composting Type (Fertilizer Type, Feed Type): This method uses microorganisms to ferment food waste and recycle it into fertilizer or feed, and it is the most widespread. They appeared quite early in the 1990s and are used in numerous locations, including businesses, local governments, and schools. The composted end product is utilized as fertilizer or animal feed depending on its composition. The advantages of the composting type are that it is familiar to users and allows for the processing of food waste in a short period of time. However, major issues with this type include odors such as ammonia generated during composting, as well as the intended uses of the resulting fertilizer and animal feed. Regarding odors, while there are differences depending on heating methods and how the food waste is stirred inside the unit, the primary cause is that rapid fermentation—necessary for quick processing—tends to generate large amounts of foul odors all at once. Manufacturers are increasingly including deodorization and odor-elimination devices to suppress odors, but this inevitably drives up the purchase price. Furthermore, the quality of the resulting fertilizer and animal feed is heavily dependent on the contents and fermentation conditions, making recycling a significant challenge. Recently, some manufacturers have begun partnering with farmers and livestock producers to take back the end products. However, issues such as quality assurance for the products, transportation costs to the collection points, labor costs for removing foreign matter, and—in the case of feed—price competition with imported feed mean that these initiatives remain limited to a few cases. This is likely to be a major challenge for widespread adoption in the future. Elimination Type: This method uses microorganisms to break down food waste into water and carbon dioxide, significantly reducing its volume. It is currently the most common type among new entrants to the market. Although the waste does not completely disappear, this term is used because the volume is drastically reduced. Basically, wood chips or similar materials are used as a substrate, which is then agitated to allow microorganisms to break down the food waste into water and carbon dioxide. If the substrate is replaced regularly, the system can be used for a long period. A major advantage is that, unlike the composting type, there is no need to consider where to use the end product. However, the decomposition type is not a panacea and has several issues. First is the price. For systems with a processing capacity of 1,000 kilograms per day or more, many models cost over 10 million yen, placing them in a higher price bracket compared to other options. The next issue is the disposal of used microbial bed material. Since food waste in Japan has a relatively high salt concentration, salt becomes concentrated in the microbial bed material during the treatment process. This salt not only shortens the lifespan of the microorganisms but also limits the subsequent uses of the microbial bed material. While some manufacturers will take back the material for use as soil conditioners, others are promoting incineration due to the salt content issue. Furthermore, because microorganisms are used, the problem of foul odors is unavoidable, just as it is with composting systems. Additionally, in the case of the drainage-type system within the decomposition category, depending on the contents, the effluent may exceed the discharge standards set by the Water Pollution Control Act; therefore, attention must be paid to this point as well. Drying Type: This method heats and dries food waste to reduce its volume. It makes it easier to handle contaminants such as foreign objects, and since heat sterilization occurs during drying, the dried material can be easily used as raw material for fertilizers or animal feed, and odor issues are less of a concern. However, the volume reduction rate is lower compared to composting or incineration types, and there are energy cost issues associated with heating. While this may be acceptable for primary treatment, it presents some challenges when considering the recycling process as a whole. Carbonization Type: While this method is often associated with carbonizing wood-based waste for use as soil conditioners or water purification materials, it is also utilized for food waste treatment. Most systems employ a method where sealed food waste is indirectly heated from the outside using electricity or a burner. Like the drying type, there are no issues with foreign matter contamination or foul odors, and the volume reduction rate is high. However, in the case of burner-type systems, compliance with the Fire Service Act can be an issue, and energy costs are also a concern. Since there are still few manufacturers in this market and limited track records of installations, it is necessary to monitor future developments. Hydrothermal Treatment Type: Although similar to the incineration type, it was classified separately because the treatment method differs significantly from conventional methods. Jointly developed by Ishikawajima-Harima Heavy Industries and Shinryo Refrigeration & Air Conditioning at the end of 1999, this system uses subcritical water technology and wet oxidation to decompose food waste into water and carbon dioxide. The treated water can be discharged directly into the sewer system. Unlike conventional incineration systems, it completely decomposes all materials except inorganic substances, resulting in virtually no residual waste. Because it operates continuously with no open sections, no odors are generated, and processing time is reduced. Since water is used, there are absolutely no byproducts after processing, making this a system that enables zero-emission food waste treatment. However, concerns remain regarding its high cost, the time required to amortize the equipment, and energy costs. There are also various other challenges, including technical issues, operational management, and maintenance of the processed materials. While technology for food waste treatment is steadily advancing, many challenges remain. It is hoped that these challenges will be overcome in the future, leading to the widespread adoption of more efficient and environmentally friendly treatment methods.