Abstract
In the Japanese agricultural industry, efforts are being made to recycle waste produced in order to use resources more efficiently. However, in some cases, when stored for long periods of time these materials generate heat through fermentation, which can eventually result in spontaneous ignition or oxygen deficiency in storage areas, resulting in the deaths of workers. In this study, we conducted a series of experiments on several types of agricultural waste (organic waste generated by agricultural production activities in Japan) frequently stored for recycling, using combinations of various thermal- and gas-analysers, in order to identify the risk factors related to spontaneous ignition and oxygen deficiency accidents. The aim of this research was to understand the circumstances leading to spontaneous ignition and oxygen deficiency accidents in storage facilities and to recommend safety measures to prevent such occurrences. Our results suggest that fermentation is likely responsible for the generation of heat and production of carbon dioxide at temperatures up to approximately 50 °C, where microbial activity diminishes. At temperatures beyond 50 °C, a transition into heat generation by the oxidation of fatty acid esters occurs. Additionally, when the barrier of heat absorption is overcome at around 100 °C due to the evaporation of water, there is a transition to thermal cracking that could lead to fire. Accidents due to oxygen deficiency may occur when a storage facility is well sealed and the amount of oxygen circulation is minimal. However, when the amount of oxygen is sufficient; the substance is stored in large deposits; and the facility is well insulated, fermentation can cause the temperature to increase. Therefore, it is desirable to periodically measure the temperature of stored materials and monitor the generated gases.
Highlights
In Japan, there is a need to build a recycling-based society which reduces environmental loads, recycles limited resources, and uses them efficiently
These results demonstrate that the process of heat generation that can lead to the spontaneous ignition of these materials begins with a small amount of heat generated from fermentation or oxidation
The fatty acid esters contained within the materials begin to oxidise as the temperature gradually rises; even if the microorganisms causing fermentation die, the temperature of the material continues to rise and results in spontaneous ignition
Summary
In Japan, there is a need to build a recycling-based society which reduces environmental loads, recycles limited resources, and uses them efficiently. To this end, various laws for controlling the generation of waste have been established. In the agricultural industry in Japan, a project to reuse commercial agricultural waste as biomass fuel has begun. Since the Great East Japan Earthquake, an increasing focus has been placed on biomass fuels as an energy source [5,6], and the government of Japan has begun implementing policies designed to encourage their widespread application. Wastewater can be used as the nutrient source for production of biodiesel feedstock. The solid waste (e.g., agricultural waste) can be used directly as biofuel [7,8,9]
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