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Under extreme weather conditions, when faced with severe heavy rains and floods in nearby rivers, it is inevitable that biogas facilities will be affected by flooding; therefore, safe and appropriate measures must be taken to minimize the damage to such facilities. Below are some measures that can be taken as a reference: I. Emergency measures before floods occur It is important to stay informed about news reports and warning alerts related to disasters such as typhoons and heavy rainfall, so as to be aware of the situation as early as possible and take necessary preventive actions promptly: 1. Emergency measures for household biogas digesters (a) Check whether the manhole cover on top of the digester is properly in place and sealed tightly. If it is not properly covered or is loose, make sure to secure it properly and seal it tightly. At the same time, cover the feed inlet, discharge outlet, and the top of the digester with solid cement plates; ensure that there are no gaps around the pipes or the top cover. This is done to prevent people from falling in when the openings are covered by water, as well as to stop debris such as mud from entering the digester. (II) Safely release the biogas in the tank in advance to eliminate any air pressure inside it. (III) Fill the biogas digester with the solution or clean water to maintain the proper water level; it is strictly prohibited to leave the digester empty to prevent floating. (IV) If there are exposed ends of biogas pipes or biogas slurry transport pipes, seal those ends properly to prevent mud and sediment from entering and blocking the pipes. (5) It is prohibited to carry out large-scale material discharge or maintenance of biogas digesters before a flood occurs; if such activities have already been carried out, they must be stopped immediately, the water level in the biogas digester should be raised to full level, and the relevant access covers should be closed. 2. Emergency measures for large and medium-sized biogas projects There are various types of large and medium-sized biogas projects, and their installation methods include underground, semi-underground, and above-ground types. Therefore, emergency measures must be tailored to each specific situation, but the general emergency measures should include the following aspects: (1) Measures to prevent electric leakage. Large and medium-sized biogas plants generally have electrical equipment and lighting facilities; the power supply to areas that may be flooded should be cut off, and it is necessary to check whether the insulation of all wires and cables is damaged and to repair any such damage properly. (II) Waterproofing measures. Take measures as much as possible to prevent water from entering electrical and power equipment and causing damage, as well as to protect electrical circuits from water ingress and leakage. The surface water inlets, as well as the acidification tanks and grid collection tanks where the pipes for gravity-fed feeding are located, are equipped with solid covers to prevent mud, sand, and other impurities from entering the tanks. (III) Safety measures to prevent flooding and falling. Exposed and uncovered openings in the ground, such as manholes, sewer access points, pipe shafts, and inlet/outlet pipes that may be covered by water, must be covered with solid lids. For larger openings for which lids cannot be used, tall warning signs should be installed around them to serve as a warning. (IV) Safety measures for the pool structure. Buried tanks and deeper semi-buried tanks must not be left empty before floods arrive to prevent them from floating ； For above-ground structures, it is essential to take thorough waterproofing measures at the foundation level to prevent the foundation soil from being damaged by water flow. (5) Waterproofing measures for toxic, hazardous, and high-risk items. If biogas stations are equipped with testing and analysis facilities, toxic and hazardous chemical reagents and drugs that may be flooded should be safely transferred away ； If a biogas plant is equipped with a tank for handling dead pigs, the inlets and outlets of this tank, as well as any manholes, should be tightly sealed with waterproof materials to prevent the liquid inside from leaking out in case the tank is flooded. (6) It is necessary to prepare plans for shutting down biogas plant operations, and such operations must be halted in emergency situations. II. Disaster relief measures after floods 1. Household biogas digesters (1) The flooded biogas digesters must be repaired by biogas technicians. (II) Repairs can only be carried out after the water has completely receded, the ground is exposed, and disinfection measures have been taken at the biogas site. (III) Before starting, it is necessary to check first whether the biogas digester, manhole covers, and seals are in good condition ； Are the inlet and outlet pipes, as well as the biogas pipes, clogged? (IV) The remaining gas in the biogas digester must first be safely vented, and it is necessary to check whether there is severe water intrusion inside the digester; then, the digester should be restarted by performing a full replacement of the contents in accordance with the operating procedures for household biogas digesters. (5) It is necessary to carry out sanitary and disinfection measures around the biogas digester in accordance with the requirements of the health authorities; however, care must be taken to prevent disinfectants from entering the digester, as this could affect the fermentation process. 2. Large and medium-sized biogas projects: In the event of a flood affecting large and medium-sized biogas projects, the project owner, relevant departments, and skilled technicians shall carry out rescue and restoration work in accordance with the disaster response procedures. Generally, this can be done following these steps: (1) Assess the damage caused by the flood. Including (1) the damage to various structures, buildings, equipment and instruments within large and medium-sized biogas plants, the roads and landscaping in the plant area, the biogas distribution system, the biogas slurry transmission network system, the power system, the water supply and drainage systems, etc ； (2) Current flood situation: Current water level, flooding conditions, or whether the water quality in the vicinity is polluted. (3) Are the containers holding harmful substances, dangerous materials, or toxic chemicals inside the site broken? ； Have there been any leaks in the biogas and dead pig treatment ponds, and what are the circumstances of those leaks and their impact on safety? (II) Clarify the objectives for cleanup and restoration. For flooded structures, buildings, equipment, and various auxiliary systems, depending on the extent of the damage, it is necessary to determine, with the aim of ensuring the proper operation of the biogas facility, which parts need to be removed or replaced. It is important to identify which parts can be repaired, which need to be removed, and which require replacement. (III) Determine the contents of the repair work and the personnel involved, and establish a timeline for the repairs. (1) The repair should be carried out by enterprises with qualifications for biogas project construction, and the repair plan must take into account the opinions of the original project design unit. (2) The repair work should include garbage removal, pumping out water, disinfection and epidemic prevention, as well as the maintenance of facilities. (IV) Before carrying out the repair work, it is necessary to first conduct an inspection of the repair site and identify potential hazards, while also taking safety measures. (1) Assessment of risks related to falling and drowning: Generally, repairs can only be carried out after the water level has completely receded and the ground is fully exposed. In areas where water remains, it is necessary to determine the depth of the water as well as the locations of openings such as pool entrances, wellheads, and ditches underwater, and to place safety warning signs to prevent people from falling in and drowning. (2) Detection of hazard leaks: Check for leaks in biogas systems and pig carcass treatment ponds, and take appropriate safety and hygiene preventive measures. (3) Electrical system hazard inspection: Check whether the insulation of wires and cables is damaged and if there is any leakage current ； Check whether the electrical equipment has water intrusion or leakage, and take safety measures to prevent electric shock. (4) Inspection for hazards in buildings and structures: Check whether the foundations of these structures have been damaged as a result of water exposure, whether there are cracks in the walls of the tanks, and whether there are any signs of collapse. Safety measures must be taken for buildings and structures at risk of collapse due to disasters to prevent secondary disasters.