Toyohashi City Biomass Utilization Center, which has started operation, is the largest-scale composite-type biomass energy facility in Japan to convert sewage sludge, human waste, septic tank sludge and food waste into resources. It will contribute to the prevention of global warming by promoting greenhouse gas reduction, recycling and the use of renewable energy.
The facilities are separated from the surrounding residential areas, and a planting zone is set to eliminate a severe feeling. Special attention is paid to prevent waste collection vehicles from waiting outside. The standby space is secured in the treatment plant for waste collection vehicle unloading.
kitchen waste, human waste and septic tank sludge are received at the receiving building. Odor is suctioned away from the entire room with an odor removal fan, and the pressure is made negative, preventing odor from leaving the building.
① Sewage sludge-thickening facilities
These facilities thicken the sewage sludge generated from the water treatment facilities of Nakajima Sewerage Treatment Plant. They strive for energy saving by adopting a low- power type belt thickener.
② Human waste and septic tank sludge-thickening facilities
Human waste and others are unloaded in the receiving building with a vacuum vehicle. These facilities remove sand and foreign substances with a screen, and thicken them.
③ Kitchen waste receiving and preprocessing facilities
Kitchen waste is unloaded in the receiving building with a waste collection vehicle. Because it contains substances that are unsuitable for methane fermentation, the Garbage Smoother remove such substances, including plastic. Then the sediment removal tank removes eggs and shells. They are mixed with water to produce muddy liquid (slurry), which is used as materials for methane fermentation.
④ Methane fermentation facilities
All sewage sludge, human waste, septic tank sludge and kitchen waste are mixed and put into the methane fermentation facilities to produce biogas, which is about 60% methane and about 40% carbon dioxide. The quantity of heat produced from biogas is about half of town gas. The temperature inside the methane fermentation tank is maintained at about 35°C utilizing heat (waste heat) produced by a gas engine generator. The fermentation tank is a water tank made of steel plates with a 5,000 m3 capacity. A low power type mixer is installed in the tank and runs for 24 hours to make the contents even.
⑤ Biogas utilization facilities
Biogas contains traces of hydrogen sulfide as impurities. Because this ingredient is corrosive to the equipment, it is removed in the microbial desulfurization facilities.
Then biogas is temporarily stored in the gas holder (2,000 m3 capacity), while a certain volume is sent to the power generation facilities as fuel to produce electricity. A highly sensitive gas detector and a temperature sensor are installed in the biogas power generation facilities, along with a safety device to automatically stop the facilities when it detects abnormalities.
The electricity generated is sold to an electric company using the Feed-in Tariff scheme (FIT) for renewable energy.
⑥ Post-fermentation sludge utilization facilities
After methane fermentation, the remaining sludge is dehydrated up to about 80% of its water content with a sludge dehydrator, and converted into carbonized fuel in the carbonization facilities. Carbonized fuel is utilized as boiler fuel and suchlike, as an alternative to fossil fuel with a heat quantity of about half the amount of coal.
|Biomass to be accepted||Sludge||472 m3 per day (volume to be accepted)|
|Kitchen waste||59 t per day (volume to be accepted)|
|Main structure||Receiving building||Reinforced concrete structure (partial steel frame)
Two floors above ground Total floor space 3,012.7 m2
|Thickening and dehydrating building||Reinforced concrete structure (partial steel frame) Two floors above ground Total floor space 1,216 m2|
|Methane fermentation tank||Made of steel plates 5,000 m3 × 2 units 21 m diameter × 18.3 m high|
|Gas holder||Made of steel plates 2,000 m3 × 1 unit 15.5 m diameter × 17.3 m high|
|Car wash building||Steel frame One floor above ground Total floor space 133.8 m2|
|Capacity of main facilities||Sewage sludge-thickening facilities
(excess sludge thickener)
|Disposal quantity: 30 m3 per hour (three lines)|
|Human waste and septic tank sludge-thickening facilities
|Disposal quantity: 9 m3 per hour|
|Kitchen waste receiving and preprocessing facilities
|Disposal quantity: 6 t per hour (three lines)|
|Methane fermentation facilities
(methane fermentation tank)
Medium temperature (about 35°C) fermentation system
|Biogas utilization facilities
(gas power generation facilities)）
|Power generator 1,000 kW: selling electricity throughFeed-In Tariff scheme (FIT)|
|Sludge utilization facilities
|6 t per day (carbide)|
(unused land utilization business)
|Solar power generation facilities||About 2.0 MW (1,995 kW): selling electricity through Feed-In Tariff scheme (FIT)|