The Ecomaster Biotunnel technology is based on a modular in-vessel system, which can be used in a variety of applications:
Biodrying of biosolids (weight reduction), green waste (renewable energy production) and mixed MSW (waste-to-energy)
Composting of separated municipal organic waste, commercial food waste, yard waste, digestate from anaerobic digestion, biosolids from waste water treatment and manure
Stabilization of mixed MSW(mechanically sorted or unsorted)
The main component of the biological reactor is a tunnel made of reinforced concrete with a sliding front door, an aerated floor and two vents. The system automatically provides the required amount of process air, which is an accurate mixture of fresh and exhaust air, to the biomass contained by the tunnels.
In addition to its air duct system, each biotunnel includes a dedicated blower and three automated dampers for the metering of the flow of fresh, exhausted and recirculated air.
The process is static, thus there are no moving parts inside the tunnels, which would be subject to fatigue, wear and corrosion. The tunnels are loaded and unloaded by wheel loader, which makes the system simple to operate and very reliable.
With the tunnel loaded and the door closed, an intensive composting process is started by adding a metered flow of fresh air. The process is maintained for the time necessary to reach the desired stabilization level of the organic material or, in biodrying applications, the moisture content specified for the product.
The temperature inside the biomass is maintained to the level set for each phase of the process by balancing the self-generated heat deriving from the biological process with the cooling caused by the evaporation of water.
In every composting system, metering the flow of fresh air is extremely important because the addition of air causes conflicting effects: on one hand oxygen supports the aerobic biological process, which generates heat, while on the other fresh air cools the mass, mainly due to evaporation of its moisture. Due to these opposite reactions, advanced software is required to control the process.
The Ecomaster system uses a proven software, based on the FLC concept (Fuzzy Logic Control), which conducts a real-time analysis of the various process parameters (temperature, pressure, oxygen concentration, etc.) and operates the system based on a set of weighed rules. The software is a proprietary design.
Generally, the material to be treated requires to be mixed with structural material, such as shredded wood waste, to provide adequate air permeability. This is particularly necessary in the treatment of source separated food waste (municipal or commercial) and biosolids.
Wood does not degrade significantly in the process time of the biotunnel system (typically in the range of 10 to 14 days), thus the greatest part of the structural material can be recovered at the end of the process and recycled for the preparation of a fresh new batch.
Waste air exhausted from the biotunnel is mixed with air coming from the hall (always maintained in slightly negative pressure conditions), and processed in a centralized odor control system, typically consisting of one or more blowers, an air humidifier and a biofilter. To reduce the size of the odor control system and limit the electric energy consumption, hall ventilation air is used as fresh air for the biotunnel process.
Air biofiltration, a natural process requiring the addition of no chemicals, is very efficient in controlling the odors generated by the composting process and does not require much electric energy, because of the low pressure drop of the biofilter bed.
Odor issues have often been raised by the nearby communities when the process is conducted outdoors using open systems. The experience in Europe, where in-vessel composting systems have been used for decades due to the scarcity of land, shows that the combination of advanced biotunnels, enclosed halls and properly-engineered biofilters has changed the reputation of this environment friendly process.