Soldo Cavitators has developed BioBANG®, a technology for the pretreatment of biomass in biogas plants based on a controlled cavitation process.
The technology makes it possible to make a higher percentage of easily attackable and digestible organic substance available to the bacterial flora present inside the digester to increase the amount of biogas produced per unit of biomass loaded and accelerate retention times inside the digesters. .
Most non-woody biomasses are a good feedstock that can be used in anaerobic digestion processes for biogas production. However, some biomass must be pretreated before being inserted into the digesters for optimal anaerobic digestion.
The BioBANG® system mixes, homogenizes, emulsifies, disintegrates, concentrates, dissolves, dilutes, hydrates, pasteurizes and sterilizes the biomass, intensifying the processes of anaerobic digestion plants with savings in time and costs in the treatment of all biomasses, including the low cost ones.
How to take advantage of the cavitation phenomenon
Hydrodynamic cavitation is a phenomenon of formation, growth and implosion of vapor bubbles in a liquid at temperatures below the boiling point.
FEATURED: BioBANG® makes it possible to control the physical phenomenon of cavitation, which acts without direct mechanical actions, on the biomass.
Vapor bubbles during the collapse phase generate extremely reactive microenvironments, "hot spots", characterized by very high temperatures, intense pressure waves and hydraulic jets that, propagating in the mass of the product, transfer three physical effects: reduction of particles, homogenization and molecular friction.
Technologies based on hydrodynamic cavitation have proven to be very competitive, capable of significantly increasing the performance of biogas production processes both operating as a single unit and integrated with other technologies; Furthermore, they allow increasing the overall performance of the processes in which they are used and are scalable.
These technologies adhere to the principles of “green and sustainable extraction methods of natural products”.
The geometry of the BioBANG® cavitator allows this physical energy to be transferred over the entire volume of treated product in a single step, resulting in a high level of disintegration of the biomass, which can be better homogenized in the fluid, increasing its biodegradability and significantly reducing viscosity. of the product within the digesters, and also increasing the yield and concentration of total solids.
How it works in biogas and biomethane plants
Treatment with BioBANG® can be done in two ways:
1. Pretreatment (coarse) in the feed line to load the biomass into the plant. Its function is to facilitate the transfer of biomass to the digester.
2. Pretreatment of the process. It allows intercepting the fraction of biomass that resists the soaking phase within the hydrolysis tanks or digesters (imbibition connects the biomass with the anaerobic bacteria).
From the analysis of the facilities it is clear that the best solution (adopted by 99% of customers) is recirculation use in the digester.
In recirculation, BioBANG® can work with much less power and more efficiency, avoiding competing with the anaerobic digestion process.
BioBANG® acts on the biomass fraction that, resisting anaerobic digestion, tends to float on the surface of the digester, creating superficial crusts and floating layers and reducing the efficiency and performance of the plant.
In a single step, BioBANG® ensures that this fraction (10-20%) that would not participate in the anaerobic production process is immediately made available like the rest of the material.
Hydrodynamic cavitation has important positive effects on the hydraulic aspect: with BioBANG® in recirculation the biomass does not need any type of dilution, since hydrodynamic cavitation implies a decrease in viscosity.
The energy used to increase plant efficiency is fully recovered from reduced mixing and pumping energy consumption.
Benefits of installing BioBANG®
Manufacturers of biogas or biomethane plants can better adapt the installation to the customer's diet by reducing design and construction costs. The greater digestibility of the fibers provided by the cavitator allows savings in the design of 5% to 20% (over the total cost of the project); On the other hand, the reduction in product viscosity guarantees energy savings in agitators and pumping systems of 30% to 60%. And finally, by reducing the biomass retention time and optimizing the volume of the digesters by up to 20%, economic savings are achieved in the construction costs of the tanks.
Biogas and biomethane plant operators are able to increase plant performance, improve miscibility and save biomass. The reduction of liquid in favor of solid increases the concentration in the digesters from 2 to 6%; Retention and recovery times are optimized for plant efficiency from 10 to 20%. The progressively reduced use of agitators reduces the self-consumption of the mixture from 30 to 60%. And, finally, there is a gradual reduction in nutrition and integration of the diet up to 100% with economic biomass, which represents a saving in the cost of the diet.
Efficiency tests on various biomasses
BioBANG®, in collaboration with biomass research and development centers, has carried out cavitation tests on different raw materials, such as straw, sewage sludge or herbaceous biomass.
As for straw, 50% of the biomass is achieved with dimensions less than 0,1 mm. Biogas production increased by approximately 26% on the twenty-sixth day.
In sewage sludge, 95% has dimensions less than 0,1 mm. On the fourth day, the maximum biogas production rate is reached: 22 Nm3 CH4/SV/day compared to 10 Nm3 CH4/SV/day from untreated straw. Biogas production increased after four weeks by 30% more than untreated straw.
Important results are also visible in the biomass from permanent grasslands. The percentage with dimensions smaller than 0,1 mm increased from 18% to 75% after cavitation treatment, and peak biogas production after four weeks increased by approximately 30%.
Economic profitability of the system
Depending on the type of biogas plant and the needs of the operator, only the cavitator or the complete system can be supplied, consisting of a cavitator plus macerator, volumetric pump, inverter, electrical panel, PLC, flowmeters and IN/OUT pressure sensors. On the other hand, the available flow range ranges between 0,5 and 100 m3/h.
The cost varies depending on the flow rate and the product chosen: the cavitator has a price between €15.000 and €110.000, while the cost of the complete system is between €80.000 and €350.000. Annual maintenance costs for the entire system are around €2.300 and never exceed €3.000.
Thanks to the improvements provided by BioBANG® in feeding, performance, concentration, mixing and pumping, it is possible to amortize the investment in approximately one year.
The electric motor that powers the cavitation is in inverter mode, allowing you to select the intensity of the cavitation treatment based on the configured energy rate (kW/m3).
The energy rate to be established for the treatment depends on the client's needs or objectives, how much efficiency they want to recover in their system and the energy that can be available for the treatment. The most notable thing about the plant is the automatic control of its energy rate depending on the viscosity levels in the digester. Normally we work with energy rates between 3 and 12 kW/m3.
Successful installations in Europe
To date, 168 BioBANG® units have been installed in biogas and biomethane plants throughout Europe: Italy, Germany, France, United Kingdom, Switzerland, Denmark and Poland.
Broadley Energy- Farm Renewables (Funtington, United Kingdom). It processes manure from a 50.000-head pig farm, straw silage and corn. Thanks to the cavitation system, it has managed to solve the problem represented by the volume of straw mixed in pig manure, breaking down the fiber contained in the straw.
After 6 months in operation, BioBANG® has improved the viscosity of the substrate inside the digesters by up to 40%, allowing a reduction in the amount of raw material, corn silage (from 30 to 25 tons/day) and pig manure with straw (70 to 50 tons/day). The amount of straw remained at 15 tons/day, but its yield increased by 15%. Thanks to all this, daily production increased from 13.740 to 15.800 kWh/d.
Malcom McAllister, owner and president of Farm Renewables Group: “The first benefit we noticed was a large reduction in viscosity in the digesters. However, the main advantage is that the gas production of the straw increased by up to 15% with the cavitation pretreatment provided by BioBANG.”
ABO Kraft & Wärme (Ramstein, Germany). Processes cow and horse manure, corn and triticale silage, grass silage and excrement. The plant produces 900 Nm3/h of biogas with a daily contribution of 90 tons of these raw materials.
The installation of BioBANG® has improved the hydraulics of the plant, the working time of the agitation and pumping systems in the digesters and, above all, it has made it possible to optimize the effective use of the most difficult biomasses and plan a more economical daily diet. thanks to the possibility of integrating a greater amount of fiber.
The Ramstein plant is one of the best examples of the use of cavitation machines in Germany and Europe.
CAZZOLA Estate (Salizzone, Italy). It processes corn silage and livestock waste in its two biogas plants of 1 MW each.
In 2018, BioBANG® was installed in transfer from the main fermenter to the hydrolysis tank. Six months later, the viscosity had been reduced by 50% in the hydrolysis tank and by 25% in the post-fermenter.
The reduction of viscosity in the hydrolysis tank has allowed the insertion of biomass with a higher fiber content, which was the critical problem of the plant, and saved 26 tons/day of corn silage, the most expensive biomass in the daily diet, with which the client saves around €300 per day compared to the previous diet (from €2100 to €1800/day). The cost of biogas production has been reduced from 0,42 to 0,36 €/Nm³/h (€700 per day).
Finca Cazzola's goal now is to increasingly reduce the amount of corn silage, until it is completely replaced by cheaper manure and agricultural crops, and access incentives to purify the biogas into biomethane.
Reims (France). It is a biomethane plant with a production of 700 Nm3/h, composed of 2 main digesters and a post-digester. The client decided to install the cavitation system after a test in which it was found that the product sample at 17% dry matter treated with BioBANG® had a significantly lower viscosity compared to the original product at 12% dry matter.
This meant being able to optimize the volumes of the plant without increasing the self-consumption resulting from the mixture.
Source: Vincenzo Grimaldi – AVEBIOM
