Frequently Asked Questions
Q: What is your experience in fermenting different substrates (what substrates)?
A: Watrec Ltd has in its full-scale reference sites total treatment capacity of 28.500 tn TS (total solids) per year. The feed TS concentration is 12 %, so the annual treatment
capacity in wet tons is 240.000 tn.
There are two plants in operation, first one has been operated since 2005 (600.000 tn of treated waste up to date). The input materials in the first plant include pig manure,
chicken waste (from egg houses), antibiotic milk, fish waste (salt solution that is used to preserve herrings from Iceland), enzyme waste (wastewater sludge, microbial cells from enzyme extraction process, nanofiltration concentrate), pre-treated biowaste from hospital, etc. Second plant has been in operation since 2009 and treats only dewatered wastewater sludge from 4 treatment plants (largest for 300.000 pe).
Third plant (under construction, scheduled start-up in March 2009) has inputs as pig manure, wastewater sludge, slaughterhouse waste (turkey and chicken), meat processing plants, fats, oils and grease (FOG) from slaughterhouses, flotation sludge from rendering plant and other cat. III material from the rendering plant. Total treatment capacity of the new plant is 8.300 tn TS/a, corresponding to 80.000 wet tons annually.
Q: Are they only industrial (municipal waste, food industry), or agriculture as well (corn, manure, beet)?
A: In our biogas plants the inputs are from industry, municipalities and from farming (no corn or other harvested biomass though).
Q: Does your technology allow certain universality; for example, changing the kind of substrate, if there are no typically agricultural?
A: Yes, the main parameters that restrict the input selection are the following; free ammonia in the process, TS concentration, other inhibitors. The most important thing is to keep the input mixture stable in the sense of organic load.
Q: How many working hours a year does your technology assume?
A: We design the plants with certain safety margin to complete the total capacity even with certain time taken for repairs and maintenance. This includes the use of buffering capacity as well as use of oversized pumping equipments. Our design enables also the upgrade of the treatment capacity by increasing the number of digesters and CHP capacity. So far our references have been able to receive the material without any interruptions on every working day.
Q: What is the detailed technical equipment of the offered technology?
A: This depends always on the final design, as the input materials and flows as well as the surrounding conditions define the specifications to the design. Major components include reception, odour treatment, pretreatment, hygienization (when necessary), digestion, post-digestion, dewatering (when applicable), biogas conditioning, and biogas utilization.
Q: What is the biomass transportation solution between the containers and in the whole technological circuit? (hydraulic, carriers, other)?
A: This depends on the input materials, in mixed waste the transportation is conducted with pumps.
Q: What is the offered service standard? (scope and reaction time)
A: Watrec Ltd. offers biogas plant management service, that include every-day monitoring of the process (via internet) and regular (monthly) audit of the plant via visiting the site by Watrec biogas experts. Other service possibilities can be negotiated and depends on the number of biogas installations ordered from Watrec.
Q: What is the substrate loading method in a biogas plant?
A: This depends on the input materials, most of the materials can be received in the reception tank (materials coming with trucks). Some substrates require pre-treatment line (e.g. crushing) or totally separate feeding line to digesters (biomass).
Q: What is the method of receiving post-slaughter substrates (termization, pasteurization, sterilization)?
A: This depends on the input material quality, if it requires for example physical treatment such as crushing. Also the material category (II or III) defines the pre-treatment by hygienization (for cat. III) or sterilization (cat. II – not recommended).
Q: What are the advantages of your fermentation system(s)?
A: Reliability, good process control, in-depth knowledge of biogas process solutions of our engineers and project people including the both academic background and experience of the existing plants, good energy efficiency (12-20 % electricity consumption from the produced electricity, 20 % heat consumption of the produced heat), and cost-efficiency in the investments compared to other industry-scale waste treatment facilities.
Q: How is biogas storage and transport solved?
A: The biogas storage and transportation are defined by the use of the biogas, we have used typically biogas holder with storage capacity between 1 to 8 hours, and biogas transportation by compressors in the range of 100 mbar to 3 bars and length of 50 meters to 1500 meters.
Q: What are the methods of desulfurization and treatment?
A: Watrec Ltd. use biological, biochemical, chemical, and physical biogas treatment systems including scrubbers, drying and activated carbon. Final design of desulfurization depends on the input materials and usage of the biogas.
Q: Is there a separation between the solid and liquid phase?
A: When required, digestate dewatering is applied. Watrec has used decanter centrifuges, filter presses, and screw presses. The input material and usage and requirements for the fertilizers define the correct selection of the dewatering systems.
Q: How have the operating systems been made?
A: Watrec Ltd. has used Siemens S7, Siemens PCS7, and Metso DNA.
Q: What is the standard of the operating systems and is there a possibility of unifying them, regarding a company managing a bigger number of biogas plants?
A: Some parts of the plants are standardized, some parts are designed depending on the surrounding conditions (environmental requirements, input materials, requirements for the endproducts). Control system will be Metso DNA that enables the plant operators to be familiar with one control system and software.
Q: What additional machines is the gas part of the biogas plant equipped with? (concerns the possibility of biogas compression and liquidate)
A: It is possible to implement an upgrading system to the biogas plant but this is very rarely applied. Liquidation is also possible but not yet recommended as the number of existing full-scale systems is very limited (not proven technology yet).
Q: What is the investment cost of particular modifications (depending on the substrate) count 1MW?
A: This is dependent of the plant total capacity, input materials and output requirements. Our references have been in the range of 3 to 5 MEUR/MWel as the plants have been industry-scale waste treatment facilities (focus not being the cheap energy production but to manage wastes in sustainable way). Other similar systems in Finland have been more expensive in the rate of 50 to 150 %.