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Frequently asked questions

What is Anaerobic Digestion?

Anaerobic digestion is a bacterial process in which microorganisms break down organic material in the absence of oxygen resulting in the production of biogas. Similar to a cow’s digestion process, microorganisms consume the fats, sugars and proteins in the food waste to produce biogas. Anaerobic digestion is widely used as a renewable energy source that produces a methane rich biogas suitable for energy production, helping to displace the consumption of fossil fuels. In addition, the digestion process produces “digestate” which is rich in nutrients and is commonly used as fertilizer.

What is Biogas?

Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen (anaerobic digestion). Biogas is a renewable fuel comprised mainly of methane and carbon dioxide plus small amounts of some other gases. Biogas can be used to generate electricity for the local electrical grid. Biogas can also be upgraded to remove carbon dioxide and other gases to produce gas with a methane content exceeding 97%. The upgraded biogas or renewable natural gas (RNG) can be used to replace natural gas in many applications including: cooking, heating, steam production, electrical generation, vehicular fuel, and as a pipeline gas.

Is the technology proven and reliable?

Anaerobic digestion is generally accepted as the most advanced method of recycling food, as it is reliable, cost effective and highly efficient in the production of both renewable energy and valuable fertilizer by-products. It is a well-established commercial technology, as stated in the 2009 International Energy Agency (IEA) Bioenergy report. The biogas industry has experienced exponential growth in various European countries during the last ten years. A significant number of Danish anaerobic digestion plants are of note due to the size and economy of scale achieved (IEA, 2009). Biogas equipment has been standardized and is proven to be reliable at thousands of facilities throughout Europe. As of 2010, there are nearly 7,000 plants operating in Europe, corresponding to 2,250 megawatts of total capacity (see figure below).

Number of Installations and Capacity in Megawatts, Europe

Is the technology common in the U.S.?

In the United States, anaerobic digestion is a common technology used at municipal wastewater treatment plants, food processing facilities and in the processing of manure at farming operations. As of 2010, 150 anaerobic digesters were in operation in the United States. Local examples of successful anaerobic digestion facilities are Stahlbush Island Farms in Corvallis and the Port of Tillamook Bay in Tillamook. Additionally there are several local wastewater treatment plants utilizing anaerobic digestion in the Portland metropolitan area including the Portland, Gresham, Durham, Portland and Oregon City plants.

Is Columbia Biogas working with the surrounding community?

Columbia Biogas is committed to being a good neighbor and providing multiple benefits to nearby residents and businesses. We have signed a Good Neighbor Agreement with the Cully Association of Neighbors that addresses communications and complaint procedures, operations, and environmental and livability standards that support long-term facility operations and sustainability. We continue to work closely with the Neighborhood Advisory Committee so that concerns are considered in the design and operation of the facility.

How many jobs will be created and will the neighborhood benefit?

We recognize that local economic development and job creation are important issues. Columbia Biogas is committed to working with its general contractor and operations manager to ensure that jobs are made available locally. We have established a Jobs Subcommittee with the Cully Association of Neighbors and are working with key individuals and organizations in the local area to develop a job training, recruiting and hiring program targeting the local community including women and minorities. The program will include an operational jobs training program focused on preparing potential candidates for skilled jobs. We have completed a construction jobs diversity specification and we plan to collaborate with local organizations to advertise job positions in community papers and electronic newsletters.

We estimate that 85 jobs will be created during the 12-month construction period. There will also be a number of indirect jobs associated with the manufacturing of equipment off-site. Plant operation will require approximately 15 full-time jobs. Several of the positions required to operate the plant will require the employee to be a “Certified Wastewater System Operator.” The remaining positions will require individuals skilled in mechanics, maintenance, lab work, administration and receiving.

Will odors be a concern?

The facility will include a state-of-the-art odor control system as the biogas plant will be handling and processing food waste that can produce odors. As a result, odor control is an important part of the plant design. Columbia Biogas is using a nationally recognized expert in odor control to design the odor control systems at the plant. All food waste delivered to the facility will be received and processed within the enclosed receiving building.

Biofilters are a proven odorous air treatment technology and were selected instead of chemical systems, as they effectively remove a large spectrum of odorous compounds without the addition of chemicals. They are a biological treatment method that utilizes a media, that together with naturally occurring bacteria, remove and oxidize odorous compounds present in the air stream. Biofilters have been successfully used in the Portland area and throughout the United States to treat odors from organic sources such as compost, solid waste and wastewater. Local examples include: Gresham, Durham, Oregon City, Corvallis, and Eugene.

Will there be air emissions?

The natural gas-fired equipment, engine generators and the flare will produce minor air emissions at the facility. The engines proposed for use in the facility are clean burn gas engines that are designed specifically to efficiently burn gaseous fuels in stationary continuous operation. High efficiency natural gas-fired equipment will be installed.

The flare is enclosed and will be used during the times when the biogas injection system is shut down for maintenance. The flare is also sized and available as a safety device in the event of an upset condition. The majority of the time the flare will not be operating. The flare has a hydrocarbon destruction removal efficiency of over 99%.

How is the plant different from the Riedel Environmental Technologies, Inc. municipal solid waste composting facility sited in the area in 1991?
  1. Reidel accepted residential and commercial garbage; we will only accept food waste from commercial and industrial sources.
  2. Reidel was an open air receiving facility whereas our trucks will enter into an enclosed receiving building.
  3. Reidel did not have an adequate odor control system whereas we are using highly proven non-chemical filters.
  4. Reidel did not control its noise sources; we will be operating in an enclosed facility and will mitigate sources of noise.
  5. Reidel was an open air composting facility whereas we utilize anaerobic digestion which occurs within sealed tanks.
Will noise be a concern?

Columbia Biogas does not expect noise to be a nuisance. The facility is designed to meet both the State of Oregon and City of Portland noise limits. Columbia Biogas engaged a local noise expert to determine the noise mitigation measures required to ensure compliance with applicable noise regulations. A 24-hour measurement was conducted at various locations in the neighborhood to better understand the existing noise levels. Noise controls have been selected to reduce noise generated by the process to the required levels. The primary sources of noise will be the trucks entering and leaving the facility during business hours. In addition, some noise will be produced by the process equipment located at the facility, although this equipment is primarily within buildings and the outside equipment is not expected to produce significant noise levels.

Power generation equipment has been selected with enclosures and mufflers that will ensure the noise radiating from the equipment is well below the applicable noise limits. Heating, ventilation and air conditioning (HVAC) and odor-control fans will be located inside the buildings and duct silencers will be provided to lower noise levels. Noise will be controlled through the proper use and maintenance of mufflers on equipment with engines, both stationary and mobile. Backup alarms on equipment will comply with all safety regulations and noise ordinances.

Will the facility have a system to capture any spills?

The hydrolysis tanks, fermenter tanks, digestate storage tank and other smaller tanks will be constructed within a containment structure. This containment structure will include concrete tank pads, a concrete floor slab and concrete retaining walls. This design will provide positive containment in the event of a major tank rupture or other spill event in accordance with City of Portland requirements. The structure captures spills and protects the soil, groundwater and nearby Columbia Slough.

Rainwater within the containment structure will be directed to a sump/retention area with closed valves where it will be collected. Under normal conditions, accumulated rainwater will be inspected to be sure it is free of contaminants and, when approved as permitted by the City, will be discharged to the storm water system. If there is an abnormal operating condition such as tank cleaning, foaming or spill from cleaning a pump or contaminants are detected in the stormwater, the runoff water and other material will be collected in the retention area with closed valves where it will be discharged into the sanitary sewer system. This sump/retention system within the containment structure will ensure that only clean rainwater will pass to the storm water system.

Will the facility pose a fire hazard to the surrounding area?

The risk of a fire hazard is low because the facility operates with very low pressures. The biogas itself is not explosive and will not burn unless oxygen is available. Redundant safety relief valves are provided on each fermenter tank to prevent over pressurizing or damage due to a vacuum. Additional safety equipment includes flame arresters to prevent flames from entering the digester through the relief valve. All other storage tanks will be vented to non-chemical filters to prevent pressure buildup.

The biogas is piped from the fermenters to the conditioning and power generation equipment units through sealed piping systems which will include pressure relief valves and flame arresters. The majority of the gas handling equipment that is used in the facility is the same equipment used in anaerobic digestion facilities at wastewater treatment plants in the Portland metropolitan area. All of the equipment will meet all applicable codes and standards including City of Portland building codes and National Fire Protection Association rules, and all plans will be reviewed and approved by the City of Portland Fire Marshall.

What waste will the plant generate?

Commercial and industrial generators will be encouraged to separate food waste from other materials for recycling at the facility. However, the food waste may contain some level of contamination including packaging material such as glass, plastic, metal or cardboard. This material will be separated by the pretreatment equipment and removed to a container for hauling to a transfer station for proper disposal. Metals and other recyclables will be separated and hauled to a recycling facility.

What are the primary by-products? What about the ‘stuff’ left over from the digestion process?

Columbia Biogas will produce two valuable by-products from the process of anaerobically digesting food waste: biogas and digestate. Biogas is the gas that is produced by the breakdown of food waste in the anaerobic digestion process. Digestate is the nutrient-rich material remaining after the anaerobic digestion process. This material is rich in high quality nutrients and will be processed into organic-based fertilizer products. These high quality products will allow Oregon’s agricultural, horticultural and landscaping businesses access to natural, nitrogen and phosphorous-rich products produced from a renewable resource.

How will the food waste be collected?

Columbia Biogas will accept solid and liquid food waste from pre-approved licensed haulers as well as commercial businesses and industrial facilities. Food waste will be collected at the source in containers, drop boxes, compactors or trailers.

What type of vehicles will transport the waste?

The food waste will be transported in various types of enclosed or covered commercial vehicles which are regulated by the Oregon Department of Transportation. These trucks will include front load waste trucks and trucks carrying drop boxes or compactors. Liquid tanker trailers and end dump trailers will also be utilized to deliver waste to the facility.

Will the facility create traffic problems or other negative impacts from the trucks?

At full capacity the facility will receive approximately 50 deliveries per day and also generate approximately eight truck trips for out hauling by-products. Food waste will be received Monday through Saturday during business hours. The traffic impact on Columbia Boulevard has been estimated by a local traffic consultant to increase the existing truck traffic by 1.8%. This does not take into account existing traffic at the site which will cease upon construction of the plant. Trucks must comply with Oregon Department of Transportation regulations requiring that all loads be secured to prevent loss of load. The facility is designed for efficient receiving which will result in reduced waiting times and related idling.

Where will the food waste come from?

The food waste will be sourced from local food and beverage producers, grocery stores and restaurants in the Portland metropolitan area. We will also receive deliveries of food waste from waste hauling companies who service smaller grocery stores and food establishments on a regular basis.

Will the plant accept residential food waste mixed with yard waste?

This biogas facility will not accept residential food waste mixed with yard waste.

My company produces food waste. How can Columbia Biogas benefit me?

Columbia Biogas offers a food waste management solution that provides reliability in service, cost effectiveness and reduction of your carbon footprint. Converting your organic waste into renewable energy by diverting it from landfill is cost efficient and ecologically sound, reduces long distance hauling costs and related emissions, and allows your organization to achieve sustainability status and become a greener brand.

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Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Renewable Energy

Energy that is capable of being renewed by the natural ecological cycle.