Rimrock Biodigester Facility – Transforming Greenhouse Gases into Renewable Energy
Rimrock Renewables LP is proposing to construct an on-farm biodigester facility to capture greenhouse gases (GHGs) from livestock manure and organic food resources and convert them to a usable energy resource called renewable natural gas (RNG). Today, those greenhouse gases (which are also odour causing), are currently being released to the atmosphere. The primary objective of the Rimrock Biodigester Facility is to capture as much of those gases as possible.
The Rimrock Biodigester Facility will be located within Foothills County, approximately 5.5 km west of the Town of High River, at the northwest corner of Coal Trail (Township Road 191) and Meridian Street (Range Road 10).
Like most biodigester facilities in Canada and globally, the facility is located adjacent to the primary source of feedstock - in this case the existing Rimrock Feeders Ltd. feedlot.
Locating these types of facilities immediately adjacent to the primary source of feedstock enhances environmental benefits (e.g., net decrease in greenhouse gas emissions) through reduced transportation requirements and hauling distances.
Feedstock for the facility will be made up of livestock manure and organic food resources. Manure will be transported to the facility via an internal road from the adjacent Rimrock Cattle Company Ltd. feedlot. Organic food resources will be sourced as close as possible to the proposed biodigester site depending on availability and qualification of the material. The feedstock will be processed on-site in fully contained anaerobic digesters where micro-organisms (bacteria) will break down the organic material within the feedstock, in the absence of oxygen, producing biogas and digestate.
The biogas will be upgraded at the facility to produce pipeline quality renewable natural gas (RNG) which will be injected into a low-pressure ATCO Gas distribution pipeline to serve the local community.
An organic, biologically stabilized, micro-nutrient and odour-reduced by-product of the anaerobic digestion process called digestate will be separated into liquid and solid fractions and spread on agricultural land, as is being done with manure by the feedlot currently. The use of digestate on agricultural land reduces the need and reliance on synthetic fertilizers.
Click on the interactive image below to learn more about how the biodigester facility will operate:
Internal Gravel Road
Rimrock Cattle Company Ltd. Feedlot and the Rimrock Biodigester Facility will be connected by an internal gravel road to transport manure from the feedlot to the manure blend building. This avoids the use of public roads for manure transportation.
Manure Blend Building & Manure Tanks
Manure will be brought directly into the fully enclosed manure blend building and dumped into 1 of 4 covered manure blend tanks. Within the covered manure tanks, manure will be heated and mixed with water before being pumped through underground piping to the digester tanks.
Organic Food Resource Tanks
Organic food resources will be trucked to the facility via external roads in contained delivery vehicles to mitigate the potential for odour releases. Some organic food resources will require de-packaging (e.g., removal of plastics, styrofoam), this will occur offsite before being transported to the facility. Upon arrival, organics will be transferred into organic food resources tanks for processing before being fed via underground piping into the digester tanks. The organics tanks will be fully enclosed to limit release of odours. See the Facility Operations section of the FAQ page to learn more about feedstock.
Freshwater Reservoir Pond
The water source for the facility is the Highwood River, granted under an approved water license transfer, not groundwater. A clay-lined freshwater reservoir will temporarily hold water from the Highwood River before being used to blend with manure and organic food resources. No process water or runoff will be stored in the freshwater reservoir. See the Water section of the FAQ page to learn more about water use.
Anaerobic Digester Tanks
There are 6 anerobic digestion tanks that will receive and process manure and organic food resources. During anaerobic digestion, micro-organisms will break down the organic material within the combined feedstock in the absence of oxygen, producing two products: biogas and digestate. The anaerobic digestion process occurs at a temperature of 38oC over approximately 30-days. These fully enclosed tanks have double-layer membranes which will contain the biogas at low pressure as well as any odours that may result from the process. See the Anaerobic Digestion section of the FAQ page to learn more.
Digestate Separation & Solid Digestate Storage
Digestate material will be taken from the 6 digesters through underground piping to the digestate separation building. Digestate has a high concentration of liquid and to be able to maximize the product, it is separated into liquid digestate and solid digestate using screw presses. Solid digestate is stored adjacent to the digestate separation building. See the Anaerobic Digestion section of the FAQ page to learn more about digestate.
Liquid Digestate Pond
Liquid digestate will be collected in an onsite digestate pond with an impermeable high-density polyethylene (HDPE) liner. In response to stakeholder feedback and as a result of additional detailed studies, Rimrock has identified an optimized configuration for the digestate pond consisting of a 3-cell design. This reconfiguration will notably reduce the total surface area, as well as potential odours. Liquid digestate will be pumped from the pond and applied to agricultural lands as a natural fertilizer alternative. As a result, the digestate pond will be drained every 6 months and take another six months to fill up again.
Biogas Upgrading & Cogeneration
Biogas taken from the anaerobic digesters needs to be upgraded before utilized as RNG. During biogas upgrading, activated carbon filters will trap volatile organic compounds (VOCs), ammonia and hydrogen sulfide (H2S), to eliminate exhaust stack odours and produce pipeline quality RNG which will be injected into the local ATCO Gas distribution system. See the RNG section of the FAQ page to learn more.
Two micro-generation sized cogeneration units, with a combined maximum output of approximately 2 MW, will be installed onsite to produce electricity and heat needed to support facility operations.
What are the Facility’s Environmental Benefits?
The on-farm biodigester facility will:
- Reduce greenhouse gases (GHGs) by capturing odour causing gases such as methane (CH4) and convert them to a usable energy resource called renewable natural gas (RNG). These gases are currently being released to the atmosphere.
- Reduce storage time for livestock manure at the Rimrock Cattle Company Ltd. feedlot, reduce odours from land application and support improved management of pens and land application.
- Produce an organic, micro-nutrient and odour-reduced digestate for land application, as an alternative to synthetic fertilizers. See the Anaerobic Digestion section of the FAQ page to learn more about digestate.
- Provide a sustainable waste management strategy in conjunction with the agricultural livestock and energy sectors.
- Produce enough renewable natural gas to heat ~6000 homes per year (450,000 Gigajoules of RNG per year) in Foothills County. RNG produced will be used in place of natural gas, reducing reliance on fossil fuels.