Anaerobic Digestion

What is anaerobic digestion?

Anaerobic digestion is a biological process that breaks down organic materials, such as organic food waste, agricultural residues, and livestock manure, in the absence of oxygen. The process involves a series of steps carried out by microorganisms, primarily bacteria. Anaerobic digestion is used as an extension to agricultural operations to convert organic waste into biogas and nutrient-rich byproducts such as digestate.

What is digestate?

Digestate is a beneficial by-product of the biodigestion process, will be used for application to lands as a less odorous, biologically stabilized, fertilizer alternative to raw manure, which is currently being land spread in the region.

Digestate does not have the same odour as cattle manure. It is less odorous. It is rich in nutrients, containing the valuable nutrients nitrogen, phosphorus and potassium required by plants for growth. Applied to land as a fertilizer, digestate can play a vital role in healthy landscape and watershed development through replenishing the soil with nutrients.

The process of anaerobic digestion will produce a stabilized digestate where pathogens are greatly reduced, and the nutrients mineralized. Digestate is recovered from the anaerobic digester tanks as a wet mixture that is then separated into a solid and a liquid fraction by screw presses. The separation of digestate provides an odour mitigation for the liquid digestate pond by removing a large portion of the remaining organic compounds that would otherwise be discharged into the liquid digestate pond following the digestion process.

The solid digestate fraction consists of a stackable fibrous material, rich in organic matter and nutrients. This organic matter provides a readily available carbon source improving biological, chemical and physical soil characteristics. The liquid digestate fraction consists of the soluble nutrients and water and can be land applied as a fertilizer, reducing the reliance on synthetic fertilizers while simultaneously reducing the associated emissions of using synthetic fertilizers.

Are biodigester facilities a proven technology?

Yes. Biodigesters are proven to have a positive effect on the environment and surrounding areas as they provide a source of renewable fuel energy by removing greenhouse gas emissions and reduce odours associated with livestock agriculture and manure handling processes.

There are over 130,000 small, medium, and large-scale biodigesters operating worldwide. The Canadian Biogas Association estimates about 200 anaerobic digesters converting manure and feed wastes into electricity or natural gas are operating in Canada today.

Rimrock has retained 40+ consultants and subject matter experts working on the proposed facility that have designed and built numerous biodigesters in Canada, including Alberta and Ontario.

Facility Operations

What safety measures will exist for protection against lightning?

A lightning study will be completed where all structures will be reviewed for lightning protection requirements to ensure an adequate amount of coverage and protection is accounted for. This facility will be protected from lightning strikes as required using grounded air terminals (e.g., lightning rods) specified and installed to meet the latest applicable Canadian Design Codes.

What kind of feedstock will the facility accept?

The types of organic material (feedstock) that are permitted to be processed by the facility will be as per the June 2023 Memorandum of Understanding (MOU) among Alberta Agriculture and Irrigation (AGI), Alberta Environment and Protected Areas (EPA), and the Natural Resources Conservation Board (NRCB) regarding the storage and application of digestate on agricultural land, as outlined by Provincial approvals.

As the primary feedstock, livestock manure from the adjacent feedlot will make up 50% or more of the total feedstock, with the remaining comprised of organic food resources such as food processing residues, kitchen and market residues, damaged and rejected grains, fats, oils, and greases from grocery stores, restaurants and cafeterias.

The facility will not have the infrastructure, or be permitted to, process specified risk materials (SRM) or carcasses.

How will noise be controlled?

The facility is being designed to comply with all noise bylaws and regulations. Equipment used onsite will be regularly maintained to ensure it is operating within recommended noise limits. Speed limits onsite will be enforced.

The Noise Impact Assessment (NIA) completed for the project has demonstrated compliance with the Alberta Utilities Commission (AUC) Rule 012: Noise Control. Updated noise assessments will be completed based on final facility design. The facility’s modelled noise sources will be compliant with the AUC’s prescribed permissible levels (PSLs) during the daytime and nighttime at all receptors within 2 km of the facility boundary, with sound levels further decreasing with distance from the facility.

How will lighting impacts be mitigated?

Outdoor lighting will be required onsite outside regular business hours for site security and safety purposes and during low-light periods in the fall and winter months during regular business hours.

Outdoor lighting fixtures will follow the MD of Foothills No. 31 Dark Sky Bylaw.

The flare will only be used occasionally (for start-up, commissioning, and operational upsets).

What will local traffic impacts be?

The main facility access will be off Range Road 10 (Meridian Street) from Coal Trial. Range Road 10 will be paved to the entrance of the facility. All appropriate road signage and intersection control will be implemented per County requirements.

At full operations, approximately 6-7 trucks are anticipated to deliver organic food resources to the facility per day.

The majority of the feedstock deliveries will be through manure (50% or greater of the feedstock) which will be transported from the adjacent feedlot using a private internal gravel access road (i.e., not a public roadway).

A Traffic Impact Assessment (TIA) was completed by professional traffic engineers specializing in transportation and is based on collected traffic data (counts and cameras). The results of the TIA indicate there will be a net decrease in annual traffic from the facility, as the facility will reduce the need by the Rimrock Cattle Company Ltd. feedlot to truck manure for spreading.

How will dust be managed?

Hydroseeding and anchoring of soil storage berms were completed in the spring of 2023 to minimize dust development from the project's footprint. This erosion and sediment control will continue to be maintained pending regulatory approval.

During construction, dust suppression using water trucks will be utilized, as needed. During operations, facility operators will utilize appropriate dust suppression techniques, as needed. Traffic speeds onsite will be limited and strictly enforced to minimize dust.

How will the facility be powered?

Electricity and heat needed to support the facility will be primarily provided onsite by two micro-generation sized cogeneration units.

What will facility operations be?

The facility will be monitored 24 hours per day, 7 days per week through the use remote communications.

Active operations at the facility will primarily be during facility operating hours (8:00 a.m. and 6:00 p.m. daily) and will follow all applicable County bylaw requirements.

The facility is expected to require 6 full time staff for regular operations.

What safety measures will be in place?

The facility will be designed, constructed, and operated to meet all applicable health and safety standards, codes, and regulations.

Detailed health and safety plans, emergency response plans, operations plans, shutdown keys, alarm systems, and control narratives are also being developed to ensure the safe operation of the facility.

Access to the facility will be granted to operational personnel and approved third-party personnel only. Restricted access to the facility off Range Road 10 south of Coal Trail will be maintained through a controlled entry point. Access to the site from the east (i.e., for livestock manure from the adjacent Rimrock Cattle Company Ltd.) will be private access.


What are the predicted odour conditions? How will odours be managed?

For more information on odour management, please see the odour abatement technology section of the Facility Information page.

The biodigester facility will capture odour-causing greenhouse gases from feedlot manure and, through a fully closed system, convert them to a usable energy resource called renewable natural gas (RNG). Today, those greenhouse gases are currently being released to the atmosphere. It will also help reduce feedlot operational odours by doubling the rate of livestock pen cleanouts and reducing the need for seasonal storage of raw manure at the feedlot (because feedlot manure will be used as feedstock instead).

Our team has spent the last several months reviewing best available technologies for odour abatement, consulting with research and industry experts, and working intensively with engineering, environmental and regulatory consultants. A 2-stage odour abatement system has been selected that will remove approximately 95% of odorous emissions from all tanks involved in feedstock receiving and digestate separation, as well as the feedstock hopper building, feedstock receiving hoppers, feedstock pumphouse building, and digestate separation building.

Mechanical separation of digestate into solid and liquid fractions using screw presses provides an odour mitigation for the liquid digestate pond by removing a large portion of the remaining organic compounds that would otherwise be discharged into the liquid digestate pond following the digestion process.

Our liquid digestate pond has undergone a redesign to optimize its performance. The new two-celled configuration, with mechanical aeration and oxidization in the first cell will remove approximately 95% of odorous emissions. Aeration is a proven technology that will stabilize the liquid digestate that is stored in the second cell.

Based on air quality modelling completed by a qualified third party in July 2023 after the implementation of the new design changes, the operation of the proposed biodigester facility is predicted to result in an approximate 47% net reduction in feedlot odour.

What are the predicted air emissions?

A detailed air quality assessment was completed for the proposed facility and submitted to AEPA as part of the EPEA application. The air quality assessment, which was conducted in accordance with the Alberta Air Quality Model Guideline, was further updated to reflect the final facility design updates and proposed odour abatement technologies and to assess specific air quality contaminants associated with odours. The updated assessment indicates that overall, the operation of the biodigester facility is predicted to result in an approximate 47% net reduction in feedlot odour.

Maximum ambient concentrations of emissions associated with the facility are predicted to be well below the Alberta Ambient Air Quality Objectives.

What measures will be in place to prevent attracting animals and pests?

Receiving and staging areas for feedstock will be actively managed and will prevent or reduce attraction of animals and pests. Feedstock staging and processing areas are also designed to be enclosed.

Anaerobic digestion had been demonstrated to greatly reduce the occurrence of certain pests (e.g., insects, and animal and plant pathogens) that may be present in feedstock, given temperatures involved in the process.

Facility operations are designed such that staging and storage areas will not be stagnant. Proper site drainage will be maintained to eliminate additional breeding grounds for insects.

Good housekeeping measures will be implemented to limit attraction of pests and wildlife, such as: implementing proper waste management practices, removing clutter from within and around buildings, and vegetation management. A housekeeping inspection and cleaning schedule will be set up to minimize buildup of feedstock or digestate collected on ledges, recesses, corners and equipment areas.

As part of routine facility monitoring, Rimrock will also watch for any onsite increases in pests. Pest control measures will be used, as required.

For additional information about wildlife, please see the Pond section of the Community page.

Will there be trees, landscaping, and other aesthetic features at the site?

Soil berms will be maintained along both the west and north sides of the facility. These berms are used as topsoil and subsoil storage (a regulatory requirement) and were strategically placed at these locations to improve aesthetics, blend into the natural environment, and reduce visibility from neighboring properties.

Rimrock will also be planting trees along the perimeter of the property along Coal Trail and Meridian Street, based on feedback received from residents through project engagement activities.


Where will the process water come from?

The water source for the facility is the Highwood River, granted under an approved water license transfer, not groundwater. No groundwater will be used in facility processes.

Rimrock proposes to reuse a portion of the liquid digestate in the facility process upstream of the liquid digestate pond. This will decrease freshwater requirements and the size of the liquid digestate pond.

For more information on water, please see the Environment section of the Community page.

How will stormwater be managed?

Stormwater and surface runoff will be collected in the drainage ditches and swales around the site and directed to the liquid digestate pond which will be constructed with an impermeable high density polyethylene liner for full containment.

The liquid digestate pond has been designed to accommodate the maximum volume from a predicted 1:100 year flood event, even when already full. Additionally, based on the proposed pond operation, it would only be 50-60% full during peak rainfall months (e.g., June and July). Based on Alberta Environment and Protected Areas’ 1:500 year flood elevations, the proposed biodigester facility is located well above the estimated flood elevation for the area. The risk of any flooding from the Highwood River to the facility is considered to be remote.

Will there be impacts to water quality from the facility or land receiving digestate?

No impacts to water quality are expected as a result of facility operations. The facility has been designed with robust containment and monitoring systems to avoid impacts to water quality.

The digestate pond will be constructed with an impermeable high-density polyethylene (HDPE) liner for full containment and no contact with groundwater.

Facility tanks and vessels have been designed with both primary and secondary containment and leak detection to prevent any inadvertent releases.

A groundwater monitoring system will be installed to provide rigorous surveillance and verification of groundwater quality during operations.

All land spreading activities associated with liquid and solid digestate will follow Alberta Agricultural Operation Practices Act (AOPA) requirements, in accordance with Rimrock's Nutrient Management Plan and under the guidance of a certified crop advisor.

Renewable Natural Gas (RNG)

What is renewable natural gas (RNG)?

Renewable Natural Gas is derived from the upgrading and purification of biogas, the gaseous by-product produced from the biological degradation of organic matter via anaerobic digestion of the cattle manure and organic food resource. Biogas is upgraded to RNG using a series of filters and scrubbers to 99% pure methane that is fully interchangeable with conventional natural gas sourced from fossil fuels.

Where will the RNG go?

RNG will be injected into a low-pressure ATCO gas line onsite to serve the local community in Foothills County. The green credits associated with the RNG are being purchased by Fortis BC as part of Clean BC Roadmap to 2030 program.