Anaerobic Digestion

What is anaerobic digestion?

Anaerobic digestion is a sequence of processes by which micro-organisms (bacteria) break down biodegradable material in the absence of oxygen.

The process is used as an extension to agricultural operations to manage waste, capture greenhouse gases (which are also odour causing), and to produce renewable fuels.

What is digestate?

Digestate is the liquid by-product output from anaerobic digestion that can be described as a nutrient, carbon and micro-rich soil amendment. It is rich in nutrients, containing the valuable nutrients nitrogen, phosphorus and potassium required by plants for growth. Applied to land as a soil amendment, digestate can play a vital role in healthy landscape and watershed development through replenishing the soil with nutrients.

Digestate does not have the same odour as cattle manure. It is less odorous. 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 digesters as a wet mixture that is then separated into a solid and a liquid fraction. The solid fraction is commonly referred to as solid digestate. The liquid fraction is commonly referred to as liquid digestate.

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 aerobic 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 kind of feedstock will the facility accept?

The types of organic material (feedstock) that are permitted to be processed by the facility will be outlined by provincial approvals. 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.

Feedstocks will be from natural sources and will be sourced locally.

All of the manure produced annually by the Rimrock Feeders Ltd. feedlot is expected to be processed by the biodigester facility.

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.

A Noise Impact Assessment (NIA) was completed for the proposed facility, to demonstrate compliance with the Alberta Utilities Commission (AUC) Rule 012: Noise Control. The facility’s modelled noise sources are predicted to 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 an existing internal gravel access road (i.e., not a public roadway).

A Traffic Impact Assessment (TIA) was completed by a reputable firm 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?

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 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?

The biodigester facility will help greatly reduce storage time for manure at the adjacent Rimrock Feeders Ltd. feedlot since manure from the feedlot will be a primary source of feedstock for the anaerobic digestion process.

Controlled anaerobic digestion in sealed, heated digester tanks, will provide a suitable environment for naturally occurring bacteria to convert odour producing gases into both biogas and a low odour digestate effluent.

For more information on odour management, please see the odour section of the Community page.

What are the predicted air emissions?

An Air Quality Assessment has been prepared for the proposed facility by a qualified professional and submitted to AEPA as part of the regulatory application for the facility. The air quality assessment completed is separate and different from the odour study.

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, given a semi-continuous operation, which 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 or even eradicate 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 solid digestate staging and storage 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?

Water required for facility operations will be sourced from the Highwood River under approved Water Transfer Licence(s).

Rimrock is also completing ongoing studies which may provide an opportunity to reuse a portion of the liquid digestate upstream of the digestate pond for use in process. Pending results, the final size of the digestate pond will be confirmed.

No groundwater will be used in facility processes. 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 digestate pond which will be constructed with an impermeable high density polyethylene liner for full containment.

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

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.