Opinion: Highlighting the Value and Safe Use of Digestate

by Sarah Stadnyk (Canadian Biomass Magazine) Canadian Biogas Association's Sarah Stadnyk explains how the first-of-its-kind Canadian Digestate Management Guide provides practical and useful information to maximize the benefits of using digestate products.

Biogas and renewable natural gas (RNG) are often the primary focus for outputs of biogas facilities as it can be monetized and sold to different markets. However, digestate is also a valuable output as a fertilizer or soil amendment. It is a nutrient rich product that contains virtually all the macro and micronutrients that were found in the original organic materials that went into the digester.

To bring attention to the value of digestate, the Canadian Biogas Association (CBA) developed a first of its kind document, the Canadian Digestate Management Guide, that summarizes best management practices in a Canadian context. Currently digestate producers and applicators follow provincial regulations and employ best management practices, however there isn’t a Canadian specific resource compiling this information. The guide was developed with input directly from stakeholders and subject matter experts to provide practical and useful information to maximize the benefits of using digestate products.

Producing safe and effective digestate

Canadian agricultural and industrial biogas facilities currently produce approximately 1.2 million tonnes of digestate annually across the country and most of this digestate is applied to farmland as fertilizer. A clear understanding of good digestate management practices builds confidence in production and use of digestate.

Digestate producers apply quality control at feedstock selection and digestate production to ensure safety. In addition to safety during production, best management practices support effective use of digestate as a fertilizer or soil amendment.

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The guide includes sections on producing digestate, digestate characteristics, best management practices, and the 4R principles of nutrient stewardship (Right Rate, Right Time, Right Place, Right Method).

The guide provides five examples of utilizing digestate adhering to the 4R principles of nutrient stewardship: digestate applied after wheat harvest with cover crop; digestate side-dress application into standing corn; digestate spring applied on growing wheat; digestate spring applied ahead of planting corn and split application or digestate and manure for organic farming. The examples are provided to illustrate common digestate product utilization scenarios and considerations, including soil testing, plant nutrient requirements, and application techniques.

The CBA published the guide in March 2023 and intends this to be the first version allowing for periodic updates as the industry evolves.

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To complement the guide the CBA has also developed two brochures, Digestate 101 and Best Management Practices for Digestate, to break down key information to help communicate the value of digestate and common uses as a sustainable source of nutrients for farms. The Digestate 101 brochure is an excellent introductory tool to share with those looking to learn more about the product, the benefits, and composition. The Best Management Practices for Digestate Brochure is a resource the outlines how digestate can be a valuable part of a farm’s fertility program and introduces how the 4Rs of nutrient stewardship can maximize the value of digestate.

Both brochures are available on CBA’s farmingbiogas.ca microsite. A full copy of the Canadian Digestate Management Guide is publicly available on the CBA website. READ MORE