Mention the term “liquid gold” in Alberta and livestock manure isn’t likely the first thing that jumps to mind.
But it’s slowly becoming part of the conversation as researchers learn more about how to harvest the nutrient benefits of this potentially abundant resource and byproduct of the livestock industry.
One of the latest and most promising forms is “digestate,” or the frothy manure-based slurry produced by biodigesters.
“In Europe, they call it liquid gold, and not in a joking way – it’s quite valuable,” says Virginia Nelson, a project engineer and researcher at Alberta Agriculture and Rural Development’s (ARD) AgTech Centre in Lethbridge.
Nelson, who has long studied emerging manure-management strategies, says, “We’re not there yet in Canada, but we’re on that path. There’s more interest and more progress every few years.”
Biodigesters are not common in Western Canada or the country as a whole, but they are adopted by an increasing number of pioneering livestock operations such as Vegreville, Alta.-based Highland Feeders with its partner company Highmark Renewables. This $100-million operation converts manure into energy and fuels an ethanol plant while making feed and high-grade fertilizer.
Biodigesters are also generating interest among a growing number of key players in industry and government as a key technology to support a more sustainable agriculture and energy future.
The science of success
A critical part of achieving this vision is science. For her part, Nelson is part of a research team looking to generate more information and more answers to help make strategies such as biodigestion and composting into more viable and predictable options for Canadian agriculture.
One ongoing study involves ARD, Highmark Renewables and Agriculture and Agri-Food Canada. Nelson is working on a component that is studying the value of digestate. Manure from the beef cattle operation is used to produce digestate, which is land applied to fields used to grow barley. The digestate is applied as a slurry, a solid separated product, and a pelletized product. Results are compared to solid manure to allow for assessments of which strategies work better under different circumstances.
“Part of what we’re trying to do is remove the guesswork for farmers on what digestate means for them,” says Nelson. “For example, if a major biodigestion facility were to be established in a city such as Lethbridge, the farmers who would use the digestate it produces would naturally want to know what performance they can expect from it in their fields, what nutrients it has, how it impacts what they’re growing, what it means for the environment, etc. Those are the types of questions we’re aiming to answer.”
One of the most direct questions being answered is what digestate means for a barley crop.
In addition to producing valuable nutrient material in the form of digestate for land application, the process of biodigestion also creates a methane mix called “biogas” which is similar to natural gas and has similar use potential.
Green energy with biogas
“What excites me about biogas is that it’s greener than any other gas technology,” says Mahendran Navaratnasamy, a research engineer with ARD and the province’s technical adviser on biogas.
There are many challenges to the viability of biogas production, ranging from high investment costs paired with long-term paybacks, to a handful of important technological and logistical difficulties to overcome. But against the current backdrop of the push to more sustainable agricultural systems and renewable energy sources, biogas production is an emerging option that is rapidly generating attention.
Biogas production using anaerobic digesters is not limited to manure, says Navaratnasamy. It can use feed spills, meat and food-processing wastes and crop residues, as source material. Biogas can be added to natural gas lines if carbon dioxide and hydrogen sulphide are removed.
“If we can make large-scale biogas production a viable option, it could go a long way to helping the agriculture industry address the issue of managing manure and other farm organic waste, while also generating additional income streams and energy sources,” says Navaratnasamy. “Every new research study in this area is another step in making this a reality in Canada.”