Breaking Down the Hot Air and Cold Truth About Carbon Emissions


Mario Tenuta has been studying greenhouse gas emissions in agriculture for longer than he’s willing to admit.

Never before has he seen this much interest in the topic.

“We’ve always had interest in carbon sequestration and the use of nitrogen fertilizers and manures, but now where we are called to some form of action and reductions, now there is great interest,” says Tenuta, who’s the chair of the agroecology program in the Department of Soil Sciences Department at the University of Manitoba.

There’s been plenty of discussion and concerns expressed about the impact of government carbon policy on agriculture after Prime Minister Trudeau announced plans for a national price on carbon several weeks ago.

In response, Tenuta took to Twitter answering questions and sharing information about greenhouse gas emissions using the clever hashtag #HotAirColdTruth.

Mario Tenuta joined Kelvin Heppner at the Canola Discovery Forum in Winnipeg this week to discuss #HotAirColdTruth and some of the basics around carbon emissions from Canadian agriculture (as heard on RealAg Radio on SiriusXM.)

As he explains in the interview above, when politicians or scientists talk about greenhouse gas or carbon emissions, there are three gases of concern for agriculture:

  • Carbon dioxide — CO2 is emitted from the decomposition of crop residue and soil organic matter. as well as from the burning of fossil fuels. As Tenuta notes, emissions from fuels are categorized nationally under transportation, not agriculture.
    Crop and grazing lands also remove CO2 from the air, storing it as soil organic carbon. Since this carbon is not considered to be sequestered permanently, it’s not included in the national reduction inventory.  (The emissions of other forms of greenhouse gases are converted into a C02 equivalent, which is why when we hear and use the terms “carbon pricing” or “carbon tax,” it can also apply to other greenhouse gases.)
  • Methane — CH4 is the gas that mainly comes from livestock production, such as enteric emissions from ruminants and from manure. Methane is 20 to 30 times more potent than C02.
  • Nitrous oxide — N2O is emitted as a result of the use of nitrogen fertilizer. N20 Is 300 times (!) more potent in terms of warming the atmosphere than C02, explains Tenuta.
    N2O emissions can vary widely from one field to another, depending on soil type, rainfall, and fertilizer practices, and other factors, he explains: “Usually we want things that are easy to develop policy on. N2O emissions on farmers’ fields are extremely difficult to predict, especially on a field-by-field basis.”

Carbon tax and government policy aside, Tenuta believes the low hanging fruit for reducing emissions from agriculture lies in implementing the 4R nutrient strategy for nitrogen fertilizer — right source, right place, right time and right rate. It’s all about maximizing nitrogen efficiency by only making it available in the nitrate form as the plant needs it. That might mean banding fertilizer rather than broadcasting it, or using nitrogen stabilizers to slow the conversion to nitrate.

Ideally, government policy should be designed to help farmers increase crop production per unit of nitrogen fertilizer, he says.

“We don’t want to see a reduction in production. The idea of optimizing what inputs you have to do, such as nitrogen…we want to get the most bang from it,” he explains.

Not only are farmers expressing interest, Tenuta says policymakers at both the provincial and federal levels are paying attention to the carbon research he and his colleagues across the country are doing.

“We need tangible data on emissions and nitrogen management practices to first of all, know how many emissions are happening, and then to figure out the impact of incentives or a tax.”

Listen to our conversation above for more on what’s known about greenhouse gas emissions from farming in Canada.

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