LISA DESJARDINS: In the battle against climate change, carbon dioxide is the greenhouse gas often grabbing the most attention.

But methane is actually more harmful in terms of trapping heat, with 80 times more of an effect than CO2 during the first decades after it's released.

Now one country is teeing up a different and controversial approach to reducing these emissions.

Ali Rogin has more.

ALI ROGIN: Landfills, oil and natural gas all contribute methane.

But according to the United Nations, 32 percent of human caused methane emissions come from livestock.

Last week, Denmark's coalition government announced that they would introduce a first of its kind annual tax on livestock greenhouse gas emissions.

It amounts to about $100 per cow in an effort to curb climate change.

Ben Lilliston is the director of Rural Strategies and Climate Change at the Institute for Agriculture and Trade Policy.

Ben, thank you so much for being here.

First of all, how big of a problem is methane and does it get enough attention as it relates to the attention that seems to be put on carbon dioxide?

BEN LILLISTON, Institute for Agriculture and Trade Policy: It's a huge problem.

It's a huge challenge.

It's also an opportunity to help us have a bigger impact on climate change faster.

So methane is only in the atmosphere for around twelve years, and it is about 80 times the potency of carbon dioxide over a 20 year period.

So as a result, if you reduce methane, you can get more near term results and allow us to have a little longer of a window to reduce carbon dioxide emission.

ALI ROGIN: And why do cows and other livestock produce so much methane?

BEN LILLISTON: Well, it's ruminants in particular.

So cows and sheep, and it has to do with their stomachs and how they work.

They have multiple stomachs, and they belch out most of that methane is coming out of their belches.

But they can also produce methane through their manure, depending on how their manure is stored.

But in particular in the United States, but also in Denmark, as we're talking about, the cows themselves are a major source of methane.

ALI ROGIN: And what do you see as the goal behind this tax that Denmark is putting in place is it to get farmers to reduce their herds?

How does this tax lead to reduced methane emissions?

BEN LILLISTON: Yeah, well, they have multiple parts of this policy, so the tax is only one part of it.

But yes, the biggest part of their agriculture sector is dairy and hog production.

And so they are trying to address that head on but they also have components of that policy that help farmers transition towards reforestation on their land to help install wetlands, what they call peatlands in Europe, which are also major sources of greenhouse gas emissions.

When you drain those wetlands, and reforestation, of course, can help pull carbon dioxide out of the air.

It's both helping farmers transition out of so much animal production.

They're still going to produce a lot of animals and still produce meat and dairy, but maybe not as much and maybe scale back and then have some of their land transition towards more climate beneficial land practices.

ALI ROGIN: And how do you see the efficacy of this?

Do you think it's going to be effective?

BEN LILLISTON: You know, we'll have to see.

I think what's really exciting about it is this plan came together when farmers sat down with food system workers and climate and environmental advocates and put this plan together.

They have a phase in period.

So it starts in 2030 and then amps up even more in 2035.

So it's a strategy and a plan, and it's sending signals to farmers.

It's sending signals to the marketplace there.

So we'll have to see how it actually turns out.

But I think I, most importantly, they actually have a plan to reduce some of these big sources of greenhouse gases, including methane.

ALI ROGIN: There's been research into other ways to address livestock methane emissions, including changing up the feed to reduce emissions.

How do those efforts factor into this broader conversation?

BEN LILLISTON: Well, this is a rising source of debate, I think right now.

I think it's still unclear how well those feed additives actually work, how well they work over time.

Do the cow system sort of make adjustments and go back to reduce emitting as much methane as they did before?

And what are the impacts on the animal's health of eating those types of feed additives over time?

The other element is that it really requires a confined system in order for those feed additives to work.

A lot of farmers have animals on pasture, and so the feed additives are not going to be as applicable for them.

Of course, those systems do emit less because of how they manage their manure.

ALI ROGIN: And so far, this tax is the first of its kind.

New Zealand had proposed something similar, but they ended up scrapping it.

But how likely is it that it could be replicated outside of Denmark, especially here in the United States?

BEN LILLISTON: I do think governments around the world are grappling with this question about how to deal with animal related methane.

And they have started down the path that Denmark has.

In the U.S., agriculture is a smaller part of our overall emissions, but we do have a problem with our large scale dairies and our large scale hog operations, which in that case, it has to do with how their manure is being managed in giant manure lagoons where it's liquefied and that creates a lot of methane.

But we haven't really gotten to the point where we're ready to have different parties sit down in the way that they did in Denmark and really hammer out a compromise proposal.

But we do need to start thinking about it.

We have a lot of programs that are public programs that sort of provide the carrot part of the policy.

We have conservation programs that are in huge demand in the U.S. two-thirds of farmers who apply for those programs get closed out.

So that tells you how big the demand is, and that has to do with all types of farming systems, but including animal agriculture.

So we have the carrot part, but the carrot part really hasn't worked very well in terms of reducing greenhouse gas emissions or water pollution or air pollution in agriculture.

And so we're going to have to think about what is, what other types of regulatory tools can we apply?

I think every country is different.

Every context is different around climate change.

But what would work in the US?

And we need to start that conversation right now.

ALI ROGIN: Ben Lilliston with the Institute for Agriculture and Trade Policy, thank you so much for joining us.

BEN LILLISTON: Oh, thanks for having me.