WILLIAM BRANGHAM: In the ongoing effort to curb# climate change, scientists are taking aim at a## surprisingly potent source of the greenhouse# gases that are warming our planet, cows.

As part of our Tipping Point series, science# correspondent Miles O'Brien traveled from## California to Mexico and even to Australia to# explore a bold idea that could make a big impact.

MILES O'BRIEN: It's 0 dark 30 at the Straus# Dairy Farm in Marin County, California.

The## cows stand patiently in line, ready for the# morning milking.

At the helm is Albert Straus.

ALBERT STRAUS, Straus Family Creamery:# I want to make a farming system that's a## positive impact on the environment, at the# same time produce high-quality organic food.

MILES O'BRIEN: So methane is never far from# his mind.

It's an especially potent greenhouse## gas.

Over 20 years, it traps about 80 times# more heat than carbon dioxide.

Dairy cows and## beef cattle emit a significant amount of it.

It# mostly comes from their burps, not flatulence.

In fact, methane emissions from livestock exceed# the oil and gas industry.

It's a stubborn problem.## And, for Albert, it threatens to derail his# goal of achieving carbon neutrality by 2030.

ALBERT STRAUS: Cows have an essential# role in reversing climate change.

MILES O'BRIEN: That's why, in 2021, he# jumped at the chance to become the first## commercial dairy in the U.S. to test# a novel methane mitigation solution,## seaweed in the feed.

He enrolled# two dozen cows in a two-month trial.

ALBERT STRAUS: The things that we were testing for# didn't have any effects on animal health or human## health.

There was no off-flavors or effects on the# quality of the milk or the quantity of the milk.

MILES O'BRIEN: The additive comes from a# red seaweed called asparagopsis taxiformis.## It was less than a half-a-percent of the# cows' diet, but the results were dramatic.

ALBERT STRAUS: An average of 52 percent reduction,## with some cows over 80 percent,# and then one cow over 90 percent.

MILES O'BRIEN: University of California# Davis animal University of California## Davis animal scientist Ermias# Kebreab consulted on the study.## He is a world leader in the quest to# cut methane emissions from livestock.

ERMIAS KEBREAB, University of California, Davis:# I think we can produce high-quality protein,## high-quality milk, at the# same time help the planet.

MILES O'BRIEN: To gather data on how# much methane a cow might be exhaling,## they use a device called GreenFeed.

As# the cows lick, chew, breathe, and belch,## the gases they exhale are sucked# into a tube for real-time analysis.

ERMIAS KEBREAB: So it will# analyze the contents of the## breath in different concentrations of the gases.

MILES O'BRIEN: Hello.

How are you.

How are you?

They are recording impressive results.# Cows that consume just a quarter of 1## percent seaweed in their diet# emit 30 percent less methane.

ERMIAS KEBREAB: We are kind of slowly# introducing the higher dose now.

MILES O'BRIEN: What do you# think the upward limit is?

ERMIAS KEBREAB: In the literature, there# is a report that 98 percent reduction.

MILES O'BRIEN: Ninety-eight?

ERMIAS KEBREAB: Ninety-eight percent re..

MILES O'BRIEN: And that's with only# one-half of 1 percent seaweed additive.

So,## why do cows produce so much# methane?

To understand that,## we need to ruminate literally on the# rumen, the first of four compartments## in a cows stomach.

Here, microbes start the# whole process of turning grass into energy.

But this fermentation also releases# carbon dioxide, CO2, and hydrogen,## H2.

With the help of a special enzyme, those# molecules are converted to methane, CH4,## and exhaled.

But this process can be disrupted# by an ingredient in seaweed called bromoform.## It disables that enzyme, preventing# the CO2 and H2 from forming methane.

And the hydrogen is now for the cow.

Effective as# it appears to be, a lot of it needs to be grown## to make a dent in livestock methane production.# That's what they are working on here in Mexico,## 140 miles south of San Diego in the tiny# community of Ejido Erendira.

The U.S. start-up## that performed the study at the Straus Dairy# Farm is shifting into large-scale production.

This is the Blue Ocean Barns seaweed farm.

HANNAH RESETARITS, Blue Ocean Barns:# So this is called the sun tube.

MILES O'BRIEN: The senior manager of operations# expansion, Hannah Resetarits, gave me a .. HANNAH RESETARITS: All of our# cultures start in this room and## then scale outside all the way up# through our different vessel sizes.

MILES O'BRIEN: Outdoors, they scale# up in 17,000-gallon shallow vessels.## Scientists are still learning what# the seaweed likes and what it doesn't.

You're trying to scale up and still understand## some basic science at the same# time, which is a challenge, right?

HANNAH RESETARITS: Oh, 100 percent, yes.

It is# something that makes this job very exciting.

It## also means that, as we go, we are also going# back and improving our systems every day.

MILES O'BRIEN: Joan Salwen is the# co-founder and CEO of Blue Ocean Barns.

JOAN SALWEN, Co-Founder and CEO, Blue Ocean# Barns: It became clear that this kind of## finicky seaweed was not just going to become# domesticated without a little bit of a fight.

MILES O'BRIEN: The company has raised# $35 million.

It is in talks with some## major food producers, scrambling for# ways to meet carbon neutrality targets.

JOAN SALWEN: Not one of them will get to# carbon neutral without our product.

And if## they continue to feel pressure to make good# on their promise, I feel very, very bullish.

MILES O'BRIEN: Nice one.

But she does face a serious roadblock.

In the# U.S., the Food and Drug.. category for products aimed at reducing# greenhouse gases.

If bromoform from## seaweed is considered a veterinary drug, the# approval process might take five to 10 years,## far too long, given the# urgency of the climate crisis.

JOAN SALWEN: We're a little# stuck in the United States.

MILES O'BRIEN: Studies show no toxicity and no## adverse effects.

Australia has already# approved seaweed feed for livestock.

I'm going to have a simply# grilled with cheese, please.

SAM ELSOM, Co-Founder and CEO, Sea# Forest: Yes, two of those, thank you.

MILES O'BRIEN: In fact, low-methane burgers have# been on the market down under for two year..

I tried one in Sydney with Sam Elsom, co-founder# and CEO of the Tasmania-based seaweed producer Sea## Forest.

Australia didn't classify the additive# as a drug, which made approval much faster.

SAM ELSOM: I'm grateful that we live in# Australia.

It should happen in the U.S.,## for sure.

It should happen all around the world.

MILES O'BRIEN: It's a solution# without a negative that I could taste.

(LAUGHTER) SAM ELSOM: That's true.

MILES O'BRIEN: Scientists say we must cut# global greenhouse .. 2030 in order to limit global warming to 2.7# degrees Fahrenheit.

But we are headed in the## opposite direction.

Emissions are still rising.

As# it turns out, a big solution might be bite-sized.

For the "PBS News Hour," I'm Miles# O'Brien in Sydney, Australia.