Organic Agriculture: A Solution to Global Warming?

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In 2008, the Rodale Institute-an organization dedicated to the promotion of organic agriculture-published a widely noted report entitled “Regenerative Organic Farming: A Solution to Global Warming.” The takeaway was that organic agriculture, due to its reliance on biological rather than chemical methods, could substantially reduce carbon emissions generated by the agricultural sector. Rodale predicted that if the world’s 3.5 billion acres of arable land were placed under organic production, 40 percent of global carbon emissions would be immediately sequestered.

It was an impressive projection and, as far as I can tell, an accurate one. Organic farming’s use of cover crops and composted manure is a remarkably effective way to sequester carbon dioxide. The Rodale report continues to garner widespread attention. As recently as a month ago, Peter Melchett, Policy Director of the U.K.’s Soil Association, championed the assertion that organic agriculture reduces global warming. He spoke as if the claim was conventional wisdom-which, in a way, it is.

But this bit of conventional wisdom is not as simple as it seems.? Yes, organic methods sequester more carbon dioxide than conventional ones. But the ultimate culprit behind agriculture-driven climate change isn’t carbon dioxide. Instead, it’s methane and nitrous oxide-two gasses conspicuously absent from the Rodale study. Agricultural production in the U.S. accounts for only 7 percent of overall carbon dioxide emissions. By contrast, it accounts for 19-25 percent of methane emissions and 70-75 percent of nitrous oxide emissions. Methane, according to the EPA, is 23 times more potent a GHG than carbon dioxide. Nitrous oxide is 310 times as potent.

So the key question, as far as GHG emissions and agriculture goes, is not how much carbon dioxide organic agriculture sequesters. Instead, it’s how much methane and nitrous oxide it sequesters. And this question, like any controversial topic in agriculture, is riddled with caveats and qualifications.? A recent conference in France dedicated to organic agriculture and climate change found that, in some cases, organic systems sometimes had higher GHG emissions and that, in other cases, conventional systems had higher levels of output. “The data,” it judiciously observed, “are very variable according to the situation and the production system.”

Not all assessments of the issue have been so moderate. The most aggressive (and, at the same time, legitimate) answer I could find came from Dr. Steve Savage, a plant pathologist and agricultural consultant based in California. Savage, who dutifully expresses deep admiration for organic production, nonetheless came to the stark conclusion that, regarding GHG emissions and organic agriculture, “gain in soil carbon on an organic farm comes at the substantial carbon cost of methane and nitrous oxide emissions.”

Savage works from two defining premises. The first is that the methods typically used by organic growers to fertilize row crops-namely planting cover crops and applying manure or compost-can, under certain circumstances, create “substantial” levels of nitrous oxide and methane emissions. How substantial?? That brings us to Savage’s other critical premise: 83 percent of the U.S.’s agricultural production today is in row crops (corn, wheat, hay, and soy) grown on a large scale. It is on the basis of these premises that Savage calculates what would happen to GHG emissions if all these staples were produced organically. His answer, which he claims to have checked out with hundreds of scientists, is eye-opening to the extreme: organic methods lead to a “carbon footprint” that’s fourteen times higher than if conventional methods were employed.

“Organic methods lead to a ‘carbon footprint’ that’s fourteen times higher than if conventional methods were employed.”

The reasons for this vast disparity-which is, of course, just a projection-can be found at the intersection of monoculture and organic fertilizer.? Composted manure-a common fertilizer for organic growers-might not require fossil fuel to manufacture, but it must be stored, shipped and distributed in order to keep pace with the demands of large-scale monocultural crop production. Putting aside for the moment the fact that the vast majority of manure used on big organic farms comes from CAFOs (or concentrated animal feeding operations; I’ll address this issue in a future post), it’s important to note that 2.7 percent of the carbon in composted manure is emitted as methane before the stuff is even spread.? Given that it takes around 4-7 tons of composted manure per acre to grow row crops, the impact of many tons of fermenting manure quickly adds up.

When compost hits the field, it not only continues to release methane, but nitrous oxide as well.? When oxygen levels in the soil are low-when the soil is wet or compacted-about 1-2 percent of the nitrogen in the manure is released in the form of nitrous oxide.? Even if the soil is frozen, nitrous oxide is released-even more so than with conventional methods (as a 2009 study revealed).? Finally, when organic growers till cover crops (such as nitrogenous legumes) back into the soil in the spring, a brief “explosion” of nitrous oxide (remember, it’s 310 times worse than carbon dioxide) occurs (see this and this). According to Savage (and others), conventional farmers are better able to prevent this gas blast by practicing no-till methods. It is the tillage factor that, in part, led an international conference on climate change and organic agriculture to note that, “when calculated per kg of product, in the case of substantially lower yields, organic farming can result in a higher global warming potential.”

What are we to make of the suggestion that organic methods may not be the global warming panacea they’ve been promoted to be?

Criticizing organic agriculture often suggests antipathy for organic agriculture. This shouldn’t be the case. As mentioned, organic agriculture has clear advantages. Most notably, it’s the only codified approach to agriculture that places top priority on soil health.? The fact that methane and nitrous oxide emissions complicate the claim that organic agriculture reduces climate change is no reason to dismiss organic agriculture as a whole. Instead, it provides an opportunity to do something that the intensely polarized agricultural world rarely does: think beyond the organic vs. conventional divide.

Doing so uncovers a world of hidden potential. What would happen, for example, if farmers anaerobically digested methane from fermenting manure and used the energy to produce high grade synthetic fertilizer? What would happen if organic farmers adopted GM crops that led to higher yields and greater nitrogen uptake efficiency? What if conventional growers mixed row crops with specialty crops-crops grown to be fed to people rather than to farm animals or biofuel plants?? What if farmers viewed sustainable farming as an agricultural balancing act, one that drew on the widest variety of possible inputs to achieve the highest yielding and most environmentally sound outputs? These questions only scratch the surface, but they all demand a perspective that transcends the organic/conventional divide.

We can debate the comparative merits and demerits of organic and conventional systems until the cows come home. But until we start substituting pragmatic realism for ideological purism we’re destined to do little more than reap the bitter fruits of a harvest sown with righteousness and extremism.


What would the productivity be on the "organic" land?


Climate Change is an intensely complex topic which does not have a simple single shot solution like generate 50% energy from wind or convert to organic agriculture.It requires a holistic approach through multiple means


I must object to the claim that organic farming cares deeply about soil health. Organic farming, while it may focus on maintaining the correct soil chemistry, requires tilling. There is no single more damaging activity than tilling the soil. When you till the soil, you break up the root structures that hold it in place, and significantly increase soil loss. A conventional farmer practicing no till methods may lose 1-2 Tons of soil per year per acre. An organic farmer may lose up to 5 tons of soil per year per acre. This loss is significantly more serious than any nitrogen depletion from conventional methods.

Bryan Larsen

"Most notably, it's the only codified approach to agriculture that places top priority on soil health."

I'm sorry, organic farming is very hard on the soil, at least for the farming I'm familiar with (dryland wheat farming in Western Canada).

To preserve soil health, farmers use zero-till farming techniques, which incidentally are often herbicide heavy.

Joel Upchurch

Of course, this begs the entire question of whether it is even remotely practical to feed 6 billion people using organic methods. It is one thing to provide boutique food for ex-hippies, but quite another to produce the food needed to prevent mass starvation. The opposition of the organic movement to GM crops has already resulted in millions of deaths from starvation in Africa and other third world regions.

Karen Anne

Organic farming certainly does NOT require tilling.

And as for "shipping" costs, all the more reason to get well away from AgriBusiness and back to local farms.

Organic farming with GM crops? That's like suggesting training nuns at a bordello. Who the heck are you, the PR manager for Monsanto?


Bryan Larsen,

Here's a clue. If a farmer is using herbicides, he or she is not farming organically.

Ian Kemmish

With my usual knack of drawing the boundaries of a system in a different place to everybody else, I'm still unconvinced by the carbon sequestration claims. What happens to the carbon in the cover crops?

If the farmer burns off stubble after harvest in the traditional way, then it's been sequestered for only six months, which is no help at all.

If he makes hay and feeds it to livestock in winter, then it's sequestered for a bit less than a year and then turned into methane! And the other farmer's meadows which would have been used to grow the hay that now doesn't need to be bought in are now loss making, so may end up getting sold to investment bankers for them to build mansions on. Also not good.

The obvious way to use plants for long-term carbon sequestration is by restoring peat bogs (which I'm pleased to say we are doing in mid Wales), but I remain unconvinced that anything else to do with agriculture - essentially an annual process - can achieve *long-term* sequestration.


Jonathan Katz

Organic agriculture is a way to starve poor people and poor countries. Maybe that is why it is so popular with the "population control" movement.


" Rodale predicted that if the world's 3.5 billion acres of arable land were placed under organic production, 40 percent of global carbon emissions would be immediately sequestered."

I think it's only sequestered while those plants are alive. When they die and rot the CO2 is released again. Look at the Annual CO2 levels, they always climb during northern hemisphere winter because all the leaves have died and begun to rot and release the CO2 back into the air.


Everytime I go to the store I demand to see the inorganic food.


And what if organic farms were to place a gigantic layer of clear plastic over the entire farm, maybe with a few holes in them, so as to prevent them from getting blown away?

Rose Lynn

Manure gives off methane and nitrous oxide, but what would be done with all that manure if it weren't composted and applied to farmlands? How much methane and NO would be released in these alternative processes?

I don't think anyone can imagine that if the manure were not composted there would be fewer CAFOs - they ultimately are the result of our huge demand for beef. Thus, it seems somewhat disengenuous to suggest that the problem of methane and NO from manure is the fault of organic farming.


Continuation of my last comment:
Why can't we have those clear plastic sheets covering the whole organic farm, and some ventilating machines will suck out the Methane and convert it into electricity to power itself.


First, if organic farming does not become widespread, what happens when the oil to produce chemical fertilizer runs out? Developing orgainic farming methods is necessary for longterm sustainability. We need to learn and spread the best techniques for doing so now.

Second, the author talks about "fermented" manure, which means manure that is not exposed to oxygen. This is the exact wrong method to make quality compost and does indeed generate a great deal of methane. But true composting of manure with oxygen does not. There are various types of "organic" agriculture. Some are only designed to be organic in name and used on large industrial farms with manure from feedlots and fermented manure which does not go through a proper composting process. Other farms are really trying to improve the health of the earth, the livestock and consumers through responsible farming.

Third, for those who say that organic farming is starving poor people, think again. The most intensive agriculture in the world is that done is small organic gardens in poor countries. I have personally seen and taken part in organic gardening in various parts of the world that produce hundreds of times more produce than a large, mechanized industrial farm, whether it be organic or conventional. It is often the methods used, rather than the name of a method of raising food that is important.



Yep, you are right - organic farming does more to cause global warming than anything else. Since you point out the Rodale study leaves certain facts out how about telling us how much money Monsanto and producers of chemical fertilizers and pesticides paid you to write this garbage?

As for the idiots who think its impractical to feed the world with organic farming and those who claim its too hard on the soil if they knew a thing about farming they would know that prior to WW II, ALL farming was organic farming. In other words it ain't no new age invention.


What if our manure came from kangaroos? Not even kidding.


Like Karen Anne, I do not think organic farming requires tilling.


If the vast majority of manure used at big organic farms comes from CAFOs, this is truly disturbing. I want to know more about this. In a truly organic system, there would not be shipping and distribution costs for organic fertilizer (manure, compost). These fertilizers would be made on site as part of a self-sustaining, diversified agricultural system.


But- the manure is already being produced, so using it to fertilize crops does not add to the carbon footprint. If you were to take it away from methane digesters, sure, but that only acccounts for a tiny percentage of current manure waste. And there would be trophic losses in using digesters to produce energy to make synthetic fertilizer. Manure should generally be used for fertilizer- it makes the most sense (and used for digesters where transport costs make using it for fertilizer infeasible). Right now too much of it washes into our waterways and aquifers, along is artifical fertilizer residue (see the dead zone in the Gulf).