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I’m probably going to irritate some people with this post. I apologize in advance because that is not at all my intention. For those readers that don’t think climate change is a real problem, I respect the fact that there is uncertainty in that science, but if the majority position of climate scientists is true, the stakes in terms of human suffering among the poor are too high not to act. For those who think Organic farming is the answer, I’m not trying to argue the whole issue here – I just want to talk about the science associated with climate change and farming. I have spent months reading the scientific literature on this topic. That science points to some very specific changes in how we need to farm. If those changes were compatible with Organic I’d be a big promoter. The short answer is “Organic farming is not the best option from a climate change point of view.”
I know this sounds like heresy in the “Green Blogosphere,” but before you react, please read on. I agree in advance that the Organic/non-Organic discussion is much broader than climate change. In fairness, climate change was never something that “Organic” was designed to address either during its origins in the early 20th century or during the development of the USDA Organic rules between 1990 and 2000. I have no desire to get in the way of Organic growers making a living (including my good friends who grow Organic of the old school category) or get in the way of Organic customers getting what they want. I simply believe that it is critical that we, the declining subset of people who take climate change seriously, be accurately informed about this issue. If we believe we “have the answer” for farming when that answer is wrong, that keeps us from continuing to find the real answer.
Focusing on the Major Crops
Because it would be far too complex to discuss this question for all crops, I’ll only be talking about the “carbon footprint” of the major row crops (see the pie chart above) – the wheat, corn, hay, barley, oats, corn, soybeans, hay, oats, dry beans, lentils… that make up the bulk of our calorie intake, our vegetable protein intake, and our animal feeds for meat and dairy. Those crops also make up the vast majority of farmed land, so they are what matters for climate change. Fruit and vegetable crops are extremely important for health and food enjoyment, but not much for climate change. Organic today is heavily weighted to the fruit and vegetable segment and beyond that, it is extremely small. Actually, all of Organic only represents 2.6MM acres ( ~0.7% of US cropland), so it has almost no effect on climate either way. This is only a discussion about the widely held opinion that Organic would help in a climate change sense.
Agriculture’s Unique Carbon Footprint
The Rodale Institute is a leading group that has been dedicated to the Organic cause since the 1950s. They released a white paper titled, “Regenerative organic farming: a solution to global warming.” In it they argued that organic methods are low in carbon emissions. They also argued that Organic farmers could sequester carbon in the soil to help reduce atmospheric CO2 to a significant degree. That all sounds great, but the problem is that in the entire 9 page report, they never mentioned the words “methane” or “nitrous oxide.” That was a major omission because the real story for Ag is all about these two particular greenhouse gasses.
The carbon footprint of agriculture is unique. Farms only represent ~2% of US CO2 emissions but around a third of the anthropogenic methane (a gas which is 21-24 times as potent as a greenhouse gas) and nearly 80% of the anthropogenic nitrous oxide (295-310 times as potent as CO2). I’ll explain why these two gasses, which are huge challenges for agriculture as a whole, are particularly problematic for Organic farming.
Biological Nitrogen Fixation
In defense of Organic farming, it does produce an admirable share of its own nitrogen supply with biologically fixed nitrogen using legume crops and legume cover crops. (“conventional agriculture” also grows millions of acres of those crops). When it comes to a legume crop like soybeans, Organic and conventional farms have a similar, and relatively small “carbon footprint;” however the “conventional” footprint can still be lower. If the soybeans are “no-till” farmed (which is common for soy – at least 33% of US soy acres – then the No-till farmer will use less diesel fuel because of the several tillage passes that are avoided. Also, when a legume cover crop, is tilled-under for planting, there is a significant burst of nitrous oxide emissions. That does not happen in a non-organic field that is “no-till” managed. I’m not saying this is true today on all “conventional” farms, but it is for far more acres than Organic.
The Climate Downside of Manures or Composted Manures Used in Organic Farming
For the non-legume crops we need (corn, wheat, barley…) an Organic grower will definitely need to supplement the contributions of the legumes in the rotation with manure or composted manure. If it is manure, that manure will have been saved for some period of time (animals make it every day, farmers only need it at certain times). The IPCC estimates that even with good storage practices, 1-2% of the carbon in that manure is emitted as methane. When you combine that with the amount of manure needed to fertilize a crop, you end up with a “carbon footprint” that is 3-8 times as large as if you delivered the same amount nitrogen with synthetic fertilizers like urea. If the Organic crop is destined for direct human consumption, the manure needs to be composted to kill human pathogens. In that process it has been documented that 2.7% of the carbon is released as methane. Combining that with how much compost it takes to fertilize a crop (on the order of ~4-6 tons/acre), and the “carbon footprint” of this Organic fertilizer is on the order of 14 times as high as for a conventional alternative.
Last June I posted a technical paper about this on SCRBD and requested feedback. I also sent it directly for review to a dozen scientists who work in this area. The paper has now been viewed by more than 850 people. I’ve gotten quite a bit of feedback, but none pointing out flaws with the basic logic or math. One Organic farmer told me that he didn’t use use compost for the nitrogen, but the rate he described (5 tons/acre) was delivering >180 lbs of N/acre when 120 lbs/acre is the average for a high nitrogen demand crop like corn. Some folks have accurately pointed out that compost emissions vary by the way the composting is done, but the study I used was based on a better than average practice. Even dropping the emissions by a factor of 2 or 4 would not address the problem. Some would like to assign that footprint to the animal producer. My answer is that the emissions occur because of the storage or composting that is required for the crop use. The very best option for manures (or any biological waste-stream) is to anaerobically digest or char the manure to turn it into a significant source of clean energy (“animal waste is a terrible thing to waste”, If you think I’m attacking composting in general, I’m not. Composting is far better than land-filling other waste streams, but it is not always the best option, and it certainly isn’t a good way to make fertilizer). To be fair I must point out that manure is used on conventional farms – about 5% of the total US cropland. I’d like to see virtually all of that practice shifted to an energy use of the manure.
So it turns out that a major climate change advantage almost universally claimed for Organic (no fossil energy to produce the N), actually represents a carbon footprint that is enormous. Then, once the manure or compost is added to the field, it continues to release methane , and to release nitrous oxide, even at sub-zero soil temperatures. As someone with strong carnivorous tendencies it pains me to admit that animal protein has a higher carbon footprint than something like lentils or tofu, bread wheat or quinoa. I’m actually trying to shift my diet more that way (something much more feasible to ask than vegetarianism. My daughter taught me a killer recipe for fried tofu!). Organic, at least for row crops, is pretty tightly tied to animal agriculture.
Nitrous Oxide – the Biggest Climate Change Challenge to All of Agriculture
For the major row crops, the largest two elements of the carbon footprint are the “embedded carbon” in the fertilizer and the nitrous oxide emissions that occur as a little bit (usually 1-2%) of the applied nitrogen is converted to nitrous oxide during periods of low oxygen availability (e.g when the soil is wet, where the soil is compressed). The Organic field has the additional issue of methane emissions from the soil. Nitrous oxide release is usually one of the largest single elements in the farm footprint because of that ~300x multiplier. A conventional grower has several tools to reduce those emission (which would ideally someday be rewarded with carbon offset income). That farmer can use “precision application” to put the fertilizer in just the right place so the plant gets more of it before it can become nitrous oxide. He/She can also use “split applications,” or “variable rate” application to give each part of a field just enough so there isn’t extra available to be converted into nitrous oxide and the overall rate reduction reduces the “embedded energy” footprint as well. The farmer can also use “Auto-steer” technology (GPS enabled) to make sure that no wheel ever rolls over most of the soil in the field. That limits compaction and thus nitrous oxide emissions. Finally, a conventional grower can use a “nitrification inhibitor” to reduce the amount of nitrous oxide produced. There are efficiency drivers that are already getting more and more growers to adopt these practices, even in the absence of greenhouse gas-related payments. Many of these nitrous oxide reduction options are impractical or are not even allowed for the Organic grower.
Carbon Sequestration
The big climate change positive that the Rodale paper claimed for Organic was net carbon sequestration because so much organic matter was added to the soil in the form of compost or manure. Building soil carbon has always been a fantastic goal of Organic farming. I’ve been on that page since hearing my Grandfather talk about it as I helped him tend his Organic garden in the early 1960s. Still, as I described, that gain in soil carbon on an Organic farm comes at the substantial carbon cost of methane and nitrous oxide emissions before and after application. There is a different way to build soil organic matter. It requires no-till cropping. There is controversy about whether no-till farming by itself can really lead to net carbon sequestration, but in combination with cover cropping, this is definitely possible. What about the synthetic chemicals used by the conventional farmers in that system? The use-rates of modern agricultural chemicals are low enough that they end up contributing very little to the carbon footprint of these row crops, and in a no-till setting they don’t move into streams or lakes because erosion is so well controlled. They break down on-site.
The Better Answer
So, if Organic is not the viable, large-scale answer to Climate Friendly Farming, what is? I believe the answer is broader adoption of the most progressive methods I’ve been describing (continuous no-till, cover crops, controlled wheel traffic, precision fertilization…). Today, employment of these practices in part or as a whole varies by geography. South America and Australia are the most advanced here. These practices are almost non-existent in Europe. I don’t have good information on China and India, but rates are small. The US adoption is significant, but not nearly as high as it needs to be for a lot of complex economic, social and technical reasons. Strong carbon markets looked like a great way to drive these optimal farming practices, but my hopes for that are fading in this political environment. Other ways will probably have to be found and I believe that is possible. As Norm Borlaug said, “pessimism has no place in action.”
You are welcome to comment on this post or you can email me at feedback.sdsavage@gmail.com.