Pathways To Climate-Friendly Food & Agriculture; A Preliminary Analysis

I was recently asked to give a lightning talk about agriculture’s contribution to climate change. The food system drives one third of climate change, so it’s hard to put that into the one slide I was allotted.

I thought about a catchy image — perhaps a hamburger (beef drives much of agriculture’s climate impact) or a coffee farm (threatened by climate change). But it seemed helpful to show the sources of agriculture’s greenhouse gas emissions (GHG) and the rough potential of various mitigation pathways.

Food and Agriculture Greenhouse Gas Emissions

The more widely cited studies indicate that the food and agriculture sector is responsible for about 18 billion tons of carbon dioxide equivalent emissions (CO₂e) worldwide. This is well over a third of total GHG emissions. More complete studies indicate that when including the climate impact of forgone carbon storage, the climate contribution of agriculture is more than double that — over 30 gigatons — with far more land use impact. Moreover, food and agriculture emissions are rising as population and income increase.

While some of this comes from burning fossil fuels, for example for the manufacture of pesticides and fertilizers, on-farm energy, and processing, the largest contributions of agriculture to climate change come from cows, corn, carbon, and crap.

Cows. Cattle continually belch methane, a very potent GHG and the about 85 million cattle in the U.S. belch more methane than the U.S. natural gas production sector. Moreover, cattle, even if finished in a feedlot, spend at least the first year of their life grazing on vast amounts of land. In the United States alone, about 800 million acres or over 35% of all U.S. is used for cattle grazing; globally two thirds all agricultural land is used for ruminant grazing.

Corn. All of the animals we eat — about nine billion a year in the U.S. alone — themselves eat a tremendous amount of food. Most of that food is grown on heavily fertilized monoculture fields, particularly of corn. On average farmers apply twice as much nitrogen fertilizer as the crops can use and as a result, corn production releases large quantities of nitrogen oxide, an even more potent greenhouse gas.

Carbon. Grazing and crop production takes place on land — over 60% of the contiguous United States — that has been largely stripped of the carbon found in natural soils, forests and grasslands. That release of carbon, and the continuing incapacity of the land to sequester much carbon, is a climate impact shared by no other economic sector. (Look closely at the map in the graphic above.)

Crap. All of those animals also produce prodigious piles of poop. That waste is usually just stored in pits before being spread on the ground — practices that further produce large amounts of methane and nitrous oxide.

These sources together produce as much of a climate impact as the transportation system or more. This is such a large impact that we cannot achieve climate stability without major reform of our food and agriculture system, no matter how successful we are at decarbonizing our energy system. (This change is also necessary to protect biodiversity and water quality as agriculture causes the greatest harm to both.)

Net Greenhouse Gas Reduction Pathways for Food and Agriculture

There is some discussion about modest changes to agricultural practices, but rarely do we examine how to achieve a truly climate-friendly agriculture system. What would we need to do to get there? The answer is that we must significantly transform how and where we produce our food, what we produce, and what we do with that production.

The literature on reduction opportunities is far from definitive and often conflicts, but one can propose some categories of mitigation strategies with a fairly high degree of confidence. The above waterfall chart demonstrates the approximate amount of net GHG reductions (including both actual reductions and offsetting sequestration increases) each category of mitigation practice offers, based on a synthesis of numerous studies, including by Project Drawdown, World Resources Institute, World Bank Group, U.N. Food and Agriculture Organization, the Intergovernmental Panel on Climate Change, and other studies. (Of course, this is and always will be a draft in progress.)

Low-GHG practices on all possible cropland and meat production. There are numerous practices, such as cover crops, no-till planting, more diversified crop rotations, improved fertilizer management, and holistic or managed grazing that have many ecological benefits, and in many regions, can both reduce needs for synthetic inputs (thus reducing GHG emissions) and increase carbon stored in the soil. Such “regenerative” practices, however, are now used on only a small portion of crops and pastureland and further research is needed to ensure they enhance, rather than reduce yields. If employed on almost all crop and pasture land, the climate impact could be significant, but far from neutralizing climate impacts. Similarly, the vast, currently unregulated, methane emissions from rice, cattle, and manure can be reduced through better rice management, improved animal feed, and manure management, although only partially under current technologies.

Trees. Sometimes included within the larger category of regenerative practices, adding trees to cropland and pasture land likely has the greatest potential for increasing carbon storage and reducing net GHG emissions of any in-field practice currently available. This would include planting trees around or within fields, as riparian buffers, in pasture land (also providing shade to animals), and as an intermixed crop. Tree crops often have higher per-acre yields than typical grains and can also offer financial and nutritional diversity. (It would also be important to replant trees in non-agricultural land, but that’s a separate strategy.)

Increased yield and decreased deforestation. The flipside of planting trees is ending deforestation. Most deforestation now is driven by demand for beef, soy, and palm oil. In addition to reducing demand for these products (discussed below), pressure for deforestation can be reduced by increasing yield on existing crop land for foods that humans need. Opportunities for yield increases are particularly great in middle and lower income economies and include full utilization of known technologies, including feed and digestion, fertilization and irrigation optimization, and crop breeding and development. History suggests that this productivity increase must be accompanied by greater law enforcement regarding deforestation prohibition and other agreements to prevent further land conversion.

Waste, biofuels, and processing. We now waste one third of the food we produce, with much of that waste rotting in landfills producing more methane. If all this food waste were a country, it would be the third largest emitter, so cutting it even in half would yield tremendous climate benefits. Moreover, we also now waste over 50 million acres of land in the United States alone, and more throughout the world, to grow crops (primarily corn and soy) to be converted into biofuels. This is highly inefficient, using 100 to 300 times more land than would photovoltaic cells powering electric vehicles, and takes us backwards in fighting climate change. Eliminating misguided government mandates for crop-based biofuels would reduce emissions and prevent millions of acres of deforestation and allow conversion of cropland to needed food or carbon sequestering uses. Finally, the manufacture of inputs, such as herbicides and fertilizers, and the processing of food from grain mills and slaughterhouses to distribution use a tremendous amount of energy; this should all be more efficient and shifted to renewable sources.

Market and Dietary shift. Numerous studies indicate that reducing consumption of meat, particularly beef and dairy, can have the largest climate impact, and that indeed, only modest success is possible without dietary change. Fortunately, there are many substitutes, from just eating more plants to plant-based meats to cultivated meats (not yet commercially available). Moreover, reducing meat consumption in high income countries would bring significant environmental and health benefits (and reductions in animal suffering). With Americans on average eating 2.5 meals of meat per day, even modest reductions could have enormous impact and still allow ample meat consumption.

But all this only takes us so far. To stabilize the climate, the food and agriculture sector must reduce its emissions by three quarters and all the above &mdas; if applied to all available farmland — would only get to somewhat over halfway. More research should find new opportunities and to date, little research has been devoted to feeding the world in a climate-friendly way.

Foundational to all these strategies is improved public understanding of the climate (and other) impacts of the food and agriculture system. Policy, corporate, and personal action depends on better disclosure and transparency about the harms and the many benefits of new approaches. So the first step in all mitigation pathways is better reporting and accounting, heightened disclosure and understanding, and more honest and accurate analysis.

As difficult as these mitigation pathways seem, they are far less costly and disruptive than building a whole new energy system. So if our society ever gets serious about addressing climate change, there are many actions that can be taken in the very short term, with a role for almost everyone. Especially at a time of governmental failure on climate change and widespread corporate abandonment of climate mitigation efforts, a more bottom-up personal action approach (along with voting) may help to spur change.