It wouldn’t be right to look at the impact of the things we use in daily life without including bread. Wheat is, of course, one of the world’s dominant crops, taking up around 220 million hectares (or 5% of agricultural land) compared to 163 million hectares for rice and 5.3 million hectares for bananas. Here, I’m going to take a look at just a couple of aspects of wheat production that suggest that it’s best to choose organic bread.
Footprint of a Loaf of Bread
A paper published last month in Nature Plants looks at the environmental impact of a loaf of bread. Researchers from the University of Sheffield took the example of a specific brand of bread sold in the UK and conducted a life cycle assessment (LCA) using 90% primary data (meaning that the LCA is quite reliable). The carbon footprint for an 800 gram loaf of bread worked out at around 0.6 kg CO2, but the surprising part was that a large part of this footprint was due to one component of the whole process – nitrogen fertilizer. The wheat used to make one loaf required agricultural inputs of 42 g of granular ammonium nitrate and 11 g of monocalcium phosphate (among other things) and 40% of the loaf’s carbon footprint was due to the ammonium nitrate alone.
Most of the news articles reporting on this story have focused on the carbon footprint of this loaf of bread as if it’s huge. It’s not at all; if you eat a loaf of bread per week your annual footprint is around 31 kg CO2, not a lot compared to a footprint of 1352 kg CO2 from eating 1 kg of beef per week.
The Problem with Nitrogen Fertilizer
But besides the carbon footprint, the authors found that the agricultural inputs are also largely responsible for the other environmental impacts of the bread, such as eutrophication and freshwater aquatic ecotoxicity. Ammonium (which is made from natural gas) is applied to the crop at levels higher than can be efficiently used, in order to achieve very high yields and protein content in the grain.
Nitrogen use efficiency (NUE) of wheat yield, defined as the ratio of harvested nitrogen to that applied to the field, ultimately determines the environmental impact of nitrogen fertilizer. In our study, NUE was estimated to be 71%, which is slightly above the UK average, and typical of intensified production.
What happens to the nitrogen that’s not taken up by the wheat? It ends up being released into the atmosphere as nitrous oxide (a greenhouse gas and ozone-depleting gas – remember the ozone? Oh right, yes, the ozone layer!) and also into waterways – causing situations like the dead zone in the Gulf of Mexico.
Eutrophication: excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.
Organic certification requires that synthetic fertilizer use must be less than 20% of required nitrogen (USDA) and in some countries is completely prohibited under organic rules. The remainder of the fertilizer, coming from compost, manure, seaweed, etc., provides a slower release of nitrogen, enriching the soil (and microbe population) and limiting run-off into rivers.
A commonly voiced concern with organic agriculture is that yields are not as high as intensively farmed crops. An important paper published in Bioscience (2005) reports on 22 years of trials conducted by researchers from Cornell University, the Rodale Institute, and the USDA. They showed that although organic wheat yields started out lower than those from intensively farmed wheat, they improved over time and matched or exceeded conventional wheat yields.
In the short term, organic systems may create nitrogen shortages that reduce crop yields temporarily, but these can be eliminated by raising the soil nitrogen level through the use of animal manure or legume cropping systems, or both.
After a few years of organic agriculture, they found significant improvements in soil quality, including increased carbon and nitrogen stored in the soil and improved biodiversity, including fungi and earthworms. A key approach was to grow legumes (soybeans) in between the wheat crops. Legumes, working with the microbes on their roots, can fix nitrogen from the air, providing a free and sustainable alternative to commercial nitrogen fertilizer.
It’s similar to an idea practiced by Native Americans – the three sisters was a cropping system that included three plants that formed a symbiotic relationship – corn, beans, and squash. The corn provides a structure for the beans to climb, eliminating the need for poles. The beans add nitrogen to the soil that the other plants can use, and the squash spreads along the ground, reducing weeds.
More and more scientific literature is coming out to support organic agriculture as (part of) the best solution to our food future; for example, this paper, published in Nature Plants in 2016. Below is a figure from it showing large differences between conventional and organic farming in terms of nitrogen source and fate.
I’ll discuss other aspects of organic agriculture in future posts, but in the meantime here are two other reasons why I prefer to buy organic bread:
- Industrial wheat fields are massive. I prefer to support organic farmers who are likely to have smaller fields and larger field margins that are crucial for wildlife. This is in addition to the benefit of increased biodiversity in the soil, mentioned above. I attempted to get an idea of just how large some of these wheat fields are. In Ireland, the average farm size is 80 acres (33 Ha) while in the US its 434 acres – that’s for an entire farm. Searching on the popular site, Combine Forum (who hasn’t spent a few happy hours browsing their threads?) I found references to Montana wheat fields of several thousand acres – one is reportedly 13,000 acres – a single field! For reference, a small regulation-sized soccer field is around 1 acre. So picture that area, with no hedges, no trees – just 13,000 continuous soccer pitches of chemically-controlled wheat.
- What do you do with the massive quantities of grain from huge industrial farms? Store it in massive silos and fumigate as needed to control insects and rodents. It would take another post to explain the problems with fumigants used on grain, such as sulfuryl fluoride and phosphine. They are not allowed on organic grain – farmers and millers have to rely on using clean, temperature- and atmosphere-controlled storage conditions and processing of grain soon after harvest.
In the next post I’ll consider a few other social and environmental aspects of bread by looking at a couple of local bakers.