Sustainability
Pulses use half the non-renewable energy inputs of other crops


Most of us are interested in the fuel mileage of the vehicles we drive or the temperature setting on our thermostats. However, few of us ever thing about how much energy is required to produce the food in our grocery carts. 12-17% of the total energy use in the US is for food nitrogen1. Surprisingly, on-farm fuel use is not the biggest contributor to energy use in crop production. It is the manufacturing of fertilizers, particularly nitrogen2.

There are two reasons that nitrogen fertilizer has a large impact on the energy balance of crop production. First, nitrogen is the nutrient required in the highest quantities worldwide for growing crops. Second, nitrogen fertilizer has an energy footprint that is over 7.5 times larger than other fertilizers such as phosphate and potash3. Up to 70% of the non-renewable energy used in crop production in Canada is attributable to inorganic fertilizers, particularly nitrogen3. Today, 40% of the world’s dietary protein needs is supplied by these nitrogen fertilizers4.

So, how can we continue to feed a growing global population with healthy food, while reducing the energy needed to grow this food? One way is to eat more pulses. As pulses require little to no nitrogen fertilizer, eating foods that contain pulses can improve the ‘fuel mileage’ of your grocery cart!

Energy use in American food production.

This essay was written in 2009 by Michael Minn, a PhD student in geography at the University of Illinois. It provides an overview of how energy is used in American agriculture. While there is no specific focus on pulses, it provides context in terms of the “big picture” of American energy use.

Energy use by Americans for food is about 12 to 17% of total American energy use, and the research and calculations used to arrive at this total are explained. Energy use from planting the crop to its final destination at the dinner table is discussed in detail. The essay first examines on-farm energy use including the production and use of farm chemicals (fertilizers and pesticides), the manufacture of machinery, and fuel to run machinery and irrigation equipment. The energy used to process and package food and transport it to the grocery store is then discussed. The energy required to operate food retail services and for household storage and preparation of food is also considered. Finally, the energy associated with imported food is summarized. The energy used to produce bottled water is also covered.

The paper then looks at specific food items as “case studies” to compare their energy use, including grains, meat, seafood, and beer. The author concludes by speculating about what the impact of rising energy costs would mean for American food consumption and lifestyles.

Effects of input management and crop diversity on non-renewable energy use efficiency of cropping systems in the Canadian Prairie.

Published in 2011, this peer-reviewed article in the European Journal of Agronomy compared the energy use of different cropping systems in Saskatchewan. Each cropping system consisted of one of three levels of inputs (i.e. fertilizer, pesticide, and tillage) and one of three crop rotations, for a total of nine different cropping systems. The three input levels were high, reduced, or organic, while the crop rotations had low, medium, or high diversity. Crops used to diversify the rotations included pulses (lentils and peas).

Results showed that unless legumes such as pulses are included in crop rotations, reliance on non-renewable energy remained high. The authors conclude that the best way to diversify the traditional cereal monoculture crop rotations of the Canadian prairies while improving energy use efficiency is to use legume crops including pulses and forages.

Effects of tillage method and crop rotation on non-renewable energy use efficiency for a thin Black Chernozem in the Canadian Prairies.

This study compared different crop rotations and tillage practices to see how they affect non-renewable energy use. It was published in the peer-reviewed journal Soil and Tillage Research in 2004.

The experiment included three different crop rotations and three different tillage practices. The three crop rotations were: 1) monoculture wheat; 2) wheat and flax; and 3) wheat, flax and peas. Each rotation was grown with conventional, minimum, or zero tillage practices. Energy use was determined by adding all the non-renewable energy used to manufacture, package, transport, maintain, and apply all inputs (such as fertilizer, fuel, and pesticide). Energy use efficiency was measured in three different ways: 1) the amount of grain produced per unit of energy input; 2) the ratio of energy output to energy input; and 3) the net energy produced (i.e. the energy produced in the harvested crop, minus the energy required to produce it).

After 12 years, the study showed that energy use efficiency was highest for the rotation that included peas. Non-renewable energy inputs required by peas were lower than flax or wheat. The addition of both peas and flax to the wheat-based crop rotation reduced total energy use by 13% compared to the rotation that added flax only. Growing wheat after another wheat crop required 8% more energy than if wheat was grown after peas. Improved energy use efficiency was attributed to the nitrogen supplied by the pea crop, reducing the need for added nitrogen fertilizer. Energy use efficiency was also improved when minimum or zero tillage practices were used to produce rotations that included peas or flax; however, tillage practices had no effect on energy use in monoculture wheat rotations.

This study confirms that adding peas to crop rotations can increase the efficiency of energy used in agriculture on the Canadian Prairies.

Nitrogen and Food Production: Protein for Human Diets.

This peer-reviewed article is unique because it connects the science behind nitrogen fertilization with its impact on world hunger as well as the environment. It focuses on the importance of efficiently using nitrogen to reduce malnutrition. It was published in 2002 in AMBIO: a Journal of the Human Environment.

Because nitrogen is a major building block of protein, it is an essential input in order to produce protein for human diets. The nitrogen can originate from manure, legume crops such as pulses, or from nitrogen fertilizer. This article reviews the cycling of nitrogen in soil, water, and air, as well as the ways in which it is lost after being applied to crops. It then explains how agriculture was transformed when nitrogen fertilizer was first produced by the Haber-Bosch process in 1909. An overview of human protein needs is given and typical diets around the globe are summarized. The relationship between nitrogen fertilizer use and malnutrition is explained.

The article concludes with ideas for reducing global hunger without increasing the environmental impact of nitrogen fertilizer. Malnutrition can be decreased by modifying diets to focus on high-quality protein, and by using management strategies to more efficiently use nitrogen.

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