Fall 1993 (v5n5)
	Energy and alternatives for fertilizer and pesticide use. Z.R. Helsel In:Fluck, R.C. (ed.) Energy in Farm Production. vol.6 in Energy in World Agriculture. Elsevier, New York. pp.177-201.1992 This review (32 references) looks at the use of pesticides and fertilizers worldwide, as well as the energy required to produce, package, transport, and apply them. In 1972, agriculture used about 3.5 percent of the world's commercial energy; this figure was generally lower for developed countries. Of the total energy used in agriculture, about 51 percent was used for farm machinery operation and manufacture, 45 percent was invested in chemical fertilizers (mostly nitrogen), and only 2 percent went to production and application of pesticides. Although the total amount of energy used for pesticides is small, on a per unit weight basis more energy is used in the production of pesticides than any other agricultural input. On average, production of pesticides takes four to five times more energy per pound than nitrogen fertilizer production. Fertilizers Table 1 shows the overall world average of energy required for production, packaging, transportation, and application of nitrogen, phosphorus, and potassium (NPK) fertilizers. In the last decade, the production process has been made slightly more energy-efficient. Nitrogen requires the largest energy input for production. In 1983-84 74.5 million short tons of nitrogen were produced in the world, requiring the equivalent of about 32 billion gallons of diesel fuel. When packaging, transportation, and application are added in, the equivalent of 36 billion gallons (about 650 million barrels) of diesel fuel were used to supply nitrogen to the world's farms. Table 1. Estimate of average energy requirements for nitrogen, phosphate, and potash (BTUs/lb). Nutrient Production Packaging Transportation Application Total Equivalent 1 N 29,899 1,119 1,936 688 33,642 0.240 P2O5 3,313 1,119 2,452 645 7,529 0.054 K2O 2,753 774 1,979 430 5,936 0.042 1 Gallons of #2 fuel oil (diesel) to produce one pound of nutrient. The author also assigned energy values to organic sources of nutrients. Based on the average amounts of NPK contained in a material, he calculated the energy equivalent it would take to produce the same amount of nutrients as chemical fertilizer. To replace the nutrients contained in a ton of beef manure (4.4% N) or sewage sludge (4.0% N) would require over 1300 BTUs (equivalent to less than 0.01 gallon of fuel); for crop residues (1.1% N) and municipal refuse (0.70% N), the value would be less than 500 BTUs per ton. These energy figures provide further evidence that "wastes" (usually viewed as a liability or disposal problem) may actually be an important resource for agriculture. In addition to providing some nutrients, organic materials also have value in terms of their effect on soil structure. (Reviewer's note: There is an energy cost to handling, transporting, and applying organic materials; this cost is not accounted for by the author.) Another organic source of nutrients, biological nitrogen fixation by legumes, produces about 88 million tons of nitrogen each year for agriculture, compared. with chemical nitrogen fertilizer production of about 55 million tons. The amount of energy used to fix the legume nitrogen was nearly four times that used to make chemical nitrogen fertilizer. It is important to note, however, that the source of energy for nitrogen fixation is sunlight, not natural gas as is the case for chemical fertilizers. Pesticides In 1984, the equivalent of over $16 billion was spent on pesticides worldwide. Over half of this money was spent on herbicides, and the U.S. contributed to nearly half the world's expenditures on herbicides-primarily on corn and soybeans. Herbicides were the major type of pesticide used in all countries except for some Central American and Asian countries where insecticides were predominantly applied. The U.S. spent one-third of all pesticide dollars, using more than three times as much pesticide as any other country. Japan and France ranked second and third, respectively. Pesticide manufacturing is energy-intensive. Most pesticides are derived from ethylene and propylene, which are obtained by catalytic cracking of crude petroleum oils, or from methane from natural gas. Some pesticides are more energy-intensive than others (table 2), however, pesticides also vary in their energy use per unit area of application. The trend in pesticide manufacturing is towards production of pesticides that are more energy-intensive per unit, but that are applied at a very low rate per acre. Following manufacturing per se, more energy (on the order of 4,300 to 13,000 BTUs per pound of material) is required to formulate these compounds into marketable products. Packaging, distribution, and transport require an additional 3,000 to 15,000 BTUs per pound. Table 2. Energy inputs required to manufacture selected pesticides (BTUs/lb). (To obtain equivalent in gallons of #2 fuel oil/lb, divide by 140,000). Pesticide Energy Input Herbicides 2,4-D 36,567 Alachlor 119,597 Atrazine 81,739 Diuron 116,155 Fluazifop-butyl 222,846 Glyphosate 195,313 Paraquat 197,894 Trifluralin 64,531 Fungicides Benomyl 170,791 Captan 49,473 Maneb 42,590 Insecticides Carbofuran 195,313 Cypermethrin 249,518 Malathion 98,517 Methyl parathion 68,833 Parathion 59,368 Reviewer Comments This chapter presents substantial data on energy requirements of pesticides and fertilizers, but it lacks quantitative comparisons to alternative systems. A valuable addition to the analysis would be to assign energy values to specific alternative practices (e.g., rearing and releasing beneficial insects, crop rotation). This information could be a valuable measure of agricultural sustainability, especially considering the growing limitations and constraints placed on world supplies of fossil fuels. Another weakness in the article is the reasoning by which the author justifies the use of pesticides. He states that there is a significant return (in terms of food energy) on the energy expended to produce and apply pesticides. His primary example is that of the yield increases obtained through the use of herbicides in corn. The calculations, however, fail to account for the environmental and social costs incurred beyond manufacturing and application. Such extra costs include farmworker medical expenses, monitoring of food for residues, pesticide container disposal, drift of pesticides onto neighboring farms or urban areas, litigation involving pesticides, as well as the effects of pesticides on air and water quality and on wildlife. An accurate cost/benefit analysis of pesticides should account for both the up-front production costs and any hidden costs that might result from their use. For more information write to: Z. Helsel, Department of Agriculture, Rutgers University, New Brunswick, NJ 08903. (CI-PEST.1 29) Contributed by Chuck Ingels [ Back | Search | Feedback ]