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  1. Energy and the New Reality, Volume 1:Energy Efficiency and the Demand for Energy ServicesChapter 7:Agricultural and Food System Energy Use L. D. Danny This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see for contact details. Publisher: Earthscan, UKHomepage:

  2. Energy Use in the Food System • Energy used in producing food • Energy used in transporting and processing food • Energy used to make packages for food • Energy used by food retailers • Energy used by consumers in getting, storing and cooking food

  3. Energy Used In Producing Food • Energy to make fertilizers and pesticides • Fuels for tractors and other equipment • Fuels for heating and ventilation of farm buildings, livestock and poultry facilities • Electricity for irrigation (if used), lighting, buildings • Embodied energy in equipment and buildings

  4. Figure 7.1 Energy used during the production of food in the US Source: Schnepf (2004, Energy Use in Agriculture: Background and Issues, CRS Report for Congress RL32677,

  5. Figure 7.2 Energy use in the US food system Total non-solar energy input: 10.8 EJ/yr Food energy produced: 1.48 EJ/yr

  6. Nitrogen • Occurs in the atmosphere as N2 (78% of air) • Needs to be converted to NH4+ (ammonium) in order to be useable (assimilable) by plants – a process called nitrogen fixation • Only certain bacteria, which live in the roots of only certain plants, can carry out nitrogen fixation • Some ammonium is oxidized to nitrate (NO3-) in a process call nitrification and taken up by plants in that form

  7. Figure 7.3 Nitrogen Cycle

  8. Non-energy issues related to N fertilizer • Leaching into groundwater and runoff into streams and eventually the oceans • Growing incidence of coastal oceanic dead zones due to eutrophication • Emissions of N2O (a powerful GHG) associated with nitrification and denitrification reactions • NO emissions, contributing to loss of stratospheric O3 • NO and NO2 emissions (NOx), contributing to buildup of tropospheric O3 and to acid rain

  9. Distribution of eutrophication-assisted coastal dead zones Source: Diaz et al (2008, Science 321, pp926-929)

  10. Distinction: • Nitrogen fertilizer is manufactured, requiring energy inputs and a source of H2, which is combined with atmospheric N2 to produce NH4+ as a first step (both the energy and H2 come from natural gas at most N-fertilizer plants, although the Chinese use coal) • Phosphorus fertilizer is mined from P-containing rocks (phosphates)

  11. Figure 7.4 Global P flow Source: Cordell et al (2009a, Global Environmental Change 19, 292–305,

  12. Figure 7.5 Distribution of P reserves

  13. Non-energy issues with respect to P fertilizer: • Environmental impacts of mining, due to contamination of most phosphate deposits with toxic heavy metals (As, Hg, Pb, Cd) • Inability to use most of the economically-available phosphate (reserves) as fertilizer due to heavy metal contamination • Likely peaking of phosphate supply within 20-30 years even without toxicity constraints

  14. Figure 7.6 Historical and projected annual P supply from mining, the latter obtained using the logistic function combined with estimates of the ultimate cumulative use Source: Cordell et al (2009a, Global Environmental Change 19, 292–305,

  15. Figure 7.7a World N Fertilizer Consumption

  16. Figure 7.7b World P Fertilizer Consumption

  17. Figure 7.7c World K Fertilizer Consumption

  18. Figure 7.8a Worldwide N Fertilizer Consumption in 2001

  19. Figure 7.8b Worldwide P Fertilizer Consumption in 2001

  20. Figure 7.8c Worldwide K Fertilizer Consumption in 2001

  21. Figure 7.9 Worldwide Fertilizer Energy Use in 2001

  22. Strategies to reduce the amount of energy used in making fertilizers Increase the efficiency in manufacturing fertilizers Reduce the demand for chemical fertilizers

  23. Strategies to reduce the demand for chemical fertilizers • Use any applied chemical fertilizers more effectively, so that less is needed • Substitute organic (natural) fertilizers for inorganic (manufactured) fertilizers

  24. Figure 7.10 Fertilizer embodied energy

  25. Ways to reduce waste and runoff of inorganic fertilizers: • Apply only what is needed based on updated measurements of soil conditions • Apply fertilizers 2-3 times per year rather than 1 large application per year (sometimes in the fall!) • Apply fertilizer in rows during seeding rather than over the entire field (10-30% savings) • Maintain fertilizer application equipment (20% savings) Overall estimated savings potential in The Netherlands: 35-40%

  26. From Table 7.4, percentage of added N fertilizer that is absorbed by plants, as measured on farms For corn in the north central US: 37% For rice in Asia when no guidance is given to farmers: 31% For rice in Asia when fertilizer application is adjusted to match needs: 40% Wheat in India, poor year: 18% Wheat in India, good year: 49%

  27. Figure 7.11 US corn yield and fertilizer use

  28. Organic fertilizers: • Manure • Crop residues • Food processing wastes • Human wastes

  29. Issues related to use of organic fertilizers: • Proximity to fields (especially with large centralized feedlot operations) • Bulk • Contaminants (an issue with municipal sewage plant sludge) • Controlled release of nutrients

  30. Pesticide use and energy intensity Table 7.5 Worldwide and US pesticide use during 1998-1999, and energy intensities. Sources: Pretty (2005, in Issues in Environmental Science and Technology, No 21, Sustainability in Agriculture, Royal Society of Chemistry, London) for use and Helser (2006, in Encylcopedia of Pest Management, Taylor & Francis, London) for intensities.

  31. A number of jurisdictions in the world have set aggressive targets for reducing pesticide use, or are experimenting with systems involving much lower use of pesticides. • 50% reduction targets for the Canadian provinces of Ontario and Quebec • Integrated Pest Management (IPM) projects have been carried out around the world • A survey of 62 IPM projects from 26 countries found that crop yield increased when pesticide use was decreased in 60% of the cases • This could be related to an overall improvement in management practice associated with the training that farmers received as part of IPM, or due to money saved on pesticides being invested in other ways to increase yields

  32. No-till agriculture Organic agriculture Urban agriculture Low-input farming systems

  33. No-till agriculture • Avoids tilling (overturning) the soil • Saves fuel, conserves soil moisture and reduces wind erosion • Usually is accompanied by increased use of herbicides (tilling removes weeds – this is no longer done) and sometimes by increased use of fertilizers • Net result: very little change in energy use

  34. Table 7.7 Comparison of energy inputs for conventional and organic farming in Finland. Required land areas are given as hectares per functional units (FUs) of either 1000 kg bread or 1000 litres milk. Source: Grönroos et al (2006, Agriculture, Ecosystems and Environment 117, 109–118)

  35. Table 7.8 Comparison of energy inputs (GJ/ha/yr) for conventional and organic systems of farming for two case studies in Denmark. Source: Jørgensen et al (2005, Biomass and Bioenergy 28, 237–248,

  36. Table 7.9 Comparison of measured energy inputs and yields for current conventional and organic farming in Denmark, and as expected for future organic farming. Source: Daljaard et al (2002, in Economics of Sustainable Energy in Agriculture, Kluwer Academic Publishers, Dordrecht, The Netherlands)

  37. Table 7.10 Comparison of energy inputs (MJ/kg) and yield (t/ha) for corn in southwestern Ontario, Canada, using chemical fertilizers or swine manure. Source: McLaughlin et al (2000, Canadian Agricultural Engineering 42, 9–17)

  38. Table 7.11 Comparison of energy inputs (GJ/ha) during the last 5-year rotation in a 32-year field experiment involving winter barley, winter wheat, and sugar beets in Germany on relatively fertile soil using either chemical fertilizers or manure. Source: Hülsbergen et al (2001, Agriculture Ecosystems and Environment 86, 303–321)

  39. Summary on low-input farming systems • There is typically a 35-50% reduction in the energy required to produce a given amount of food using organic methods compared to conventional methods • Yields (food production per unit of land area) typically fall by 10-20% (sometimes by 35%,sometimes not at all) • However, current crop varieties have been optimized through breeding for conventional systems of production. Re-optimization for organic systems may result in no reduction in yield • If this is insufficient, modest reductions in meat consumption could readily compensate for decreases in agricultural yields due to a shift to organic agriculture

  40. Energy Use by Fisheries • Fish are one of the most energy-intensive food products • Energy intensities have increased in recent years due to the use of larger ships (one huge shipped trawling until it is full carries more tonne-km of cargo than many smaller ships with the same total capacity) and the greater distances travelled now from the home port for most fleets • Extermination of the world’s commercial fisheries will occur by 2050 if current trends continue (algae will take over the oceans) • As the remaining stock is further depleted, the energy expended for tonne of fish harvested will increase further

  41. Table 7.12 Ratio of fossil fuel energy input to protein energy output for various US fisheries. Source: Rawitscher and Mayer (1977, Science 198, 261–264)

  42. Table 7.13 Ratio of fossil fuel energy input to protein energy output for various aquaculture fisheries. Source: Pimental and Pimental (2008, Food, Energy, and Society, 3rd Edition, CRC Press, Boca Raton)

  43. Role of diet

  44. Figure 7.12 Phytomass energy flows in the world food system. Source: Wirsenius (2003, Journal of Industrial Ecology 7, 47–80)

  45. Table 7.15 Ratio of phytomass energy input to the metabolizable energy of animal products consumed by humans (MJ/MJ). Source: Computed from data in Wirsenius (2000, Human use of land and organic materials, Ph D Thesis, Chalmers University of Technology, Göteborg, Sweden)

  46. Table 7.16 Food energy consumption (including losses by wholesalers and beyond) and phytomass energy requirements for different diets assuming inverse efficiencies of 1.5 for plant food, 7.7 for dairy products and 44.6 for land meat products.

  47. Figure 7.13 Diet and waste in the food system

  48. Figure 7.14a Trends in global meat consumption

  49. Figure 7.14b Trends in total global and average per capita meat consumption

  50. Figure 7.15 Per capita meat consumption in various countries