Energy and Cropping Systems. Thomas G Chastain CROP 200 Crop Ecology and Morphology

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1 Thomas G Chastain CROP 200 Crop Ecology and Morphology

2 The energy supply and economic security of a nation are inextricably linked. Our nation s energy supply was threatened in the 1970s by world events, but the underlying factors for that disruption have not changed. A reliable supply of energy is required to support modern mechanized agriculture and associated processing industries. The need for alternative energy sources is self-evident. Vehicles lined up for gas in the 1970s

3 Energy supply and farm profits are linked. Rising fuel costs reduce the profitability of farming enterprises. Farmers are large consumers of diesel and other fuels. Profit Cost Low fuel prices Profit Cost High fuel prices

4 Agriculture is energy farming. A crop canopy captures solar energy much like solar panels but very much more efficient in energy capture. Growing a crop is all about making the best possible solar energy harvesting system. The solar energy from captured in agriculture is stored as chemical energy in the harvested farm products. Agriculture currently uses about 2% of all US energy consumption. Corn crop canopy (top), solar panels (bottom)

5 Materials have differing energy content petroleum products, fertilizers, and pesticides have very high energy content embodied in the material and in their manufacture. Off-farm energy inputs have contributed greatly to the productivity of agriculture. Wood averages 9 MJ energy per pound of wood combusted in a fire Chemical Energy Content of Materials Material Energy content (MJ/lb.) Sugar 7 Ryegrass Seed 8 Wood 9 Coal 11 Ethanol 13 Natural Gas 16 Vegetable Oil 18 Diesel 20 Gasoline 20 Nitrogen 27 Diuron 122 Prowl 191 Quilt 215

6 The energy used and produced by a corn crop is illustrated with an energy budget. Energy consumed (EC) for crop production activities, in producing planting seed, and in manufacturing machinery are determined in this lifecycle energy budget. Energy output (EO) for crop production (capturing solar energy and converting it to a harvested corn crop) far exceeds the energy used to produce the crop. Input Energy Consumed MJ/hectare Labor 280 Machinery 366 Diesel Fuel 2104 Gasoline Fuel 1136 Nitrogen Fertilizer Phosphorus Fertilizer 1097 Potassium Fertilizer 1076 Seed 384 Herbicide 1314 Fuel for Drying 2607 Electricity for Drying 86 Total Inputs Output (Corn yield = 8.8t/ha)

7 Fertilizers, pesticides, and PGRs account for nearly 80% of the energy used in perennial ryegrass seed production. But for many crops, fertilizers and pesticides account for about only about 30% of the total energy consumed in crop production. Energy budgets can be useful tools in identifying potential energy cost savings. Energy budget for perennial ryegrass seed production the Willamette Valley (Chastain and Garbacik, 2011). Management Input Energy Consumed % of Total Energy Use MJ/acre % Stand Establishment Fertilizer Lime Pesticides PGR Harvest Post-harvest Labor Total Energy Use

8 The efficiency of energy use is measured as the ratio of the total energy produced or output by the crop (EO) to the energy used or consumed (EC). There is a wide range of energy use by crops and efficiencies among those crops. Crops that are typically irrigated such as sugarbeet have his energy use values while dryland grain crops such as barley can have low energy use. Energy budgets can be useful tools in identifying potential energy cost savings. Energy use and efficiency for several crops. Crop Energy Use Energy Efficiency MJ/acre EO/EC Wheat 6,070-12, Barley 4,047-11, Sugarbeet 10,117-24, Soybean 6,900-14, Perennial Ryegrass 8,344-8,

9 The energy required for crop production can be reduced through conservation and improved efficiency. The efficiency of energy use by US farmers has increased dramatically as the energy use per unit of farm output has declined about 44% since the late 1940s. Despite these gains, there is increasing scrutiny regarding the amount and the cost of energy used in agricultural production. Energy-conserving no-till drill (John McManigal photo)

10 Measures to increase energy conservation and efficiency of energy use include: 1. Replacing older inefficient irrigation pumps 2. Converting to low pressure irrigation systems 3. Using no-till systems 4. Reducing application rates for fertilizers and pesticides or increasing the efficiency of application through use of precision agriculture Low pressure nozzle (TG Chastain photo)

11 Persons fed per US farmer Energy and Cropping Systems Growing fuels for agriculture. Prior to the advent of mechanized agriculture, farms produced much of their energy needs on the farm. Some of the increase in agricultural productivity can be attributed to the import of fuel from outside the farming operation. Growing crops for biofuels would permit farmers to regain a stake in their own energy production. The questions are: Can we grow our own fuels and can we grow enough? Does it make sense to grow our own fuels? Year

12 Biofuels are renewable fuels derived from the sun via green plants. The primary biofuels are ethanol, biodiesel, biobutanol, and biomass for biogas or combustion for electricity generation. Combustion of biofuels releases CO 2 recently captured from the atmosphere while combustion of petroleum-based fuels releases CO 2 extracted from the atmosphere millions of years ago. Petroleum is a product of the earth s geologic processes, but the energy found in petroleum originated from the sun. US Energy Use 28% 37% 8% 18% 9% Natural Gas Nuclear Renewables Coal Petroleum

13 Gallons Produced (millions) Gallons Produced (millions) Energy and Cropping Systems US Biodiesel Production US Ethanol Production Year Year Biofuels in the form of biodiesel and ethanol constitute a small but growing segment of our nation s energy supply.

14 Energy Balance. If crops are to be used as feedstocks for the production of biofuels, then the energy required for crop production and fuel processing (inputs) must be less than the energy derived from the biofuel (output). The energy balance for petroleum is 0.8:1 (source, US Dept. of Energy). Energy Balance = Output (Fuel Energy Value) Inputs (Production + Processing Energy)

15 Energy Budget for Sugar Cane for Ethanol Production Output/input ratio = 8.3 Input Energy (MJ/MT) Farm Operations 38 Transportation 43 Fertilizers 66 Lime, Herbicides, etc. 19 Seed 6 Equipment 29 Ethanol Production 49 Total Inputs 251 Output - ethanol 1921 Output - bagasse 169 (Macedo et al., 2003) Sugar cane (USDA photo)

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