Modern agriculture is designed around annual plants instead of the generally more energetically efficient perennials. And most of the annuals are C3 plants, rather than the more optimal C4s. The C4s used are typically highly mismanaged in energy terms. Additionally, many fields are not properly oriented for solar capture and structures to capture solar energy are poorly designed, e.g., greenhouses.
As energy is always lost the more consumption stages it passes through, eating closer to the sun definitely helps with overall system energy efficiency. When humans consume products from animals that are fed crops humans can consume, or on land that can appropriately be devoted to human food crops, energy and land use efficiencies decrease. In contrast, efficiencies tend to increase when animals are fed plant matter that humans cannot digest (including crop residues), on land better suited to pasture than field and horticultural crops (MacRae et al., 2010).
 C3 and C4 refer to the metabolic pathways of carbon fixation in photosynthesis. Fewer plants are C4 and in evolutionary terms are likely more recent developments. C4 fixation is thought to be more metabolically efficient than C3.
Land use inefficiencies (adapted from MacRae et al., 2010)
It used to be that farmers would adapt cropping and livestock production to soil and climatic conditions. Now they use chemical fertilizers, pesticides and irrigation to “compensate” for biotic and abiotic deficiencies, often unsuccessfully. The consequence is that soil quality is not necessarily well matched to crop production practices that minimize resource expenditure. Related to this, crop and animal production are often separated (sometimes referred to as stockless systems for crop production and factory farming for industrial animal production facilities) and nutrients from animal manure are squandered, because there is insufficient cropping to optimize use and transporting nutrients to other farms is too expensive.
In Canada, farming is considered a private sector activity governed by private property rights. Consequently, there is limited landscape level planning and execution to ensure that cropping and animal production reflect the ecological realities of a region. Such planning is more complex than just matching crops to soil types. Some degree of specialization (within the bounds of system rotation and diversity requirements) might occur based on landscape features and farmer collaboration (e.g., sharing land to create suitable rotational crop patterns and building on landscape integrity). Of course, the competition with other land uses, particularly urbanization, makes such planning more complicated. However, many urban areas also have land that could be used for food production, especially if such production is organized to avoid competition with peri-urban producers.
A significant (but not necessarily well quantified), amount of high quality land area is devoted to non-food uses, including tobacco, flowers, landscaping plants, horse racing, and crops for industrial, pharmaceutical and beverage production. Many of such lands may be better suited to food crops, with non-food crop production shifted to less valued locations. However, there is no current mechanism to make such shifts.
Water use inefficiencies
As animals, crops and rotations are not usually selected for the prevailing moisture conditions, irrigation is often required. This is problematic for food crops, but even more so for irrigation of exotics and non-edibles destined for export markets. Irrigation systems are not very efficient, frequently with poor timing and targeting, inefficient distribution and pumps. Around 70% of water use in the world is for irrigation, with much of it very inefficient. And with food waste, a great deal of water is effectively lost (Cuellar & Webber, 2010).
Processing also contributes to water waste. In 2005, the Canadian Food and Beverage Industry (FBI) accounted for about 20% of all water withdrawals of manufacturers. Of this, 77% of water taken was discharged, 19% was incorporated into product, waste sludge and solid waste, or evaporated and only four percent was reused (Maxime, Arcand, Landry, & Marotte, 2010).
The amount of water used each year to grow and produce lost and wasted food would fill 70 million Olympic-sized swimming pools (UNEP, 2013a). U.K. food waste used six percent of the U.K.’s water requirements and nearly twice annual household water use (WRAP U.K., 2011).
Nutrient inefficiencies (adapted from MacRae et al., 2010)
The shift to synthetic nutrient sources from biological ones creates new inefficiencies in nutrient use and the energy expended to produce them. This is particularly acute for nitrogen, the most energy expensive of the main crop nutrients. For example, N use efficiency of cereals decreased globally from 80% in 1960 to about 30% in 2000 because of inefficiencies related to synthetic N utilization (Erisman, Sutton, Galloway, Klimont, & Winiwarter, 2008). Green manure nitrogen recovery is typically much higher than synthetic N (70 to 90% vs. 30 to 50%) but is spread out over much longer time horizons with usually only five to ten percent available in the first following crop (Crew & Peoples, 2005). Consequently, it requires more sophisticated management and seems “inconvenient” relative to synthetic N.
Regarding plant varieties, the focus in plant breeding on high optimal harvest index may reduce overall system efficiencies associated with the plant, and increase off-farm export of nutrients. Farming systems that make better use of the non-human edible parts of the plant – either for organic matter, for animal feed, for bedding, or for weed management (taller, more competitive plants with lower nitrogen requirements) – is desirable.
Metabolic inefficiencies (Smil, 2001)
North American agriculture focuses excessively on large animals that are metabolically inefficient. Cattle are very popular in North America, but pigs have 40% lower energy requirements than would be anticipated from their size, largely because of low basal metabolism. Cattle have much higher basal and reproductive metabolism, although dairy animals have a favorable conversion ratio for milk. Pigs also tolerate a wider range of environments. Chicken and eggs are next on the energy conversion scale, suggesting they warrant more attention in landscape level planning for energy efficiency. Ultimately, fish are much more efficient feed converters than farm livestock, so it makes sense to devote more attention to ecological herbivorous and omnivorous fish systems in the longer term.
To optimize both human and animal feeding systems, ruminants should eat primarily forages/grass and monogastrics residues and seeds (other than the dominant crop seeds). Other countries have more appropriate balances. For example, only five percent of human edible grains are fed to livestock in India compared to 60% in the U.S. Crop residues and wastes, feed oil seed crush, processing residues, and lower quality feed grade crops should be more effectively used for livestock. As well, pasturing hogs and poultry is feasible as part of the diet (Honeyman, 2005). Reducing feed losses will improve overall system efficiency. Additionally, animals fed such a diet tend to be leaner. The U.K. Institute of Grocery Distributors (IGD) and the Lean Enterprise Research Centre (LERC) found, for red meat production, that producers were feeding animals until they were overly fat. This is not only a waste of feed, but also costs processors who have to put resources into trimming off unnecessary fat (Gooch et al., 2010).
In the dominant production models, animal are typically raised in environments that are not conducive to their innate behaviours and this typically requires more energy to sustain them. For example, many beef cattle breeds are bred for primarily outdoor living and do not require barns. Pigs do well in more open structures such as hoop houses and open air sheds (Honeyman, 2005). Such systems have lower energy use associated with the structure, and may have lower overall energy use depending on the feeding regime (the biggest consumer of energy in hog systems) (Honeyman & Lammers, 2011).