Food system, energy requirements

Declining amounts of arable land, increasing world populations, and increasing costs of fertilizer and food and energy needs will make it increasingly difficult to maintain our soil resources. A key component for sustaining soil productivity is the maintenance of soil organic carbon (SOC). SOC maintenance requires the amount of carbon added to the system to equal the amount of relic carbon mineralized... 

The energy required to pump a liquid food through a pipe line can be calculated from the mechanical eneigy balance (MEB) equation. The MEB equation can be used to analyze pipe flow systems. For the steady-state flow of an incompressible fluid, the MEB can be written as follows (Brodkey, 1%7) ... 

Emulsions are thermodynamically unstable systems because of the positive energy required to increase the surface area between the oil and water phases. It is thermodynamically favored for the emulsions to reduce that surface area by separating into a systan that consists of a layer of oil (lower density) on top of a layer of water (higher density), unless they are effectively stabilized. Generally, the stability of food onulsions is complex because it covers a large number of phenomena, including flocculation, coalescence, CTeaming, and final phase separation. "... 

In the US system, NE values for lactation (NEj) are calculated fromTDN, DE or NE by an equation similar to that used in the Dutch system. For example, in the US system, foods containing 10 or 12 MJ ME/kg DM would be calculated to provide 6.0 and 7.1 MJ NEi/kg DM, respectively, whereas in the Dutch system, they would be calculated to provide 5.8 and 7.2 MJ NEi/kg DM, respectively. Net energy requirements for body maintenance and milk synthesis are expressed as NE, as they are in the Dutch and related European systems. 

As stated above, until recently, the energy system used for pigs in the UK was based on DE. However, after extensive consultation with the industry and other stakeholders, an NE system was introduced in 2003 (see Further reading). In this system, both energy requirements and the energy value of foods are expressed in terms of NE. As explained previously (see Chapter 10), the NE value of a food is... 

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