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Science

Food Production

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A growing population brings with it a necessity to produce more food. However, the potential impact on the local and global environment must be considered. Part of the solution lies in careful management to reduce energy losses in food chains, as well as looking to new food sources. It is necessary to find a compromise between the priority of obtaining food and the priority of protecting ecosystems.

Efficiency of food production

Both biomass [biomass: The dry mass of an organism. and the energy within it decrease up a food chain. [food chain: A sequence (usually shown as a diagram) of feeding relationships between organisms, showing who eats what and the movement of energy through trophic levels. At each level in the chain, energy/biomass is lost through waste (eg faeces) or through respiration [respiration: Chemical change that takes place inside living cells, which uses glucose and oxygen to produce the energy organisms need to live. Carbon dioxide is a by-product of respiration. and associated processes (such as movement and maintaining body temperature).

The efficiency of food production can be improved by reducing the number of levels in the food chain. This is because fewer energy losses occur along a shorter food chain, meaning a greater proportion of the energy that entered the food chain is available to humans and more people can be fed.

The amount of available energy decreases at every step in a food chain

The amount of available energy decreases at every step in a food chain

The efficiency of food production from animals can be improved by reducing the amount of energy lost to the surroundings. This can be done by:

  • Preventing animals moving around too much - this conserves energy which can be used to increase biomass.

  • Keeping their surroundings warm - this preserves the energy which would have been used to maintain their body temperature, so that it can be used to increase biomass.

Such practices are known as factory farming.

Rows of pigs on a factory-style pig farm

Pig farm

The main advantages for keeping animals in warm sheds with little space to move are that it results in more efficient food production - and therefore cheaper food. However, there are disadvantages in terms of reduced animal welfare, increased risk of injury, and increased risk of diseases (eg salmonella amongst chickens).

A balance must be reached between the needs of farmers and consumers and the welfare of the animals.

Calculating energy efficiency

Calculating energy efficiency

Calculating energy efficiency

This bullock has eaten 100 kJ of stored energy in the form of grass, and excreted  [excreted: Discharged as waste. 63 kJ in the form of faeces, urine and gas. The energy stored in its body tissues is 4 kJ. So how much has been used up in respiration?

The energy released by respiration

= 100 - 63 - 4 = 33 kJ

Only 4 kJ of the original energy available to the bullock is available to the next stage in the food chain, which might be humans.

The efficiency of this energy transfer is:

4/100 × 100 = 4%

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