Question

compared to a heavier liquid fuel like gasoline, why might ethylene be a more desirable source? (Think about thermodynamic features, such as ideality, as well as other factors such as weight, cost, storage, etc.

Answer 1

Ethylene may be more desirable source becasue its commercial use, some of its commercial use mentioned below:

Ethylene shortens the shelf life of many fruits by hastening fruit ripening and floral senescence. Ethylene will shorten the shelf life of cut flowers and potted plants by accelerating floral senescence and floral abscission. Flowers and plants which are subjected to stress during shipping, handling, or storage produce ethylene causing a significant reduction in floral display. Flowers affected by ethylene include carnation, geranium, petunia, rose, and many others.

Ethylene can cause significant economic losses for florists, markets, suppliers, and growers. Researchers have developed several ways to inhibit ethylene, including inhibiting ethylene synthesis and inhibiting ethylene perception. Aminoethoxyvinylglycine (AVG), Aminooxyacetic acid (AOA), and silver salts are ethylene inhibitors. Inhibiting ethylene synthesis is less effective for reducing post-harvest losses since ethylene from other sources can still have an effect. By inhibiting ethylene perception, fruits, plants and flowers don't respond to ethylene produced endogenously or from exogenous sources. Inhibitors of ethylene perception include compounds that have a similar shape to ethylene, but do not elicit the ethylene response. One example of an ethylene perception inhibitor is 1-methylcyclopropene (1-MCP).

Commercial growers of bromeliads, including pineapple plants, use ethylene to induce flowering. Plants can be induced to flower either by treatment with the gas in a chamber, or by placing a banana peel next to the plant in an enclosed area.

Chrysanthemum flowering is delayed by ethylene gas and growers have found that carbon dioxide 'burners' and the exhaust fumes from inefficient glasshouse heaters can raise the ethylene concentration to 0.05 ppmv causing delay in flowering of commercial crops.

Ethylene is a colorless gas that is naturally produced by plants and functions as a plant growth regulator. In this way, ethylene behaves in the same way as hormones in mammals. It triggers specific events during a plant’s natural course of growth and development, such as ripening. Through this action, it induces changes in certain plant organs, such as textural changes, color changes, and tissue degradation. Some of these changes may be desirable qualities associated with ripening; in other cases, it can bring damage or premature decay.

Fruits and vegetables may be classified depending on their response to ethylene. Climacteric species produce ethylene as they ripen, and the harvested produce is capable of ripening during the postharvest period. These commodities, such as bananas, apples, and peaches, tend to get sweeter and softer after harvest. Non-climacteric plants, such as leafy vegetables, do not continue to ripen after harvest; they will soften and rot, but this is due to moisture loss, decay, and tissue deterioration.

In addition to being naturally produced by plants, ethylene is produced by a variety of other sources. These include internal combustion engines, cigarette smoke, and natural gas leaks. Even low concentrations of ethylene throughout the postharvest life of a commodity can affect quality, so care must be taken to minimize exposure from both natural sources (i.e. climacteric fruit or veggies being stored with non-climacteric ones) or to artificial sources (engine exhaust, heaters, etc). All ethylene-producing sources should be considered when optimizing postharvest storage conditions as inadvertent exposure to ethylene can contribute to loss of quality in some fruits and vegetables.