Any good, which is not superabundant is scarce.  Their availability is finite.  Apples, water, cars, ipods, etc. are examples of scarce goods.

Some goods are not scarce.  Knowledge is often a good that is not scarce.  Once something is known, and published, everyone can acquire that knowledge.  A recipe does not diminish if one person knows it, or everyone knows it.  It does not wear out, it can be used an infinite number of times.  The distribution of the knowledge may require the use of scarce factors, such as ink & paper.  The recipe, which exists on a sheet of paper, may be scarce, but the recipe itself is not enhanced or diminished or changed, by transcribing the knowledge to paper.  A recipe book may be sold, but often one is buying more than just the paper and the knowledge therein.  The buyer may also consider that, in buying the book, he is acquiring a brand, a recommendation, some quality whose value may be difficult to evaluate.  In purchasing a book containing a non-scarce good, the buyer is not necessarily paying for something which he should be able to acquire for free, he is buying more than just the knowledge contained within.

Non-scarce goods cannot be consumed.  They may be used in combination with scarce goods, but they cannot be consumed.  A cake cannot be made without both the recipe and the scarce ingredients.  The cake may be consumed, but the recipe remains.  Certain laws have been enacted to make knowledge scarce.  Patent law is such an example, in which inventions or techniques are given legal protection so that the knowledge can acquire an exchange value, or be protected, to give the owner a monopoly privilege.

All consumption is actually transformation of scarce goods.  Some products may take hundreds of years to consume, such as a house, or other products may be consumed in an instant, such as a firework.  Once, rocks, trees and labour are transformed into a house, the owner and subsequent owners may enjoy that indefinitely.  However, wood plastic and chemicals, once transformed into a firework are transformed into their broken and waste components once the product is ignited.

A food, once eaten is transformed by the body into components which can be used to sustain it.  Even at rest, the body is transforming stored nutrients into energy, protein, lipids, nucleic acids etc. to maintain itself.  Once the body is finished, the transformed waste products are discharged by the lungs, digestive system and other systems.  These transformed waste products are another organism’s food or energy.  This principle is true of every material product ever produced.

The only exception to this rule is that every transformation dilutes the concentration of energy so that energy (while it is not lost), cannot be transformed back into its original form, without the expenditure of a greater amount of energy.  Thus petrol & air, once transformed into CO2 and H2O, to power a car, can be re-transformed back into petrol, but only by using more energy than the re-transformed petrol can release.  Energy can be considered to be consumed.  Energy is lost, never to be recovered.  Modern production systems have become very dependent on fossil fuels as an energy source.  This is clearly a concern today, especially with the potential negative effects of increasing the amount of atmospheric CO2.