In the entire concept of ecology, few terms cause more confusion than the description of objects, resources, or practices as “sustainable.” To some, sustainable materials are those which are renewable; for instance, crops that can be harvested but continually replanted and grown again. Others consider sustainable materials to be those which can be repeatedly reused through recycling. Although there is no universally agreed-upon definition for sustainability, most definitions include the concept that the material can be used at a rate that will allow future generations access to the same abundance of resources without causing ecological harm.
Fossil fuels are a clear example of a completely unsustainable resource. Although the Earth naturally produces fossil fuels as part of the breakdown of organic material, the rate at which humans consume the fuel means that the quantity is continually diminishing. Additionally, as the burning of fossil fuels adds polluting elements to the air, land, and sea, the use of this non-sustainable set of materials cannot be seen as having no impact on the environment.
Renewable materials can be, but are not always, sustainable materials. When corn is grown, it can be harvested and replanted using some of the harvested seeds. Theoretically, this cycle can continue endlessly, particularly if green practices are employed to offset damage to the local ecosystem. If the corn is refined into ethanol, the resulting product may be renewable, but is not sustainable, due to the environmental pollution caused by the refining process.
Some people consider recyclable materials to be sustainable materials, but with the caveat that the material must also be biodegradable. Cotton cloth, for instance, can be used repeatedly until biodegradation takes over and the materials rot back into organic compounds, leaving no measurable negative impact on the Earth. Plastic, however, may be recyclable but is not usually considered sustainable, because it may take hundreds or thousands of years to degrade. Additionally, depending on the chemical composition of the plastic, the environment may be harmed as detrimental chemicals leech into the Earth from the material.
Perfectly sustainable materials are very hard to find; it is rare that the growth, refinement, life cycle, and decomposition of any material can occur with no impact on the Earth. Much of what determines sustainability has to due with the rate of consumption; wild berries might be considered sustainable in an unvisited, healthy forest, but if a thousand people ran in and harvested them, the formerly sustainable crop would be quickly obliterated.
For those looking to live an environmentally-friendly existence, it is important to investigate all claims of sustainability carefully. In many cases, materials deemed sustainable are actually renewable or recyclable, but not sustainable. Yet materials that do not quite match the concept of perfect sustainability may still be considerably less harmful to the environment than non-renewable or recyclable sources. Wood from forests continually re-planted and maintained, recycled denim insulation, and food from organic sources that take care in ensuring a safe turnover of the Earth, and tactics that offset any ecological damage may not be perfectly sustainable materials, but may still do a lot of good.