Reply #17: Nothing really new with ethanol

[Fledermaus]

The first attempt at commercializing a process for ethanol from cellulose was done in Germany in 1898

Using trash as a feed stock is relatively novel. People will pay to have their trash/feed stock piked up.

Cellulose is just part of the carbon cycle. I'm quite sure there are other carbon compounds in trash that can be used.

Overview
The main concepts we are trying to get across in this section concern how energy moves through an ecosystem. If you can understand this, you are in good shape, because then you have an idea of how ecosystems are balanced, how they may be affected by human activities, and how pollutants will move through an ecosystem. If you had Biology 101, this should be review; if you had Geology 101, this is new stuff. Either way, it is pretty basic and you shouldn't have much trouble reading this material or the associated material in the text.

Roles of Organisms
Organisms can be either producers or consumers in terms of energy flow through an ecosystem. Producers convert energy from the environment into carbon bonds, such as those found in the sugar glucose. Plants are the most obvious examples of producers; plants take energy from sunlight and use it to convert carbon dioxide into glucose (or other sugars). Algae and cyanobacteria are also photosynthetic producers, like plants. Other producers include bacteria living around deep-sea vents. These bacteria take energy from chemicals coming from the Earth's interior and use it to make sugars. Other bacteria living deep underground can also produce sugars from such inorganic sources. Another word for producers is autotrophs.

Consumers get their energy from the carbon bonds made by the producers. Another word for a consumer is a heterotroph. Based on what they eat, we can distinguish between 4 types of heterotrophs:

consumer trophic level food source

Herbivores primary plants

Carnivores secondary or higher animals

Omnivores all levels plants & animals

Detritivores --------------- detritus



A trophic level refers to the organisms position in the food chain. Autotrophs are at the base. Organisms that eat autotrophs are called herbivores or primary consumers. An organism that eats herbivores is a carnivore and a secondary consumer. A carnivore which eats a carnivore which eats a herbivore is a tertiary consumer, and so on. It is important to note that many animals do not specialize in their diets. Omnivores (such as humans) eat both animals and plants. Further, except for some specialists, most carnivores don't limit their diet to organisms of only one trophic level. Frogs, for instance, don't discriminate between herbivorous and carnivorous bugs in their diet. If it's the right size, and moving at the right distance, chances are the frog will eat it. It's not as if the frog has brain cells to waste wondering if it's going to mess up the food chain by being a secondary consumer one minute and a quaternary consumer the next.

The diagram above shows how both energy and inorganic nutrients flow through the ecosystem. We need to define some terminology first. Energy "flows" through the ecosystem in the form of carbon-carbon bonds. When respiration occurs, the carbon-carbon bonds are broken and the carbon is combined with oxygen to form carbon dioxide. This process releases the energy, which is either used by the organism (to move its muscles, digest food, excrete wastes, think, etc.) or the energy may be lost as heat. The dark arrows represent the movement of this energy. Note that all energy comes from the sun, and that the ultimate fate of all energy in ecosystems is to be lost as heat. Energy does not recycle!!

The other component shown in the diagram are the inorganic nutrients. They are inorganic because they do not contain carbon-carbon bonds. These inorganic nutrients include the phosphorous in your teeth, bones, and cellular membranes; the nitrogen in your amino acids (the building blocks of protein); and the iron in your blood (to name just a few of the inorganic nutrients). The movement of the inorganic nutrients is represented by the open arrows. Note that the autotrophs obtain these inorganic nutrients from the inorganic nutrient pool, which is usually the soil or water surrounding the plants or algae. These inorganic nutrients are passed from organism to organism as one organism is consumed by another. Ultimately, all organisms die and become detritus, food for the decomposers. At this stage, the last of the energy is extracted (and lost as heat) and the inorganic nutrients are returned to the soil or water to be taken up again. The inorganic nutrients are recycled, the energy is not.

Many of us, when we hear the word "nutrient" immediately think of calories and the carbon-carbon bonds that hold the caloric energy. IT IS VERY IMPORTANT that you be careful in your use of the word nutrient in this sense. When writing about energy flow and inorganic nutrient flow in an ecosystem, you must be clear as to what you are referring. Unmodified by "inorganic" or "organic", the word "nutrient" can leave your reader unsure of what you mean. This is one case in which the scientific meaning of a word is very dependent on its context. Another example would be the word "respiration", which to the layperson usually refers to "breathing", but which means "the extraction of energy from carbon-carbon bonds at the cellular level" to most scientists (except those scientists studying breathing, who use respiration in the lay sense).

To summarize: In the flow of energy and inorganic nutrients through the ecosystem, a few generalizations can be made:

The ultimate source of energy (for most ecosystems) is the sun
The ultimate fate of energy in ecosystems is for it to be lost as heat.
Energy and nutrients are passed from organism to organism through the food chain as one organism eats another.
Decomposers remove the last energy from the remains of organisms.
Inorganic nutrients are cycled, energy is not.

http://www.marietta.edu/~biol/102/ecosystem.html