Mother Nature Invented Zero Waste

Consider an aspen bluff . In fall, the leaves turn a brilliant gold and then flutter down to the forest floor. No one shows up with a rake and the leaves are not carted off to the landfill. Instead, with time, moisture and microbes, they decompose. Some chemicals in the leaves are slow to break down and will stay in the soil for a long time as organic matter. Others are quickly released and absorbed into other living things, including the trees from which the leaves fell. It is a remarkable system. Nature is the original ‘cradle-to-cradle’ designer and the model for zero waste practices. We have a lot to learn about how nature cycles material.

Nature has three big strategies for accomplishing her zero waste approach: controlled shaping for molecules, biodiversity and enzymes.

Controlled shaping for molecules (precision engineering) : Living systems build and use molecules of many sizes. Large molecules are built from smaller subunits like sugars or amino acids. Whether living systems are building large or small molecules, they use a careful molding process so that each one of a given type has exactly the same shape. This gives a predictable end product. The chemical processes in living organisms take advantage of this predictability by fitting shape to shape. It is like reading by Braille. The predictable shapes of biologically-produced molecules make it much simpler to take them apart when it is time for them to decompose.

Any chemist will tell you it is much harder to achieve predictability when we make chemicals in test-tube reactions. Two molecules of the same test-tube-made chemical will have the same atoms in the same general positions but there can be slight positional differences. These slightly different forms of a molecule are called isomers. One can think of isomers as right- and left-handed gloves. Natural systems read these ‘gloves’ as being quite different and will often only make a left- or a right-hand version.

Biodiversity (different ‘folks’ for different jobs) : Decomposition is mostly accomplished by microbes—really small living things. Bacteria and fungi are the main kinds of microbes involved. Each species of microbe prefers a certain temperature range, oxygen level, acidity and stage of decomposition. Essentially, nature seems to have microbes for every circumstance. Every ‘natural’ circumstance, that is. Problems do to arise when microbes try to degrade some of the chemicals that humans have invented.

Enzymes (the right tool for every job) : Enzymes are the tools that microbes use to deconstruct materials; they are also involved in other life processes. Enzymes carry out their chemical chores by recognizing shapes and electrical charges—they are looking for those precisely-made molecules discussed above. As would seem likely, there are many different enzymes and each is involved in a very specific chemical reaction. Enzymes are proteins that act as catalysts, meaning that they assist a reaction but are not used up in the process. Microbes don’t have mouths or teeth. They depend on enzymes to digest material outside their cell walls and then move the smaller breakdown products back inside.

Decomposer enzymes are named for the material they break down. An enzyme that breaks down proteins is a peptidase; one that breaks down cellulose, a cellulase. Each microbe species has a tool kit of enzymes that break down many but not all the possible food sources.

Let Nature Complete the Cycle: As we have pointed out above, natural systems make a great model for industrial design, but this will take a while. In the meantime, we need to make certain that our waste management systems recognize the built-in recyclability of organic materials like banana peels and dead petunias. Let the nutrients cycle.

(Source: February 2007 WasteWatch)

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