Part of what makes renewable energy so attractive is that people understand intuitively that using solar and wind energy helps society live within its means. Renewable energy sources are flows that are continually replenished. Sunshine continues to fall on the earth whether or not it is captured for energy. Using renewable energy is like living off your monthly salary. Fossil fuels, like coal are ‘stocks’ that represent a fixed amount. Once they are gone, they are gone. Burning fuels like coal is like racking up your credit card. But where does bioenergy fit into this analogy?
Bioenergy is the idea of using things that grow, like wood or corn, for energy rather than furniture or food. Using traditional crops including wheat or sugarcane to make ethanol is one example; as is using non-food matter like wood or straw for fuel. Organic wastes can also be used, like using methane from water treatment plants as a substitute for natural gas (the organic portion of waste is ultimately derived from growing plants). The age-old idea of burning wood for heat is another form of bioenergy. As long as it’s done right, bioenergy is like living off the interest of your savings account.
In some respects bioenergy is a stock. Like coal, it is fuel that can be seen, gathered and saved for later use. Because it regrows continually it also has properties of a flow; and is thus classified as renewable. In the forestry sector the concept of the ‘annual allowable cut’ has long been recognized. It means that if you replant the same number of trees that you cut every year, your forest will stay the same size. This principle also applies to agriculture. As long as you do not deplete the soil or water you can expect similar crop volumes year after year. If you use more than can be naturally replenished, your bioenergy source becomes a shrinking stock. To do it right bioenergy cannot be used faster than stock grows back.
Consuming bioenergy faster than it can grow back, forces society to acknowledge it is living beyond its means and going into resource debt. However, the mismanagement of a bioenergy crop is likely to be discovered within one person’s life time. As a result the feedback loop is much faster than with coal. Hopefully the feedback is fast enough to allow management practices to be changed. In the case of coal mismanagement, several generations may pass before a problem is even discovered.
Of course society should not rack up bioenergy debt. On the contrary, bioenergy needs to be managed even more carefully than other renewables. The point is, that if you use bioenergy faster than it can be replenished, the collection agency will be knocking on your door sooner than if you use too much coal. Using bioenergy to replace fossil fuels can help ensure our society lives within its means and always has a place to call home.
Jeff Bell specializes in clean energy and currently works for the government of the Canadian province of Alberta. This article is the opinion of the author.