Burning wood for heat, just like in the good old days, seems particularly attractive in times of high oil prices. Wood pellet heating has developed such that it is now just as comfortable as oil or gas. Indeed, the days of stoking your own fire are a thing of the past, now it is fully automatic. Still, the units need to be cleaned and serviced every few months.
Bio-energy can also be used to power automobiles. Biodiesel or ethanol has the advantage that, when burned, the fuels only release as much CO2 as the plants used to make them absorbed out of the atmosphere when growing. A perfect cycle that doesn't harm the climate one bit. That, at least, is the theory. When it comes to biofuels, practice often looks quite a bit different, particularly given the fact that forest land is often cleared to plant crops used in the production of biofuels.
The production of wood pellets, however, has in general been more sustainable. For the most part they are produced using wood waste that would otherwise be simply thrown away. But wood pellet heating also releases fine dust particles that can lead to respiratory disease.
Biomass is one of the most important renewable energies in Germany. Biogenic combustibles (usually wood) and fuels (biodiesel for example), biogas and combustible bio-waste make up some 73 percent of all renewable energy used in Germany. Wind power, by comparison, provides 14.9 percent.
The greatest advantage is that biomass is essentially stored energy. When one wants to set that energy free is a matter of choice -- as opposed to wind or solar energy. Plus, biomass plays a role in all energy markets: wood can be used for heating; bio-fuel can be used in cars; and biogas can be used to generate electricity. A further advantage is that they reduce dependence on foreign sources of energy.
Recently, bio-energy has come in for intense criticism. The central question is whether the burning of biomass is really as environmentally friendly as it appears at first.
Forestry worker and author Peter Wohlleben has pointed out that it is not just the trees in forests that function as carbon sinks. The ground too absorbs CO2. Which means that when trees rot, not all of the CO2 they contain reaches the atmosphere -- some of it remains in the ground. In other words, when one burns wood, more CO2 is released than otherwise would have been. Furthermore, increasingly all parts of trees are being used, from the roots to the very tips of the branches -- a process which robs the forest floor of vital minerals.
The production of bio-fuels is perhaps even more problematic. Crops needed to produce bio-fuels require space -- space that can also be used for the production of food. A moral dilemma quickly becomes apparent: Can one justify using corn for the production of fuel when others need that corn for food? The early years of the bio-fuel boom were characterized by euphoria. That enthusiasm, however, has largely waned.
An additional problem is represented by the sheer amounts of space necessary to slake the thirst for energy. Were Germany to meet all of its gasoline and diesel needs with biofuels, it would require cropland greater than the area of the entire country. The same is true were all Germans to heat their homes with wood pellets. Imports would be necessary -- which would quickly destroy the ecological advantage of wood pellet heating. The CO2 balance of the process is strongly linked to how far one must transport the wood. In addition, were wood from rain forests to be used in the production of wood pellets instead of carefully managed forests, the method would contribute to further deforestation and destruction of one of the world's most important carbon sinks.
The CO2 balance of biofuels is also worse than it appears at first glance. Indeed, a recent study conducted in the US found that biofuels actually do more damage than traditional fossil fuels. The reason: in order to meet the growing demand, forests must be chopped down, resulting in a disappearance of CO2 sinks. Furthermore, the fertilization of biofuel crops results in the release of N20 into the atmosphere, a greenhouse gas that is much more damaging than CO2. Plus, the entire process is inefficient. Energy is lost in the process of transforming plants into liquid fuel. It would be much better just to burn the plants and use the resulting heat to heat homes or to power turbines, thus producing electricity that could be used to power electric cars.
Scientists, though, are still reluctant to abandon the dream of biofuels. Second generation biofuels are to be produced by plants that cannot also be used for food and which can grow in poorer soil -- where food crops can't. Plants such as the oil-rich Central American native Jatropha are seen as a possible solution as is agricultural waste. Algae may also play a larger role in the future of biofuels.
But technological problems remain. Transforming agricultural waste into biofuel is a complicated procedure. The cell walls of plants are made of cellulose. These molecules must first be broken down before fungus or bacteria can produce alcohol. One can either use chemicals in the process, or micro-organisms. But finding the right "superbug" to do the job has proven difficult -- standard yeast can make no progress against cellulose. So far, the low yields obtained from the process make it unlikely that this type of bio-fuel will be able to compete anytime in the near future.
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