This probably goes without saying and won’t be belabored here, but burning biofuels, which are mostly hydrogen and carbon, produces carbon dioxide, which contributes to global warming. So, even though biofuels may be able to help ease our energy needs, they won’t solve all of our problems.
Now, it may be true that biofuels produce LESS GHG emissions that fossil fuels, but that can only serve to slow global warming and not to stop or reverse it. Thus, biofuels can only be substitutes for the short term as we invest in other technologies. The key to implementing them is to mitigate environmental impact by being mindful of the drawbacks discussed in this article.
Land Use Changes and Global Warming
Land use changes are perhaps the hardest to quantify in terms of impact on the environment. It was originally thought that because of biofuels absorb carbon dioxide as they grow, the carbon dioxide that they release when burned would be offset. This became known as “carbon neutral” fuel production. Unfortunately, these original estimates neglected to consider the impact that deforestation and changes to natural environments would have. Deeper study of the issue can result in what is called a “carbon debt.”
The carbon debt occurs when carbon dioxide is released in the preparation of land for the growth of biofuels. The level of debt acquired depends on the land itself. For instance, converting abandoned agricultural land requires fewer resources and amasses a very small carbon debt. In this case, the reduction in carbon emissions from using biofuels, provided the feedstock has a low requirement for water and energy input, will easily offset the carbon debt in a short period of time. Alternatively, converting native forest or other wild land for growing biofuels can we do a carbon debt as large as 500 years. In other words, the advantages of using biofuels won’t offset the carbon death for five centuries.
Energy Investment and Energy Return
The other important aspect of growing biofuels that must be kept in mind when calculating net environmental benefit, is the amount of energy that must be put into a given crop before energy can be derived from it. As it turns out, the majority of feedstock currently being considered for use in the production of biofuels requires that more energy be put in to production than can ever be derived. In other words, if the economy ran entirely on biofuels, we would slowly but surely run out of energy as the investment in feedstock would be greater than the energy that can be derived from harvesting it.
The problem lies in the fact that even biofuel feedstock require water, fertilizer, pesticides, and land preparation. Crops like corn and soybean require for more energy input as a result of these needs than could ever be derived from them. The only current alternative that appears viable is algae. The reason algae may work is that it can be grown in relatively high density with low needs for fertilizer and pesticide and with most of the energy input been derived from the sun. Of course, the potential for algae is theoretical. Current experimentation has shown that algae still requires more energy input and can be derived from harvesting it. The theoretical potential for algae lies in the assumption that genetic engineering will be able to overcome the limitations that algae currently demonstrate.