Disadvantages of biofuels from energy crops are the higher level of eutrophication, acidification, and ozone depletion associated with the use of nitrogen compounds from agricultural production:
Corn is one of the planet's most energy-intensive crops. Industrial corn production requires huge quantities of synthetic nitrogen fertilizers (derived primarily from natural gas) and petroleum based pesticides like atrazine, a known endocrine disrupter. Soybeans need less nitrogen, but farmers douse bean fields with other nutrients and with chemicals like Roundup to keep them pest-free.
The effects of corn and soybean production in the Midwest include massive topsoil erosion, pollution of surface and groundwater with pesticides, and fertilizer runoff that travels down the Mississippi River to deplete oxygen from a portion of the Gulf of Mexico called the dead zone that has, in the last few years, been the size of New Jersey.
As ethanol use pushes corn prices higher, farmers are increasingly abandoning the traditional corn-soybean rotation to what's known in farm country as corn-on-corn. High prices have encouraged farmers to plant corn year after year, an intensification that boosts fertilizer and pesticide requirements.
Biofuels, made by producing ethanol, an alcohol fuel made from maize, sugar cane, or other plant matter - may be a penny wise but pound foolish way of doing so.
Much of the fuel that Europeans use will be imported from Brazil, where the Amazon is being burned to plant more sugar and soybeans, and Southeast Asia, where oil palm plantations are destroying the rainforest habitat of orangutans and many other species. Species are dying for our driving.
If ethanol is imported from the US, it will likely come from maize, which uses fossil fuels at every stage in the production process, from cultivation using fertilizers and tractors to processing and transportation. Growing maize appears to use 30% more energy than the finished fuel produces, and leaves eroded soils and polluted waters behind.
It is little wonder that many are calling biofuels "deforestation diesel", the opposite of the environmentally friendly fuel that all are seeking.