The use of fertilizer is essential if we are to produce enough biofuel to meet our energy needs. Unfortunately, fertilizer has a number of drawbacks and can seriously impact the environment. The scale on which fertilizer would be needed to produce biofuel is astronomical, with some estimates suggesting that it could be as much as three to four times the quantity used in producing food.
Greenhouse Gas Emissions
One of the proposed benefits of biofuels is their potential to reduce greenhouse gas emissions. This benefit arises from the fact that plants consume carbon dioxide and so should take in as much carbon dioxide as is produced when the fuel is burned. As it turns out, there is yet another place in which GHGs are produced and it may not only offset the potential savings, but could make biofuels more damaging than fossil fuels in terms of global warming.
The problem is fertilizer, which can be summarized as a nitrogen rich compound. Nitrogen is consumed by bacteria in soil and those bacteria produce nitrous oxide. Nitrous oxide is a GHG that is roughly TWICE as potent as carbon dioxide. Given that a significant amount of fertilizer spread on crops ends up in bacteria, the implications are quite profound. The energy invested into fertilizer production, crop growth, and crop harvesting combined with the nitrous oxide output from fertilizer all combine to make biofuels at least as disruptive as fossil fuels and perhaps more so in terms of global warming.
The sheer quantity of fertilizer needed for biofuel production is also unsustainable. Algae, which are reasonably economical in terms of fertilizer use, would require fifteen million metric tons of nitrogen and two million metric tons of phosphorus just to meet the needs of 5% of the U.S. transportation fuel market. The use of nitrogen fertilizer amount to 100 million metric tons per year, which means that meeting only a small fraction of fuel needs in the U.S., would require 15% of all the fertilizer produced in a year. If production is scaled up, fertilizer production would need to triple just to meet fuel demands for the United States. Production would need to increase exponentially to meet fuel demands the world over in addition to meeting food needs.
Water pollution and other Issues
Fertilizer has other problems as well. Run-off from fields ends up in streams where it promotes the growth of algae and other microorganisms. This enhanced growth leads to decreases in the amount of oxygen dissolved in the water and subsequently to the death of amphibians and fish.
Other problems include soil acidification, toxic trace mineral deposition, fertilizer dependency, damage to beneficial soil organisms, and trace mineral depletion. The net result is damage to soil over the long term along with the problems already mentioned.