Land Use and Biofuels

One of the major concerns surround biofuels is the amount of land that is required to grow enough biomass to meet current energy demands. The quantity of land required is so great that we cannot simultaneously meet our energy needs and grow enough food as well. The solutions, as we will see, range from producing more energy dense food, to growing plants that don't utilize the same resources as food crops, to using only left over biomass as feedstock.

Arriving at a Number

Calculating just how much land will be needed to grow a biofuel and how that will impact food crops is difficult. The difficulty doesn't actually lie in how much land will be needed, but rather in how using that land will impact both the food supply and carbon emissions. This section starts with looking at basic land quantities needed for various biofuels feedstock.

Land Area

The amount of land needed to supply fuel demands depends directly on the type of biomass used. The one thing that is clear in this regard is that corn and soybeans are never going to work. Here is why.

Crop

Fuel Output (gallons/acre/year)

Land area (acres/ sq mi) needed to meet total fuel demands of U.S.*

Soybean

40

3.36 billion/5.6 million

Corn

400

336 million/563,000

Sugarcane

800

168 million/263,000

Algae

4,000 - 6,000

34 - 22 million/53,000 - 34,000

*Based on U.S. usage of 368 million gallons per day of gasoline and diesel fuel (~134 billion gallons annually)

** Demand expected to reach 135 billion gallons

If the numbers above don't seem impressive to you, consider that that United States has a total land area of 3.7 million square miles. So, to grow enough soybeans to meet just the gas and diesel fuel demands of the U.S. would require land area equivalent to 1.5 times the size of the United States. Using corn would mean devoting 15% of the United States to growing fuel. This also accounts for 70% of all the corn grown in the world in a given year. Using algae, on the other hand, would require an area roughly between the sizes of the state of Arkansas or Maine.

Land Use Changes

The total amount of land used is not the only concern many scientists have over the large-scale use of biofuels. What is more concerning is what some have come to refer to as the “carbon debt.” This concept revolves around the idea that farming land on a large scale requires an input of energy and thus the production of greenhouse gases, particularly carbon dioxide. Because biofuels also produce carbon dioxide, the amount of energy put into the equation puts us at a net loss in the beginning. Then, because the land is being constantly farmed and energy is reinvested, the repayment of that debt is greatly impeded. In one estimate, converting all of the peatlands in Southeast Asia to palm oil used in the production of biodiesel would create carbon debt we would need 423 years to pay back. In other word, the change in land associated with growing biofuels would increase carbon output in the near term and worsen global warming.

The solution, at least in current thinking, is to look for a higher density feedstock, which is to say a feedstock that produces more energy for a given amount of area. One such solution is algae, as expressed above. Some experts believe that with advances in technology, algae could be producing as much as 15,000 gallons of fuel per acre.

Biodiversity

The last thing to consider with land use is biodiversity. The extent to which growing a single crop over a large tract of land affects the environment varies from region to region and from crop to crop. What is clear, however, is that the impacts can be profound. For instance, loss of biodiversity can lead to insects and other pests that are better adapted to destroying certain crops, like the one just planted. It can also lead to extinction, habitat loss, fragmentation, and more. In the end, biodiversity concerns may limit the use of biofuels, though the solution may simply be a matter of careful planning, selection of appropriate feedstock, and avoidance of monoculture.