This blog post was originally published in The Guardian on January 29, 2015.
Powering cars with corn and burning wood to make electricity might seem like a way to lessen dependence on fossil fuels and help solve the climate crisis. But although some forms of bioenergy can play a helpful role, dedicating land specifically for generating bioenergy is unwise. It uses land needed for food production and carbon storage, it requires large areas to generate just a small amount of fuel, and it won’t typically cut greenhouse gas emissions.
First, dedicating areas to bioenergy production increases competition for land.
Roughly three-quarters of the world’s vegetated land is already being used to meet people’s need for food and forest products, and that demand is expected to rise by 70 percent or more by 2050. Much of the rest contains natural ecosystems that keep climate-warming carbon out of the atmosphere, protect freshwater supplies, and preserve biodiversity.
Because land and the plants growing on it are already generating these benefits, diverting land—even degraded, under-utilised areas—to bioenergy means sacrificing much-needed food, timber, and carbon storage.
Second, bioenergy production is an inefficient use of land.
While photosynthesis may do a great job of converting the sun’s rays into food, it is an inefficient way to turn solar radiation into non-food energy that people can use. Thus, it takes a lot of land (and water) to yield a small amount of fuel from plants. In a new working paper, WRI calculates that providing just 10 percent of the world’s liquid transportation fuel in the year 2050 would require nearly 30 percent of all the energy in a year’s worth of crops the world produces today.
The push for bioenergy extends beyond transportation fuels to the harvest of trees and other sources of biomass for electricity and heat generation. Some research suggests that bioenergy could meet 20 percent of the world’s total annual energy demand by 2050. Yet doing so would require an amount of plants equal to all the world’s current crop harvests, plant residues, timber, and grass consumed by livestock–a true non-starter.
Third, bioenergy that makes dedicated use of land does not generally cut greenhouse gas emissions.
Burning biomass, whether directly as wood or in the form of ethanol or biodiesel, emits carbon dioxide just like burning fossil fuels. In fact, burning biomass directly emits a bit more carbon dioxide than fossil fuels for the same amount of generated energy. But most calculations claiming that bioenergy reduces greenhouse gas emissions relative to burning fossil fuels do not include the carbon dioxide released when biomass is burned. They exclude it based on the assumption that this release of carbon dioxide is matched and implicitly offset by the carbon dioxide absorbed by the plants growing the biomass.
Yet if those plants were going to grow anyway, simply diverting them to bioenergy does not remove any additional carbon from the atmosphere and therefore does not offset the emissions from burning that biomass. Furthermore, when natural forests are felled to generate bioenergy or to replace the farm fields that were diverted to growing biofuels, greenhouse gas emissions go up.
That said, some forms of bioenergy do not increase competition with food or land, and using them instead of fossil fuels could reduce greenhouse gas emissions. One example is biomass grown in excess of what would have grown without the demand for bioenergy, such as winter cover crops for energy. Others include timber processing wastes, urban waste wood, landfill methane, and modest amounts of agriculture residues.
Using so-called second-generation technologies to convert material such as crop residues into bioenergy has a role to play and avoids competition for land. A challenge will be to do this at scale, since most of these residues are already used for animal feed or needed for soil fertility, and others are expensive to harvest.
There are good alternatives to bioenergy made from dedicated land. For example, solar photovoltaic (PV) cells convert sunlight directly into energy that people can use, much like bioenergy, but with greater efficiency and less water use. On three-quarters of the world’s land, solar PV systems today can generate more than 100 times the usable energy per hectare as bioenergy. Because electric motors can be two to three times more efficient than internal combustion engines, solar PV can result in 200 to 300 times as much usable energy per hectare for vehicle transport compared to bioenergy.
One of the great challenges of our generation is how the world can sustainably feed a population expected to reach 9.6 billion by 2050. Using crops or land for biofuels competes with food production, making this goal even more difficult.
The world’s land is a finite resource. As Earth becomes more crowded, fertile land and the plants it supports become ever more valuable for food, timber and carbon storage—things for which we don’t have an alternative source.