World Resources Institute (WRI) has published a report that is likely to put the food vs. fuel issue back in play as the 114th Congress considers options to reform the Renewable Fuel Standard (RFS) program.
In Avoiding Bioenergy Competition for Food Crops and Land, authors Tim Searchinger (Princeton University) and Ralph Heimlich argue that “any dedicated use of land for growing bioenergy inherently comes at the cost of not using that land for growing food or animal feed, or for storing carbon.”
From the report’s key findings:
Dedicating crops and/or land to generating bioenergy makes it harder to sustainably feed the planet.
- The world needs to close a 70 percent “food gap” between crop calories available in 2006 and those needed in 2050. If crop-based biofuels were phased out by 2050, the food gap would shrink to 60 percent. But more ambitious biofuel targets—currently being pursued by large economies—could increase the gap to about 90 percent.
- Wider bioenergy targets—such as a goal for bioenergy to meet 20 percent of the world’s total energy demand by 2050—would require humanity to at least double the world’s annual harvest of plant material in all its forms. Those increases would have to come on top of the already large increases needed to meet growing food and timber needs. Therefore, the quest for bioenergy at a meaningful scale is both unrealistic and unsustainable.
Figure 4 from the report makes the latter point — that biomass cannot supply more than a small fraction of global energy without courting disaster — stunningly clear:
Another key finding explains why.
Bioenergy is an inefficient use of land to generate energy.
- Fast-growing sugarcane on highly fertile land in the tropics converts only around 0.5 percent of solar radiation into sugar, and only around 0.2 percent ultimately into ethanol. For maize ethanol grown in Iowa, the figures are around 0.3 percent into biomass and 0.15 percent into ethanol. Such low conversion efficiencies explain why it takes a large amount of productive land to yield a small amount of bioenergy, and why bioenergy can so greatly increase global competition for land.
WRI being a maintstream green group, the report unsurprisingly touts solar energy as a superior alternative to bioenergy:
- Solar photovoltaic (PV) systems’ conversion efficiency—and therefore their land-use efficiency—is much higher. On three-quarters of the world’s land, PV systems today can generate more than 100 times the useable energy per hectare than bioenergy is likely to produce in the future even using optimistic assumptions.
However, PV systems are inferior to ‘conventional’ (nuclear and fossil) energy in several respects, including land intensity. According to Ghenai and Janajreh (2013), a study published last year in the International Journal of Thermal and Environmental Engineering:
. . . the solar power system has the highest capital intensity compared to all power systems as it requires more capital and energy to construct the same nominal generating capacity; the system efficiency of solar power is only 10% to 18% compared to 30-50% for conventional and nuclear power systems; and the capacity factor for solar power is as low as 10% compared to 80% for conventional power system.
The chart below from the study shows that while the area (land) intensity of solar power is lower than that of biomass, the area intensities of nuclear and fossil power systems are lower still.