A new study shows that converting annual crops to perennial bioenergy crops can induce a cooling effect on the areas where they are cultivated.
“Cultivation area under bioenergy crops accounts for 3.8% ± 0.5% of the global total land area, but they exert strong regional biophysical effects, leading to a global net change in air temperature of −0.08 ~ +0.05 degrees Celsius. Researchers found that global air temperature decreases by 0.03~0.08 °C, with strong regional contrasts and inter-annual variability, after 50 years of large-scale bioenergy crop cultivation.” – Down to Earth.
Bioenergy crop cultivation can have biophysical or warming effects that can weaken or strengthen the effectiveness of bioenergy crop cultivation with carbon capture and storage in limiting the temperature rises, depending on the cultivation map and the bioenergy crop type.
“Compared to the herbaceous crops, changes in the energy fluxes induced by woody crops in the cultivation regions are larger, and the cooling effect is stronger and healthier across different cultivation maps”, said the study published in Nature Communications.
The researchers analyzed the biophysical climate effects of large-scale bioenergy crops to assess their role in climate mitigation.
The researchers simulated the biophysical climate impact of several future bioenergy crop cultivation scenarios. Eucalyptus, poplar, willow, miscanthus and switchgrass were the bioenergy crops used in the study.
After simulating four scenarios, the researchers saw warming effects in Alaska and northwestern Canada which may cause greenhouse gas release from thawing permafrost. Meanwhile, strong cooling effects in Eurasia may protect permafrost from thawing or reduce methane emissions from wetlands.
Additionally, the study showcased the impact of the crop type choice, the original land use type upon which bioenergy crop are expanded, the total cultivation area and its spatial distribution patterns.
Cultivating eucalypt shows superior cooling effects than if switchgrass is used as the main bioenergy crop. Cooling effects are more for eucalypt and the greatest warming effects are seen for switchgrass.
The study also concluded that “the biophysical effects of bioenergy crop cultivation do not only alter global temperature directly, but also induce secondary effects on natural greenhouse gas fluxes, which should also be taken into account when considering large-scale BECCS deployment”.