Efficiencies of Various Biofuel Crops
Popular choices for plant biofuels include: oil palm, soybean, castor oil, sunflower oil, safflower oil, corn ethanol, and sugar cane ethanol.
An analysis of a proposed Hawaiian oil palm plantation claimed to yield 600 gallons of biodiesel per acre per year. That comes to 2835 watts per acre or 0.7 W/m2. Typical insolation in Hawaii is around 5.5 kWh/(m2day) or 230 watts. For this particular oil palm plantation, if it delivered the claimed 600 gallons of biodiesel per acre per year, would be converting 0.3% of the incident solar energy to chemical fuel. Total photosynthetic efficiency would include more than just the biodiesel oil, so this 0.3% number is something of a lower bound.
Contrast this with a typical photo-voltaic installation, which would produce an average of roughly 22 W/m2 (roughly 10% of the average insolation), throughout the year. Most crop plants store ~0.25% to 0.5% of the sunlight in the product (corn kernels, potato starch, etc.), sugar cane is exceptional in several ways to yield peak storage efficiencies of ~8%.
Ethanol fuel in Brazil has a calculation that results in: "Per hectare per year, the biomass produced corresponds to 0.27 TJ. This is equivalent to 0.86 W/m2. Assuming an average insolation of 225 W/m2, the photosynthetic efficiency of sugar cane is 0.38%." Sucrose accounts for little more than 30% of the chemical energy stored in the mature plant; 35% is in the leaves and stem tips, which are left in the fields during harvest, and 35% are in the fibrous material (bagasse) left over from pressing.
Read more about this topic: Photosynthetic Efficiency
Famous quotes containing the word crops:
“She planted corn and left the rest
to elements, convinced that God
with giant faucets regulates the rain
and saves the crops from frost or foreign wind.”
—Richard Hugo (1923–1982)