Biofuel production is limited by the quantity of biomass on the planet. As we’ve demonstrated in our report Biofuel vs. Photovoltaics, there isn’t enough arable farmland on the planet for biofuel to even begin to replace crude oil. But what if farmland is not the only source for biofuel feedstock?
There are two primary categories of biofuel; bioethanol which is distilled from fermented plant sugars, and biodiesel which is refined from plant oils. Sugar cane is a good example of a bioethanol feedstock, and the African oil palm is a good example of a biodiesel feedstock. In most of these cases biofuel must come from an actual crop, usually from a crop that is also part of the human food chain.
What if biofuel could be extracted from crop waste after the food is harvested, or from grasses or from wood? An interesting report entitled “The World’s Most Productive Ethanol Plant” from The BioPact, a website that promotes economic cooperation between European and African nations to develop biofuel, describes the potential for extracting biofuel from plant fibers.
In this report, the author claims that one of the world’s best sources of biodiesel, the African oil palm, will yield bioethanol from its leaf and trunk fiber. Harvested and replaced on 25 year cycles, these trees grow so rapidly that their leaf and trunk fiber can potentially yield, on a yearly average, nearly twice as much ethanol as the same tree will yield each year in biodiesel oil!
As always, the devil is in the details. These so called “2nd generation ethanols” have to be produced from cellulose fiber, the actual material of plants, becoming “lignocellulosic ethanol.” The methods to extract ethanol from cellulose are not as energy-efficient or cost-efficient as the methods used to extract ethanol from crops. To find out more read “Extracting Ethanol From Cellulose” written by P.C. Badger in 2002.
As the report on the BioPact website states “In the world of second generation biofuels, total biomass yield is the single most important factor determining the final energy balance of those green fuels.” If we are to properly assess the potential of biofuel to replace crude oil, we need to consider not just yields of current biofuel crops, but the potential of all biomass on earth – from crop residue, or sustainably harvested forest biomass, or farmed algae, to name a few examples. With feedstock literally everywhere, and extraction methods still being rapidly developed and improved, it is unwise to underestimate the role biofuel may someday play in balancing energy supply with demand.