We have reported on the state of cellulosic ethanol development, and the potential of cellulosic ethanol, in our recent feature entitled (not surprisingly) “Cellulosic Ethanol.” But if you take an interest in the future of biofuel, this is only half the story, if that. What about biofuel derived from algae? Despite the title of this post, it isn’t an either/or choice, and comparing the potential of algae versus cellulose as a biofuel feedstock is an interesting topic – both claim immense potential and neither are here yet. Will both of these biofuels end up in industrial scale production in the next few decades? Here are some comparisons:
(1) Algae can be converted into ethanol or diesel, depending on the process. Typically algae is associated with biodiesel, and cellulose is associated with ethanol.
(2) Cellulose has an extremely diverse array of potential feedstocks, but the quantity of many cellulosic feedstocks are significantly affected by seasonal variations. Algae, on the other hand, can be grown in ponds where conditions are precisely managed, or even in enclosed tanks.
(3) Cellulose feedstock, generally speaking, has a much larger geographic footprint than proposed algae designs – tinder harvesting from forests, vast plantings of winter cover crops, and extraction of agricultural waste, for example, require the cellulosic harvesting infrastructure to be more or less pervasive across the landscape – not necessarily in a bad way. Algae ponds, like dedicated cellulosic crops, are far more concentrated, promising fuel yields as high as 25,000 gallons per acre per year, or more – but these are very early projections. Algae grown in enclosed tanks have an even higher theoretical limit to their yield per acre, since they can build upwards.
(4) Both algae and ethanol can be grown utilizing waste streams. Algae ponds, or enclosures, can be nourished with CO2 from fossil fuel burning utility power stations, for example. Ethanol can be directly extracted from syngas or flue gas. Fossil fuel emissions can provide feedstock or nutrients for both algae and ethanol.
(5) Cellulosic feedstock for ethanol is available now, with the exception of dedicated crops that deliver some of the higher projected yields. But everything else; forest tinder, crop residue, municipal waste, etc., is already waiting for harvesting. Algae feedstock is not clearly ready – there have been successful experiments with regular algae, but most companies pursuing this technology are attempting to modify algae into strains that are more commercially exploitable.
(6) For both of these very promising feedstocks, algae and cellulose, we are going to wait a few more years before we’ll hopefully get a clear indication as to whether or not they truly emerge as major sources of transportation fuel.
Three very interesting companies working on algae to fuel technologies are Algenol, Greenfuel, and Sapphire Energy. Two companies working on interesting cellulosic ethanol technologies are Coskata and Mascoma. There are hundreds of companies currently pursuing algae and cellulose solutions to our energy challenges.