North Carolina State University researchers have developed a relatively inexpensive technique for removing lignin from the plant material used to make biofuels, which they say may drive down the cost of biofuel production.
Lignin is difficult to break down or remove from plant biomass, such as the non-edible parts of the corn plant. However, that lignin needs to be extracted in order to reach the energy-rich cellulose that is used to make biofuels.
Finding inexpensive ways to remove lignin is “one of the largest barriers to producing cost-effective biofuels,” says Ezinne Achinivu, lead author of a study describing the new technique, which is published in the current issue of Green Chemistry.
The researchers began by making a number of liquid salts called protic ionic liquids (PILs). These PILs are inexpensive to prepare because they are made by mixing together an acid, such as acetic acid (vinegar), and a base. As part of the pretreatment process, one of the PILs is mixed with biomass and then heated and stirred. The lignin dissolves into the PIL, leaving the cellulose behind as a solid. The cellulose, which is now much easier to process, is then easily filtered from the mixture for use in the next biofuel production steps.
The remaining PIL-lignin liquid mixture can then be heated to distill the PIL, leaving the lignin behind as a black powder. The vapors from the PIL are collected and cooled to recover the liquid PIL so that it can be re-used. The lignin is also valuable, because it can be used to manufacture polymers or other chemical products, which researchers say could supplement the cost of running the biofuel production facility.
The US produced 132 million gallons of biodiesel in October, a record amount that is 75 percent more than the same month in 2012, according to the latest data released by the US Energy Information Administration.