FARGO, N.D. — Amyris and Gevo are two of the highest-flying stocks in the biofuels sector in 2011. Each has posted spectacular gains since January. Both firms are intriguing because their emphasis is on the production of advanced biofuels.By: Cole Gustafson, Cole GustafsonFARGO, N.D. — Amyris and Gevo are two of the highest-flying stocks in the biofuels sector in 2011. Each has posted spectacular gains since January. Both firms are intriguing because their emphasis is on the production of advanced biofuels.Advanced biofuels reduce greenhouse gas emissions by at least 50 percent under the nation’s renewable fuel standard program. Amyris is unique in that it is focusing on the production of biodiesel using specialized yeast that utilizes sugarcane as its feedstock.First-generation biodiesels were derived from transesterification of agricultural oils, especially soybean and canola oils. More recently, corn oil obtained from additional fractionation of corn entering ethanol plants also has been used as a biodiesel feedstock.Not the sameProducing next-generation biodiesel or “renewable diesel” is a completely different process than the production of traditional biodiesel. Instead of relying on chemical catalysts, these new diesel fuels are produced from biohydrocarbons obtained from inedible plants, algae or waste streams and then processed into biodiesel using proprietary bacteria. This reduces the pressure on global food production and tailpipe emissions. Furthermore, they are designed to be “drop-in” true diesels that can be placed in a pipeline and used without any limitations on how much can be used.Minnesota, Hawaii, Oregon and Washington have state biodiesel blending requirements. Minnesota’s statute, which was enacted in 2005, has been waived several times because of biodiesel quality problems. However, the law is in effect again.Last year, Amyris announced that it had surpassed critical ASTM testing and received Environmental Protection Agency approval to raise its registered blend level of ultralow sulfur diesel from 20 to 35 percent, which is the highest blend rate approved for either ethanol or biodiesel.Gevo is constructing a plant in southern Minnesota to produce biobutanol from sugar beets. The common denominator between Amyris and Gevo is the use of sugar instead of cellulose. Sugar is abundant in many other crops, including sweet sorghum.Producing biodiesel from algae has garnered much public attention during the past couple of years. However, recent studies have questioned how ready the industry is for commercialization. For example, the Energy Biosciences Institute categorized the effort as a “nascent industry” that will require more substantial long-term research, development, demonstration and deployment.