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Patent Picks: Biofuels

A look at recent patenting activity in biofuels for transportation, brought to you by C&EN and CAS

February 24, 2014 | A version of this story appeared in Volume 92, Issue 8


Credit: CAplus
Commercial interest in biofuels has spiked in recent years, as evidenced by CAS patent data. SOURCE: CAplus
Image of a bar graph showing biofeuls.
Credit: CAplus
Commercial interest in biofuels has spiked in recent years, as evidenced by CAS patent data. SOURCE: CAplus

Beginning in 2005, the federal government mandated that transportation fuels sold in the U.S. contain renewable fuels, typically ethanol added to gasoline or biodiesel blended with petroleum. So it’s perhaps not surprising that data from Chemical Abstracts Service databases indicate that research and commercialization of biofuels have been heating up in recent years. The data demonstrate that interest has already shifted from first-generation biofuels—such as biodiesel or ethanol produced from the sugar or starch of food crops—to the next wave, including cellulosic ethanol (produced from crop residues and dedicated biomass crops), biobutanol, and algae-based biofuels. Evidence of that shift is highlighted here.


;The basic processes for converting cellulosic biomass to transportation fuels are already in widespread commercial use. Conversion typically starts with a pretreatment step, which makes cellulose from biomass feedstocks more accessible to enzymatic breakdown. Various enzymes then hydrolyze the cellulose into its component sugars, and microbes turn those sugars into fuels such as ethanol. Patenting in these areas frequently focuses on process improvements. A 2013 patent application (WO 2013083816) filed by researchers at Shell Oil provides an example. In this case, the emphasis is on the pretreatment stage. Shell researchers used tertiary polyamide additives such as polyvinyl pyrrolidones and poly(alkyl oxazolines) to enhance the breakdown of cellulosic biomass into its component sugars. In one example from this patent, the researchers ground up and homogenized wheat straw with and without a polyvinylpyrrolidone additive. They then used enzymes to hydrolyze washed and unwashed samples of this mixture. They measured the extent of hydrolysis by looking at the amount of glucose produced. The researchers found that the additive improved cellulose conversion by about 50%. Interestingly, they saw improvements in both the washed and unwashed samples. Because washing might be expected to remove the water-soluble pyrrolidones, the results suggest that the additive might be interacting directly with the biomass in some way.


This is a photo of Unitel’s hydrolysis reactor.
Credit: Unitel Technologies
Unitel’s hydrolysis reactor could reduce the energy required to make biofuels from algae.

Another area of active R&D interest involves using algae as a feedstock for biofuels. Compared with other feedstocks, algae contain more biofuel lipid precursors per unit area, grow faster, and can be harvested quicker. Scientists are eager to reduce the amount of energy it takes to extract these lipids from the algae. This process typically involves removing the water from the algae, then extracting the lipids. A 2013 patent application from Unitel Technologies (U.S. Patent Application No. 20130287917) describes a process that bypasses these two energy-intensive steps. The researchers use a specialized hydrolysis reactor to make fatty acids directly from a slurry of water and cultivated algae. The process converts the algal lipids to their component fatty acids, which can be used to manufacture biofuels and other products. The researchers suggest that the water stream containing the lipids’ glycerol backbone can be recycled to promote phytoplankton growth and the remaining algal biomass can potentially be used as an ingredient in animal feed.


This graphic shows the relationship between bauxite, alumina, red mud, and aluminum.

Blending ethanol into gasoline oxygenates the fuel, reduces pollution, and stretches petroleum supplies. But biobutanol appears to many an even more attractive alternative. Biobutanol’s advantages over ethanol include its higher energy content and its compatibility with existing vehicles and refueling infrastructure. These benefits are driving increased patenting of ways to ramp up the fuel’s production from nonpetroleum sources. One common strategy is to engineer microbes to produce the fuel. But such strategies face a common challenge: The butanol product is often toxic to the microbe. BP Biofuels recently reported an approach for skirting this problem. In its world patent application (WO 2012004572), the firm describes how various ruthenium phosphine catalysts can convert ethanol to butanol. Selectivity and conversion rates are high, on the order of 20%. The patent shows that it doesn’t matter if the ethanol starting material comes from a petrochemical or biological source. That means the technology could be applied at existing cellulosic ethanol facilities.

Patent Picks is a collaborative effort by C&EN and CAS. This feature reports on trends CAS scientists observe from patents in the CAS databases, which now generate more than 70% of the new substances appearing in the literature.


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