Scientists advance search for cheap, clean energy

• Create crude oil from algae in minutes

• New, inexpensive production materials boost promise of hydrogen fuel

• Make fine diesel fuel from plastic shopping bags 

• Oil eating microbes dominate deep sandstone formations

SCIENTISTS have made major breakthroughs in the search for cheap, alternative and environmental-friendly energy sources with: creation of crude oil from algae in minutes; discovery of new, inexpensive production materials for hydrogen fuel; making of fine diesel fuel from plastic shopping bags; and the discovery that oil eating microbes dominate deep sandstone formations.

    Generating electricity is not the only way to turn sunlight into energy one can use on demand. The sun can also drive reactions to create chemical fuels, such as hydrogen, that can in turn power cars, trucks and trains.

      The trouble with solar fuel production is the cost of producing the sun-capturing semiconductors and the catalysts to generate fuel. The most efficient materials are far too expensive to produce fuel at a price that can compete with gasoline.

       But researchers in a study published last week in the journal Science, combined cheap, oxide-based materials to split water into hydrogen and oxygen gases using solar energy with a solar-to-hydrogen conversion efficiency of 1.7 percent, the highest reported for any oxide-based photoelectrode system.

     A chemistry professor at the University of Wisconsin–Madison, United States, Kyoung-Shin Choi, created solar cells from bismuth vanadate using electrodeposition- the same process employed to make gold-plated jewelry or surface-coat car bodies- to boost the compound’s surface area to a remarkable 32 square meters for each gram.

      Bismuth vanadate needs a hand in speeding the reaction that produces fuel, and that’s where the paired catalysts come in.

      Choi created solar cells from bismuth vanadate using electrodeposition- the same process employed to make gold-plated jewelry or surface-coat car bodies- to boost the compound’s surface area to a remarkable 32 square meters for each gram.

    Bismuth vanadate needs a hand in speeding the reaction that produces fuel, and that’s where the paired catalysts come in.

    While there are many research groups working on the development of photoelectric semiconductors, and many working on the development of water-splitting catalysts, according to Choi, the semiconductor-catalyst junction gets relatively little attention.

      Also, researchers report that plastic shopping bags, an abundant source of litter on land and at sea, can be converted into diesel, natural gas and other useful petroleum products.

       The conversion produces significantly more energy than it requires and results in transportation fuels – diesel, for example – that can be blended with existing ultra-low-sulfur diesels and biodiesels. Other products, such as natural gas, naphtha (a solvent), gasoline, waxes and lubricating oils such as engine oil and hydraulic oil also can be obtained from shopping bags.

        A report of the new study appears in the journal Fuel Processing Technology.

       There are other advantages to the approach, which involves heating the bags in an oxygen-free chamber, a process called pyrolysis, said Brajendra Kumar Sharma, a senior research scientist at the Illinois Sustainable Technology Center who led the research. The ISTC is a division of the Prairie Research Institute at the University of Illinois.

      Meanwhile, engineers have created a continuous chemical process that produces useful crude oil minutes after they pour in harvested algae- a verdant green paste with the consistency of pea soup.  

       The research by engineers at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) was reported recently in the journal Algal Research. 

         A biofuels company, Utah-based Genifuel Corporation, United States, has licensed the technology and is working with an industrial partner to build a pilot plant using the technology.

       In the PNNL process, a slurry of wet algae is pumped into the front end of a chemical reactor. Once the system is up and running, out comes crude oil in less than an hour, along with water and a byproduct stream of material containing phosphorus that can be recycled to grow more algae.

       With additional conventional refining, the crude algae oil is converted into aviation fuel, gasoline or diesel fuel. And the waste-water is processed further, yielding burnable gas and substances like potassium and nitrogen, which, along with the cleansed water, can also be recycled to grow more algae.

       Also, a Duke research team has developed a better recipe for synthetic replacement cartilage in joints. Combining two innovative technologies they each helped develop, lead authors Farshid Guilak, a professor of orthopedic surgery and biomedical engineering, and Xuanhe Zhao, assistant professor of mechanical engineering and materials science, found a way to create artificial replacement tissue that mimics both the strength and suppleness of native cartilage. Their results appear December 17 in the journal Advanced Functional Materials.

       Articular cartilage is the tissue on the ends of bones where they meet at joints in the body — including in the knees, shoulders and hips. It can erode over time or be damaged by injury or overuse, causing pain and lack of mobility. While replacing the tissue could bring relief to millions, replicating the properties of native cartilage - which is strong and load-bearing, yet smooth and cushiony - has proven a challenge.

          Also, halomonas are a hardy breed of bacteria. They can withstand heat, high salinity, low oxygen, utter darkness and pressures that would kill most other organisms. These traits enable these microbes to eke out a living in deep sandstone formations that also happen to be useful for hydrocarbon extraction and carbon sequestration, researchers report in a new study. 

       The analysis, the first unobstructed view of the microbial life of sandstone formations more than a mile below the surface, appears in the journal Environmental Microbiology.

         Meanwhile, while algae have long been considered a potential source of biofuel, and several companies have produced algae-based fuels on a research scale, the fuel is projected to be expensive. The PNNL technology harnesses algae’s energy potential efficiently and incorporates a number of methods to reduce the cost of producing algae fuel.

            PNNL scientists and engineers simplified the production of crude oil from algae by combining several chemical steps into one continuous process. The most important cost-saving step is that the process works with wet algae. Most current processes require the algae to be dried- a process that takes a lot of energy and is expensive. The new process works with an algae slurry that contains as much as 80 to 90 percent water.

             While a few other groups have tested similar processes to create biofuel from wet algae, most of that work is done one batch at a time. The PNNL system runs continuously, processing about 1.5 liters of algae slurry in the research reactor per hour. While that doesn’t seem like much, it’s much closer to the type of continuous system required for large-scale commercial production.

       The PNNL system also eliminates another step required in today’s most common algae-processing method: the need for complex processing with solvents like hexane to extract the energy-rich oils from the rest of the algae. Instead, the PNNL team works with the whole algae, subjecting it to very hot water under high pressure to tear apart the substance, converting most of the biomass into liquid and gas fuels.

       The system runs at around 350 degrees Celsius (662 degrees Fahrenheit) at a pressure of around 3,000 PSI, combining processes known as hydrothermal liquefaction and catalytic hydrothermal gasification. Elliott says such a high-pressure system is not easy or cheap to build, which is one drawback to the technology, though the cost savings on the back end more than makes up for the investment.

             The products of the process are:

• Crude oil, which can be converted to aviation fuel, gasoline or diesel fuel. In the team’s experiments, generally more than 50 percent of the algae’s carbon is converted to energy in crude oil — sometimes as much as 70 percent.

• Clean water, which can be re-used to grow more algae.

• Fuel gas, which can be burned to make electricity or cleaned to make natural gas for vehicle fuel in the form of compressed natural gas.

• Nutrients such as nitrogen, phosphorus, and potassium — the key nutrients for growing algae.

        An analysis of the microbes’ metabolism found that these bacteria are able to utilize iron and nitrogen from their surroundings and recycle scarce nutrients to meet their metabolic needs. (Another member of the same group, Halomonas titanicae, is so named because it is consuming the iron superstructure of the Titanic.)

     Perhaps most importantly, the team found that the microbes living in the deep sandstone deposits of the Illinois Basin were capable of metabolizing aromatic compounds, a common component of petroleum.