Tag Archives: biofeedstocks

No more butts: biodegradable filters a step to boot litter problem.

 

Robertson, R, W Thomas, J Suthar and D Brown. 2012.  Accelerated degradation of cellulose acetate cigarette filters using controlled-release acid catalysis. Green Chemistry http://ds.doil.org/10.1039/C2GC16635F.

 


Synopsis by Marty Mulvihill and Wendy Hessler, Aug 14, 2012

Context

Every year over 6 trillion cigarettes are manufactured globally. Approximately 99 percent have a filter tip. After the cigarette is smoked, the used filter is called a butt and is thrown out. When littered, cigarette butts often take years to break down.

Most filters are made using cellulose acetate fibers. More than 2 billion pounds of cellulose acetate is produced every year to meet the world demand for filters. To make it, acetic anhydride is added to cellulose fibers made from wood or cotton. The reaction creates a type of plastic that provides a stronger, more rigid filter.

By itself, cellulose fibers degrade naturally in the environment. Cellulose acetate plastic degrades very slowly.

The slow degradation, along with indoor smoking bans, mean increasingly large numbers of cigarette butts are found in public places, including parking lots, parks and beaches every year. Cigarette waste is the number one reported item collected during beach clean-ups, according to the Ocean Conservancy. In some coastal towns as many as 1 in 10 cigarette butts end up polluting the waterways.

The discarded butts are more than just an eyesore. The filters contain chemical residue from the tobacco. The residue can be toxic to marine animals. Cigarette butts are commonly found in the stomachs of dead shore birds.

One way to decrease the litter would be to create cigarette filters that degrade quickly. Previous attempts used plant-based products like cornstarch, hemp, flax or cotton. One brand of biodegradable filter, Greenbutts, incorporates plant seeds that would germinate after disposal. To date, cigarette manufacturers have not widely adopted alternative filters.

The demand for degradable filters may increase as states – including New York – consider levying taxes on non-biodegradable cigarette filters. In response, there is renewed interest to make cigarette filters degrade faster.

What did they do?

A group of chemists wondered if a cellulose acetate plastic filter could be converted back into natural, degradable cellulose after it was used. If so, the cigarette butts should degrade much more quickly.

They guessed that small amounts of acid added to the filter should speed the degradation process.

First, they measured the degradation rate of cellulose acetate using a wide range of acids with different strengths. Combinations of acids were also tested to find which worked best to make cigarette filters that retained their structure and function while degrading faster.

Next, they created an effective additive based on which acids worked best. The additive needed to be acidic, non-toxic and allow the cigarette to burn normally. To find one, they looked to acids common in food, including citric acid, phytic acid and vitamin C (ascorbic acid), as well as stronger mineral acids not commonly considered safe food additives.

The new filter design was tested. A smoking machine “smoked” the cigarettes, and the butts were left outside and monitored.

What did they find?

In the first tests, the butts exposed to water and a small amount of acid broke down faster than those not exposed to acid. Strong acids worked best to efficiently speed the degradation of the cellulose acetate fibers. In particular they found that sulfuric acid was the most effective catalyst.

Sulfuric acid, however, is not safe to put into cigarette filters. The researchers devised a way to generate the stronger acid only after the cigarette was smoked. The smoker would not be exposed to any additional harmful compounds, and the filter would degrade more quickly.

To make the acid additive, the researchers combined safer chemicals – cellulose sulfate, citric acid and phytic acid – into a tablet. When the tablet got wet, these ingredients mixed and released small amounts of sulfuric acid that degraded the filter material. The tablets were coated with ethyl cellulose and cellulose acetate to shield the acid precursors from premature exposure to water.

After 14 days outside, the butts containing the acid tablet were more acidic and tested positive for the presence of sulfuric acid, while the control butts remained unchanged. At the end of the 90-day trial, the new filters were considerably more degraded than the controls. Unfortunately they had not degraded as much as expected based on the laboratory experiments.

What does it mean?

Small amounts of strong acid increase the degradation rate of the cellulose acetate fibers found in cigarette butts. Although the idea worked in principle, the outside trials did not live up to the promise of the laboratory results.

The research is important because it is a step towards making a truly degradable and functional cigarette filter. This research shows how green chemistry can improve existing technology. The researchers designed the new filters for degradation while making safer chemical choices. This approach will ultimately minimize waste and hopefully prevent some of the toxic exposures to birds and other wildlife.

Under laboratory conditions, the acid converted the filter plastic into a biodegradable material within 30 to 60 days, depending on temperature. The food grade acids and materials generated the strong acid only after the cigarette had been smoked. These preliminary results indicate that acidic additive in the filter could reduce the time it takes for cigarette butts to degrade in the environment.

Several problems will need to be resolved before large manufacturers could adopt the use of acid tablets in cigarette filters. The filter’s effectiveness – improved degradation and materials safety of materials – will need to be quantified in clinical and environmental trials. This will take more research to design and incorporate the acid precursors into the filter body.

Cost and performance are also issues. The acid materials must be incorporated into cigarettes at a low cost without harming the performance of the product.

Researchers will llkely pursue this technology as well as other approaches to a biodegradable cigarette filter in an effort to reduce cigarette butt litter.

Resources

Clean Virginia Waterways and Longwood University. 2012. Cigarette butt litter. http://www.longwood.edu/cleanva/cigarettelitterhome.html.

Novotny, T, K Lum, E Smith, V Wang, and R Barnes. 2009. Cigarettes butts and the case for an environmental policy on hazardous cigarette waste. International Journal of Environmental Research and Public Health http://dx.doi.org/10.3390/ijerph6051691.

Ocean Conservancy. A rising tide of ocean debris, International Coastal Clean-up 2009 Report. http://www.oceanconservancy.org/pdf/A_Rising_Tide_full_lowres.pdf.

Register, K. 2000. Cigarette butts as litter: Toxic as well as ugly. Underwater Naturalist: Bulletin of the American Littoral Society http://www.longwood.edu/CLEANVA/ciglitterarticle.htm.

Leather trash turns to medical treasure.

Synopsis by Wim Thielemans and Audrey Moores, Apr 20, 2012

Catalina, M, J Cot, AM Balu, JC Serrano-Ruiz and R Luque. 2011. Tailor-made biopolymers from leather waste valorisation. Green chemistry http://dx.doi.org/10.1039/c2gc16330f.

A versatile and potentially valuable natural material could be easily collected from the abundant waste produced when leather is made from animal hides, according to researchers from Spain who explain their novel process in the journal Green Chemistry.

Leather processing generates large amounts of remnant hides that are generally thrown away. But this solid waste is rich in a valuable and medically useful protein called collagen. This new method to recycle or reuse the waste alleviates the dumping, produces a necessary product and increases sustainable manufacturing.

Collagen is abundant in mammals and is an important part of muscle, tendons, ligaments, skin, guts, vessels and bone. The resilient, soft and flexible material does not trigger immune reactions, making it a rich resource for medical, cosmetics and veterinary applications. Collagen is used for implants, as sutures and in regenerative medicine – a field of medicine that grows new human cells, tissues or organs for transplant.

The researchers tested different extraction scenarios for their effect on the amount and quality of the collagen. They extracted the protein from two different types of processed cowhides to demonstrate the versatility of the technique.

The hides were cut, treated with acid and ground into a water solution. This process allowed the collagen molecules to dissolve in water. The collagen particles ranged in size from a few nanometers to a few dozen nanometers. Because size matters for collagen applications, the particles were filtered and separated according to their size.

To find the best method, they varied a number of factors, such as temperature, leather pieces, size after grinding, the nature of the acid, stir speed and type of water solution. The optimal results for yield came from an extraction using acetic acid – basically vinegar – for 24 hours at 25oC and a smaller particle size after grinding.

Next, they manipulated the extracted collagen molecules to determine their stability and mechanical properties. In fact, the use of collagen from leather is often limited because of the poor mechanical properties of the recovered collagen. Specifically, collagen must be rigid enough while not swelling too much when exposed to water. Here the researchers found a simple chemical treatment to render the collagen firm and stable.

From this method, they made several different kinds of materials – fibers, sponges, films, threads and gels – with rigidity and swelling in water properties necessary for biomedical applications.

The research is a good example of finding new ways to use a waste material for high value applications. More work will need to be done to compare the properties of these materials with commercial collagens. The next step will be to show the collagen source is reliable and free of contamination.

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Based on a work at www.environmentalhealthnews.org.

Chemists build a better biodiesel process.

Thitsartarn, W, and S Kawi. 2011. An active and stable CaO-CeO2 catalyst for transesterification of oil to biodieselGreen Chemistry http://dx.doi.org/10.1039/c1gc15596b.

Synopsis by Wim Thielemans, Dec 20, 2011

Scientists in Singapore develop a new chemical catalyst with fewer drawbacks than current versions to help make biodiesel production more attractive and sustainable.

A modified version of a well-known but inefficient chemical catalyst can propel faster, cleaner reactions that turn plants into diesel fuel better than existing methods.The new calcium-based catalyst is more reactive, stable and easier to recover from the final product, the Singapore researchers report in the journal Green Chemistry. While the catalyst may solve a major stumbling block in the effort to produce biodiesel, the process will need more testing in industrial settings.

Biodiesel production is gaining in importance as petroleum supplies become more limited and concern about climate change grows. Biodiesel can be used in unmodified diesel engines. Its use results in near-zero carbon dioxide emissions, if estimates consider plant growth, which extracts carbon dioxide from the atmosphere.

Biodiesel is generally produced from plant oils. Plant oils are star-like molecules with three arms. To turn the plant oil into biodiesel, the three arms need to be removed from the center. The separated arms then form the biodiesel.

Unfortunately, this transformation does not happen readily without chemical help. Chemists must use other molecules, called catalysts, to speed up this reaction.

Current catalysts make the reaction go faster, but they have various drawbacks that hamper their use on the large scale of a commercial biodiesel process. These drawbacks include: large amounts of catalyst may be needed; high temperatures are necessary to propel the reactions; the catalyst may be less stable if it is used for a longer time; it can be difficult to remove the catalyst from the final product; and the solid catalysts may be slow to dissolve into the biodiesel product.

Calcium-based catalysts – which are cheap and abundant – can break up the star-like plant oils. Unfortunately, they dissolve into the biodiesel and removing them generates large amounts of wastewater.

To solve this problem, researchers from Singapore made a new and very reactive calcium-based catalyst with high stability. The catalyst was formed from a solution containing calcium and cerium – a metal found in a number of minerals. By making the solution less acidic, the catalyst precipitates out and is recovered by filtering and drying.

The ratio of calcium and cerium was varied to see which combination would give the best catalyst performance. Cerium alone does not work very well.

The best catalyst found could be reused up to 18 times with more than 90 percent of plant oils separated into their arms. Very low amounts of the catalyst dissolved into the biodiesel.

This work is certainly promising as it may make biodiesel production more sustainable and cheaper. Of course, the catalyst will need to be tested in an industrial process. Read more science at Environmental Health News.

 

Brewing bioethanol in a single pot.

Synopsis by Wim Thielemans, Nov 01, 2011

Nakashima, K, K Yamaguchi, N Taniguchi, S Arai, R Yamada, S Katahira, N Ishida, C Ogino and A Kondo. 2011. Direct bioethanol production from cellulose by the combination of cellulase-displaying yeast and ionic liquid pretreatment. Green Chemistry http://dx.doi.org/10.1039/c1gc15688h.

An innovative process promises to produce bioethanol from plants in one step instead of three, but finding an easy way to purify the needed plant cellulose hinders its usefulness.

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A more efficient way to produce biofuels from plants is possible by pretreating the woody material with a liquid salt before fermentation, report researchers in Japan who perfected the process in the lab. Yet, coming up with the usable, purified cellulose remains a big hurdle to the industry.

This experimental method is unique because it pairs an enzyme-yeast unit with ionic liquids to convert the plants into the liquid fuel known as bioethanol. The successful trial yielded 90 percent ethanol and 82 percent of the ionic liquid was recovered.

The one-step, one-container procedure is outlined in the journal Green Chemistry.

Cellulose is the most abundant renewable material available. Plants, algae and some bacteria produce in excess of 100 billion metric tons per year. The non-food material is an agricultural waste material. The ability to turn the unwanted cellulose into liquid fuel would be an important step toward reducing dependence on crude oil without using food crops.

It takes three steps to convert cellulose into the liquid fuel bioethanol. Step one treats cellulose and turns its rigid and ordered structure into more chemically accessible pieces. In step two, enzymes further break down cellulose into glucose, a sugar. Then, in step three, microorganisms such as yeast ferment the glucose to ethanol.

The new process takes a different approach. The cellulose is broken down with ionic liquids (step 1) then converted into ethanol (steps 2 and 3) with a yeast-enzyme pairing – all in a single pot.

This is a remarkable step forward because the enzyme, yeast and ionic liquid are together but don’t interfere with one another.

Ionic liquids are salts – a designation for chemicals made up of both a positively and a negatively charged component – that are liquid at low temperatures, unlike common salts such as kitchen salt. Bulky positive and negative groups that make up the ionic salts hinder their packing into a solid crystal. Thus, they stay liquid to much lower temperatures – even room temperature. Some ionic liquids have been shown to be good solvents for cellulose, which is otherwise very difficult to dissolve.

In this study, the authors attached cellulase – an enzyme that breaks down cellulose – to the outside of the yeast. By itself, this yeast-cellulase combination is not very effective at tearing apart the rigid and inaccessible cellulose structure. But, a winning recipe was found by combining a small amount of specific ionic liquids with the cellulase-yeast. The ionic liquid disrupts cellulose enough so that ethanol can be produced directly and efficiently from the pieces of cellulose.

This work shows some real promise, but as the authors point out, most cellulose is not pure. To turn biomass directly into bioethanol, this new one-pot process will need to either extract cellulose efficiently or convert the other natural materials that coexist with cellulose in the plants. Read more science at Environmental Health News.

 

Shortcut converts common cellulose into useable parts.

Synopsis by Wim Thielemans, Sep 23, 2011

Long, J, B Guo, X Li, Y Jiang, F Wang, SC Tsang, L Wang and KMK Yu. 2011. One step catalytic conversion of cellulose to sustainable chemicals utilizing cooperative ionic liquid pairs. Green Chemistry http://dx.doi.org/10.1039/c1gc15597k.

A new one-step process blends a pair of specially selected solvents with cellulose, overcoming a big hurdle in the race to use the plant-based material as a reliable source of chemicals and fuels.

Pairing up a unique blend of specialized chemical solvents with plant cellulose has solved a looming problem for chemists grappling to find an efficient method to break apart naturally abundant cellulose.

The one-step process uses two ionic liquids to break cellulose down into its smaller chemical pieces and convert these pieces into useful chemicals. This is an important feat since cellulose is targeted as an alternative source for the chemicals and fuels currently derived from fossil fuels.

The results show for the first time that combinations of ionic liquids can be very useful in guiding more efficient chemical reactions that create less waste and more product. The findings are interesting because they show it is possible to combine several processing steps just by choosing the correct mixture of solvents.

Cellulose is a major part of plant cells and is the most abundant renewable material on Earth. Every year, plants, algae and some bacteria produce in excess of an estimated 100 billion metric tons. Cellulose is not a food and is a waste product of agriculture.

An enormous research effort is underway to understand how to use cellulose as a starting material for biofuel and chemical production in order to replace crude oil. In this process, cellulose – a long chain of identical chemical units – needs to be separated into the individual units.

The key challenge to convert cellulose into chemicals is its poor solubility – that is, it does not break up easily in liquids. Chemical reactions, though, require close contact between all the parts to work well. In 2002, researchers reported that some ionic liquids were very good at dissolving cellulose.

Ionic liquids are salts – a designation for chemicals made up of both a positively and a negatively charged component– that are liquid at low temperatures, unlike common salts such as table salt. Bulky positive and negative groups that make up the ionic salts hinder their packing into a solid crystal. Thus, they stay liquid to much lower temperatures – even room temperature.

In this work, Chinese researchers used a mixture of two ionic liquids. The first was chosen to dissolve cellulose. The second was chosen because it increases cellulose breakdown into its individual units, and further, into useful chemicals.

Under the right conditions, all the cellulose was broken down. The reaction products were also removed from the ionic liquid mixture by simply adding an insoluble solvent such as methanol or hexane. While there were a variety of different reaction products, up to 48.5 percent of the cellulose could be converted to a single product: 2-(diethoxymethyl)furan. This chemical, in turn, can be easily converted into a variety of other products useful for the chemical and pharmaceutical industries.

The choice of the solvent to extract the reaction products from the ionic liquid also allows researchers to select the reaction products that are recovered.

The ionic liquid mixtures were also reused. No real difference in performance and composition was noticed over 10 repeated reactions.

The researchers chose to dissolve cellulose first followed by a reaction to convert cellulose into smaller, more useful products. However, the results suggest the system is versatile and – depending on which ionic liquids are selected – could be extended to several reactions in a row. Ionic liquids will certainly hold some surprises in the future.

Read more science at Environmental Health News.

 

Sustainable method naturally divides wood’s parts.

Synopsis by Wim Thielemans and Wendy Hessler, Jul 22, 2011

vom Stein,T, PM Grande, H Kayser, F Sibilla, W Leitner and P Domınguez de Marıa. 2011. From biomass to feedstock: one-step fractionation of lignocellulose components by the selective organic acid-catalyzed depolymerization of hemicellulose in a biphasic system. Green Chemistry http://dx.doi.org/10.1039/c1gc00002k.

 


2011-0717poplartrees
timabbott/flickr

A single-step process using only natural materials may transform the way lignocellulosic biomass is separated into its prized parts of cellulose, lignin and hemicellullose.

All three are valued raw materials for a wide variety of products and processes, including the cellulose for biofuels. The sustainable procedure can run continuously and is being considered for industrial use.

Current methods to separate the trio use harsh conditions that damage part of the end products and produce too much waste.

 

Context

Plants are a complex mix of materials that differ among various vegetative groups. Corn, wheat, trees and other woody plants contain lignocellulosic biomass. This is made up of three major components: cellulose, lignin and hemicellulose.

Cellulose is a water friendly part of these plants. It provides strength and structure and helps transport water from the roots to the leaves. Lignin is like a water tight glue that binds the cellulose together. It also protects cellulose from degrading under the sun’s ultraviolet rays and decomposing from microbes, bugs and fungi. Hemicellulose binds the cellulose and lignin, which are not very compatible.

Plants naturally make cellulose in staggering quantities, with some estimates topping several hundred billion tons per year. Since cellulose is abundant, it is an obvious target as a source for renewable feedstocks – the raw materials used by industry to produce products. Once processed, cellulose – more commonly known as pulp – is used widely in paper products, cellophane, as food additives and, more recently, in the production of bioethanol.

Lignin currently has only minor industrial uses, for example as dispersants and a feed additive. The majority of lignin is burned to recover the energy that os used in separating it from the biomass. However, it is the only natural source of large amounts of aromatic compounds, which are vital for making plastics – such as polystyrene – and drugs. Therefore,  a large amount of research is focusing on breaking down pure lignin into these aromatic compounds.

Industrial use of lignocellulosic biomass to make chemicals and fuel is hindered by its complex mix of cellulose, lignin and hemicellulose, which are difficult to separate. Harsh processes – high temperatures and caustic chemicals – that degrade the raw materials and make waste are commonly used.

What did they do?

In this study, researchers from Germany describe a very clever way to separate cellulose, lignin and hemicellulose in a single process.

They mixed lignocellulosic biomass – which can be wood, corn or wheat stalks or other cellulose and lignin containing materials – with three natural, benign additives. The additives were: water; oxalic acid – an acid obtained from the simple sugar glucose and found in many plants, including black tea; and 2-methyltetrahydrofuran (2-MTHF), a solvent that can be obtained from biomass.

The concoction was heated to an industrial low temperature of 140 degrees Celsius.

What did they find?

The enzymes and low temperatures work together to separate the lignocellulosic biomass into its component parts. During the process, the oxalic acid breaks down the hemicellulose and turns it into water-soluble sugars. The lignin and cellulose are not affected.

Since lignin and cellulose are very different, they spontaneously separate when the hemicellulose the glue that holds them together is degraded. The cellulose remains as an insoluble pulp that can be filtered off and used as a feed to make bioethanol or other chemicals. The lignin is extracted from the water-oxalic acid mixture using 2-MTHF.

Lignin is recovered by boiling off the 2-MTHF via distillation. This also allows recovery of the 2-MTHF, which is recycled in the process of extracting the lignin.

Equally, the oxalic acid can easily be recovered from the water-sugar mixture. It is recycled back into the process again to break down hemicellulose anew.

So in the end, the process yeilds an inlet stream of lignocellulosic materials and three outlet streams: lignin, cellulose and a mixture of water and sugars.

What does it mean?

Natural additives and lower temperatures offer a more sustainable way to divide certain types of plants into three main components. These lone parts are valuable starting products for many industrial applications.

This process is a very important development since it shows that it is possible to separate lignocellulosic materials using benign conditions and in a straightforward manner. It solves many of problems that plague current methods, such as high temperature, waste generation and product damage.

The researchers also designed the process so it can run continuously. This is a major advantage for industrial use and may make the process very attractive to industry.

However, this is a small scale study and further work will be needed to investigate whether it works as well on a very large scale and for a wide variety of different materials.

Resources

Taherzadeh, MJ and K Karimi. 2009. Pretreatment of lignocellulosic wastes to improve ethanol and biogas production:  review. International Journal of Molecular Sciences, http://dx.doi.org/10.3390/ijms9091621.

Can synthetic silk beat nature’s own?

 

Kinahan, ME, E Philippidi, S Koster, X Hu, HM Evans, T Pfohl, DL Kaplan and J Wong. 2011. Tunable silk: using microfluidics to fabricate silk fibers with controllable properties. Biomacromolecules http://dx.doi.org/10.1021/bm1014624.

 


Jul 09, 2011

 

2011-0601silkworm
CameliaTWU/flickr
A silkworm (Bombyx mori).

For the first time, people can do what only spiders and silkworms can do: spin silk fibers to specific specifications.

The new technique opens the door to customizing fibers to use in medicine, engineering and – of course – clothing. It relies on a special device to build silk protein chains that are then spun together into fibers with predicted and controlled strength, rigidity and width.

The researchers will continue to refine the method that may lead to a cheaper and more directed silk product than spiders and silkworms currently provide. The innovative method to make synthetic silk is explained in the journal Biomacromolecules.

Context

Silk is a very attractive material for clothing and other textiles due its smooth, cool and comfortable qualities. Manufacturers also find silk tantalizing. Silk’s mechanical properties – it is as strong as steel yet six times lighter – and ecofriendliness – it is biocompatible and biodegradable – make it an attractive material for biomedical and engineering applications. In fact, silk is used for suture threads and in tissue grafts.

In all the world, only silkworms and spiders can make silk. A mysterious spinning process produces the strong threads that are weaved together into webs and cocoons. The animals make the unique silk protein and spin it together in just the right way to form a special structure that gives the fiber its desired properties. The invertebrates do this with apparent ease. More so, they can control its properties, depending on where and for what purpose the silk thread will be used.

Obtaining natural silk for consumer uses, then, comes with a set of problems. The properties of natural silk – its strength, width, length – is determined by the specific species of spiders and worms. Basically, people get what the animals produce. It is also expensive and laborious to keep the silk-producing creatures – normally silkworms – and harvest the product.

So, there is need for a rapid method to fabricate silk and control its mechanical properties. The first step in this process has already been solved. A variety of other organisms – ranging from bacteria to goats – have been genetically modified and can produce silk proteins. The type of silk protein can be easily varied. It can also be produced in large quantities. However, the second challenge of how to spin those proteins into fibers with the desired properties remains.

What did they do?

Researchers from Boston, Mass., and Göttingen, Germany, used a microfluidic device that mimics the silkworm glands by extruding silk proteins from an aqueous solution. The solid device is infused with two crossing channels similar to the thickness of a human hair. Liquids can flow through the channels, which come together to allow a very small point of mixing. Through one channel flows the aqueous silk protein solution. Through the two intersecting channels flows an acidic solution of polyethylene glycol. Where the two channels meet, the fluids mix. Polyethylene glycol is a benign molecule  – a polymer – that envelops the active drug ingredients and acts as a lubricant in a variety of medicines.

Several different flow speeds and ratios of silk protein to polyethylene glycol solution were tested. The ensuing mechanical properties of the spun fiber – such as strength, strain and stress failure – were measured.

What did they find?

The device created a single strand of silk fiber with very well-defined properties. The fiber’s properties were altered by varying the spinning conditions, such as flow speed and the speed with which the dry fiber was drawn out of the device.

A small amount of original material was required – as little as 50 microliters, which is about the volume of a drop of water. This makes it a very interesting tool to screen different processing parameters and determine their effects on the spun fiber properties.

The authors related the flow characteristics inside the device to the fiber’s mechanical properties – strength, rigidity – and the internal structure formed by the silk proteins inside the fiber. They were able to control the fiber diameter and fiber strength. They even could vary the diameter of the fiber as it was spun.

While they did not yet match the properties of natural silk in this work, the control they showed over properties is very promising.

What does it mean?

The researchers designed a device that can rapidly produce synthetic silk fibers from silk proteins. The spinning conditions are easily controlled to determine the effect on the properties of the spun fibers.

This new technique opens up the possibility to customize fiber properties so they be used for specific applications. Of several methods being investigated to produce synthetic silk, this one is closest to the natural process, so it offers a very clean method to produce silk fibers on a large scale. No real waste is generated, and the polyethylene solution can be recycled.

More generally, the process is an example of how green chemists can develop a clean manufacturing process straight away and avoid creating pollution problems right from the start.

This work has a great potential to improve understanding of how to make synthetic silk fibers and possibly make them stronger, softer, more stretchable or thinner than natural silk. Different silk proteins can be produced from bacteria, goats and other animals – or even synthetically in the lab – so it is now possible to study the effect of spinning conditions and variations on the silk fibers that are produced. The small starting volume reduces the amount of silk protein required making the tests cheaper and faster to run.

The authors investigated only two processing parameters, but their new device can easily be used to screen all others quite rapidly. The process will no doubt increase understanding of both synthetic and natural silk production.  More importantly, the device may produce better, designer silk fibers.

Resources

Silkworm information. Center for Insect Science Education Outreach. University of Arizona.

Ford Looks to Dandelions for Natural Rubber

By Jonathan Bardelline
Published in GreenBiz.com May 11, 2011

Ford Looks to Dandelions for Natural Rubber
DEARBORN, MI — Ford continues to diversify its research into plant-based materials by turning a common weed into a replacement for synthetic rubber.

The company has already introduced soy foam and wheat straw components into its vehicles. Now, it’s looking to produce cup holders, floor mats and other parts with the help of dandelions.

Through work with Ohio State University, Ford will make and test car components created with rubber derived from the Russian dandelion, Taraxacum kok-saghyz. OSU’s Ohio Agricultural Research and Development Center is growing the dandelion, which produces a milky-white substance from its roots that can be turned into rubber.

Debbie Milewski, technical leader of Ford’s plastics research group, said the dandelion rubber will be used in parts that are part-plastic, part-rubber. That includes materials all over the interiors of cars like plastic trim as well as exterior parts like bumper covers. Some of those components have rubber content up to 40-50 percent.

Before dandelion-based cup holders find their way into cars, Ford will test how the rubber performs with different plastics to make sure it meets durability requirements.

“We’re going to look at a wide range of plastics and then we’ll narrow the scope from there,” Milewski said. The timeframe for getting the new rubber into vehicles depends on what issues crop up during testing. Soy foam, which is now in seats for every vehicle sold in North America, took six years of development, while the wheat straw bins went from concept to implementation in 18 months.

The dandelion-based rubber has the potential to find its way into any part that currently includes rubber, and Milewski said Ford might even try making parts completely from the natural rubber. The change would not only shift Ford away from petroleum-based synthetic rubber, but also use a plant source that can grow easily in the United States.

OSU’s research on making rubber from the Russian dandelion was a continuation of work done by a Russian university, Milewski said. Ford got involved after a local Ford car dealer near OSU, who knew about the company’s other bio-materials work, heard about the project and wrote to Executive Chairman Bill Ford about it, she said.

As part of Ford’s overall plan to make vehicles lighter and explore alternative materials, the company has also created fabrics out of recycled plastic bottles and engine cylinder head covers from recycled carpet.

Dandelions at OSU – Courtesy Ford

Chemists convert seaweed to chemicals and fuels.

Kim, B, J Jeong, S Shin, D Lee, S Kim, H-J Yoon and JK Cho.  2011.  Facile single-step conversion of macroalgal polymeric carbohydrates into biofuelsChemSusChem 3:1273-1275.
Synopsis by Evan Beach
Apr 28, 2011

An innovative idea – if adapted to a large scale – could take advantage of an abundant but so far little-used raw material to make biofuels, according to a team of green chemists in Korea. The secret ingredient: seaweed.

Many varieties of seaweeds thrive in the world’s saltwater oceans and seas. Their growth is fueled by carbon dioxide. Unlike most conventional land-based plants, it is possible to produce multiple crops in a year without requiring fertile land and fresh water.

In recent years, microalgae – which are invisible to the naked eye – have been researched and exploited for use as fuels. Mostly ignored in this boom were the macroalgae – the kind you can see with your naked eye and find at the seashore. These seaweeds usually have lower oil content and have not attracted as much attention from chemists and manufacturers.

What they lack in oil, many types of seaweeds make up for in carbohydrates. The red algae species used in the current study is almost 80 percent carbohydrates. These sugars form long chemical chains called agar.

The Korean researchers found two ways to convert the agar into useful products.

In one, they found that agar reacts with an acid catalyst to produce a small molecule known as HMF. HMF is a valuable precursor to a variety of chemicals. To draw an analogy with petroleum refining, HMF would be considered the bio-based equivalent of a petrochemical like toluene that serves as the ultimate starting material for many commercial chemicals. The yield of HMF from the red algae was higher than expected, and this was attributed to unusual simple sugars and linkage patterns in the agar structure.

By adding a different catalyst to agar and introducing a solvent for the reaction, the yield was improved and two different chemical products were formed. Both of these chemicals are well known as biofuels and could be used as building block structures for specialty chemicals as well.

The product yields might be further improved by changing the seaweed growth conditions or even the species. Since the researchers discovered that the agar structure leads to unique reactivity, future work could take advantage of ways to tweak it towards a more favorable composition. Other combinations of catalyst and solvent could be explored as well.

Carbon dioxide can be a chemical building block.

Synopsis by Evan Beach, Mar 17, 2011

Beckman, EJ, and P Munshi. 2011. Ambient carboxylation on a supported reversible CO2 carrier: ketone to b-keto ester. Green Chemistry http://dx/doi.org/10.1039/c0gc00704h.

Laboratory trials of a coated silicone material may pave the way for the use and reuse of carbon dioxide in the chemical industry. Carbon dioxide can be used as a raw material for ingredients found in pharmaceuticals, pesticides and other specialty chemical products. The landmark process is explained in a recent article in the journal Green Chemistry.

The discovery won’t significantly impact global carbon dioxide emissions, but it will make it easier for chemists to work with an inexpensive, abundant source of carbon that’s widely available as a waste material.

Carbon dioxide has been widely used in the preparation of larger molecules, but the need for high pressure to make the reactions go is a major limitation. The scientists found that by using a specially designed carrier material, carbon dioxide can be used at room pressure.

The carrier material is based on silicone with a permanent chemical coating that absorbs the carbon dioxide. The carbon dioxide binds at room temperature, but is only released if the material is heated to 120 degrees Celsius (about 250 F). These properties allow the bound carbon dioxide to be used within a wide range of temperatures.

The material can be easily separated from reaction mixtures, making it easy to purify the chemical products. This represents a major improvement over liquid-based carbon dioxide absorbents, which require extra steps to separate. The solid carrier is also easily recycled: the researchers saw no loss of activity after five cycles of carbon dioxide binding and release.

The material was tested for its ability to promote chemical reactions that add carbon dioxide to other molecules. Good efficiency was found at room temperature and pressure. No silicon was found in the chemical products, indicating that the carrier material is very stable.

The researchers also showed the carrier material could improve the reactivity of other molecules besides carbon dioxide, so it could be more widely useful. Future work might explore a wider variety of carbon dioxide chemistry, including manufacturing of plastics.