Tuesday, October 18, 2011

New standard specification may facilitate use of additives that trigger biodegradation of oil-based plastics in landfill

Despite efforts to encourage the recycling of plastic water bottles, milk jugs and similar containers, a majority of the plastic packaging produced each year in the United States ends up in landfills, where it can take thousands of years to degrade.  To address that problem with traditional polyethylene, polypropylene, Styrofoam and PET products, researchers at the Georgia Institute of Technology are working with the Plastics Environmental Council (PEC) to expand the use of chemical additives that cause such items to biodegrade in landfills.

Added during production of the , the compounds encourage anaerobic landfill bacteria and fungi to break down the plastic materials and convert them to biogas methane, carbon dioxide and biogenic carbon – also known as humus.  These additives – simple organic substances that build on the known structures of materials that induce polymer biodegradation – don’t affect the performance of the plastics, introduce heavy metals or other toxic chemicals, or prevent the plastics from being recycled in current channels.

If widely used, these additives could help reduce the volume of plastic waste in landfills and permit much of the hydrocarbon resource tied up in the plastic to be captured as methane, which can be burned for heating or to generate electricity.

“Research done so far using standard test methods suggests that the treated plastics could biodegrade completely within five to ten years, depending on landfill conditions,” said Lisa Detter Hoskin, a principal research scientist in the Georgia Tech Research Institute (GTRI) and co-chair of the PEC’s technical advisory committee.  “However, legislators, regulatory agencies and consumers need more assurance that these containers will perform as expected in actual landfills. We need to provide more information to help the public make informed buying decisions.”

To provide this information, Hoskin and other Georgia Tech researchers are working with the Atlanta-based PEC to develop a set of standards that would ensure accuracy and consistency in the determination and communication of the plastic containers’ biodegradation performance.

“We are working to develop a new standard specification for anaerobically biodegradable conventional plastics,” Hoskin said.  “This certification is intended to establish the requirements for accurate labeling of materials and products made from oil-derived plastics as anaerobically biodegradable in municipal landfill facilities. The specification, along with a certifying mark, will allow consumers, government agencies and recyclers to know that the item carrying it is both anaerobically biodegradable and recyclable.”

The standard specification will provide detailed requirements and test performance criteria for products identified as anaerobically biodegradable, and will include rates for anaerobic biodegradation in typical U.S. landfills.  These rates will be based on biodegradation test data and results from research being undertaken by Georgia Tech and North Carolina State University.

With support from the PEC and its member companies, Hoskin has directed testing efforts that show mechanistically how the additives work, and are showing that the degraded plastic leaves behind no toxic materials.  With that part of the project largely completed, she now leads the development of the standard specification and certifying mark, and plans to organize a network of accredited laboratories that will test products made with the biodegradable additives to certify that they do degrade within a specific period of time.

Full development and adoption of the new standard specification by ASTM International will likely take between 18 months and two years, Hoskin said.  The project will involve research being done using landfill simulations at North Carolina State University and other independent laboratories.

Using information from laboratory-scale anaerobic reactors operated under a range of temperatures, moisture levels and solids contents, researchers will compare the time required to break down known anaerobically biodegradable materials – such as newsprint, office waste and food waste – against the time required to degrade those same wastes in real landfills.  That information will be used to project the biodegradation rate for the treated plastics in a range of real landfills, which vary considerably in moisture and other factors.

Though they are recyclable, plastics made from hydrocarbons had not been biodegradable until development of microbe-triggering additives. Bioplastics such as those made from corn may be composted, while a small percentage of specialized plastic products – known as oxobiodegradables – are designed to degrade when exposed to oxygen and ultraviolet light.  But the bulk of the plastic resins used in bottles and other containers are made from materials that will last virtually forever in landfills, noted Charles Lancelot, executive director of the PEC.

Many communities operate programs for plastics and other materials such as newsprint, aluminum and steel cans or cardboard.  But because the cost of collecting, sorting, cleaning and reprocessing most plastics can be more than the cost of producing new products, such programs struggle financially unless they are subsidized, he noted.

“If you can make a product like a bread tray and use it over and over again, that is the most efficient alternative,” said Lancelot, who developed successful business-to-business recycling programs while working at Rubbermaid.  “But if you can’t reuse it and it’s not cost-effective to recycle it, where is the product going to go?  The fact is that despite the best wishes of everybody involved, 75 to 85 percent of the plastics used today end up in landfills.  We are addressing that unfortunate reality.”

Although biodegradation occurs to varying extents in all U.S. landfills receiving waste today, many of today’s landfills are optimized for biodegradation, he noted.  Moist conditions and recirculation of leachate liquids accelerate the activity of anaerobic bacteria, which will attack plastic materials containing the additives. Such landfills typically do a better job of collecting and beneficially using the methane biogas, Lancelot said.

“When the anaerobic microorganisms that thrive in landfills contact these treated plastics, they begin to colonize on the surface of the plastic and adapt to the base resin,” he explained.  “Until the bugs come in contact with the plastic, the additives remain inert and do not affect the properties of the plastic container.  We are not changing the overall plastics production process, and the base plastic is the same.”

The compounds, which have been approved by the U.S. Food & Drug Administration (FDA), are typically added to the plastic resin in small amounts, between one-half and one percent by weight.

Expanding the use of anaerobically biodegradable additives must be done in such a way that doesn’t detract from recycling programs, said Matthew Realff, a professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and co-chair of the PEC’s technical advisory committee.

“From a lifecycle perspective, it is important to quantify the benefit of recycling over landfill disposal with methane recovery to energy, and to continue to make the case that whenever possible, recycling is significantly better than disposal, even if you have methane production and capture from biodegradation,” he said.

While the biodegradation of plastic materials may solve one problem, the production of methane and carbon dioxide – both atmospheric warming gases – could worsen global climate change, he noted.

“Landfill capture of methane is not 100 percent efficient, nor does it begin immediately after the material is put into the landfill,” Realff said.  “Therefore, there will be emissions from biodegradation that will reach the atmosphere.  It is important to be aware of how accelerating the production of methane would change overall emissions.”

A 45-year veteran of the U.S. plastics industry, Lancelot says he is pleased to be working with Georgia Tech on a potential solution to the problem of plastics in .  The research will help close a gap in plastics “end-of-life” options where reuse or recycling are not feasible.

“Nobody had commercially biodegraded petroleum-based commodity like polyethylene, polypropylene and polystyrene before these additives became available,” he noted.  “This is ground-breaking work that is based on a solid scientific platform that defines biodegradability as a practical and useful end result.”

Provided by Georgia Institute of Technology (news : web)

First detection of pregnancy protein in older people destined for Alzheimer's disease


In an advance toward a much-needed early diagnostic test for Alzheimer's disease (AD), scientists have discovered that older women destined to develop AD have high blood levels of a protein linked to pregnancy years before showing symptoms. Their report appears in ACS' Journal of Proteome Research.

Theo Luider and colleagues explain that more than 26 million people worldwide already have AD, and the numbers are rising with the graying of the population. Doctors can prescribe any of several drugs to slow the disease's advance. But it is important to start treatment as early as possible. Unfortunately, however, no test exists to diagnose patients before obvious and other symptoms appear. Luider's team decided to look for proteins in the blood that might be used in such a test.

They looked for those proteins in blood samples of 86 people aged 60-90 who participated in a larger study of aged-related conducted in The Netherlands. Surprisingly, Luider's group found that significant elevations in pregnancy zone protein (PZP) occurred in women an average of 4 years before diagnosis of AD. Scientists long have known that PZP levels rise during pregnancy, but this was the first link with AD. Luider further discovered the apparent source of the PZP in the brain of these women, who were not pregnant: PZP was being produced in , degenerated areas of the brain associated with AD.

More information: “Serum Levels of Pregnancy Zone Protein Are Elevated in Presymptomatic Alzheimer’s Disease” J. Proteome Res., Article ASAP. DOI: 10.1021/pr200270z

We have sought for disease-related proteins that could predict the onset of Alzheimer’s disease (AD) in a study population derived from the Rotterdam Scan Study, a population-based prospective cohort study designed to investigate the etiology and natural history of age-related brain changes in the elderly. The serum proteome of 43 persons who developed AD, after an average of 4.2 years (±2.6 years SD) after blood sampling, and 43 gender- and age-matched controls who remained dementia-free during follow-up was investigated by liquid chromatography mass spectrometry. We identified 61 differentially expressed peptides between presymptomatic AD and controls, 9 of which were derived from pregnancy zone protein (PZP). Quantitative measurements using a multiple reaction monitoring assay showed a significant increase in concentration of PZP in presymptomatic AD (34.3 ± 20.6 mg/L) compared with controls (23.6 ± 13.6 mg/L) (p = 0.006). The difference in PZP was significant in women. Immunohistochemical validation of the findings on brain tissue sections showed strong PZP expression in senile plaques and in microglial and glial cells in AD with only low expression in some scattered glial cells in controls.

Provided by American Chemical Society (news : web)

Full to the brim with hydrogen: Porous form of magnesium borohydride can store hydrogen

Hydrogen could be one of the most important fuels in a new energy economy based on renewable resources. However, no ideal hydrogen storage material has yet been found. A team led by Yaroslav Filinchuk at the Université Catholique de Louvain, Belgium, and Torben R. Jensen at the University of Aarhus in Denmark has now introduced a new highly porous form of magnesium borohydride in the journal Angewandte Chemie. This material can store hydrogen in two ways: chemically bound and physically adsorbed.

The perfect must store hydrogen efficiently and securely in a small volume, and should release it on demand. It must be rapidly refillable under mild conditions, while being as light and inexpensive as possible. One approach to this is solid-state storage. In such systems, hydrogen can be chemically bound, as in borohydride compounds, or it can be adsorbed as a molecule into a nanoporous material, as in some metal–organic frameworks.

The researchers have now found a material that can do both. It is a new, highly porous form of magnesium borohydride—the first light-metal hydride that is porous like a metal–organic framework and is capable of storing molecular hydrogen.

Magnesium borohydride (Mg(BH4)2) is one of the most promising for chemical because it releases hydrogen at relatively low temperatures and can hold a high proportion by weight (about 15 %) of hydrogen. Two forms of this compound, ? and ß, were previously known. The researchers have now made a third form, designated the ? form. Its pore volume comprises about 33 % of the structure, and its channels are wide enough to take up and store small gas molecules, such as nitrogen, dichloromethane, and most importantly hydrogen.

Interestingly, under high pressure this material converts into a nested, non-porous framework with a density that is nearly 80 % higher. This makes the ? form the second densest in hydrogen content and more than twice as dense as liquid hydrogen. Furthermore, this conversion results in a 44 % reduction in volume, which is the largest contraction yet observed for a hydride.

“A combination of the chemical (through covalent bonding) and physical (through adsorption in the pores) storage of hydrogen seems to be difficult in practical applications,” explains Filinchuk. “However, this research has a broader impact, as it reveals a new class of hydride-based porous solids for storage and separation of various gases.”

More information: Yaroslav Filinchuk, Porous and Dense Magnesium Borohydride Frameworks: Synthesis, Stability, and Reversible Absorption of Guest Species,

March on, Hydrogen! Mild but very efficient: new catalytic process extracts hydrogen from bioalcohols

March on, Hydrogen! Mild but very efficient: new catalytic process extracts hydrogen from bioalcohols


(PhysOrg.com) -- Over 80% of the worlds energy demands continue to be met with fossil fuels. The environmental problems associated with this, such as global warming, are well-known. The efficient supply of energy based on renewable resources is becoming more pressing. Hydrogen technology, which involves the production of hydrogen from biomass for use in electricity production in fuel cells, is a very promising approach.

In the journal , researchers led by Matthias Beller at the Leibniz Institute for in Rostock (Germany) have now introduced a new catalyst that allows for the use of bioalcohols for the production of hydrogen. Their novel process proceeds efficiently under particularly mild conditions.

Ethanol and other alcohols do not willingly give up their ; this type of reaction requires highly active catalysts. Previous catalytic processes require downright drastic reaction conditions: temperatures above 200 C and the presence of strong bases. The Rostock researchers thus aimed to develop a catalyst that would also work efficiently at significantly milder temperatures.

Martin Nielson, working on Beller’s team thanks to an Alexander von Humboldt scholarship, has now been successful. The new catalyst demonstrates previously unachievable high efficiency in the extraction of hydrogen from alcohols under mild reaction conditions. Says Beller, “This is the first catalytic system that is capable of obtaining hydrogen from readily available ethanol at temperatures under 100 C without the use of bases or other additives.”

After initial successful tests with a relatively easily converted model alcohol (isopropanol), the researchers turned their attention to ethanol, also known as the “alcohol” in alcoholic beverages. Ethanol has taken on increasing importance as a renewable resource but is significantly harder to convert. “Even with ethanol, this new catalyst system demonstrated an unusually good conversion rate under milder conditions (60–80 C),“ says Beller. “In comparison to previous catalyst systems, this one is nearly an order of magnitude higher.”

The active catalyst consists of a ruthenium complex that is formed in situ. The starting point is a central ruthenium atom that is surrounded by a special ligand that grasps it from three sides. The other ligands are a carbon monoxide molecule and two hydrogen atoms. Upon heating, a hydrogen molecule (H2) is released from the complex. When the remaining complex comes into contact with ethanol or isopropanol it grabs two replacement hydrogen atoms, allowing the cycle to begin again.

More information: Matthias Beller, Efficient Hydrogen Production from Alcohols under Mild Reaction Conditions, Angewandte Chemie International Edition 2011, 50, No. 41, 9593–9597, http://dx.doi.org/ … ie.201104722

Provided by Wiley (news : web)