A new environmentally-friendly polymer degrades under very mild acidic conditions

Preparation of new degradable synthetic polymer. CREDIT Ehime University

A research team in Ehime University prepared a new type of synthetic polymer, which can be degraded into a combination of well-defined low molecular weight compounds under very mild acidic conditions. The new polymer, poly(?-keto enol ether), has great potential to be utilized as an environmentally friendly material in the near future.

The research team, led by E. Ihara and H. Shimomoto, has been utilizing unique reactivities of a diazocarbonyl group for polymer synthesis where they have succeeded in preparing a variety of polymers with unprecedented chemical structures by the polymerization of some bis(diazocarbonyl) compounds bearing two diazocarbonyl groups in one molecule. Now they have found that three-component polymerization of an appropriated combination of a bis(diazocarbonyl) compound, bis(1,3-diketone), and tetrahydrofuran (THF) as monomers yields a new type of polymer structure containing the ?-keto enol ether framework in the main chain, which has been known to be readily cleaved with a small amount of acid.

The polymerization catalyzed by a Rh catalyst proceeded as they expected, affording poly(?-keto enol ether) with a molecular weight higher than 10000. More importantly, the polymer was found to be cleanly degraded into a combination of two low molecular weight compounds in high yield under mild acidic conditions; one of the degraded products was the monomer itself, bis(1,3-diketone) (indicating recyclability of the monomer), and the other one was a dihydroxy compound derived from the bis (diazocarbonyl) compound and THF used as other monomers.

The acid-sensitivity of the ?-keto enol ether framework of the polymer was so high that the degradation proceeded even in a chloroform solution because the solvent usually contains a very small amount of acid spontaneously generated from the solvent molecule under an ambient condition. On the other hand, in other solvents without an acidic trace, such as dimethylsulfoxide, the polymer did not degrade at all, demonstrating the extremely high sensitivity of the polymer structure to an acidic stimulus.

The highly acid-sensitive degradability can be useful for some important applications. For example, a drug-encapsulating material made of the polymer would release the incorporated active component by rapidly responding to a mild acidic environment. In addition, materials made of the polymer can be easily degraded to the above-described low molecular weight compounds, including one of the monomers, after they are used in neutral conditions. Synthetic polymers with such degradability are especially desired because of the serious environmental damage caused by non-degradable synthetic polymeric materials.

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Green growth: Shoots, greens and leaves

English: Satellite image of Lake Naivasha, Kenya

Rich countries prospered without worrying much about the environment.

Poor and middle-income countries do not have that luxury

ON THE southern shore of Lake Naivasha, Kenya’s lush Rift Valley holds an unexpected scent of English summer. For inside vast plastic greenhouses grow mile upon mile of roses. Exported to Europe, they account for a fifth of the commercial roses sold there and provide a tenth of Kenya’s foreign exchange. But the business is a victim of its own success.

Attracted by a scent more pungent than flowers, a quarter of a million Kenyans followed the rose growers into the valley, hoping to make money. To feed themselves, they ploughed the surrounding hills, felling the trees that filter and constrain the streams that flow into the lake; it is now polluted by silt and run-off.

That might seem a classic story of development choked by the environmental damage it causes. But this one has a twist. The rose growers have started lending money to the smallholders, encouraging modern farming methods which leave the trees in place. Though it is early days, the results are promising; they benefit growers, small farmers and the lake.

Paying for environmental services is not a new idea. Pioneered in Mexico and Costa Rica, such projects keep clean the water supplies of many of Latin America’s giant cities. In China’s north-west, the Loess plateau, an area the size of France, was brought back from near-desert by paying farmers to stop uncontrolled grazing and to look after terraces and waterways. Local incomes doubled in a decade.

These schemes have a wider significance. They are examples of “green growth”, an attempt to improve the often destructive relationship between economic development and the environment. In the run-up to the “Rio+20” conference on sustainable development in Brazil on June 20th-22nd, it has become the new mantra for business people and policymakers. But does it work?

Read more . . .

via The Economist
 

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Deep Thinking About the Future of Food

Organic cultivation of mixed vegetables on an ...

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The future of global agriculture

Trying to tap into the best thinking about the future of global agriculture, as I have tried to do in my work as a reporter, can be an exercise in frustration. Many groups and many bright people go at the problem, but not many of them go at it in a holistic way.

The environmental crowd is worried mainly about the ecological damage from agriculture and is prone to recommend solutions that farmers say would undercut the food supply. Traditional agronomists are mainly worried about supply — and tend at times to recommend fixes that might worsen the environmental damage.

A separate crowd is primarily worried about the inequities in the global food system: that a billion people at the top end are killing themselves eating overly rich diets while a billion poor people live desperate lives circumscribed by malnutrition.

Can’t we figure out how to fix all this at once?

It’s a tall order, but a heartening development in global agricultural policy is that some people are starting to try. Now comes an interesting new installment in the literature of the Big Fix. It’s an analysis by an international team of scientists led by Jonathan A. Foley, director of the Institute on the Environment at the University of Minnesota.

Their paper, “Solutions for a Cultivated Planet,” was released online and is scheduled as the cover article of the Oct. 20 issue of the journal Nature. Dr. Foley is also publishing a piece in the November issue of Scientific American, due on newsstands next week, that summarizes the team’s analysis in layman’s terms.

The group finds, as others have before them, that the challenge of doubling global food production in coming decades can probably be met, albeit with considerable difficulty. The interesting thing to me about the analysis is that it doesn’t treat any of the problems confronting the food system as superior to the others — it treats the environmental problem, the supply problem and the equity problem as equally important, laying out a case that they all need to be tackled at once.

“Feeding nine billion people in a truly sustainable way will be one of the greatest challenges our civilization has ever faced,” Dr. Foley says in the Scientific American article, referring to the projected global population at midcentury. (He outlines some of the links between environmental problems and agriculture in this talk, and his group produced a popular animated clip that gives a sense of the scale of the problems here.)

Many elements of the new paper will be familiar to readers who follow these issues. Yet it is interesting to see these building blocks of a smarter food system spelled out in one paper, with hard numbers attached.

For starters, the group argues that the conversion of forests and grasslands to agricultural use needs to stop now; the environmental damage we are doing chopping down the Amazon far exceeds the small gain in food production, it says.

Next, the paper contends that increases in food supply need to come from existing farmland by a process of intensified production in regions where yields are low: northeastern India, Eastern Europe, parts of South America and large parts of Africa being good examples.

If yields in these regions could be brought to within 75 percent of their known potential using modern farming methods, including fertilizer and irrigation, total global supply of major foodstuffs would expand by 28 percent, the paper found. If yields were brought to 95 percent of their potential, close to those achieved in rich countries, the supply increase would be a whopping 58 percent.

The paper does not say so, but I suspect that either development would be enough to reverse the soaring food prices of recent years.

Another important strategy laid out in the paper is to improve the efficiency of agriculture in places where yields are already high. If farmers in Africa need more fertilizer, farmers in the United States need less.

The paper essentially argues that high yields can be attained with fewer chemicals and less water, which would not only cut pollution but in some cases also cut costs for farmers.

And finally, the paper argues that more of the food we grow needs to wind up on people’s plates. That means cutting food waste, not just the kind so common in Western kitchens but also the tremendous post-harvest losses caused by bad storage conditions in poor countries.

And it means a shift in diets away from meat and dairy products, which are inefficient to produce, and toward plants. The paper acknowledges that a massive transition to vegetarianism is unlikely but argues that even incremental changes — getting many people to move from less-efficient beef to more-efficient chicken, for instance — would make a difference.

The paper studiously avoids taking sides in the ideological wars over the food system. It does not adopt the left-leaning argument that organic production is the answer to the world’s food issues, nor the rightward view that markets will solve all problems.

It does argue for pulling as many good ideas as possible from emerging food movements into the conventional system — but only if they serve the three goals of increasing supply, reducing environmental damage and improving food security.

As a scientific report, not a policy document, the Foley paper does not offer any big new proposals for how to make all these things happen. Many commentators who have studied these issues have come to the conclusion that the barriers are not primarily technical but involve a lack of political will to solve the problems, leading to low public investment in agriculture.

In his Scientific American article, Dr. Foley does make one intriguing proposal. Pointing to the certification system that has encouraged the construction of green buildings, he asks: what about a new certification system for sustainably produced food?

Instead of catering to a single ideological predilection, the way the organic label does now, the new label would be based on a system that awards points for public benefits and subtracts them for environmental harm. Foods produced according to the best practices would get the highest scores, or possibly the highest letter grades. If consumers adopted it, such a certification would put pressure on companies and farmers to clean up their practices.

“This certification would help us get beyond current food labels such as ‘local’ and ‘organic,’ which do not tell us much about what we are eating,” Dr. Foley writes in Scientific American.

Read more . . .
Bookmark this page for “Future of Food” and check back regularly as these articles update on a very frequent basis. The view is set to “news”. Try clicking on “video” and “2” for more articles.

Oil field brine proposed to treat Hungary’s red sludge spill

The bauxite residue container pond spill near Kolontar, Hungary

It might sound like fighting fire with fire, but geologist Chen Zhu proposes the application of another industrial waste to the Hungarian bauxite residue spill, with the aim of reducing toxicity via a technique called carbon sequestration.

While he says it wouldn’t render the residue completely harmless, it would at least minimize the environmental damage.

Bauxite residue is created as a by-product of the aluminum industry, and since there is currently no regulation or imposed company responsibility to neutralize the waste, the corrosive material is often left in container ponds. It is estimated that worldwide there are in excess of 200 million tonnes (220.46 million US tons) of “red sludge” in ponds like this.

When the pond near Kolontar, Hungary burst on October 4th, it released between 598 and 697 million liters (158-184 million US gallons) of toxic waste – between 79-92 percent of the entire gulf spill that dominated the press this summer. Thirteen people have been killed, 150 injured and several communities destroyed and potentially abandoned. The immediate and long-term damage to the ecosystem is untold, covering an area of 40 square kilometers (15.4 square miles). The devastation spread as the spill reached the Danube, Europe’s second-longest river, having already killed all the fish in the Marcal river.

It is ironic, then, that this could be addressed by the addition of another industrial waste – oil field brine – the by-product of oil and gas production. This approach has been proposed by Indiana University Bloomington geologist Chen Zhu, who submitted a U.S. Department of Energy patent application in 2007 describing the technique.

“Carbon sequestration” is the process by which carbon is removed and stored. In this case, the brine provides the medium in which the carbon dioxide can dissolve. Once dissolved, CO2 reacts with water to create carbonic acid which will reduce pH (currently between 11 and 13) and cause the precipitation of salts that would otherwise react with living matter.

It’s important to realize, however, that this is both expensive and certainly not a cure-all solution. “By reducing the pH and causing the precipitation of problematic salts, what we’re left with is not something that’s non-toxic, but less toxic than what we started with,” says Zhu.

Read more . . .

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