New Breakthroughs Propel the Field of Green Chemistry

In late June, the American Chemical Society (ACS), a nonprofit organization chartered by Congress, held its 16th annual Green Chemistry & Engineering Conference in Washington, D.C. The conference, which was sponsored by the American Chemical Society’s Green Chemistry Institute (ACS GCI), had a theme this year of “Innovation, Jobs, Sustainability – The Role of Green Chemistry.” A number of noteworthy new green chemistry processes were presented at the event.


Making Green Jeans Using Less Water and Energy

Textile manufacturing involves some of the world’s most resource-wasting processes. According to the Environmental Protection Agency, it takes about 2,900 gallons of water to produce a single pair of jeans. Most of this water is used in what’s known as wet processing, as well as in the dyeing of fabric.

Specialty chemicals company Clariant may soon change that. It has debuted a new process called Advanced Denim, which it says can produce a pair of jeans using up to 92 percent less water and up to 30 percent less energy than conventional methods. The process also generates up to 87 percent less cotton waste (which is often burned) and virtually no waste water, according to Miguel Sanchez, a textile engineer at Clariant.

While traditional denim production requires up to 15 dyeing vats that contain a cocktail of chemicals, Clariant’s process uses a single vat of liquid sulfur dyes that require only a single, sugar-based reducing agent, says Sanchez. The reducing agent, sodium hydrosulfite, is a much greener alternative to traditional reducing agents.

The result is a more eco-friendly process that cuts out most of the waste from traditional jean production. Sanchez says that if even one-quarter of the jeans produced in the world were made via the Advanced Denim process, enough water — about 2.5 billion gallons — would be saved to cover the needs of 1.7 million people each year. It would also prevent the release of 8.3 million cubic meters of wastewater each year and save up to 220 million kilowatt hours of electricity. At the same time, it would cut down carbon dioxide emissions significantly.

The jeans produced via Advanced Denim look similar to other commercially produced jeans, or even better, Sanchez says. Clariant claims that the process can produce “looks and effects not possible today with current technologies.”

Cutting the Steps from Algae to Fuel

One thing the world has a lot of today is algae. One thing it’s getting short on is fuel. For years, scientists have been searching for ways to make fuel out of algae, and many have succeeded at least in the lab. It’s an economical process that, thus far, has eluded most researchers.

At the Green Chemistry & Engineering Conference, a team of researchers from Yale University presented a breakthrough toward a long-sought viable process, which turns algae into biodiesel.

The new process extracts from algae fatty molecules called lipids and transforms them into usable fuel in a single process. It would make biodiesel from algae much cheaper, faster and greener than current multistep methods that require separate stages and chemicals. The reaction involves supercritical carbon dioxide, which at elevated pressures and temperatures fills its container like a gas but is as dense as a liquid, according to the researchers.

“Algae has great promise as a next-generation biofuel, a fuel that is sustainable and renewable,” says research team leader Julie Zimmerman,

Algae being grown in flasks at Yale University.
Credit: Lindsay Soh

Ph.D. “It has more oil per pound than corn and soybeans, does not divert crops from the food supply and can potentially be grown in sewage water and seawater without impacting the freshwater supply,” she says.

Supercritical carbon dioxide is used in a number of commercial and industrial processes, from decaffeinating coffee to a greener process for dry cleaning clothing. The process developed by the university is nontoxic, which makes it an attractive alternative to some of the harsher, potentially toxic chemicals used in existing algae-to-biofuel technologies, according to research team member Lindsay Soh, a graduate student in Zimmerman’s lab.

“But this really is the first time that scientists have realized that a green system like supercritical carbon dioxide might have applications in producing biofuel from algae,” Soh told R&D Magazine.

While others have proposed using supercritical methanol and ethanol for the production of algae biodiesel, the supercritical carbon dioxide process works at lower temperatures, making it easier and less energy intensive. In addition, Zimmerman says, supercritical carbon dioxide, which acts as a solvent for oil, can be “fine-tuned” so that it extracts only specific components from algae oils. This also can make the process faster, cheaper and less resource intensive.

Using Straw to Sustainably Make Paper

The world has plenty of straw. Aside from animal bedding, county-fair seating and perhaps making the odd green building, there isn’t a lot that can be done with it. At the ACS event, Taiwan-based YFY Corp. demonstrated a new chemical process that converts straw into pulp for the purpose of paper making.

Besides saving trees, the process is said to be less energy intensive and cleaner in terms of emissions compared with traditional paper making. In addition, it could help create new revenue streams and economic development opportunities for rural farms and communities that produce straw.

YFY’s process, called NPulp, has been in development for more than a decade. Both the NPulp product and a related economic sustainability program will debut this month in several farming communities in China, where straw will be collected and converted into straw pulp via a proprietary “bio-pulping” enzymatic process that eliminates the need for harsh chemicals. With the new process, YFY says it can take advantage of the more than 600 million tons of agricultural straw biomass available in China. This represents a potential supply of 345 million tons of biopulp, equal to the amount of wood pulp produced globally every year.

Not only is the process a greener way to make paper, but it helps the environment by eliminating the traditional burning of waste straw, which contributes to air pollution and greenhouse gas emissions.

Making Use of Vast Leftover Citrus Peel

While it may not be the first thing you think of when it comes to agricultural waste, the amount of discarded orange peel and pulp from the world’s orange juice industry is massive. (The United States and Brazil are the world’s largest orange growers and producers.)

After juicing, about 50 percent of the orange remaining is discarded, generally by burning or by dumping into landfills, neither of which helps the environment much. Burning, of course, creates pollution and greenhouse gases. Dumping in landfills leaves the acidic citrus oils to leach from the rotting peels into the soil, harming nearby plant life. Occasionally, the residual pulp and peel is dried and detoxified and used in animal feeds, and, on an even smaller scale, peel oils are sometimes extracted in energy-intensive and chemical-laden processes for the food and cosmetics industries.

What if something can be done with the 15.6 million tons of orange and other citrus peels produced worldwide each year? At the ACS event, scientists from the United Kingdom announced they’ve found a sustainable way to extract and find uses for virtually every bit of discarded citrus product.

The project, rather cleverly called OPEC (for Orange Peel Exploitation Company), is a partnership between researchers at the University of York, the University of Sao Paulo and the University of Cordoba, in Spain. OPEC is in the process of setting up a prototype biorefinery that could lead to using citrus peels for biosolvents, fragrances and water purification.

“This is a great example of what can be done with something that is produced in quantities that would astound people,” says James Clark, director of the University of York’s Green Chemistry Centre of Excellence. “At the moment, orange peel has very little value and actually can have a negative effect on the environment. We believe that using the biorefinery concept in combination with the principles of green chemistry will allow us to make a whole series of products that can displace traditional, often petrochemical-based, manufacturing processes.”

According to the research team, it’s a green one-step process that efficiently extracts useful compounds that could be used as safer and greener alternatives in a number of industries. The citrus peels are exposed to high-intensity microwaves at low temperatures, resulting in a liquid from which several useful products can be obtained, plus cellulose, which can be used as a food additive or a thickening agent or be converted into a solid biofuel, the researchers say.

“We’re aiming to create a zero-waste biorefinery,” Clark says. “We want to use everything. We want to give value to every component of the peel.”

EPA Has Keen Interest in Green Chemistry

The EPA actively participated in the ACS’s event, announcing the winners of its 17th Annual Green Chemistry Challenge Awards. The initiative recognizes innovative chemical technologies that have the potential to prevent pollution and create safer, more sustainable designs, processes and products. The awards are broken into five categories: Academic, Small Business, Greener Synthetic Pathways, Greener Reaction Conditions and Designing Greener Chemicals.

Winners in the Academic category included a process that removes hazardous metals used in the production of plastics and a process that synthesizes biodegradable polymers from carbon dioxide and carbon monoxide that can be used in a range of adhesives, foams and plastics and replace bisphenol A in food-container and beverage-can linings.

In the Small Business category, Elevance Renewable Sciences was recognized for its production of green specialty chemicals at more economical costs and using less energy while significantly reducing greenhouse gas emissions compared with petrochemical technologies.

For the Greener Reaction Conditions category, Cytec Industries was recognized for its MAX HT “Bayer process” scale-inhibitor products that result in a more energy-efficient and less hazardous process for the production of alumina, a raw material for making aluminum.

In the Designing Greener Chemicals category, Buckman International received a nod for its enzymes used in paper-making that modify the cellulose in wood to increase the number of fibrils that bind the wood fibers to each other, resulting in paper with improved strength and quality without the need for additional chemicals or energy.

Finally, for the Greener Synthetic Pathways category, Codexis and Yi Tang, a researcher at UCLA, together received an award for a more efficient, safer green chemistry approach to manufacturing Simvastatin, a statin drug used to treat cardiovascular diseases.

While green chemistry seldom grabs the lion’s share of attention in the sustainability sector, it’s an area that is experiencing a rapid wave of new processes and materials that will ultimately change the face of green manufacturing.

[Editor's Note: Green & Clean contributor Michael Lewis spoke with some of the EPA's Green Chemistry Challenge Awards winners. His article appears here.]

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