|
|||||||||||||||||
|
|
|||||||||||||||||
|
This has been a stellar year for green chemistry. A number of national and international conferences were dedicated to green chemistry, and the topic popped up on the technical programs at American Chemical Society and other meetings. Several journals, including Science and Accounts of Chemical Research, published special sections or issues focusing on green chemistry, while others now flag green chemistry papers. The Royal Society of Chemistry's journal Green Chemistry is in its fourth year of publication, and the U.S.'s Presidential Green Chemistry Challenge Awards program celebrated its seventh anniversary.
Green chemistry, also called sustainable chemistry, was formally delineated at the Environmental Protection Agency a dozen years ago with the aim of preventing pollution through better process design rather than by managing emissions and waste--the "end of the pipe" solution. Green chemistry is based on a set of 12 principles that provide a jumping-off point for all chemists and chemical engineers to use classical chemistry as well as emerging fields of biotechnology and nanotechnology to design chemical products and processes that have little or no impact on the environment. Proponents of green chemistry are now eager to assess how far it has gone in providing environmental and economic benefits for the chemical and other manufacturing industries. Although there are few examples of green processes that have had an industrywide impact, hundreds of individual products or processes have been improved through the principles of green chemistry (PDF file). It's clear that progress has been made, but most observers agree that the pace of implementing green technologies needs to be picked up. One of those observers is organic chemistry professor Jürgen O. Metzger of the University of Oldenburg, in Germany. Metzger and coauthors wrote a review earlier this year, in advance of the United Nations World Summit on Sustainable Development held in Johannesburg [Angew. Chem. Int. Ed., 41, 414 (2002)]. The review takes a critical look at progress made in reaching the goals set forth in Agenda 21, a comprehensive plan of action that resulted from the UN Conference on Environment & Development held in Rio de Janeiro 10 years ago. Some aspects of Agenda 21 have been addressed, they note. For example, regarding the safety of chemicals, the chemical industry's Responsible Care environmental, health, and safety initiative makes a considerable contribution. "In general, it must be said that chemical companies are attempting to understand the implications of sustainable development for them," they write. IMPORTANT AREAS of ongoing focus include the use of renewable raw materials, direct oxidations using oxygen, improved separations technology, and all forms of catalysis. However, the current pace is much too slow, Metzger believes. "Progress toward sustainable chemistry has to increase drastically to meet the challenges of this century," he tells C&EN. For example, Metzger points to Vision 2020, an initiative of U.S. chemical companies that has the goal of accelerating innovation and technology development that may be beyond the risk threshold of individual companies. Under Vision 2020, one goal is to reduce chemical industry energy consumption per product unit by 30%, Metzger notes. Similar aims have been formulated in Europe, he adds. Metzger also cites a National Research Council report that predicts 25% of organic chemical production in 2020 will come from renewable feedstocks. "However, I cannot see technologies available now to accomplish those goals," he says. "Even the results of basic research that are necessary to develop these technologies are only fragmentarily available." The Johannesburg summit aimed to assess progress toward attaining the goals of Agenda 21, strengthening commitment of parties to the program and setting priorities for further action (C&EN, April 22, page 15). The outcome of the summit indeed was recommitment of governments to meet specific targets for water, sanitation, health, agriculture, energy, and biodiversity and ecosystem management, as well as the need for corporate responsibility (C&EN, Sept. 9, page 12). But more than anything else, the summit was a message to the world to stop talking about what needs to be done and to get on with implementation. One reason for the apparent slow change, Metzger believes, is that chemical companies are comfortable with petrochemicals and are reluctant to process alternative renewable feedstocks such as plant oils and carbohydrates, which may not be suited for usual petrochemical processing. "Chemists learn to think in petrochemical product lines," Metzger observes. "It's difficult for them to develop alternative thinking." An exception is Cargill Dow's NatureWorks brand polylactic acid (PLA), which is prepared by a novel synthesis starting from corn-derived dextrose. NatureWorks, recipient of a 2002 Presidential Green Chemistry Challenge Award, is the first polymer class to be produced from annually renewable resources. NatureWorks polymers are expected "to bridge the gap in performance between conventional synthetic fibers and natural fibers" used in clothing and carpeting, the company says, and compete head-to-head with plastics for food packaging and for agricultural or gardening applications. Cargill Dow's PLA production requires 20 to 50% less fossil-fuel resources than comparable plastics, the company says, and it is biodegradable or readily hydrolyzed back into lactic acid for recycling. The first world-scale NatureWorks PLA plant, located in Blair, Neb., became operational earlier this year and has an annual capacity of 140,000 metric tons. Cargill Dow expects to sell up to 50,000 metric tons of PLA in 2002 and to achieve a global capacity of 500,000 metric tons by 2006.
But if process intensification is such a good idea, then why isn't everyone doing it? That question was recently addressed by technical director Andrew Green and chemistry consultant Richard Jackson of BHRSolutions, Cranfield, England, a business that provides process intensification equipment and services for the chemical industry. In an article in the August issue of tce (The Chemical Engineer), the monthly magazine published by the U.K. Institution of Chemical Engineers, Green and Jackson discuss the conservative nature of the chemical industry when it comes to adopting new technologies. "No one can shake the industry and say, 'Stop being conservative,' " the authors note, but "conservatism is often rooted in good sense." One example they cite is a pharmaceutical industry study showing that a six-month delay in product introduction using a new process could reduce a product's contribution to profits by 50% over its lifetime. Thus companies tend to stick with a proven technology, Green and Jackson state. The "rush to be second" is another manifestation of industry's conservatism, they note. Most companies would like to see a similar process up and running before committing to their own development project. On the other hand, if a company gains a competitive advantage from a process intensification improvement, it likely won't want to tell its competitors. The company probably wouldn't disclose that a project had failed either. In the end, the success of process intensification will need to be more than implementing clever technologies, Green and Jackson note. "It needs to integrate not just chemistry and chemical engineering, but finance and marketing as well." Despite the progress of green chemistry, many chemists and chemical engineers are still in the dark about what makes a reaction or overall process greener. Atom economy, one of the key principles of green chemistry, is one of the primary metrics that chemists and chemical engineers can use to guide their work. Introduced by Stanford University chemistry professor Barry M. Trost in 1991, the concept holds that synthetic methods should be designed for maximum incorporation of all reagents into the final product. In other words, atom economy tracks how much of what is put into a pot ends up in the product. Selectivity is an important component of atom economy. Ideal atom economy would be 100%: No protecting groups would be used and no by-products would be generated. Thus elimination and substitution reactions are less green and should be either reworked or replaced in favor of rearrangements, additions, or other concerted reactions. Trost recently reiterated the concept of atom economy and the high impact it can have in chemical synthesis [Acc. Chem. Res., 35, 695 (2002)]. "There are many issues that must be addressed to make organic synthesis more environmentally benign by design," Trost points out. "One fundamental consideration is the stoichiometry of the process. Until the present, virtually all attention focused on solving problems of selectivity regardless of the price that might be paid in terms of atom economy. There is no reason to believe that selectivity and atom economy are mutually exclusive goals." "Progress toward sustainable chemistry has to increase drastically to meet the challenges of this century." THE DIELS-ALDER reaction is a good example, Trost says, since it comes close to being the ideal reaction for forming C2C bonds. It can be chemo-, regio-, diastereo, and enantioselective as well as atom economical. "Surprisingly, few industrial processes make use of such a reaction," Trost notes, "although it is an extremely important research tool for the synthesis of complex molecules." Hydroformylation, on the other hand, represents an atom-economical reaction that has gained use industrially, he says, while catalytic hydrogenation comes the closest to being an ideal reaction that is practiced both industrially and academically. "Unfortunately, in multistep syntheses very few of the reactions used, if any, are additions because so few such reactions really exist," Trost points out. While atom economy is a useful way of comparing alternative pathways to a particular product on paper, it does not take into account yield, excess amounts of reactants, solvent losses, reagents used during work-up, or energy consumption. These parameters are considered in another primary green chemistry metric, called the E-factor, which was introduced in 1992 by organic chemistry professor Roger A. Sheldon of Delft University of Technology, in the Netherlands. THE E-FACTOR is determined by dividing the amount of waste in a process by the amount of the product. Waste is determined by subtracting the mass of the product from the known or estimated mass of reagents, unrecovered solvent, energy, and other inputs in a process. A higher E-factor means more waste and consequently greater negative environmental impact; a value of 0 is optimum. Sheldon developed the E-factor "to show students how (in)efficient chemical processes in the fine chemicals industry actually are," he says. Sheldon based the concept on his work at DSM Andeno (now DSM Fine Chemicals) in the late 1980s. The overall E-factor for the company was about 20, Sheldon relates. "We thought that this was, relatively speaking, not bad." Because E-factor and related metrics consider only the amount and not the nature of the waste formed, they are still not a true measure of the environmental impact of processes, he points out. For example, 1 kg of sodium chloride does not have the same impact as 1 kg of a chromium salt. Sheldon and others have addressed this point. For example, in some papers Sheldon has multiplied the E-factor by an unfriendliness factor (Q) to give a parameter he calls the environmental quotient (EQ). "The magnitude of Q is obviously debatable, but the point is one can put a number to a waste stream," Sheldon says. "Indeed, the challenge is to come up with a metric system for quantitatively assigning a Q value." Sheldon believes that in time EQ or a related metric will become an industry standard for evaluating the business and environmental implications for chemical processes before manufacturing, rather than attempting to adapt after the fact. The important aspect of these metrics is that the chemical industry is now seriously thinking and talking about green chemistry and sustainability, Sheldon adds. The use of atom-efficient, low-salt catalytic processes as replacements for antiquated classical stoichiometric reagents in the fine chemicals and pharmaceuticals industries is becoming quite commonplace, he notes. Homogeneous, heterogeneous, and enzymatic catalysis are now important considerations in process research departments. Solvent usage is also receiving increasing attention, which was not the case 10 years ago. "There is clearly a conscious effort by fine chemicals and pharmaceuticals industries to clean up their act," Sheldon concludes. While useful to help guide industrial chemists and chemical companies, metrics and anecdotal information still don't provide a good measure of the degree to which green technologies are being implemented. One of several efforts to assess industrial adoption of green chemistry is a patent analysis conducted by the American Chemical Society. The analysis was described by Raymond J. Garant, manager of environmental policy in ACS's Office of Legislative & Government Affairs, at the 6th Green Chemistry & Engineering Conference held in June in Washington, D.C. The goal of the analysis is to determine which industrial sectors are conducting patentable green chemistry research and which sectors are taking those patents and carrying them through to downstream products and processes. Although the term "green chemistry" is increasingly appearing in chemical research papers, references to "green chemistry" do not appear in patent titles or abstracts, Garant noted. Therefore, a set of about 50 applicable search terms--including "biocatalysis," "waste minimization," "pollution prevention," and "inherently safer"--was generated and tested by trial and error. Many green technologies also may not be patented but instead treated as trade secrets and kept undisclosed, he added. Thus the ability to obtain an accurate measure of green chemistry patent activity is limited, he said, and the results must be examined only to find general trends, not to draw specific conclusions. The search turned up 3,235 U.S. patents for the period 1983–2001 that were classified as green chemistry. Some 10,000 related utilization patents were found that referenced the initial set as prior art. The U.S. is the origin of 65% of the patents, followed by Europe, with 24%, and Japan, with 8%.
THE PATENT RATE was steady through the mid-1980s at about 70 patents per year, Garant reported. From 1989 to 1994, there was a jump from 92 to 251 patents per year. From 1995 to 2001, the rate leveled off to an average of 267 patents per year. For comparison, total U.S. chemical patents awarded for 2001 was 45,788 (C&EN, Oct. 28, page 60). The period of rapid increase in the early 1990s corresponds to the time when the Montreal protocol, reauthorization of Superfund law, the Clean Air Act Amendments, and the Pollution Prevention Act were enacted. It was also the time that EPA established its Green Chemistry and Design for the Environment programs. Since that time, no major environmental regulatory laws have been reauthorized or enacted. The preliminary data suggest that green chemistry may be implemented as a means to reach regulatory compliance, Garant said. Regulatory issues, he pointed out, are just one factor among many, including economics and public perception. He further commented that it may be too early to tell which factor carries the most weight, adding that additional work needs to be done. A paper is being prepared with full analysis of the patent search. A ROUNDABOUT MEASURE of the benefits of green chemistry can be made by looking at data provided by companies and individuals in their Presidential Green Chemistry Challenge Award nomination package. EPA has kept a summary of the combined benefits of the award-winning technologies since the awards began in 1996. These numbers include potential elimination of some 800,000 tons per year of chemicals, including chlorofluorocarbons; volatile organic solvents; and persistent, toxic, and bioaccumulating chemicals. An additional 650 million gal per year of chemicals and organic solvents has reportedly been eliminated. More than 38 billion gal per year of process water has been saved in the production of photographic film, semiconductors, textiles, and other products. Some 90 trillion Btu per year of energy consumption and 430,000 tons per year of CO2 emissions have also been eliminated. As impressive as these numbers seem, they are a drop in the bucket compared to the savings being made by the chemical industry overall, which in turn is a drop in the bucket compared to what could be done. For example, EPA's Toxics Release Inventory report for 2000 noted that some 3.5 million tons of about 650 listed chemicals were released directly to the environment. This is in addition to the nearly 19 million tons of production-related managed waste included on the EPA listing that is handled by recycling, waste treatment, energy recovery, and other methods. Not all of the push to develop more sustainable chemical practices comes from environmental advocacy groups, the chemical industry, or government regulators. Some of the pressure to improve comes from downstream users of chemicals who discover that their goals of contributing to sustainable development are often based in chemistry. "Companies are starting to ask manufacturers to help them green their products and therefore are driving some demand for new or greener products and processes," notes Lauren Heine, director of green chemistry and engineering at Zero Waste Alliance, a nonprofit organization that provides education and technical assistance to companies. "Many of these companies are doing this in part because it is the 'right' thing to do, but also because they are being proactive and see trends that indicate increasing costs of resources such as water and waste disposal as well as public opinion, liability, and potential for a competitive advantage are playing a larger role in an increasingly informed marketplace." These companies may work with vendors by requesting reformulation of a product to exclude certain toxics or materials derived from certain feedstocks, Heine says. They may ask for full chemical disclosure on dyes, fabrics, and polymers. While this is common for ingredients used in the pharmaceutical industry, it is not nearly as common in retail apparel, carpeting, and cleaning products, she notes. Zero Waste Alliance helps product formulators and other users of chemicals to implement environmental management systems such as the ISO 14000 family of standards, Heine says. Having an environmental management system or the framework of Responsible Care is extremely important, she adds. "But just because you have the structure doesn't mean your performance will be exceptional. Goals still need to be set--they can be very modest or even very ambitious--but the framework is helpful in meeting those goals." Improving the function of that framework to help boost sustainable development is a key reason the chemical industry's Responsible Care program was recently revitalized, according to chemical engineer Barry Stutts, manager for Responsible Care at Bayer Corp. and one of the leaders in shaping the changes. "Philosophically, Responsible Care is changing from defining the important actions that need to be taken to managing how those tasks are going to be done," Stutts says.
THE ORIGINAL GOALS of Responsible Care when it was implemented in the U.S. by the American Chemistry Council 15 years ago were to improve the chemical industry's environmental, health, and safety performance and to build public trust. An underlying goal was to help soften the blow of new regulatory controls that threatened the industry's economic performance. At first, Responsible Care was designed to be ahead of regulations, Stutts says, but now that regulations have been catching up, it's time to take the next step. The new Responsible Care is designed to better embrace the public's growing interest in product safety and sustainable development and to raise public perception of the industry's environmental, health, and safety performance, Stutts explains. Besides adding a new code for security, Responsible Care will now require ACC member companies to report a number of environmental and business metrics on an annual basis starting in January 2004. The metrics data must be verified by a third party and will be publicly available. Some of the metrics include data on Toxics Release Inventory chemical emissions, which are already required to be reported to EPA, as well as greenhouse gas emissions and energy efficiency. Additional data that will be reported include health-effects test results from the chemical industry's High Production Volume Chemical Test Program and the Long-Range Research Initiative. "Reporting data and being open about the results will help motivate the industry toward better performance," Stutts believes. And a communication and outreach campaign slated to begin in a couple of years will emphasize that better performance to the public. The new framework for Responsible Care, which is based on ISO 14001, will aid companies in considering initiatives such as green chemistry as they pursue R&D on new product lines or reevaluate existing products and processes for possible improvement, Stutts says. It also could provide a framework that proponents of green chemistry can use to better gauge progress. But it won't be a cure-all. Safety and environmental protection are certainly key factors in making business decisions, Stutts observes. But there are also financial risks and public perception risks. So there needs to be a fair balance. "If making a process improvement or a raw material improvement will cost more money in the short term, but in the long term provide a greater benefit in environmental performance and product quality, then a company is going to make the improvement," he says. "Realistically, however, a company is not going to sell a product if it is going to lose money. These are the issues that the chemical industry--and all industries--wrestle with on a daily basis, and they need to be wrestled with daily." But making a profit is not just to satisfy shareholders, he adds. It is an important part of corporate responsibility to provide an economic benefit to local communities and to be a good neighbor. "This greater understanding of what's important is where the chemical industry is starting to move," Stutts says. He points to Bayer's company pride at winning the 2002 Responsible Care Leadership Award for large companies, a highly coveted prize in the industry. This award and the company's two Presidential Green Chemistry Challenge Awards, received in 2000 and 2001, are something the company can share with its local communities. "It's an exciting time to be a part of this significant, positive change in how Responsible Care is implemented," Stutts remarks. Even with that kind of enthusiasm, many questions remain for achieving sustainability through green chemistry: Can petroleum feedstocks successfully be replaced with biomass-derived feedstocks? Can CO2 or other emissions be converted into useful chemicals? Can hydrogen be the energy source of the future? Can agricultural chemicals and pharmaceuticals be formulated so they have better selectivity and bioavailability and are completely biodegradable and benign in the environment? Some doubters in the chemistry community say that achieving sustainable growth through green chemistry is an impossible dream. Proponents of green chemistry would counter by saying that sustainability is a direction, not a destination, and that green chemistry is a fundamental tool to address environmental and sustainability issues at the molecular level. Either way, to be serious about sustainability, chemists and chemical engineers of all walks of life will need to take the principles of green chemistry to heart and not delay putting them into practice. |
|||||||||||||||||
|
Chemical & Engineering News |
|||||||||||||||||
