The methodology and the ranking process covered in this chapter are limited by the unit operations or manufacturing processing options that are being compared in each case scenario and to a lesser extent, by the subjectivity of the experts ranking the options. These limitations also mean that general conclusions about the technologies should not be drawn from the specific rankings developed for a given case scenario if the technologies are applied using very different conditions or scenarios.
Despite these limitations, this methodology represents a standardized, documented, and systematic approach to performing technology comparisons. In addition, the methodology integrates environmental, health, and safety considerations with efficiency and operational aspects to assist with choosing technologies and equipment.
As has been demonstrated in the examples in this chapter, clear differentiation among technology options is possible, and the results of the analysis may be presented and communicated in a very concise, clear, and easy-to-understand manner. At the same time, the detailed analysis and calculations are transparent and easy to share if desired. As chemists and engineers expand their understanding of what constitutes green or clean technologies, we should be able to move at a faster pace toward more sustainable business practices.
Technology Environment Safety Efficiency Energy
A Yellow Red Yellow Yellow
B Yellow Yellow Yellow Red
PROBLEMS
23.1 You are evaluating technology A, a well-understood, well developed technology, against technology B, an emerging technology. How would you account for the different degree of development of the new and traditional technologies?
23.2 We noted earlier that other methodologies are available for a systematic comparison of technologies from a green engineering or sustainability perspective.
(a) Investigate two of these technologies and explain at a high level the basis for the comparisons.
(b) How do they differ from the methodology described in this chapter? Highlight the advantages and disadvantages.
23.3 The metrics in Table P23.3 were calculated for a fermentation process and a chemical process for the production of an active pharmaceutical ingredient (API). Both processes use organic solvents in the workup, and there is the possibility of recovering the solvent at different rates. You are the head of technology development and have to select one of the processes. Which would you recommend?
TABLE P23.3 Metrics for API Production
Parameter Chemical Process Fermentation Process
Purity (%) 98 98
Yield (mol%) 19 39
Cycle time (months) 18 3
Mass intensity excluding water (kg/kg API)
350 468
Mass productivity 0.3 0.2
Solvent intensity, excluding water (kg/kg API)
332 452
% Solvent 95 97
Water mass (kg) 118 259
Solvent recovery mass 114 405
E-factor kg waste/kg API, including wastewater
467 726
kg waste/kg API, including wastewater, with solvent recovery
353 321
Materials of concern DCM, hexane Pentane
Occupational exposure limits Dichloromethane, 50 ppm Acetic acid, 10 ppm TWA 8 h
Diisopropylamine, 5 ppm Glycerol, 10mg/m3TWA 8 h
HCl (as gas), 2 ppm ceiling Peracetic acid, 1 ppm TWA 8 h
Hexane, 50 ppm Sodium hydroxide, 2mg/
m3ceiling
MTBE, 50 ppm Sulfuric acid, 0.2mg/m3 Sodium hydroxide,
2mg/m3Ceiling
TWA 8 h
23.4 Use the technology comparison methodology to assess the chemical and biocatalytic routes to 7-ACA, as presented in Example 8.1. Are the conclusions the same as in Example 8.1? The descriptions follow:
(a) Chemical route description. A four-step process is used to convert the potassium salt of cephalosporin C to 7-ACA, as shown in Figure 8.2(a). In the first step, a common protection strategy is used convert the acid to an anhydride and the amine to an amide using chloracetyl chloride in the presence of the base, dimethyl aniline. Next, phosphorous pentachloride is added to the mixed anhydride, which is held at 37C to form the imodyl chloride, which is followed sequentially by the addition of methanol to form the transient imodyl ether and then water to form 7-ACA. 7-ACA is precipitated by using ammonia to change the pH to the isoelectric point, and the 7-ACA is recovered methanol wet and then dried under vacuum.
(b) Biocatalytic route. A three-step process is used to convert the potassium salt of cephalosporin C to 7-ACA, as shown in Figure 8.2(b). A solution of cephalo- sporin C is stirred with the immobilized biocatalystD-amino acid oxidase (DAO) while air is bubbled through the solution to supply the required oxygen. The by- product of the bioconversion, hydrogen peroxide, reacts spontaneously with the keto intermediate to give glutaryl 7-ACA. The reaction is carried out at a constant temperature (18C) and elevated pressure (5 bar) under controlled pH (starting at pH 7.3 and rising to 7.7 at completion) to ensure the desired conversion. Additional hydrogen peroxide may be added to promote greater conversion to glutaryl 7-ACA if desired. Upon completion, the solution contain- ing glutaryl 7-ACA is separated from DAO, and immobilized glutaryl 7-ACA acyclase (GAC) is added at pH 8.4 and temperature 14C to obtain the desired 7-ACA. Dilution may be required to control the concentration, but upon completion of the reaction, the 7-ACA is separated from GAC and isolated.
In both cases, the enzymes may be recovered and reused.
23.5 In Example 15.2 we compared microreactors with full-scale production batch reactors for the reaction between a carbonyl compound and an organometallic agent
Parameter Chemical Process Fermentation Process
Sulfuric acid, 0.2mg/m3 TWA, 8 h
THF, 50 ppm
Solvents DCM, ethyl acetate,
heptane, Hexane, methanol, methyl acetate, THF
Acetic acid; acetone, heptane; pentane
Process energy (MJ/kg API) 693 1,829
Waste treatment energy (MJ/kg API)
1,382 2,121
Life cycle energy (MJ/kg API) 7,281 15,211
Parameter Chemical Process Fermentation Process
to produce a fine chemical.25How would the technologies compare based on the metrics calculated in Example 15.2? The reaction proceeds as
( )n
M R2
R1 O
( )n
OM
R2 R1
+
in the liquid phase and is exothermic (standard heat of reaction ca. –300 kJ/mol).
The main reaction and most side reactions are fast (<10 s), some parallel and consecutive reactions can occur, and the compounds are sensitive to temperature.
Experiments were carried out in microreactors and were compared with laboratory- and full-scale operations. The characteristics of the reactor systems evaluated are given in Table P23.5.
23.6 In Example 15.4 we studied centrifugal separators compared with gravity separators.
How would the two technologies compare based on the metrics calculated in Example 15.2? The centrifugal separators were used in the extraction of a pharma- ceutical intermediate. The phase separations are used in the mother liquors contain- ing methylene chloride (MDC, specific gravity of 1.33) and water washes. For the batch process, the extraction can be described in a simplified manner as an MDC–
water extraction, two 2000-L water washes, and one MDC final wash. The standard batch output is the extraction of 179 kg of intermediate per batch. The data for this comparison are given in Table P23.6.
TABLE P23.5 Reactor System Characteristics Reactor Type T(C)
Residence
Time Yield (%)
Volume/Area
(m2/m3) Dimensions
Flask 40 0.5 h 88 80 0.5 L
Stirred vessel (production)
20 5 h 72 4 6000 L
Microreactor 10 <10 s 95 10,000 216 channels
ofwhẳ40 220mm
TABLE P23.6 Data for Equipment Comparison
Centrifugal Separators Gravity Separators
Volume of MDC (L/batch) 4,165 4,900
Volume of water washes (L/batch) 10,000 4,000
Yield (% difference from gravity separators due to losses in spent stream)
10 0
Power usage 7.5 hp at 30 gpm 2 h of agitation
Process time (h) 12 22
1. Saling, P., Kicherer, A., Dittrich-Kr€amer, B., Wittlinger, R., Zombik, W., Schmidt, I., Schrott, W., Schmidt, S. Eco-efficiency analysis by BASF: the method.Int. J. Life Cycle Assess., 2002, 4, 203–218.
2. Cabezas, H., Bare, J., Mallick, S. Pollution prevention with chemical process simulators:
the generalized waste reduction (WAR) algorithm—full version.Comput. Chem. Eng., 1999, 23 (4–5), 623–634.
3. U.S., Environmental Protection, Agency.Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts(TRACI):User’s Guide and System Documentation. EPA 600/R- 02/052. National Risk Management Research Laboratory, Cincinnati, OH, 2003.
4. Jimenez-Gonzalez, C., Curzons, A. D., Constable, D. J. C., Overcash, M. R., Cunningham, V. L.
How do you select the “greenest” technology? Development of guidance for the pharmaceutical industry.Clean Products Process., 2001, 3, 35–41.
5. Gani, R., Jứrgensen, S. B., Jensen, N. Design of sustainable processes: systematic generation and evaluation of alternatives. Presented at the 7th World Congress of Chemical Engineering, 2005.
6. Carvalho, A., Gani, R., Matos, H. , et al. ( 2008)Design of sustainable chemical processes:
Systematic retrofit analysis generation and evaluation of alternatives.Process Saf. Environ. Prot., doi:10.1016/j.psep.2007.11.003.
7. Carvalho, A., Gani, R., Matos, H. Design of sustainable processes: systematic generation and evaluation of alternatives. In16th European Symposium on Computer Aided Process Engineer- ing and 9th International Symposium on Process Systems Engineering, Vol. 2, Marquardt, W., Pantelides, C. (Eds.) Elsevier, New York, 2006, pp. 817–822.
8. Curzons, A. D., Constable, D. J. C., Mortimer, D. N., Cunningham, V. L. So you think your process is green, how do you know? Using principles of sustainability to determine what is green: a corporate perspective.Green Chem., 2001,3.1–6.
9. Lapkin, A., Constable, D.J.C.,Eds.Green Chemistry Metrics. Blackwell Publishers, Hoboken, NJ, 2008.
10. Jimenez-Gonzalez, C., Constable, D. J. C., Curzons, A. D., Cunningham, V. L. Developing GSK’s Green technology guidance: methodology for case-scenario comparison of technologies.Clean Techno. Environ. Policy, 2002, 4, 44–53.
11. Jimenez-Gonzalez, C., Constable, D. J. C., Henderson, R., De Leeuwe, R., Cardo, L. Embedding sustainability into process development: GlaxoSmithKline’s experience. InProceedings of the 7th International Conference on Foundations of Computer-Aided Process Design(FOCAPD):
Design for Energy and the Environment. Breckenridge, CO, June 12–17, 2009.
12. Swiss Federal Laboratories for Material Testing and, Research.ECOPRO: Life Cycle Analysis Software. EMPA, St. Gallen, Switzerland, 1996.
13. PEMS 4: Life Cycle Assessment Software. PIRA International. Leatherhead, UK, 1998.
14. Dumas, R. D.Energy Usage and Emissions Associated with Electric Energy Consumption as Part of a Solid Waste Management Life Cycle Inventory Model. Department of Civil Engineering, North Carolina State University, Raleigh NC, 1997.
15. Jimenez-Gonzalez, C., Kim, S., Overcash, M. R. Methodology for developing gate-to-gate life cycle inventory information.Int. J. Life Cycle Assess., 2000, 5, 153–159.
16. Jimenez-Gonzalez, C., Overcash, M. R. Energy sub-modules applied in life-cycle inventory of processes.Clean Products Process., 2000, 2, 57–66.
17. Ecoinvent: Swiss Centre for Life Cycle Inventories. 2008.http://www.ecoinvent.org, accessed Nov. 10, 2008.
18. Bundesamt f€ur Umwelt, Wald und Landschaft. O¨ kobilanzen von Packstoffen., Schriftenreihe Umwelt 132. BUWAL, Bern, Swetzerland, 1991.
19. SimaPro. PRe Consultants. http://www.pre.nl/simapro/default.htm.
20. DEAM Database. EcoBilan. http://www.ecobalance.com/uk_deam.php.
21. UMBERTO software. Institute for Environmental Informatics, Hamburg, Germany.http://www.
umberto.de/en/.
22. GaBi Software. PE International.http://www.gabi-software.com/.
23. Lewis, R. J.Sax’s Dangerous Properties of Industrial Materials,10th ed. Wiley, New York, 2000.
24. Jimenez-Gonzalez, C., Curzons, A. D., Constable, D. J. C., Cunningham, V. L. Int. J. Life Cycle Assess., 2004, 9, 114.
25. Jenssen, K. F. Micromechanical systems: status, challenges and opportunities.AIChE J., 1999, 45, 2051–2054.
24