Functional priorities in LCA and design for environment

Aim, Scope and Background  The interest in environmental questions has increased enormously during the last decade. Environmental protection has become an issue of strategic importance within the manufacturing industry and many companies are now working in the field of Design for Environment (DFE). The main purpose of DFE is to create products and services for achieving a sustainable society. Designers are widely believed to have a key role in adapting products to a sustainable society and one of the major instruments in the context of Design for Environment is Life Cycle Assessment (LCA). However, product development creates particular challenges for incorporating environmental issues that combine functional and environmental assessment. A natural and important part of product design is to define and analyse the functions of the product. Consequently, the functional unit in LCA is a core issue in DFE. Most recent research in DFE has focused on how to reduce the environmental impact of products throughout their life-cycle by addressing environmental aspects, while little attention has been given to the functionality of the product. Additionally, early product development phases, so called re-think phases, are considered to have the influence on major changes in products in general. These phases have thus the highest potential for changing products and product systems towards a sustainable development. Main Features  This paper discusses an extended functional representation in design for environment methods to evaluate sustainable design solutions, especially in early (re-think) phases of product design. Based on engineering-design science and several case studies, a concept has been developed describing how functional preferences can be visualised in design for environment and product development. In addition, the functional unit in LCA is discussed. The concept is called Functional Profile (FP) and is additionally exemplified in a case study on radio equipment. Discussion  The new functional characterisation concept helps identify functional priorities in design for environment. The Functional Profile is a structured, systematic and creative concept for identifying the necessary functions of a new product. The FP is envisioned to complement existing design for environment methods, not to replace them. Instead of being a product-development tool or method, the concept is an approach that increases understanding of inter-reactions between functional characteristics of products and their environmental characteristics, which furthermore facilitates trade-off decisions. One of the objectives behind the concept is to highlight the importance of balancing functional requirements and environmental impacts, presenting both the advantages and disadvantages of the product. Outlook  A second paper will be produced to complement the functional-environmental characterisation concept in early product development phase, presenting the environmental characterisation part and illustrating correlations between the functional and environmental sides.     

Simulation and analysis for sustainable product development

Purpose

Simulation plays a critical role in the design of products, materials, and manufacturing processes. However, there are gaps in the simulation tools used by industry to provide reliable results from which effective decisions can be made about environmental impacts at different stages of product life cycle. A holistic and systems approach to predicting impacts via sustainable manufacturing planning and simulation (SMPS) is presented in an effort to incorporate sustainability aspects across a product life cycle.

Methods

Increasingly, simulation is replacing physical tests to ensure product reliability and quality, thereby facilitating steady reductions in design and manufacturing cycles. For SMPS, we propose to extend an earlier framework developed in the Systems Integration for Manufacturing Applications (SIMA) program at the National Institute of Standards and Technology. SMPS framework has four phases, viz. design product, engineer manufacturing, engineer production system, and produce products. Each phase has its inputs, outputs, phase level activities, and sustainability-related data, metrics and tools.

Results and discussion

An automotive manufacturing scenario that highlights the potential of utilizing SMPS framework to facilitate decision making across different phases of product life cycle is presented. Various research opportunities are discussed for the SMPS framework and corresponding information models.

Conclusions

The SMPS framework built on the SIMA model has potential in aiding sustainable product development.     

Product label identification with OCR for model-specific reuse,repair, and recycling: A case study for washing machines

In this study, a procedure to automatically identify the product model by evaluating an image of the label is presented. First, object character recognition (OCR) extracts text from the product label. Second, to identify the product model, the extracted text is compared with unique model references in a database, giving access to other model-specific information. For this comparison, a novel variation of the partial ratio matching algorithm was developed. The product-model identification procedure is integrated into an interactive web application, which allows for model identification to be performed during preparation for reuse, repair, and recycling: The SmartRe application. Three datasets consisting of 466, 422, and 771 images of washing machine product labels were gathered in collaboration with a (1) professional repair company for consumer devices, (2) a nonprofit repair and reuse center that resells devices in second-hand stores, and (3) a large recycling company. Results demonstrate that 96%, 91%, and 40% of the product models were correctly read from the product label with OCR, respectively. Of these recognized models, 51%, 88%, and 76% were successfully identified with the SmartRe application by comparing the extracted text with the model database. Further analysis also demonstrated that 72% of the washing machine models identified at the nonprofit repair and reuse center were also found at the recycling facility and that 12% of these models are predicted to be less than 10-years-old. This highlights the potential of the SmartRe application to assist in product triage for reuse at recycling centers.     

Setting Single-Period Optimal Capacity Levels and Prices for Substitutable Products

In this paper, we consider how a company that has the flexibility to produce two substitutable products would determine optimal capacity levels and prices for these products in a single-period problem. We first consider the case where the firm is a price taker but can determine optimal capacity levels for both products. We then consider the case where the firm can set the price for one product and the optimal capacity level for the other. Finally, we consider the case where capacity is fixed for both products, but the firm can set prices. For each case, we examine the sensitivity of optimal prices and capacities to the problem parameters. Finally, we consider the case where each product is managed by a product manager trying to maximize individual product profits rather than overall firm profits and analyze how optimal price and capacity decisions are affected.     

Microbial export of lactic and 3-hydroxypropanoic acid: implications for industrial fermentation processes

Lactic acid and 3-hydroxypropanoic acid are industrially relevant microbial products. This paper reviews the current knowledge on export of these compounds from microbial cells and presents a theoretical analysis of the bioenergetics of different export mechanisms. It is concluded that export can be a key constraint in industrial production, especially under the conditions of high product concentration and low extracellular pH that are optimal for recovery of the undissociated acids. Under these conditions, the metabolic energy requirement for product export may equal or exceed the metabolic energy yield from product formation. Consequently, prolonged product formation at low pH and at high product concentrations requires the involvement of alternative, ATP-yielding pathways to sustain growth and maintenance processes, thereby reducing the product yield on substrate. Research on export mechanisms and energetics should therefore be an integral part of the development of microbial production processes for these and other weak acids.     

Introducing Templates for Sustainable Product Development

We have previously developed a method for sustainable product development (MSPD) based on backcasting from basic sustainability principles. The MSPD informs investigations of product‐related social and ecological sustainability aspects throughout a concurrent engineering product development process. We here introduce “templates” for sustainable product development (TSPDs) as a complement. The idea is to help product development teams to arrive faster and more easily at an overview of the major sustainability challenges and opportunities of a product category in the early development phases. The idea is also to inform creative communication between top management, stakeholders, and product developers. We present this approach through an evaluation case study, in which the TSPDs were used for a sustainability assessment of televisions (TVs) at the Matsushita Electric Group. We study whether the TSPD approach has the ability to (1) help shift focus from gradual improvements of a selection of aspects in relation to past environmental performance of a product category to a focus on the remaining gap to a sustainable situation, (2) facilitate consensus among organizational levels about major sustainability challenges and potential solutions for a product category, and (3) facilitate continued dialogue with external sustainability experts, identifying improvements that are relevant for strategic sustainable development. Our findings indicate that the TSPD approach captures overall sustainability aspects of the life cycle of product categories and that it has the above abilities.     

Kinetics of microbial product formation and its consequences for the optimization of fermentation processes

Different types of product formation kinetics are discussed with respect to their significance for fermentation process economics. Microbial products belonging to various classes are formed in a growth-coupled manner. It is often found that the specific rate of product formation increases with the specific growth rate, approaching a maximum at higher growth rates. It is illustrated that for such types of relationship between the product formation rate and the growth rate process conditions are optimal when the specific rate of product formation is about half-maximal.     

Pilot- and process-scale techniques for cell disruption

Microorganisms are a source of protein with catalytic and/or biological activity, which are of increasing commercial interest for applications in industry or therapy. For the isolation of intracellular products cell disruption is necessary. In principle, chemical, biological, or physical means may be employed to release proteins from cells. These different approaches are reviewed with special emphasis on scale-up and possible industrial operation. Mechanical devices have been improved considerably in recent years and appear most universally suited to cell disintegration. Chemical extraction or enzymatic lysis offers improved selectivity but requires individual procedures for each product. For a final process design, product yield and cost of the unit operation must be considered as well as the possible implications for the subsequent steps in product recovery, especially on solid/liquid separation.     

A downstream process for production of a viable and stable Bacillus cereus aquaculture biological agent

Biological products offer advantages over chemotherapeutics in aquaculture. Adoption in commercial application is lacking due to limitations in process and product development that address key end user product requirements such as cost, efficacy, shelf life and convenience. In previous studies, we have reported on the efficacy, physiological robustness and low-cost spore production of a Bacillus cereus isolate (NRRL 100132). This study examines the development of suitable spore recovery, drying, formulation and tablet production from the fermentation product. Key criteria used for such downstream process unit evaluation included spore viability, recovery, spore balance, spore re-germination, product intermediate stability, end product stability and efficacy. A process flow sheet comprising vertical tube centrifugation, fluidised bed agglomeration and tablet pressing yielded a suitable product. The formulation included corn steep liquor and glucose to enhance subsequent spore re-germination. Viable spore recovery and spore balance closure across each of the process units was high (>70% and >99% respectively), with improvement in recovery possible by adoption of continuous processing at large scale. Spore re-germination was 97%, whilst a product half-life in excess of 5 years was estimated based on thermal resistance curves. The process resulted in a commercially attractive product and suitable variable cost of production.     

The electrophysiological bases for linear and for nonlinear product term lateral inhibition and the consequences for wide field textured stimuli

The electrophysiological bases of linear, and of nonlinear product term recurrent lateral inhibition are defined and the general equations derived. Defining texture as sinusoidal spatial luminance functions, the response characteristics of nonlinear product term lateral inhibitory arrays to wide field textured stimuli are derived, and applications to locust DCMD and Y retinal ganglion cells discussed.     

Some inequalities for the expectation of a product of functions of a random variable and for the multivariate distribution function at a random point

Under certain assumptions the expectation of a product of functions of a random variable is greater (smaller) than the product of expectations. The multivariate distribution function of m independent random variables at a random point is greater than the product of the distribution functions of the m variables.     

Effectiveness factors for substrate and product inhibition

The transformation technique of Na and Na (Math. Biosci., 6 , 25, 1970) is extended to convert boundary-value problems involving the steady-state diffusion equation for spherical immobilized enzyme particles exhibiting substrate and product inhibition to initial-value problems. This allows a study of the influence of external mass transfer resistances on the effectiveness factors. It also considerably reduces the number of calculations required to investigate the effect of changes in the kinetic parameters on the overall rate of reaction. The existence of multiple steady states for substrate inhibition kinetics in spherical catalyst particles is illustrated and a criterion for uniqueness of steady states is developed. Effectiveness factors for competitive and noncompetitive product inhibition increase with increasing value of the Sherwood number for the substrate and increasing value of the ratio of substrate to product effective diffusivities within the particle.     

Internal thermodynamics of enzymes determined by equilibrium quench: values of Kint for enolase and creatine kinase

The equilibrium constant (Kint) for the enzyme-bound substrate and product of a one substrate/one product enzyme (enolase) and for those of a two substrate/two product enzyme (creatine kinase) have been determined. The values of Kint were determined by the rapid quenching of equilibrium mixtures of enzyme and radiolabeled substrate and product, under conditions where all of the marker substrate and product are bound. The scope and limitations of this method are discussed. Values of Kint have been collected from the literature, and it is shown that these data are consistent with the theory for kinetically optimized enzymes that is developed in the preceding paper.     

Improved performance with multiple fermentors for repeated batch cultivation for non-growth-associated products

Based on batch cultivation data for the production of L-glutamic acid from glucose, a comparative evaluation was made for repeated batch cultivations using one and more fermentors. The problem was formulated as maximizing the productivity of metabolic product with the specified conversion with respect to the cell age and the volume fraction used as seed for the subsequent repeated batch cultivation. Simulations were carried out with the assumption of no lag in product formation for the cases where the total operation time was specified as 200 h with reproducible batch cultivation cycles. The product production was assumed to be solely a function of product concentration. The computation results show the advantage of using more than one fermentor from the viewpoints of productivity and conversion, which will apply in general to non-growth-associated product production with delay time. In particular, three fermentors are recommended for the production of L-glutamic acid chosen as an example in this article.     

Chorismate lyase: kinetics and engineering for stability

By removing the enolpyruvyl group from chorismate, chorismate lyase (CL) produces p-hydroxybenzoate (p-HB) for the ubiquinone biosynthetic pathway. We have analyzed CL by several spectroscopic and chemical techniques and measured its kinetic (kcat=1.7 s(-1), K(m)=29 microM) and product inhibition parameters (K(p)=2.1 microM for p-HB). Protein aggregation, a serious problem with wild type CL, proved to be primarily due to the presence of two surface-active cysteines, whose chemical modification or mutation (to serines) gave greatly improved solution behavior and minor effects on enzyme activity. CL is strongly inhibited by its product p-HB; for this reason activity and inhibition measurements were analyzed by both initial rate and progress curve methods. The results are consistent, but in this case where the stable enzyme-product complex rapidly becomes the predominant form of the enzyme, progress curve methods are more efficient. We also report inhibition measurements with several substrate and product analogs that give information on ligand binding interactions of the active site. The biological function of the unusual product retention remains uncertain, but may involve a mechanism of directed delivery to the membrane-bound enzyme that follows CL in the ubiquinone pathway.     

Modeling the Potential Effects of New Tobacco Products and Policies: A Dynamic Population Model for Multiple Product Use and Harm

Background

Recent declines in US cigarette smoking prevalence have coincided with increases in use of other tobacco products. Multiple product tobacco models can help assess the population health impacts associated with use of a wide range of tobacco products.

Methods and Findings

We present a multi-state, dynamical systems population structure model that can be used to assess the effects of tobacco product use behaviors on population health. The model incorporates transition behaviors, such as initiation, cessation, switching, and dual use, related to the use of multiple products. The model tracks product use prevalence and mortality attributable to tobacco use for the overall population and by sex and age group. The model can also be used to estimate differences in these outcomes between scenarios by varying input parameter values. We demonstrate model capabilities by projecting future cigarette smoking prevalence and smoking-attributable mortality and then simulating the effects of introduction of a hypothetical new lower-risk tobacco product under a variety of assumptions about product use. Sensitivity analyses were conducted to examine the range of population impacts that could occur due to differences in input values for product use and risk. We demonstrate that potential benefits from cigarette smokers switching to the lower-risk product can be offset over time through increased initiation of this product. Model results show that population health benefits are particularly sensitive to product risks and initiation, switching, and dual use behaviors.

Conclusion

Our model incorporates the variety of tobacco use behaviors and risks that occur with multiple products. As such, it can evaluate the population health impacts associated with the introduction of new tobacco products or policies that may result in product switching or dual use. Further model development will include refinement of data inputs for non-cigarette tobacco products and inclusion of health outcomes such as morbidity and disability.     

Benzidine dihydrochloride as a chromogen for single- and double-label light and electron microscopic immunocytochemical studies

Although very sensitive chromogens have been adapted for localization of horseradish peroxidase in anterograde and retrograde tracing studies, they have not been successfully applied in immunocytochemical studies. This report describes a protocol which uses benzidine dihydrochloride (BDHC) as the chromogen for light (LM) and electron microscopic (EM) immunocytochemical studies. The protocol is comparable to that used for tetramethylbenzidine, except that the pH of the reaction is above 6.0. At the LM level, the BDHC reaction product is bluish-green and crystalline. Both the color and form of the product are readily distinguished from the reddish-brown DAB reaction product. LM double-labeling studies are therefore feasible. The use of BDHC also increases significantly the sensitivity of the immunoreaction. Higher fixative concentrations can be used, less detergent is necessary, and higher primary antibody dilutions are possible. By osmicating at 45 degrees C in an s-collidine buffer it is possible to preserve the soluble BDHC reaction product for EM analysis. Immunoreactive cells are particularly well labeled with this new protocol. The BDHC crystals are easily detected at the EM level and can be distinguished from flocculent DAB reaction product. This feature makes EM double-labeling studies possible.     

Steady-state,Pre-steady-state,and Single-turnover Kinetic Measurement for DNA Glycosylase Activity

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization of OGG1 is undertaken to measure the rates of 8-oxoG excision and product release. When the OGG1 concentration is lower than substrate DNA, time courses of product formation are biphasic; a rapid exponential phase (i.e. burst) of product formation is followed by a linear steady-state phase. The initial burst of product formation corresponds to the concentration of enzyme properly engaged on the substrate, and the burst amplitude depends on the concentration of enzyme. The first-order rate constant of the burst corresponds to the intrinsic rate of 8-oxoG excision and the slower steady-state rate measures the rate of product release (product DNA dissociation rate constant, k_off). Here, we describe steady-state, pre-steady-state, and single-turnover approaches to isolate and measure specific steps during OGG1 catalytic cycling. A fluorescent labeled lesion-containing oligonucleotide and purified OGG1 are used to facilitate precise kinetic measurements. Since low enzyme concentrations are used to make steady-state measurements, manual mixing of reagents and quenching of the reaction can be performed to ascertain the steady-state rate (k_off). Additionally, extrapolation of the steady-state rate to a point on the ordinate at zero time indicates that a burst of product formation occurred during the first turnover (i.e. y-intercept is positive). The first-order rate constant of the exponential burst phase can be measured using a rapid mixing and quenching technique that examines the amount of product formed at short time intervals (<1 sec) before the steady-state phase and corresponds to the rate of 8-oxoG excision (i.e. chemistry). The chemical step can also be measured using a single-turnover approach where catalytic cycling is prevented by saturating substrate DNA with enzyme (E>S). These approaches can measure elementary rate constants that influence the efficiency of removal of a DNA lesion.     

A kinetic model for product formation of microbial and mammalian cells

Growth of microbial and mammalian cells can be classified into substrate-limited and substrate-sufficient growth according to the relative availability of the substrate (carbon and energy source) and other nutrients. It has been observed for a number of microbial and mammalian cells that the consumption rate of substrate and energy (ATP) is generally higher under substratesufficient conditions than under substrate limitation. Accordingly, the product formation under substrate excess often exhibits different patterns from those under substrate limitation. The extent of increase or decrease in product formation may depend not only on the nature of limitation and cell growth rate but also on the residual substrate concentration in a relatively wide range. The product formation kinetic models existing in literature cannot describe these effects. In this study, the Luedeking-Piret kinetic is extended to include a term describing the effect of residual substrate concentration. The extended model has a similar structure to the kinetic model for substrate and energy consumption rate recently proposed by Zeng and Deckwer. The applicability of the extended model is demonstrated with three microbial cultures for the production of primary metabolites and three hybridoma cell cultures for the production of ammonia and lactic acid over a wide range of substrate concentration. The model describes the product formation in all these cultures satisfactorily. Using this model, the range of residual substrate concentration, in which the product formation is affected, can be quantitatively assessed. (c) 1995 John Wiley & Sons, Inc.     

A concurrent development tool for flexible assembly systems

Global competition and the rapid pace of technological change now require the almost continual introduction of product upgrades by any manufacturer. Thus, such a manufacturer is likely to market older and newer versions of a product simultaneously, not to mention niche-specific editions of any product upgrade. An increasingly successful response to this product proliferation is the implementation of flexible assembly systems. In the context of a flexible assembly system (FAS), the ability to estimate the impact of various product and process options on the maximal level of system output becomes crucial to managing the ever-changing product mix. This paper presents a tool for such impact estimation that can facilitate concurrent development and engineering. Experience with an actual FAS is the basis for the reported results. The tool is a specialized combination of discreteevent computer simulation, experimental design, and regression analysis. Application of the tool assumes FAS use with a cellular manufacturing philosophy. Thus, uncluttered process flow for a family of products in the sense of group technology places the focus on potential bottlenecks. The new tool here models the impact of process and product options on bottleneck and, hence, FAS behavior.