Brandon Kuczenski

Tracking toxicants: toward a life cycle aware risk assessment.

The policies concerning product development and use are increasingly informed by life cycle assessment (LCA) and risk assessment (RA): LCA is often invoked to achieve “sustainability” whereas RA is used when seeking to avoid harm when dealing with toxic substances. In this Feature, Kuczenski et al. argue that green chemistry principles—which encourage reducing the use of toxic chemicals and processes—suggest a way to combine LCA and RA in product assessment.

Partial ordering of life cycle inventory databases

PurposeLife cycle inventory (LCI) databases provide information of fundamental importance to the mainstream practice of life cycle assessment (LCA). Development and management of LCI data resources is a tremendous task. This paper seeks to develop design principles for organizing efforts around distributed database management by considering the structure of inventory networks.MethodsA number of LCI databases in wide use are placed into a partial ordering using graph theoretic techniques. First, strongly connected components, which indicate cyclic dependencies, are identified in each network. Then, those components are collapsed to single nodes, rendering the graphs acyclic. The acyclic graphs are then ordered topologically.Results and discussionLarge databases were found to contain a single large strongly connected component, designated the background, that satisfied dependencies of other processes in the database. Processes with a lower position in the ordering than the background, designated the foreground, depended on inputs from the background in order to operate, but no background processes required inputs from any foreground processes. Processes higher in the order than the background, designated the downstream, satisfied dependencies in the background but did not themselves require the background. Databases sharing a common set of product flows could be compared on the basis of their foreground, background, and downstream segments.Making a distinction between an acyclic foreground and a strongly connected background has computational utility because the foreground and background databases can be managed independently. Describing LCA studies on the basis of their dependence on background product flows would allow them to be easily moved among distinct databases that provide the same products and would also facilitate critical review. Background databases themselves can be broken up by scope into mutually dependent systems that can be independently maintained.ConclusionsLCI database maintainers should consider maintaining the foreground and background components of their databases separately because of the differing implications of modeling decisions made in each of the two cases. A framework for database-independent enumeration of intermediate flows would advance distributed data management.

Privacy-preserving aggregation in life cycle assessment

Life cycle assessment (LCA) is the standard technique used to make a quantitative evaluation about the ecological sustainability of a product or service. The life cycle inventory (LCI) data sets that provide input to LCA computations can express essential information about the operation of a process or production step. As a consequence, LCI data are often regarded as confidential and are typically concealed through aggregation with other data sets. Despite the importance of privacy protection in publishing LCA studies, the community lacks a formal framework for managing private data, and no techniques exist for performing aggregation of LCI data sets that preserve the privacy of input data. However, emerging computational techniques known as “secure multiparty computation” enable data contributors to jointly compute numerical results without enabling any party to determine another party’s private data. In the proposed approach, parties who agree on a shared computation model, but do not trust one another and also do not trust a common third party, can collaboratively compute a weighted average of an LCA metric without sharing their private data with any other party. First, we formulate the LCA aggregation problem as an inner product over a foreground inventory model. Then, we show how LCA aggregations can be computed as the ratio of two secure sums. The protocol is useful when preparing LCA studies involving mutually competitive firms.

LCA capability roadmap—product system model description and revision

PurposeLife cycle assessment (LCA) practitioners face many challenges in their efforts to describe, share, review, and revise their product system models, and to reproduce the models and results of others. Current life cycle inventory modeling techniques have weaknesses in the areas of describing model structure, documenting the use of proxy or non-ideal data, specifying allocation, and including modeler’s observations and assumptions—all affecting how the study is interpreted and limiting the reuse of models. Moreover, LCA software systems manage modeling information in different and sometimes non-compatible ways. Practitioners must also deal with licensing, privacy/confidentiality of data, and other issues around data access which impact how a model can be shared.MethodsThis letter was prepared by a working group of the North American Life Cycle Assessment Advisory Group to support the UNEP-SETAC Life Cycle Initiative’s Flagship Activity on Data, Methods, and Product Sustainability Information. The aim of the working group is to define a roadmap of the technical advances needed to achieve easier LCA model sharing and improve replicability of LCA results among different users in a way that is independent of the LCA software used to compute the results and does not infringe on any licensing restrictions or confidentiality requirements. This is intended to be a consensus document providing the state of the art in this area, with milestones for research and implementation needed to resolve current issues.Results and ConclusionsThe roadmap identifies fifteen milestones in three areas: “describing model contents,” “describing model structure,” and “collaborative use of models.” The milestones should support researchers and software developers in advancing practitioners’ abilities to share and review product system models.

A platform for building PIC applications for control and instrumentation

The authors have developed a minimal software environment for PIC 18F-series microcontrollers that can he used to rapidly develop mechatronic applications. The environment includes initialization of commonly utilized hardware features such as analog-to-digital conversion, pulse-width modulation control, serial communication and a programmable interrupt-driven timing loop that can he used to provide a sampling interval for a discrete-time control system. The environment also supports simple mathematical operations, interfacing with an LCD display, capturing user input and developing a flexible menu-style user interface. The software will be publicly available to facilitate rapid development of PIC-based mechatronic systems.

An Automated System for Controlling the Laminar Flow Interface in a Microfluidic System

The interface between adjacent laminar flow streams in the output channel of a Y-shaped confluent microfluidic network is useful for investigating the response of individual living cells to steep chemical gradients. This paper reports the design and performance of an automated pressure-feedback system for accurately and rapidly changing the position of that interface. The device will be employed to investigate the dynamic response of cells to time-varying chemical stimulation. The system works by controlling the pressure difference between the two adjoining inputs of the microfluidic network, altering the relative flow rate of the laminar streams in the output microchannel. Continuity of incompressible fluids dictates that the plane of the interface between the two streams will move from side to side as the flow rates change. The sample-data control system samples a temperature-compensated monolithic piezoresistive pressure sensor at 1 kilohertz, allowing the control of high-bandwidth microfluidic systems. This automated system enables long-duration, high-precision experiments that involve time-varying parameters to be performed simply, rapidly, and inexpensively.Copyright

Privacy-Preserving Certification of Sustainability Metrics

Companies are often motivated to evaluate their environmental sustainability, and to make public pronouncements about their performance with respect to quantitative sustainability metrics. Public trust in these declarations is enhanced if the claims are certified by a recognized authority. Because accurate evaluations of environmental impacts require detailed information about industrial processes throughout a supply chain, protecting the privacy of input data in sustainability assessment is of paramount importance. We introduce a new paradigm, called privacy-preserving certification, that enables the computation of sustainability indicators in a privacy-preserving manner, allowing firms to be classified based on their individual performance without revealing sensitive information to the certifier, other parties, or the public. In this work, we describe different variants of the certification problem, highlight the necessary security requirements, and propose a provably-secure novel framework that performs the certification operations under the management of an authorized, yet untrusted, party without compromising confidential information.

Towards Practical Privacy-Preserving Life Cycle Assessment Computations

Life Cycle Assessment(LCA) is crucial for evaluating the ecological sustainability of a product or service, and the accurate evaluation of sustainability requires detailed and transparent information about industrial activities. However, such information is usually considered confidential and withheld from the public. In this paper, we present a rigorous study of privacy in the context of LCA. The main goal is to explore the privacy challenges in sustainability assessment considering the protection of trade secrets while increasing transparency of industrial activities. To overcome privacy concerns, we apply differential privacy to LCA computations considering the idiosyncratic features of LCA data. Our assessments on a specific real-life example show that it is possible to achieve privacy-preserving LCA computations without losing the utility of data completely.

Controlled Waveform Chemical Stimulus of Cellular Subdomains for System Identification

The dynamic behavior of cells is a subject of extensive investigation. Current attempts to model and describe cell behavior show similarity to traditional engineering models of dynamic systems, often making use of the same vocabulary and principles (e.g. amplification, feedback, regulation, instability). A significant difference between biological dynamic systems and engineered ones is that the latter often feature a designed compensator whose dynamic behavior modulates the dynamic response of the system through closed-loop feedback control. In biological systems, by contrast, the feedback is often implicit, and the investigator has no direct control over modulations which are internal to the system. Although disruptive techniques like synthetic siRNA [1] or genetic modification can certainly change cellular behavior, in some cases it is desirable to probe the dynamics of cellular processes without changing their essential operation, or without substantial delay between applying a perturbation and observing its effects.Copyright