GreenPro-I: a risk-based life cycle assessment and decision-making methodology for process plant design

Abstract

In recent years, significant attention and emphasis has been given to cleaner and greener technologies in processes and product manufacturing. This is recognized as a key element in pollution prevention (P2) and development of sustainable strategies. Life cycle assessment (LCA) is a systematic approach that enables implementation of cleaner and greener product and process concepts in industry. In recent times substantial progress has been made in the use of LCA for product evaluation and selection. However, its use in cleaner and greener process design and decision-making has not been explored to a great extent.

Process design and decision-making are challenging activities that involve trade-off of conflicting objectives, namely costs, technical feasibility and environmental impacts. These conflicting objectives can be analysed at the early design and decision-making stage by considering the full life cycle of a process or a product. A cleaner and greener process is the one that is cost optimal, technically feasible, and environmentally benign. To obtain these results LCA requires various tools and techniques in a systematic methodology. This paper proposes a holistic and integrated methodology GreenPro-I for process/product design by combining the traditional LCA approach with multi-criteria decision-making methods. This methodology is simple and applicable at the early design stage and is more robust against uncertainty in the data. Application of the methodology has been demonstrated in the paper through a urea production case study.

Introduction

Life cycle assessment (LCA) is a systematic approach to estimate environmental impacts associated with products, processes and services. It is described as a process to evaluate environmental burdens by identifying and quantifying energy and materials used and wastes released into the environment, and to identify and evaluate opportunities to affect environmental improvements. The assessment includes the entire life cycle of the product, process or activity encompassing extraction and processing of raw materials, manufacturing, transportation and distribution, use, recycle, and final disposal (Fava et al., 1991, USEPA, 1995, Tukker, 2000. The LCA is a decision-making tool for designer, regulatory agencies, and business organizations. It is used to evaluate the environmental impacts of products and process and also identifies a section within a product or process’s life cycle where the greatest reduction in resource requirements and emissions can be achieved.

Generally the LCA employs a product-centered approach, but recent efforts suggest a great potential of the LCA in process design. For a designer it has been serious question how to accommodate various constraints such as economic, technology and environment to the design and operation of cleaner and greener process. Earlier design approaches were economics centered and based on cost–benefit analysis. These approaches attempt to trade-off environmental and economic assets with an aim to maximize differences between socioeconomic benefits of an activity against the financial and environmental liabilities. Such practices ultimately seek to attach a monetary value to the environment and are therefore fraught with difficulty (Jacobs, 1991).

The LCA may prove to overcome many of the problems faced in the conventional approaches and therefore establish a link between the environmental impacts, operation, and economics of a process. It offers an expanded environmental perspective, considering impacts from resource extraction to the end product use and disposal. The LCA relates these effects to the mass and energy flows into, out of, and within a process (Kniel et al., 1996, Choong and Sharratt, 2000). According to the ISO 14040 series standards, the LCA should assess the potential environmental issues and aspects associated with a product or service by compiling an inventory of relevant inputs and outputs; evaluating the potential environmental impacts associated with those inputs and outputs; and interpreting the results of the inventory and impact phases in relation to the objectives of the study. Considering these, we believe that the LCA has an ability to focus both process operational feasibility and environmental concern along with other attributes.

The present work focuses on the development of process selection and design methodology considering assessment and minimization of risks/impacts of process systems by embedding the LCA principles within a formal process design and decision-making framework. It has implications to process synthesis as it includes environmental objectives together with technology and economics at the design stage to determine cost efficient solutions. Authors believe that employing the LCA with a process design and decision-making would yield an optimal design and a best management alternative. This paper presents a detailed description of a revised methodology for cleaner and greener process design. The applicability of methodology has been demonstrated through a case study.