UNIT 3 System boundaries

1. UNIT 3 System boundaries The objectives of the �Life Cycle Assessment: Critical Points� distance-learning course are: To provide a quality and interactive distance education on LCA. More precisely, the course aims to enable participants: To know the relationships between Life Cycle Assessment (LCA) and other environmental tools, to know the existing LCA methodologies, the basic rules and frameworks for good LCA practice, To criticise an existing LCA, looking rapidly at the key issues, To identify the main environmental issues in a production process; To enhance both formal and informal learning opportunities through collaborative and cooperative processes; To improve information and knowledge sharing as well as inter-university collaboration and tuition for industry collaborators. The objectives of the �Life Cycle Assessment: Critical Points� distance-learning course are: To provide a quality and interactive distance education on LCA. More precisely, the course aims to enable participants: To know the relationships between Life Cycle Assessment (LCA) and other environmental tools, to know the existing LCA methodologies, the basic rules and frameworks for good LCA practice, To criticise an existing LCA, looking rapidly at the key issues, To identify the main environmental issues in a production process; To enhance both formal and informal learning opportunities through collaborative and cooperative processes; To improve information and knowledge sharing as well as inter-university collaboration and tuition for industry collaborators.

3. 1.2 LCA Steps, where are we ? The second main step of the LCA goal definition is the determination of the system and the system boundaries (SB). This lesson treats about these SB. As you already know, LCA provides a method: to collect and manage materials and energy data for each process within the SB, to assess the potential adverse environmental impacts of materials and energy flows through the SB. Consequently, the SB setting is to be done with care. Ideally SB include everything in the economy which contributes to the system function. Hence the importance to have clearly defined the function. Here I�ll describe very quickly the main stage of a LCA. I�ll insist on interpretation at each stage but I�ll come back on this point further. I think to give this picture (photocopy) to everybody so that they can see where we are in the description. Here I�ll describe very quickly the main stage of a LCA. I�ll insist on interpretation at each stage but I�ll come back on this point further. I think to give this picture (photocopy) to everybody so that they can see where we are in the description.

4. 1.3 Product system The system boundaries are closely linked to the product system. In the ISO 14041 standard, the product system has the following definition: "A product system is a collection of unit processes connected by flows of intermediate products which perform one or more defined functions. A product system description includes unit processes, elementary flows and product flows accross the system boundaries and intermediate product flows within the system. The essential property of a product system is characterized by its function and cannot be defined solely in terms of the final products." Here I�ll describe very quickly the main stage of a LCA. I�ll insist on interpretation at each stage but I�ll come back on this point further. I think to give this picture (photocopy) to everybody so that they can see where we are in the description. Here I�ll describe very quickly the main stage of a LCA. I�ll insist on interpretation at each stage but I�ll come back on this point further. I think to give this picture (photocopy) to everybody so that they can see where we are in the description.

5. 1.4 Unit process The product system can be desagregated into unit processes (UP). Flows of intermediate products connect these UP together. In addition each unit can have inputs or extractions from the environment (consumption of resources, energy�) and outputs or emissions to the environment (to water, air, soil...) also called elementary flows. Here I�ll describe very quickly the main stage of a LCA. I�ll insist on interpretation at each stage but I�ll come back on this point further. I think to give this picture (photocopy) to everybody so that they can see where we are in the description. Here I�ll describe very quickly the main stage of a LCA. I�ll insist on interpretation at each stage but I�ll come back on this point further. I think to give this picture (photocopy) to everybody so that they can see where we are in the description.

7. 1.6 System boundaries According to ISO 14041 standard, "the SB define the UP to be included in the system to be modeled". Usually, the ideal case where only elementary flows cross the SB is not reached. Lack of money, time and resources often leads to hypothesis settings. As the study goes on, the SB can be refined. Indeed, LCA being iterative, results coming in can affect the former assumptions - and the SB.

8. 1.7 Process tree Process trees are often used to describe the product system (UP and elementary flows) and the SB. Let�s try with a short example: The aim of the study is to compare plastic bottles made of different polymers. The functional unit is 1 bottle, non recycled.

9. 2.1 Rules to follow when setting system boundaries This example illustrates the necessity to define consistency rules:

10. 2.2 Rules to follow � Rule 3: Identical processes in different scenarios can only be excluded if the reference flows corresponding to these processes are strictly equal (total output of the system must also be identical). Special care must be taken when comparing packages. e.g. for toothpaste: if there is some remaining toothpaste in the �empty� tubes, their manufacturing has to be taken into account when comparing different kinds of toothpaste.

11. 3.1 Illustration, context In 1990, an environmental comparison between a take-away (hamburger, french fries type) and a conventional restaurant was carried out. This study showed that the fast-food requires 6 time less energy, 7 time less water, and 5 time less waste per customer than a conventional restaurant.

12. 3.2 Sources of error Centralized conditioning, dishes manufacturing and waste treatment are excluded from the take-away boundaries. These processes are included for the conventional restaurant, they take place within its walls.

13. 3.3 Complementary study As a consequence of these bias, a new complementary study was undertaken. This time, it considers a full cradle to grave LCA. Following points have been checked: One does not compare a conventional restaurant with a fast-food anymore but two different types of fast-foods. One of them with paper packages and cardboard plates. The other one proposing a wider menu choice and offering �true� plates, forks and knives if eating inside. Attention has been paid to the system boundaries. They were chosen on a function basis. They include, for both scenarios : raw material extraction; energy production; dishes and packing production, transport, consumption and disposal; food transport and preparation; restaurant functioning (including toilets !). For more details and clarity, refer to figure on next slide.

14. 3.3 bis Annexe - Illustration

15. 3.4 Results It shows that the �cardboard fast-food� leads to a twice higher environmental load. This higher impact is essentially due to cooking and heating.

16. 4. Questions of understanding What is a production system? Considering a soap example, where would you set the system boundaries? What kind of representation helps to have a clear idea of the system? What are the rules for setting system boundaries?