Methodology of supporting decision-making of waste management with material flow analysis (MFA) and consequential life cycle assessment (CLCA): case study of waste paper recycling
Introduction
Waste recycling is thought to offer some of the most significant greenhouse gas (GHG) emissions savings in waste management practices (Friedrich and Trois, 2011). Thus, the recycling objectives set by waste policies (i.e., Directive 2004/12/EC (European Commission, 2004)) are based on the notion that increase collection rates will increase recycling rates and thereby increase the GHG savings. However, the rationale for and understanding of the consequences of these measures are often incomplete, and attempts to promote recycling levels beyond the market-clearing level must address the consequences and the importance of market behavior (Blomberg and Söderholm, 2009). Similarly, recycling may be largely driven by government objectives to divert waste from landfills. Therefore, the market for recycled material is only partially connected to market drivers because some market participants are legally obligated to participate and are not motivated by profit maximization (Angus et al., 2012). This creates interesting dynamics, and even in recessions, the supply of recycled materials will continue to flow into the market despite a lack of demand (Angus et al., 2012). Therefore, the supply and demand of waste can be in disequilibrium, and in some cases, the export of waste can serve as a significant adjustment mechanism for such imbalances (Stromberg, 2004).
For example, the Chinese demand for paper products has grown by approximately 10% per year since 1995 (FAO, 2012), accounting for more than half of the worldwide increase in demand (WRAP, 2007). Conversely, in recent years, in Europe and North America, the production and consumption of paper products have decreased, while waste paper collected has increased (FAO, 2012). Therefore, on one hand China is highly dependent on the importation of fibers to produce sufficient pulp for its paper production (NEP, 2009) and on the other hand, there has been an excess of supply of waste paper in Europe and North America which has resulted in large flows to Asia (NEP, 2009). This may cause a possible imbalance not only economic but also environmental (OECD, 2000, Rodrigue et al., 2001, ITENE, 2008) and the consequences should be considered. Moreover, due to globalization, the local consumption of goods and resources in European countries depends increasingly on countries outside Europe and the local use of resources in the European countries is stabilizing through increased resource use in other parts of the world (Reinhard and Zah, 2009). In the case of virgin pulp, imports to Europe have increased from 33% in 1995 up to 40% in 2011 while the European production has stagnated (FAO), what suggest that most competitive virgin pulp is displacing higher-cost fibers in the market, such as the European fibers (Hawkins Wright, 2011). Thus, it is essential to consider how waste and raw material fits into a bigger economic picture (Gadner, 2013), one that suggests that market mechanisms should be included in the GHG quantifications of recycling and considered when making waste policies.
Life Cycle Assessment (LCA) studies have been promoted to provide an informed and science-based support to a more environmentally sustainable decision-making in waste management (JRC, 2011) and several LCA studies have been published on municipal solid waste (MSW) management systems (Björklund and Finnveden, 2005, Cleary, 2009, Rives et al., 2010, Lazarevic et al., 2010, Wang et al., 2012). Many of them focus exclusively on the internal flows of a production system, without considering the effects that the system and its final flows may have on other related economic systems. This perspective, known as the attributional LCA approach (ALCA), has been predominant in life cycle thinking, but this perspective does not account for the consequences that increased waste collections or increased virgin pulp imports may generate on GHG emissions. In this regard, a more recent approach, named consequential LCA (CLCA), includes additional life cycles and products affected by a change of physical flows in the respective life cycle (Reinhard and Zah, 2009). The consequential approach seeks an environmental assessment that takes the evaluation a step further, in order to analyze how physical flows and, therefore, environmental burdens, may vary in response to changes with market implications in a specific life cycle beyond the foreground system (Vazquez-Rowe et al., 2013). In this regard, CLCA is a more effective methodology for address the GHG quantifications because it provides a modeling approach that seeks to describe the consequences of decisions (i.e., to increase waste paper collection) when processes are linked via market mechanisms (Weidema et al., 2009) and allows the limits of the system to be expanded beyond national boundaries.
However due to globalization, the relations between the production, use and waste are each time more complex and geographically dispersed. Thus, in order to properly perform and assess all the market links between raw material, product and waste, it is essential in first place, to establish the cause-effect chains made up of physical flows (Sandén and Karlström, 2007). In this sense, material flow analysis (MFA) has demonstrated its potential to evaluate the interaction between material flows, economy and the environment. Besides, with MFA dynamic perspectives, it is also possible to observe variability over time and determine possible changes in trends in raw materials and waste markets (Brunner and Rechberger, 2005, Moriguchi, 2009, Mathieux and Brissaud, 2010). Therefore, this paper proposes to integrate the methodologies of MFA and CLCA for assessing market effects on the GHG quantifications of recycling activities with the aim of helping to make better decisions. On one hand, this integration would help assessing the amount of the waste generated and consumed in one country, the trade along the whole production chain or the origin and destination of the products traded. On the other hand, the integration would also help evaluating the consequences in previous years, such as if the increase of waste collection implied in an increase of recycling or if an increase of consumption relied in an increase of production or whether these changes have consequences outside of studied area. With all this information it is possible to project more realistic scenarios to assess the future consequences and quantify the GHG emissions derived. In this study, we have applied the integration of both methodologies to evaluate the Spanish paper and cardboard recycling system, and we evaluate the increase of waste paper collection in Spain.
Section snippets
Methodology
The methodology proposed in this study consists of two steps: conducting a dynamic MFA to monitor trends and changes in the dynamics of raw materials, products and waste, and integrating MFA results in consequential life cycle inventory (LCI) modeling to quantify the GHG of recycling. In the following sections, the methodologies followed for the quantification of flows and stocks (2.1) and the GHG savings (2.2) are explained.
Spanish paper MFA from 2006 to 2011
The following sections present the results for the MFA (Section 1 Introduction, 2 Methodology, 3 Results). Firstly, the Spanish paper and board life cycle in 2006 is presented. Afterwards, trend for trade flows, transformation flows and loss flows for wood cultivation, virgin pulp production, PB manufacturing, PB product production and use life cycle stages are evaluated from 2006 to 2011. Finally, the waste paper flows and recovered paper flows and recycling are presented and also evaluated
Recovered paper flows
For the case study of paper and board in Spain, the MFA has revealed that in recent years, there has been an elevated supply of low-quality fibers due to both high import rates of packaging products and more waste paper collected. Additionally, there has been a decline in the demand for a domestic quantity of low-quality fibers due to a decrease in the consumption and production of corrugating products (which have a higher content of low-quality fibers). Consequently, there has been an
Conclusion
LCA studies on waste management have been promoted because they can help policy makers choose the best environmental options (JRC, 2011). However, the impacts of imports and export have historically been excluded from LCAs (James, 2012), but as this study reflects, the effect of the markets may affect the GHG quantifications. The consequences are reflected not only in terms of increasing waste export flows, which increase the environmental impacts attributed to transport, but also in terms of
Acknowledgment
The authors would like to thank the project “Ecotech Sudoe: international network in life cycle analysis and ecodesign for environmental technology innovation” (SOE2/P2/E377) for its financial support.
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