Exergy-based natural resource accounting in sustainability assessment of agricultural production systems

We consume global natural resource stocks at an unsustainable rate, which endangers long-term resource availability and which causes environmental pollution. Mitigating pollution and increasing resource efficiency is a major challenge in our society’s sustainable development. To measure and evaluate natural resource use of entire production chains, exergy analysis and life cycle assessment are increasingly performed. Exergy analysis, however, was primarily elaborated for the energy, chemical and metallurgical industries; it therefore needs further development to evaluate natural resource use in an agricultural context. The aims of this thesis were to further develop the exergy-based framework for its application on agricultural production systems, and to provide insight into its value by case study illustrations. In the quantification of natural resource efficiency, it is unclear today how to account for land resources, on which agriculture largely depends. The photosynthetic process is not properly addressed. Also, the ancient photosynthesis during the formation of fossil resources is currently overlooked. The methodological part of this thesis investigated how to calculate an overall resource efficiency indicator that takes these aspects into account. For two products (electricity and PVC), the bio-based alternative was compared with its fossil-based counterpart. Because many agricultural systems have been intensified to achieve a higher productivity, an overall resource footprint evaluation is highly relevant. In this thesis, natural resource use of specialized dairy farms in Flanders was studied. Feed was responsible for the majority of natural resources used throughout the production chain of milk. Because feed is also the most important cost, it plays a pivotal role in improving the economic and environmental farm performance. How farms could achieve simultaneous savings in costs and natural resource demand of feed was investigated using frontier analysis and analysis of key performance indicators that are traditionally used by farm advisors

Towards a circularity indicator to assess products’ materials and lifetime : in-use occupation

Slowing and closing loop strategies have the ultimate goal of avoiding materials’ losses, hibernation, and emissions, therefore all kind of actions that hamper useful applications. Consequently, there is a need to develop indicators that can deal with mass and time. A way to indicate circularity is by measuring the in-use occupation of resources, that is, keeping materials in a useful state, avoiding dissipation, and adverse effects, such as burden transfer. The objective of this work is to advance in-use occupation as an indicator for the circularity of products; therefore, we schematically present a framework and parameters for such indicators

A framework for using the handprint concept in attributional life cycle (sustainability) assessment

Handprint refers to the good society does for the environment, but this definition gives room for different interpretations. While in life cycle (sustainability) assessment (LC(S)A) its use is still at infancy, the effective communication potential of Handprint terminology gives room for increasing its application in the future. The objective of this article is to propose a framework to distinguish and classify various types of handprint, when they are intended to be used in LC(S)A studies. Building on the current structure of LC(S)A regarding the cause-effect chain, from flows to impacts, a framework to allow understanding the beneficial, adverse and net effects various flows can cause to different actors is created. Based on that, three handprint types are proposed, i.e., Direct, Indirect and Relative. These types can be subdivided into more specific/complex types of handprint, e.g., Indirect Relative Handprint (adverse). Illustrations with case studies (fictive and from literature) are used to suggest some guidance. With this proposal, a first step to consistently introduce the handprint concept into LC(S)A is achieved, but future challenges still exist (e.g., development of quantitative methods for beneficial impacts from product’s functionality, in footprint-consistent units)

Analysis of the overall resource consumption of a Flemish dairy farm using Exergetic Life Cycle Assessment

To deal with environmental challenges such as pollution and resource depletion, the potential environmental impact of agricultural products is commonly evaluated using the Life Cycle Assessment (LCA) methodology. For livestock systems, emission-related impacts such as global warming have been frequently studied in this way. During the past decades, intensifi-cation of agricultural systems to improve yields coincided with an increased material and energy throughput. Therefore, we focus on resource consumption in this paper. We applied an exergy-based approach to quantify total resource use and to calculate resource efficien-cies, both at system level and at life cycle level. We have performed a case study of an in-tensive confinement-based dairy farm in Flanders to illustrate our approach

Circular economy indicators : what do they measure?

Circular Economy (CE) is a growing topic, especially in the European Union, that promotes the responsible and cyclical use of resources possibly contributing to sustainable development. CE is an umbrella concept incorporating different meanings. Despite the unclear concept, CE is turned into defined action plans supported by specific indicators. To understand what indicators used in CE measure specifically, we propose a classification framework to categorise indicators according to reasoning on what (CE strategies) and how (measurement scope), Despite different types, CE strategies can be grouped according to their attempt to preserve functions, products, components, materials, or embodied energy; additionally, indicators can measure the linear economy as a reference scenario. The measurement scope shows how indicators account for technological cycles with or without a Life Cycle Thinking (LCT) approach; or their effects on environmental, social, or economic dimensions. To illustrate the classification framework, we selected quantitative micro scale indicators from literature and macro scale indicators from the European Union 'CE monitoring framework'. The framework illustration shows that most of the indicators focus on the preservation of materials, with strategies such as recycling. However, micro scale indicators can also focus on other CE strategies considering LCT approach, while the European indicators mostly account for materials often without taking LCT into account. Furthermore, none of the available indicators can assess the preservation of functions instead of products, with strategies such as sharing platforms, schemes for product redundancy, or multifunctionality. Finally, the framework illustration suggests that a set of indicators should be used to assess CE instead of a single indicator

Resource consumption assessment of Pangasius aquaculture in the Mekong delta, Vietnam

In light of full exploitation and overexploitation of marine fish stocks on a global scale, aquaculture has gained prominence to meet the increasing fish demand induced by population growth and rising incomes. Pangasius production in Vietnam is widely known as a success story in the aquaculture sector due to a tremendous expansion by volume and value in recent years. However, a growing concern has arisen about the environmental sustainability of this system, particularly in terms of resource extraction. We addressed this issue here by expressing all resources in one common unit: Joules of exergy. Exergy is defined as the amount of maximum useful energy obtained from a resource. Analysis using this metric was performed at process level through Exergy Analysis (EA; Table 1) and from a life cycle perspective via quantification of the Cumulative Exergy Extraction from the Natural Environment (CEENE; Figure 1), which was subdivided into seven resource categories. This allows one to identify hotspots over the life cycle stages, including feed production, juvenile production and fish cultivation. Results show that the largest contributors were the feed input (73% of the total CEENE) and the water renewal of the ponds (25%), mainly assigned to the farm phase (90%). Land (62%) and water (31%) account for the main share in the resource footprint, which is reasoned by the agricultural production of the crop-based feed ingredients and the high water exchange in pond farming, respectively. Improvements therefore should focus on lowering water input into the ponds and increasing the efficiency of the feed supply chain. The latter option represents a great challenge while the former could be feasible through the application of a recirculating aquaculture system (RAS). Further research is needed to explore whether RAS is a feasible sustainable alternative. Overall, Vietnamese farm and feed mill managers play a key role in improving the environmental performance of Pangasius products. Focus should not only lay on their own farming and processing, but also on the selection of their feed suppliers