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Life Cycle Assessment (LCA) is a widespread tool used to guide decision-makers towards optimal strategic choices for sustainable growth. A key aspect of LCA studies of waste management systems where recycling activities are present is to account for resource recovery and the related substitution effects. Although multiple scientific papers assume a 1:1 substitution ratio between similar materials/products, this is often incorrect as the actual ratio is likely to vary. The focus of this paper is on the calculation of the substitutability coefficient for secondary materials based on technical characteristics. A state of the art literature review showed that many different calculation procedures were applied, which led to a wide variety of substitutability coefficients (sometimes provided under different terminology). In this perspective, the objective of this paper is to provide guidelines on the procedure to be followed to calculate the substitutability coefficient for secondary materials, based on technical characteristics. These guidelines are then applied to two waste management case studies, one dealing with bottom ashes from incineration and the other with plastic waste. In total, sixteen technical substitutability coefficients are given for ten secondary materials, based on state of the art and presented case studies. The paper thus represents a step forward in quantifying the substitutability of secondary materials in waste management LCA studies. The guidelines presented may allow other case studies to enrich the list of coefficients, useful for all LCA practitioners in a harmonized way allowing a more correct evaluation of the environmental impacts associated with recycling activities.

Shifting from a linear to a circular economy has consequences on how the sustainability of products is assessed. This is the case for products recovered from resources such as sewage sludge. The “zero-burden” assumption is commonly used in Life Cycle Assessment and considers that waste streams are burden-free, which becomes debatable when comparing waste-based with virgin material-based products in the context of the growing circular economy. If waste streams are considered as resources rather than waste, upstream burdens should be partly allocated to all products to allow a fair comparison with their virgin material-based equivalents. In this paper, five allocation approaches are applied to allocate the resource use of upstream processes (consumer goods production) to products recovered from the processing of sewage sludge in the Netherlands, which produces biogas, (phosphorus-based) chemicals and building materials. Except for the approach which allocates 100% of the impact from resource recovery processes to the preceding consumer goods, the allocation approaches show a resource use 27 to 80% higher than with the “zero-burden” assumption. In this particular case, using these allocation approaches is likely to find little support from recyclers. The producers of household products, recyclers and policy makers should find a consensus to consider the shift from a linear to a circular economy in sustainability assessment studies while avoiding discouraging the implementation of recovery technologies. This paper suggests starting the discussion with the approach which allocates the impacts from upstream processes degressively to the downstream products as it best translates the industrial ecology principles.

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).

The environmental sustainability of aquaculture wastewater treatment by microalgal bacterial flocs (MaB-flocs) in an outdoor raceway pond was analyzed using life cycle assessment. Pikeperch aquaculture wastewater treated at pilot scale (Belgium; 28 m 2 ) and industrial scale (hypothetical up-scaling; 41 ponds of 245 m 2 ) were compared. The integration of the MaB-floc raceway pond in a broader aquaculture waste treatment system was studied, comparing the valorisation of MaB-flocs as shrimp feed and as biogas. Up-scaling improves the resource footprint of the plant (848 MJ ex,CEENE kg −1 MaB-floc TSS at pilot scale and 277 MJ ex,CEENE kg −1 MaB-floc TSS at industrial scale) as well as its carbon footprint and eutrophication potential. At industrial scale, the valorisation of MaB-flocs as shrimp feed is overall more sustainable than as biogas but improvements should be made to reduce the energy use of the MaB-floc raceway pond, especially by improving the energy-efficiency of the pond stirring system.

Anaerobic digestion of cow dung with new feedstock such as crop residues to increase the biogas potential is an option to help overcoming several issues faced by India. Anaerobic digestion provides biogas that can replace biomass cooking fuels and reduce indoor air pollution. It also provides digestate, a fertilizer that can contribute to compensate nutrient shortage on agricultural land. Moreover, it avoids the burning of rice straw in the fields which contributes to air pollution in India and climate change globally. Not only the technical and economical feasibility but also the environmental sustainability of such systems needs to be assessed. The potential effects of implementing community digesters co-digesting cow dung and rice straw on carbon and nutrients flows, human health, resource efficiency and climate change are analyzed by conducting a Substance Flow Analysis and a Life Cycle Assessment. The implementation of the technology is considered at the level of the state of Chhattisgarh. Implementing this scenario reduces the dependency of the rural community to nitrogen and phosphorus from synthetic fertilizers only by 0.1 and 1.6%, respectively, but the dependency of farmers to potassium from synthetic fertilizers by 31%. The prospective scenario returns more organic carbon to agricultural land and thus has a potential positive effect on soil quality. The implementation of the prospective scenario can reduce the health impact of the local population by 48%, increase the resource efficiency of the system by 60% and lower the impact on climate change by 13%. This study highlights the large potential of anaerobic digestion to overcome the aforementioned issues faced by India. It demonstrates the need to couple local and global assessments and to conduct analyses at the substance level to assess the sustainability of such systems.

The world is facing a tremendous resource supply challenge. One strategy of regions and nations to address this issue is to encourage research and innovation through funding programs. Most of the time, these programs require that research and innovation projects quantify potential increases in resource efficiency achieved by the projects. However, no consensus exists on how to calculate resource efficiency; therefore, a wide range of approaches is followed. As a result, resource efficiency results are not comparable between projects, and because no rules or guidelines exist to help project developers, the approach followed is not always appropriate. This paper aims to discuss the existing approaches and methods used to evaluate resource efficiency. In this context, resource efficiency is defined as the ratio between the benefits obtained from resources and the impact or amount of resources used. The most challenging step is the determination of this ratio’s denominator because a wide range of methods to quantify resource consumption exist and are being used. They can be classified as gate-to-gate or life cycle based methods and can be subdivided into accounting methods and impact assessment methods. Each method considers different aspects of resources; thus, no single method aims to answer the same research questions. Therefore, project developers must make a well informed choice about which method to use. This paper provides recommendations to support this choice, as well as the overall evaluation and the valorization of the resource efficiency ratio in the framework of research and innovation programs.