Life cycle assessment of volatile fatty acids production from protein- and carbohydrate-rich organic wastes.

Volatile fatty acids (VFAs) are platform molecules with numerous applications. They can be obtained by adjusting the operational conditions of anaerobic digestion to avoid methanogenesis while focusing on fermentative stages. There are gaps in the knowledge of how, from a life-cycle perspective, the fermentative process performs in VFAs production from waste, including environmental consequences of substituting common commodities in the current market. Mass and energy balances of VFAs production from protein-rich microalgal and carbohydrate-rich agro-industrial wastes were used herein as a key source of inventory data for life cycle assessment. Two waste treatment options were considered: (i) VFAs production (anaerobic fermentation) plus anaerobic digestion of the resulting waste after VFAs separation, and (ii) anaerobic digestion of the original waste for bioenergy. Several scenarios were formulated to evaluate their life-cycle performance. VFAs production generally shows a better environmental behaviour than conventional anaerobic digestion, principally due to the substitution of conventional chemicals.

The impact of incineration phase-out on municipal solid waste landfilling and life cycle environmental performance: Case study of Madrid, Spain.

Reducing the amount of municipal solid waste (MSW) fed to incineration while enhancing source separation and biological treatments is being considered a mean to protect the environment and human health and promote recycling. However, such a strategy can compromises the landfill reduction targets while the associated environmental benefits remain so far unexplored and, in any case, any potential benefit should be evaluated for specific situations. In this study we applied material flow analysis (MFA) and life cycle assessment (LCA) to quantitatively evaluate the potential impact of phasing-out incineration in Madrid, Spain. The current MSW management system was assessed against future scenarios that describe the elimination of incineration as well as the increase of source separation, recycling, composting, and anaerobic digestion. The results revealed that incineration phase-out jeopardizes landfill reduction. However, phasing-out incineration can reduce the impact on acidification, terrestrial and marine eutrophication, photochemical ozone formation, human toxicity cancer effects, and ecotoxicity. The climate impact ranges from irrelevant to largely beneficial depending on how the biogenic carbon is considered. The transition towards a renewable electricity mix and the increase in source separation of biodegradable waste seriously compromise the climate benefits of incineration over landfilling. Overall, actions are required in order to align incineration phase-out with the landfill reduction objective, namely upgrading material recovery facilities to reduce rejects and seeking alternative pathways for the rejects that will always exist.

Robust eco-efficiency assessment of hydrogen from biomass gasification as an alternative to conventional hydrogen: A life-cycle study with and without external costs.

Hydrogen is a key product for the decarbonisation of the energy sector. Nevertheless, because of the high number of technical options available for hydrogen production, their suitability needs to be thoroughly evaluated from a life-cycle perspective. The standardised concept of eco-efficiency is suitable for this purpose since it relates, with a life-cycle perspective, the environmental performance of a product system to its value. Hence, this work benchmarks the eco-efficiency performance of renewable hydrogen produced through biomass gasification against conventional hydrogen from the steam reforming of natural gas. For the eco-efficiency assessment, the harmonised environmental indicators of global warming, acidification and cumulative non-renewable energy demand were individually used, while the product system value was based on the levelised cost of hydrogen with/without internalisation of the external socio-environmental costs associated with climate change and human health. On the one hand, when the environmental and economic performances are separately considered, hydrogen from biomass gasification performs significantly better than hydrogen from steam methane reforming under environmental aspects (e.g., greenhouse gas emissions saving of 98%), whereas the opposite conclusion was found from an economic standpoint (levelised cost of 3.59 € and 2.17 € per kilogramme of renewable and fossil hydrogen, respectively). On the other hand, when combining life-cycle environmental and economic indicators under the umbrella of the eco-efficiency assessment, it is concluded that the renewable hydrogen option outperforms the conventional one, which is further remarked when implementing socio-environmental externalities. In this regard, a relative eco-efficiency score above 14 was estimated for the renewable hydrogen option when benchmarked against conventional hydrogen.

Environmental improvement of product supply chains: proposed best practice techniques, quantitative indicators and benchmarks of excellence for retailers.

Retailers are strategically positioned to leverage environmental improvement over product supply chains through actions targeted at suppliers and consumers. Informed by scientific evidence on environmental hotspots and control points across 14 priority product groups, and a review of 25 major European retailers' actions, this paper proposes a framework to guide and assess retailer best practice in supply chain environmental improvement. Commonly used product standards and improvement measures are classified into "basic" or "good" levels of environmental protection. A hierarchy of eight Best Environmental Management Practices (BEMPs) is proposed to systematically identify and improve the most environmentally damaging supply chains across retail assortments. Widespread third party environmental certification is the most transparent and verifiable mechanism of improvement but may not be appropriate for some supply chains. The enforcement of retailer-defined environmental requirements, and supplier improvement programmes based on performance benchmarking and dissemination of better management practices, are alternative BEMPs that may be used in combination with third party certification. Facilitating consumer selection of frontrunner ecological products is a lower priority BEMP owing to the well documented limitations of this approach. From available data, the highest current or credible-target sales shares of products improved according to the highest priority BEMP and environmental protection level were used to derive "benchmarks of excellence" for each of the 14 product groups. The assessment framework is demonstrated through application to three retailers.