Analysis of the potentials of multi criteria decision analysis methods to conduct sustainability assessment

Sustainability assessments require the management of a wide variety of information types, parameters and uncertainties. Multi criteria decision analysis (MCDA) has been regarded as a suitable set of methods to perform sustainability evaluations as a result of its flexibility and the possibility of facilitating the dialogue between stakeholders, analysts and scientists. However, it has been reported that researchers do not usually properly define the reasons for choosing a certain MCDA method instead of another. Familiarity and affinity with a certain approach seem to be the drivers for the choice of a certain procedure. This review paper presents the performance of five MCDA methods (i.e. MAUT, AHP, PROMETHEE, ELECTRE and DRSA) in respect to ten crucial criteria that sustainability assessments tools should satisfy, among which are a life cycle perspective, thresholds and uncertainty management, software support and ease of use. The review shows that MAUT and AHP are fairly simple to understand and have good software support, but they are cognitively demanding for the decision makers, and can only embrace a weak sustainability perspective as trade-offs are the norm. Mixed information and uncertainty can be managed by all the methods, while robust results can only be obtained with MAUT. ELECTRE, PROMETHEE and DRSA are non-compensatory approaches which consent to use a strong sustainability concept, accept a variety of thresholds, but suffer from rank reversal. DRSA is less demanding in terms of preference elicitation, is very easy to understand and provides a straightforward set of decision rules expressed in the form of elementary “if … then …” conditions. Dedicated software is available for all the approaches with a medium to wide range of results capability representation. DRSA emerges as the easiest method, followed by AHP, PROMETHEE and MAUT, while ELECTRE is regarded as fairly difficult. Overall, the analysis has shown that most of the requirements are satisfied by the MCDA methods (although to different extents) with the exclusion of management of mixed data types and adoption of life cycle perspective which are covered by all the considered approaches

Comparison of tools for the sustainability assessment of nanomaterials

Nanomaterials are becoming widely used in areas such as biomedical applications, food, environmental protection, energy production, information technology and agriculture. As such, more research has been conducted on their synthesis and manufacturing from a variety of feedstocks. However, concerns regarding their impact on human health and the environment leads researchers to conduct a variety of ‘sustainability’ assessments. The purpose of this paper was to review the current opinion of sustainability assessments concerning nanomaterials. Major assessment tools were reviewed including life cycle assessment, risk assessment and multi-criteria decision analysis, along with subcategories. The review found that each assessment tool did positively contribute to sustainability assessments, but each also had drawbacks of varying degrees. In particular, multi-criteria decision analysis provides the most relevant tool for conducting a sustainability assessment as it can handle criteria of any typology and provide multiple types of decision recommendations, including rankings, scores and classifications

Improved hydrogen gas production in microbial electrolysis cells using inexpensive recycled carbon fibre fabrics

Growing energy demands of wastewater treatment have made it vital for water companies to develop less energy intensive processes for treating wastewater if net zero emissions are to be achieved by 2050. Microbial electrolysis cells (MECs) have the potential to do this by treating water and producing renewable hydrogen gas as a product, but capital and operational costs have slowed their deployment. By using recycled carbon fibre mats, commercially viable MECs can brought closer to reality, where recycled carbon fibre anode MECs treating real wastewater (normalised ~3100 L d−1) were producing 66.77 L H2 d−1 while graphite felt anode MECs produced 3.65 L H2 d−1 per 1 m3 reactor, anodes costing £5.53 m−2 and £88.36 m−2 respectively, resulting in a total anode cost saving of 93%. This could incentivise the development of larger pilot systems, opening the door for generating greater value and a more sustainable wastewater treatment industry

Optimisation of waste vegetable oil-based thermoset polymers

Bio-based thermoset polymers were produced from epoxidized waste vegetable oils cured with anhydrides at different molar ratios. Properties were compared to analogues produced with neat oil and DGEBA as a feedstock. Thermal stability proved to be affected by the molar ratio, and the use of feedstock from waste oil resulted in no effect on this property. DMA has shown that higher concentrations of anhydride enhance the storage modulus, Tg (up to 42.5 °C) and crosslink density. The frying process proved to play a minor role in tuning the dynamic-mechanical properties. However, the contribution of the anhydride demonstrated to be significant enough to mitigate the losses caused by the waste oil, as shown statistically in a DOE study. All formulations were chemically resistant to aqueous, organic and acidic media. The identification of the effects of critical parameters on the properties of WVO-based thermosets enables further production of polymers from waste streams

Sustainable alternative composites using waste vegetable oil based resins

Laminates were produced with epoxy resins from waste vegetable oil (WVO) intended for the manufacturing of environmentally-friendly alternatives for the composites industry. Post-use cooking oil appears a promising source of triglycerides for polymer manufacturing. Matrices cured with methylhexahydrophthalic anhydride (MHHPA) were reinforced with glass and flax fibres, creating a library of composites that were compared to analogues from virgin oil and benchmarked against commercial diglycidyl ether of bisphenol A (DGEBA). Glass fibre-reinforced composites presented Young’s moduli similar to the benchmark but reduced tensile strength. Chemical pre-treatment of the flax fibre (NaOH and stearic acid) countered the limited tensile performance observed for materials with untreated flax; improvements were evidenced by DMA and SEM. Moreover, WVO-based resins greatly improved impact properties and reduced density with no effect on thermal stability. Therefore, WVO-based composites appear as more sustainable alternatives in applications demanding toughness, stiffness and lightweight over strength

Epoxy resin blends and composites from waste vegetable oil

Thermosets and composites were prepared from blends of epoxidized waste vegetable oils and diglycidyl ether of bisphenol-A to investigate this material as an alternative triglyceride source for epoxy resins. Purification of the waste oil was developed to remove impurities derived from thermal degradation in the frying process and different epoxidation methodologies were investigated. Effects of epoxidized vegetable oil content (up to 30 wt%) and origin on the tensile properties were studied and revealed that purified waste oils performed similarly to neat oil in contents up to 10 wt%, proving that this strategy does not compromise tensile properties when waste oils are used in suitable proportions. Furthermore, a more prominent plasticizing effect was observed when more than 15 wt% of bio-based resin was used as confirmed by DMA. Composites were prepared with recycled carbon fibres (up to 30 wt%) and thermosets with 10 wt% of bio-based epoxy resins, significantly improving the mechanical properties

Life cycle assessment and judgement

It has become a standard for researchers carrying out biotechnology projects to do a life cycle assessment (LCA). This is a process for assessing the environmental impact of a technology, product or policy. Doing so is no simple matter, and in the last decades, a rich set of methodologies has developed around LCA. However, the proper methods and meanings of the process remain contested. Preceding the development of the international standard that now governs LCA, there was a lively debate in the academic community about the inclusion of ‘values’ within the process. We revisit this debate and reconsider the way forward for LCA. We set out ways in which those outside of science can provide input into LCAs by informing the value assumptions at stake. At the same time, we will emphasize that the role of those within the scientific community need not (and sometimes, will inevitably not) involve value-free inquiry. We carry out this exploration through a case study of a particular technology project that sought ways to produce industrial and consumer products from algal oils

A framework of criteria for the sustainability assessment of nanoproducts

AbstractNanotechnology applications (nanoproducts) have entered the market or are expected to do so in the near future. Robust and science-based criteria are required to appraise and manage their sustainability. This paper describes the approach used to develop a comprehensive and reliable framework of criteria, which was missing until now, for evaluating the sustainability of nanoproducts. A literature review of the frameworks and tools employed to assess nanoproducts sustainability implications was firstly performed to select an initial set of criteria. A survey of experts in the sustainable nanotechnology domain was then conducted to elicit their knowledge in terms of completeness, reliability and validity of the criteria set. Ranking and correlation analyses completed the research by identifying the parameters of major interest as well as the links and dependencies between them. A total of 54 and 65 experts replied to the pilot and main survey, respectively. The reliability and validity of the criteria was assessed with the responses from both questionnaires, whereas the answers from the main survey were used to calculate the relative index of the criteria as well as their correlations. This research resulted in a framework composed of 68 criteria, which are structured into six main areas: (i) economic performance; (ii) environmental impacts, (iii) environmental risk assessment; (iv) human health risk assessment; (v) social implications and (vi) technical performance. This study helps to broaden the understanding on the identification of criteria for sustainability assessments. It also provides those interested in evaluating nanotechnology implications with the basis for real case studies, possibly by integrating available information with the stakeholders using tools that support decision-making

Recovery of ammonia from wastewater through chemical precipitation

Chemical precipitation is a consolidated technique applied in wastewater treatment to remove and recover phosphorous and ammonium that remain in the effluent after the anaerobic digestion treatment. The precipitate is magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O), also known as struvite, and it is sold as a slow-release fertiliser. However, the value of struvite is quite low and has a limited market. Furthermore, it precipitates with heavy metals and other impurities that need to be removed to make the fertiliser commercially viable. This study looked at the thermal decomposition of struvite to recover added value products and recycle the magnesium for further precipitation. A kinetic study was carried out to understand the mechanism of decomposition and the formation of the different solid phases, which is fundamental for the design and optimisation of the technology. The thermogravimetric study confirmed that thermal decomposition is possible, but ammonia could not be completely released below 250 °C. The thermal analysis also led to the determination of the energy required for the decomposition, found to be 1.87 kJ g−1, which also includes the evaporation of water and ammonia. The kinetic study through the isoconversional method showed the presence of two major reactions, and the model-fitting approach identified the diffusion model as the best fit for the first reaction. The activation energy of the first reaction found with this method was 0.24 kJ g−1, comparable with the data obtained from the isoconversional method. The two-stage decomposition reactions were proposed, and the final calcination product was confirmed as magnesium pyrophosphate, which could be used in agriculture or dissolved in diluted mineral acids solution to separate the phosphate from the magnesium

Life cycle assessment of lignocellulosic biomass pretreatment methods in biofuel production

Purpose: In converting lignocellulosic biomass into biofuel, a pretreatment stage is required in order to make the biomass more readily available for the transformation. There are numerous pretreatment techniques that can be chosen, which are broken down into four categories: chemical, physical, physicochemical, and biological. The aim of this work is to provide a new assessment for some of the emerging technologies using life cycle assessment (LCA) combined with an analysis of the overall product yield. Methods: Using literature data, an LCA of four different pretreatment methods was carried out. Liquid hot water (LHW), steam explosion (SE), dilute acid (DA), and organosolv (OS) were chosen as the most common techniques with high scalability potential. Models were constructed using GaBi software. A cradle-to-gate analysis was selected with a common model of the corn stover growth and harvesting cycle being combined with the individual models for each pretreatment. Four impact categories were analyzed, and a selection has been discussed based on relevance to the biofuel production process. Results and discussion: In nearly all of the impact categories, DA performs the worst due to the length of the process (12 h) and the amount of electricity required to elevate the temperature to 60 °C for that time period. In many of the other categories, the remaining three pretreatments perform comparably to each other with the exception of LHW which has significantly reduced CO2 emissions. LHW has slightly higher water depletion rates than both SE and OS, which is to be expected given the nature of the process. In terms of product yield, LHW produced twice as much total sugar than any of the other processes. Conclusions: The project concluded that while LHW and SE are viable options for the pretreatment of biomass, LHW is the most suitable technique for the pretreatment of corn stover. This pretreatment was environmentally friendly as it produced the lowest CO2 emissions, aligning with the main objective behind developing biofuels from agricultural residues. The process was also technically the most effective as it resulted in the highest sugar yields. Methods: Using literature data, an LCA of four different pretreatment methods was carried out. Liquid hot water (LHW), steam explosion (SE), dilute acid (DA), and organosolv (OS) were chosen as the most common techniques with high scalability potential. Models were constructed using GaBi software. A cradle-to-gate analysis was selected with a common model of the corn stover growth and harvesting cycle being combined with the individual models for each pretreatment. Four impact categories were analyzed, and a selection has been discussed based on relevance to the biofuel production process. Results and discussion: In nearly all of the impact categories, DA performs the worst due to the length of the process (12 h) and the amount of electricity required to elevate the temperature to 60 °C for that time period. In many of the other categories, the remaining three pretreatments perform comparably to each other with the exception of LHW which has significantly reduced CO2 emissions. LHW has slightly higher water depletion rates than both SE and OS, which is to be expected given the nature of the process. In terms of product yield, LHW produced twice as much total sugar than any of the other processes. Conclusions: The project concluded that while LHWand SE are viable options for the pretreatment of biomass, LHWis the most suitable technique for the pretreatment of corn stover. This pretreatment was environmentally friendly as it produced the lowest CO2 emissions, aligning with the main objective behind developing biofuels from agricultural residues. The process was also technically the most effective as it resulted in the highest sugar yields