Adisa Azapagic’s research while affiliated with University of Manchester and other places

Most of plastic packaging waste does not degrade over time, which can lead to harmful effects on aquatic life and humans, highlighting the need for packaging materials that are easily degradable. Poly(mandelic acid) (PMA) is a biodegradable polymer that has been proposed as an alternative to polystyrene for use in packaging. However, its potential to replace the existing packaging materials also depends, among other factors, on the environmental sustainability of its production. This study aims to estimate and compare the life cycle environmental impacts of the production of PMA via polymerisation of 5-phenyl-1,3-dioxolane-4-one (Ph-DOX route) and o-carboxyanhydride (OCA route) monomers. For each route, the impacts are evaluated for 18 ReCiPE categories for reported laboratory scales and potential scaled-up commercial production. The results suggest that most of the impacts of PMA production via the Ph-DOX route are significantly lower (≥20 %) than that of the OCA route for both the laboratory and large scales. However, compared to polystyrene, the impacts of large-scale PMA production via the (better of the two) Ph-DOX route are more than five times higher. This is largely due to the use of benzaldehyde, enzymes, hydrocyanic acid and sodium phosphate in the production of mandelic acid and the solvents utilised in monomer synthesis. A sensitivity analysis shows that the bio-transformation of bio-glycerol to produce mandelic acid would reduce 16 out of 18 life cycle impacts of PMA by 6-77 %. The impacts are also sensitive to the assumptions used in the scaling-up of laboratory data for solvents. However, the results indicate clearly that, despite all the uncertainties in the scaling-up method, the proposed production routes for PMA would still have several times higher environmental impacts than polystyrene. Therefore, further research would be needed to improve significantly the production process for (bio-)mandelic acid, synthesis of monomers and their polymerisation before PMA can be considered an environmentally sustainable option for packaging applications.

Waste PVC is scarcely recycled due to its high chlorine content and its use in composite materials, which reduces the applicability of conventional waste treatment methods, including thermal, mechanical and chemical recycling. For this reason, alternative treatment options are being developed to increase the recyclability of waste PVC. This paper focuses on one such option which utilises ionic liquids (ILs) for material separation and dehydrochlorination of PVC contained in composite materials. Taking blisterpacks used as a packaging for medicines as an example of a composite material, the paper presents for the first time the life cycle environmental impacts of this novel PVC recycling method, in comparison with thermal treatment (low-temperature pyrolytic degradation of PVC). Three ILs were considered for the PVC recycling process: trihexyl(tetradecyl)phosphonium chloride, bromide and hexanoate. The results suggested that the impacts of the process using the first two ILs were comparable, while the system with hexanoate-based IL had 7-229 % higher impacts. Compared to the thermal treatment of waste blisterpacks, the IL assisted process had significantly higher impacts (22-819 %) in all 18 categories considered due to the greater heat requirements and the IL losses. Reducing the latter would lower most impacts by 8-41 %, while optimising the energy requirements would reduce the impacts by 10-58 %. Moreover, recovering HCl would increase significantly the environmental sustainability of the process, resulting in net-negative impacts (savings) in most categories. Overall, these improvements would lead to lower or comparable impacts to those of the thermal treatment. The findings of this study will be of interest to the polymer, recycling and related industries, as well as to process developers.

Graphene oxide (GO)-enhanced membranes are being developed to solve major limitations in both reverse osmosis (RO) and membrane distillation (MD) technologies, which include high electricity and thermal energy consumption. This study performed, for the first time, a life cycle assessment to determine the effects of using GO-enhanced membranes on the environmental impacts of seawater desalination via RO and MD. Four scenarios were evaluated and eighteen environmental impacts were quantified according to the ReCiPe impact assessment method. The average impacts for the RO-GO scenarios were lower than those of RO by 3–7 %. The reduction in the climate change impact was 3–8 %, which could avoid the release of 380–850 kt CO2 eq. per year globally if these membranes were used in current seawater RO systems. The MD-GO scenarios had, on average, 27–34 % lower impacts than the MD scenarios. Overall, the RO-GO systems were the most favourable, with lower impacts than MD-GO for most categories. However, using solar-thermal energy instead of natural gas in MD desalination would lead to 43–93 % lower impacts in nine categories than RO powered predominantly by fossil fuels. This includes climate change, which would be 64 % lower; however, freshwater ecotoxicity would be more than four- times higher. The results of this work indicate the potential environmental benefits of GO-enhanced membranes and discuss the future developments needed to improve the performance of RO and MD.

Forest residues, as cheap and abundant feedstock, can replace current fossil-energy sources, helping to reduce greenhouse gas (GHG) emissions and improve energy security. Given 27 % of total lands covered with forests, Turkey has a remarkable potential of forest residues from harvesting and industrial activities. This paper thus focuses on evaluating the life cycle environmental and economic sustainability of heat and electricity generation utilising forest residues in Turkey. Two types of forest residues (wood chips and wood pellets) and three energy conversion options are considered: direct combustion (heat only, electricity only and cogenerated heat and power (CHP)), gasification (for CHP) and co-firing with lignite. Results suggest that direct combustion of wood chips for cogeneration of heat and power has the lowest environmental impacts and levelised costs for both functional units (per MWh heat and per MWh electricity generation) considered. Compared to fossil-fuel sources, energy from forest residues has a potential to reduce the climate change impact as well as fossil-fuel, water and ozone depletion by >80 %. However, it also causes an increase in some other impacts, such as terrestrial ecotoxicity. The bioenergy plants have also lower levelised costs than electricity from the grid (except those using wood pellets and gasification regardless of the feedstock) and heat from natural gas. Electricity-only plants using wood chips achieve the lowest LCC, generating net profits. All biomass plants, except the pellet boiler, pay back in their lifetime; however, the economic feasibility of electricity-only and CHP plants is highly sensitive to subsidies for bioelectricity and efficient use of heat. Utilising the currently available forest residues in Turkey (5.7 Mt/yr) for energy provision could potentially reduce the national GHG emissions by 7.3 Mt/yr (1.5 %) and save $0.5 bn/yr (5 %) in avoided fossil-fuel import costs.

Wastewater treatment plants can become a source of valuable resources, such as clean water, energy, fuels and nutrients and thus contribute to the sustainable development goals and a transition to a circular economy. This can be achieved by adopting advanced wastewater and sludge treatment techniques. However, these have to be evaluated on their sustainability to avoid any unintentional consequences. Therefore, this paper presents a life cycle sustainability assessment of advanced wastewater and sludge treatment techniques by integrating the environmental, economic and social aspects. The options considered for advanced wastewater treatment are: i) granular activated carbon; ii) nanofiltration; iii) solar photo-Fenton; and iv) ozonation. The technologies for advanced sludge treatment are: i) agricultural application of anaerobically digested sludge; ii) agricultural application of composted sludge; iii) incineration; iv) pyrolysis; and v) wet air oxidation. The results for the advanced wastewater treatment techniques demonstrate that nanofiltration is the most sustainable option if all the sustainability aspects are considered equally important. If, however, a higher preference is given to the economic aspect, ozonation and granular activated carbon would both be comparable to nanofiltration; if the social aspect is considered more important, only activated carbon would be comparable to nanofiltration. Among the sludge treatment methods, agricultural application of sludge is the most sustainable technique for mean-to-high resource recovery. If the recovery rate is lower, this option is comparable with incineration and pyrolysis with high recovery of their respective products. This work helps to identify the most sustainable techniques that could be combined with conventional wastewater treatments for promoting wastewater reuse and resource recovery across a wide range of operating parameters and products outputs. The findings also support the notion that more sustainable wastewater treatment could be achieved by a circular use of water, energy and nutrients contained in urban wastewaters.