Comparative assessment of environmental impacts of 1st generation (corn feedstock) and 3rd generation (carbon dioxide feedstock) PHA production pathways using life cycle assessment.

Polyhydroxyalkanoates (PHA) are bio-based and biodegradable alternatives to conventional plastic types and have the potential to reduce the environmental impacts along the life cycle. In comparison to already established production routes for PHA (heterotrophic production) based on renewable feedstock like glucose (first generation feedstock), novel production routes, such as the photoautotrophic production of PHA based on CO2 as feedstock (third generation feedstock) could offer new perspectives with regard to the reduction in the environmental impacts. To quantify the environmental impacts of PHA produced via photoautotrophic and heterotrophic production pathways, life cycle assessment (LCA) methodology based on ISO 14040/44 was applied, thus conducting a first of its kind comparative study for PHA based on third generation feedstock. The results show that the photoautotrophic production of PHA has advantages in comparison to heterotrophic PHA based on glucose originating from corn as feedstock in all the assessed environmental impact categories, thus showing the environmental potential of novel production routes for bioplastics. Additionally, the results of the LCA show that the chloroform-based extraction method, commonly used in the downstream processes of both the technologies, has a significant contribution of environmental impacts in the production of PHA. Therefore, the reduction of chloroform loss during the extraction process can reduce its environmental impact. Our results indicate that PHA production from CO2 using the photoautotrophic production route is a promising technology with regard to the environmental impacts when compared to the heterotrophic production based on glucose feedstock.

Economic, technical, and environmental evaluation of retrofitting scenarios in a full-scale industrial wastewater treatment system.

The use of mathematical models is a well-established procedure in the field of (waste) water engineering to "virtually" evaluate the feasibility of novel process modifications. In this way, only options with the highest chance of success are further developed to be implemented at full-scale, while less interesting proposals can be disregarded at an early stage. Nevertheless, there is still lack of studies, where different plant-wide model predictions (effluent quality, process economics, and technical aspects) are comprehensibly verified in the field with full-scale data. In this work, a set of analysis/evaluation tools are used to assess alternative retrofitting options in the largest industrial wastewater treatment plant in Northern Europe. A mechanistic mathematical model is simulated to reproduce process behavior (deviation < 11%). Multiple criteria are defined and verified with plant data (deviation < 5%). The feasibility of three types of scenarios is tested: (1) stream refluxing, (2) change of operational conditions and (3) the implementation of new technologies. Experimental measurements and computer simulations show that the current plant´s main revenues are obtained from the electricity produced by the biogas engine (54%) and sales of the inactivated bio-solids for off-site biogas production (33%). The main expenditures are the discharge fee (39%), and transportation and handling of bio-solids (30%). Selective treatment of bio-solid streams strongly modifies the fate of COD and N compounds within the plant. In addition, it increases revenues (+3%), reduces cost (-9%) and liberates capacity in both activated sludge (+25%) and inactivation reactors (+50%). Better management of the buffer tank promotes heterotrophic denitrification instead of dissimilatory nitrate conversion to ammonia. In this way, 11% of the incoming nitrogen is removed within the anaerobic water line and does not overload the activated sludge reactors. Only a marginal increase in process performance is achieved when the anaerobic granular sludge reactor operates at full capacity. The latter reveals that influent biodegradability is the main limiting factor rather than volume. Usage of either NaOH or heat (instead of CaO) as inactivation agents allows anaerobic treatment of the reject water, which substantially benefits revenues derived from higher electricity recovery (+44%). However, there is a high toll paid on chemicals (+73%) or heat recovery (-19%) depending on the inactivation technology. In addition, partial nitration/Anammox and a better poly-aluminum chloride (PAC) dosage strategy is necessary to achieve acceptable (< 2%) N and P levels in the effluent. The scenarios are evaluated from a sustainability angle by using life cycle impact assessment (LCIA) in form of damage stressors grouped into three categories: human health, ecosystems quality, and resource scarcity. The presented decision support tool has been used by the biotech company involved in the study to support decision-making on how to handle future expansions.

Inclusion of multiple climate tipping as a new impact category in life cycle assessment of polyhydroxyalkanoate (PHA)-based plastics.

The merits of temporary carbon storage are often debated for bio-based and biodegradable plastics. We employed life cycle assessment (LCA) to assess environmental performance of polyhydroxyalkanoate (PHA)-based plastics, considering multiple climate tipping as a new life cycle impact category. It accounts for the contribution of GHG emissions to trigger climate tipping points in the Earth system, considering in total 13 tipping elements that could pass a tipping point with increasing warming. The PHA was either laminated with poly(lactic acid), or metallized with aluminum or aluminum oxides to lower permeability of the resulting plastics toward oxygen, water vapor and aromas. The assessments were made accounting for potential differences in kinetics of evolution of greenhouse gases (CO2, CH4) from bioplastic degradation in the end-of-life. Results show that: (1) PHA films with high biodegradability perform best in relation to the climate tipping, but are not necessarily the best in relation to radiative forcing increase or global temperature change; (2) sugar beet molasses used as feedstock is an environmental hot spot, contributing significantly to a wide range of environmental problems; (3) increasing PHA production scale from pilot to full commercial scale increases environmental impacts, mainly due to decreasing PHA yield; and (4) further process optimization is necessary for the PHA-based plastics to become attractive alternatives to fossil-based plastics. Our study suggests that multiple climate tipping is a relevant impact category for LCA of biodegradable bioplastics.

Multiple Climate Tipping Points Metrics for Improved Sustainability Assessment of Products and Services.

Mounting evidence indicates that climate tipping points can have large, potentially irreversible, impacts on the earth system and human societies. Yet, climate change metrics applied in current sustainability assessment methods generally do not consider these tipping points, with the use of arbitrarily determined time horizons and assumptions that the climate impact of a product or service is independent of emission timing. Here, we propose a new method for calculating climate tipping characterization factors for greenhouse gases (carbon dioxide, methane, and nitrous oxide) at midpoint. It covers 13 projected tipping points, incorporates the effect that the crossing of a given tipping point has on accelerating the crossing of other tipping points, and addresses uncertainties in the temperature thresholds that trigger the tipping points. To demonstrate the added value of the new metric, we apply it to emissions stemming from end-of-life of plastic polymers and compare them with commonly used metrics. This highlights the need to consider climate tipping in sustainability assessment of products and services.

Environmental and economic impacts of biochar production and agricultural use in six developing and middle-income countries.

The feasibility of using biowaste for the production of biochar and its use in agriculture depends on its environmental and economic performance. This paper quantifies environmental and economic life cycle impacts of biochar production and agricultural use in six developing and middle-income countries (Ethiopia, Indonesia, Kenya, Peru, Vietnam, and China). Two types of production technologies typical for rural and urban areas were investigated (flame curtain kiln and gasifier, respectively), and comparisons were made with composting (either home composting or windrow composting) as alternative biowaste management systems. The results showed that both pyrolysis systems performed better than composting and both were expected to bring environmental benefits. The largest environmental benefits were observed for the gasifier systems, mainly due to the substitution of electricity production from the grid. Damage to ecosystems and human health ranged from -1 × 10-7 to -2 × 10-8 species×yr and from -1 × 10-5 to -5 × 10-6 DALY per kg of biowaste treated, respectively (negative scores indicating environmental benefits). However, net economic benefits were only achieved when low-cost simple kilns were used in countries with low labor cost, like Ethiopia, Kenya and Vietnam (net profit from 0.01 to 0.08 USD per kg of biowaste treated). Further, high investment and operating costs and relatively small electricity revenue from substituting the grid electricity resulted in gasifier scenarios being economically unsustainable (net loss from 0.29 to 1.58 USD per kg of biowaste treated). Thus, there are trade-offs between positive environmental impacts for society and net market loss for the individual decision-maker (company or individual farmer) that should be considered when making decisions regarding the implementation of biochar technology in developing and middle-income countries. The use of simple kilns in countries with relatively low labor costs appears to be favorable.

An (Eco)Toxicity Life Cycle Impact Assessment Framework for Per- And Polyfluoroalkyl Substances.

A framework for characterizing per- and polyfluoroalkyl substances (PFASs) in life cycle impact assessment (LCIA) is proposed. Thousands of PFASs are used worldwide, with special properties imparted by the fluorinated alkyl chain. Our framework makes it possible to characterize a large part of the family of PFASs by introducing transformation fractions that translate emissions of primary emitted PFASs into the highly persistent terminal degradation products: the perfluoroalkyl acids (PFAAs). Using a PFAA-adapted characterization model, human toxicity as well as marine and freshwater aquatic ecotoxicity characterization factors are calculated for three PFAAs, namely perfluorooctanoic acid (PFOA) perfluorohexanoic acid (PFHxA) and perfluorobutanesulfonic acid (PFBS). The model is evaluated to adequately capture long-term fate, where PFAAs are predicted to accumulate in open oceans. The characterization factors of the three PFAAs are ranked among the top 5% for marine ecotoxicity, when compared to 3104 chemicals in the existing USEtox results databases. Uncertainty analysis indicates potential for equally high ranks for human health impacts. Data availability constitutes an important limitation creating uncertainties. Even so, a life cycle assessment (LCA) case study illustrates practical application of our proposed framework, demonstrating that even low emissions of PFASs can have large effects on LCA results.

Influence of metal speciation on soil ecotoxicity impacts in life cycle assessment.

It is unknown whether metallic elements remain important contributors to terrestrial ecotoxicity impact scores in life cycle assessment (LCA) when solid- and liquid-phase speciation are considered in environmental fate, exposure and effects. Here, a new speciation-based method for calculating comparative toxicity potentials (CTP) of 23 metallic elements in soils was compared with two other widely used methods which do not consider speciation (i.e., IMPACT, 2002+ and ReCiPe 2008) for nearly 13,000 life cycles of unit processes taken from different sectors. Differences in impact scores between method were driven either by differences in characterization models (ReCiPe 2008) or both by differences in characterization models and substance coverage (IMPACT, 2002+). Strong correlations (r > 0.98) and seemingly constant shifts in impact scores were found for those processes where one or few substances (usually metals) contributed most to total impact and there were large differences in CTPs between methods for these substances. Weaker correlations but often better agreement in impact scores were found for those processes where organic substances were dominant contributors to total impact. Our results suggest that metals are expected to remain important contributors to soil ecotoxicity impacts in LCA when speciation is considered.

Comparative life cycle assessment of coffee jar lids made from biocomposites containing poly(lactic acid) and banana fiber.

Composites containing bio-based materials, like banana fiber and poly(lactic acid) (PLA), are potential food-packaging materials. We carried out an environmental life cycle assessment (LCA) of coffee jar lids made from high density polyethylene (HDPE), PLA, and banana fiber to assess their environmental performance. We considered differences in the type of blend (content of PLA and banana fiber in the composite), origin of the banana fiber feedstock (considered as either biowaste or as a co-product from banana production) and banana fiber pretreatment conditions (either no pretreatment or pretreatment using chemicals). Irrespective of the scenario, a lid made from 40% banana fiber and equal amounts of HDPE and PLA performed significantly better in all 18 impact categories when compared to a lid made from 100% PLA. By contrast, the same lid performed significantly better in 3 impact categories only (climate change, photochemical oxidant formation and fossil depletion) when compared to a lid made from 100% HDPE. Thus, environmental performance of the biocomposite strongly depends on which polymer base is replaced by the banana fiber in the composite. Replacing PLA with banana fiber is generally expected to bring environmental benefits.

Toward harmonizing ecotoxicity characterization in life cycle impact assessment.

Ecosystem quality is an important area of protection in life cycle impact assessment (LCIA). Chemical pollution has adverse impacts on ecosystems on a global scale. To improve methods for assessing ecosystem impacts, the Life Cycle Initiative hosted by the United Nations Environment Programme established a task force to evaluate the state-of-the-science in modeling chemical exposure of organisms and the resulting ecotoxicological effects for use in LCIA. The outcome of the task force work will be global guidance and harmonization by recommending changes to the existing practice of exposure and effect modeling in ecotoxicity characterization. These changes will reflect the current science and ensure the stability of recommended practice. Recommendations must work within the needs of LCIA in terms of 1) operating on information from any inventory reporting chemical emissions with limited spatiotemporal information, 2) applying best estimates rather than conservative assumptions to ensure unbiased comparison with results for other impact categories, and 3) yielding results that are additive across substances and life cycle stages and that will allow a quantitative expression of damage to the exposed ecosystem. We describe the current framework and discuss research questions identified in a roadmap. Primary research questions relate to the approach toward ecotoxicological effect assessment, the need to clarify the method's scope and interpretation of its results, the need to consider additional environmental compartments and impact pathways, and the relevance of effect metrics other than the currently applied geometric mean of toxicity effect data across species. Because they often dominate ecotoxicity results in LCIA, we give metals a special focus, including consideration of their possible essentiality and changes in environmental bioavailability. We conclude with a summary of key questions along with preliminary recommendations to address them as well as open questions that require additional research efforts. Environ Toxicol Chem 2018;37:2955-2971. © 2018 SETAC.

Limitations of experiments performed in artificially made OECD standard soils for predicting cadmium, lead and zinc toxicity towards organisms living in natural soils.

Development of comparative toxicity potentials of cationic metals in soils for applications in hazard ranking and toxic impact assessment is currently jeopardized by the availability of experimental effect data. To compensate for this deficiency, data retrieved from experiments carried out in standardized artificial soils, like OECD soils, could potentially be tapped as a source of effect data. It is, however, unknown whether such data are applicable to natural soils where the variability in pore water concentrations of dissolved base cations is large, and where mass transfer limitations of metal uptake can occur. Here, free ion activity models (FIAM) and empirical regression models (ERM, with pH as a predictor) were derived from total metal EC50 values (concentration with effects in 50% of individuals) using speciation for experiments performed in artificial OECD soils measuring ecotoxicological endpoints for terrestrial earthworms, potworms, and springtails. The models were validated by predicting total metal based EC50 values using backward speciation employing an independent set of natural soils with missing information about ionic composition of pore water, as retrieved from a literature review. ERMs performed better than FIAMs. Pearson's r for log10-transformed total metal based EC50s values (ERM) ranged from 0.25 to 0.74, suggesting a general correlation between predicted and measured values. Yet, root-mean-square-error (RMSE) ranged from 0.16 to 0.87 and was either smaller or comparable with the variability of measured EC50 values, suggesting modest performance. This modest performance was mainly due to the omission of pore water concentrations of base cations during model development and their validation, as verified by comparisons with predictions of published terrestrial biotic ligand models. Thus, the usefulness of data from artificial OECD soils for global-scale assessment of terrestrial ecotoxic impacts of Cd, Pb and Zn in soils is limited due to relatively small variability of pore water concentrations of dissolved base cations in OECD soils, preventing their inclusion in development of predictive models. Our findings stress the importance of considering differences in ionic composition of soil pore water when characterizing terrestrial ecotoxicity of cationic metals in natural soils.