Sustainability of cellulose micro-/nanofibers: A comparative life cycle assessment of pathway technologies.

Cellulose micro- and nanofibers (CNFs) are commonly regarded as "greener" than petro-based materials. The high energy input that their production still demands, along with the use of chemicals or heat in some pretreatments, asks for a critical view. This paper attempts a life cycle assessment of CNFs produced from bleached hardwood kraft pulp via three different pre-treatments before mechanical homogenization. First, a fully mechanical route, based on a Valley beating pre-treatment. Second, an enzymatic route, based on endoglucanases and requiring certain temperature (~50 °C). Third, a TEMPO-mediated oxidation route, considering not only the impact of the chemical treatment itself but also the production of TEMPO from ammonia and acetone. The main output of the study is that both, mechanical and TEMPO-mediated oxidation routes, present lower impacts than the enzymatic pre-treatment. Although the mechanical route presents slightly milder contributions to climate change, acidification, eutrophication, and other indicators, saying that TEMPO-mediated oxidation is environmentally unfeasible should be put under question. After all, and despite being disregarded in most assessment publications up to date, it is the only well-known way to selectively oxidize primary hydroxyl groups and thus producing kinds of CNFs that are unthinkable by other ways.

Substance flow analysis of mercury in Turkey for policy decision support.

Identification and quantification of mercury flows in Turkey are essential for better policy development regarding to the implementation of water-related legislation. To this end, substance flow analysis (SFA) of mercury in Turkey was conducted in order to identify and quantify mercury releases to different environmental compartments and help policy decision makers to better understand their options to reduce mercury flows. For the quantification of mercury flows, United Nations Environment Programme (UNEP) Mercury Toolkit, which is develop by UNEP Chemicals Branch with the aim of assisting countries to develop their own mercury inventory, was used. Results of the study showed that a total of 34.61 t of mercury is released annually from the activities in Turkey to different environmental compartments. It was found that most of the mercury releases were to the atmosphere (74 %) and smaller amounts were to land (21 %) and to water (5 %). Mercury naturally found in the lithosphere was found to be responsible for most of the releases while intentional mercury uses have smaller shares and decreasing importance because of the phasing out of mercury.