Publications

Significant knowledge and data gaps associated with the fate of product-embedded engineered nanomaterials (ENMs) in waste management processes exist that limit our current ability to develop appropriate end-of-life management strategies. This review paper was developed as part of the activities of the IWWG ENMs in Waste Task Group. The specific objectives of this review paper are to assess the current knowledge associated with the fate of ENMs in commonly used waste management processes, including key processes and mechanisms associated with ENM fate and transport in each waste management process, and to use that information to identify the data gaps and research needs in this area. Literature associated with the fate of ENMs in wastes was reviewed and summarized. Overall, results from this literature review indicate a need for continued research in this area. No work has been conducted to quantify ENMs present in discarded materials and an understanding of ENM release from consumer products under conditions representative of those found in relevant waste management process is needed. Results also indicate that significant knowledge gaps associated with ENM behaviour exist for each waste management process investigated. There is a need for additional research investigating the fate of different types of ENMs at larger concentration ranges with different surface chemistries. Understanding how changes in treatment process operation may influence ENM fate is also needed. A series of specific research questions associated with the fate of ENMs during the management of ENM-containing wastes have been identified and used to direct future research in this area.

Hydrothermal carbonization (HTC) is a wet, low temperature thermal conversion process that continues to gain attention for the generation of hydrochar. The importance of specific process conditions and feedstock properties on hydrochar characteristics is not well understood. To evaluate this, linear and non-linear models were developed to describe hydrochar characteristics based on data collected from HTC-related literature. A Sobol analysis was subsequently conducted to identify parameters that most influence hydrochar characteristics. Results from this analysis indicate that for each investigated hydrochar property, the model fit and predictive capability associated with the random forest models is superior to both the linear and regression tree models. Based on results from the Sobol analysis, the feedstock properties and process conditions most influential on hydrochar yield, carbon content, and energy content were identified. In addition, a variational process parameter sensitivity analysis was conducted to determine how feedstock property importance changes with process conditions.

The goal of this study was to use life cycle assessment to evaluate whether using liquid hazardous waste as an alternative fuel source in cement manufacturing processes located in the United States improves system environmental impact when compared with a facility using coal. Results from this study indicate that replacing coal with hazardous waste reduces the environmental impacts associated with the global warming impact, acidification impact, and freshwater ecotoxicity, while the human toxicity impacts for cancer and eutrophication-related environmental impacts increase. Reducing grid purchased electricity by recuperating waste heat from the process, cooling the exhaust gases and generating electricity to offset electrical demand, could reduce environmental impacts associated with off-site grid purchased electricity and should be considered for further environmental impact reductions. In addition, these results confirm that there are certain positive environmental effects associated with the co-burning of hazardous waste during cement manufacturing and replacing fossil fuels, such as coal, with high energy content hazardous waste.

Significant efforts have been direct towards developing environmentally sustainable and economically beneficial treatment of olive mill wastes. Recently, hydrothermal carbonization (HTC) has been shown to be a potentially beneficial approach for the treatment of olive mill wastes. When considering the use of HTC to treat these wastes, however, it is critical that its environmental implications be evaluated and subsequently compared to other commonly used treatment approaches. In this study, the environmental impacts associated with using HTC to treat olive mill wastes were evaluated and compared to aerobic composting, anaerobic digestion, and incineration using life cycle assessment. Results indicate that HTC coupled with subsequent energy recovery from the combustion of the generated hydrochar results in net environmental benefits and that the energy offsets derived from electricity production from hydrochar combustion are critical to achieving these savings. In addition, results indicate that HTC process water discharge significantly influences system environmental impacts, indicating that research investigating treatment alternatives is needed. Changes in carbonization temperature and hydrochar moisture content also influence system environmental impact, suggesting that both are important when considering possible industrial applications. In comparison with current management approaches, alternatives using HTC are more environmental advantageous than composting and anaerobic digestion. However, the use of HTC is not as environmentally advantageous as incineration with energy recovery because 45-35% of the energy contained in the olive mill waste is lost during HTC. However, if the electricity recovery efficiency from incineration increases to greater than 30%, the environmental impacts associated with HTC and subsequent energy generation are equal to or better than direct TPOWM incineration with energy recovery. It is recommended that future research efforts focus on the evaluation of appropriate and environmentally beneficial HTC process water treatment approaches and methods to improve the energetic retention efficiencies of the hydrochar.

Food waste represents a rather large and currently underutilized source of potentially available and reusable nutrients. Laboratory-scale experiments evaluating the hydrothermal carbonization of food wastes collected from restaurants were conducted to understand how changes in feedstock composition and carbonization process conditions influence primary and secondary nutrient fate. Results from this work indicate that at all evaluated reaction times and temperatures, the majority of nitrogen, calcium, and magnesium remain integrated within the solid-phase, while the majority of potassium and sodium reside in the liquid-phase. The fate of phosphorus is dependent on reaction times and temperatures, with solid-phase integration increasing with higher reaction temperature and longer time. A series of leaching experiments to determine potential solid-phase nutrient availability were also conducted and indicate that, at least in the short term, nitrogen release from the solids is small, while almost all of the phosphorus present in the solids produced from carbonizing at 225 and 250°C is released. At a reaction temperature of 275°C, smaller fractions of the solid-phase total phosphorus are released as reaction times increase, likely due to increased solids incorporation. Using these data, it is estimated that up to 0.96% and 2.30% of nitrogen and phosphorus-based fertilizers, respectively, in the US can be replaced by the nutrients integrated within hydrochar and liquid-phases generated from the carbonization of currently landfilled food wastes.

A two-step research program for undergraduate students was developed and implemented across the 2015 spring-summer terms in the Department of Civil & Environmental Engineering at _____. The first step requires students to complete a research course in the semester prior to the research experience. This course is different from an independent learning or special research topics course. It is taught in a traditional classroom setting but emphasizes interactive learning of the research process. Students are taught how to identify meaningful research topics and develop research questions based on the identification of gaps in knowledge in the relevant literature. The course culminates with the submission of a research proposal, which is the main deliverable and student assessment instrument for the course. Students are required to meet and work with their research mentor during the semester. The second step is to conduct the research as outlined in the proposal.

This program was implemented as part of a NSF-supported project to create the Nanotechnology LINK (Learning Integration of New Knowledge) curriculum enhancements. This project exposes undergraduate students in our department to fundamental concepts and applications in nanotechnology, with an emphasis on end-of-life management of products containing nanomaterials. This content is delivered across multiple linked courses. To complement and extend student learning of nanotechnology within the curriculum, research-based learning opportunities were created for a select cohort of students. The first cohort of five students was assembled from a group of 22 internal applications. This paper will describe the application and selection process, which was conducted during the fall 2014, and the subsequent impacts of the research course (spring 2015) and summer research experience (summer 2015) on student understanding of the research process.

Students are encouraged to culminate the research program through the pursuit of Graduation with Leadership Distinction (GLD) in Research. Four of the five students in the first cohort intend to earn the GLD in Research, which is a university-wide program available to all undergraduate students. Successful recipients must demonstrate (1) extensive, purposeful engagement beyond the classroom; (2) understanding of course concepts in “real world” settings; and (3) application of learning to make decisions and solve problems. Requirements include participation in enhancement activities (lectures, workshops, events); completion of approved courses relating to their experience; delivery of a public presentation; and production of an e-portfolio that demonstrates their learning. This paper will provide an example of one student’s completed requirements towards the distinction.

As stated on the US National Academy of Engineering (NAE) Grand Challenges website,‘‘the challenges facing engineering today are not those of isolated locales, but of the planet as a whole and all the planet’s people. Meeting all those challenges must make the world not only a more technologically advanced and connected place, but also a more sustainable, safe, healthy, and joyous—in other words, better—place”(NAE, 2015). Likewise, the growing solid waste generation rates pose significant health and technical challenges. According to the US Environmental Protection Agency (2015), the US produced 254 million tons of MSW in 2013, although some sources suggest that the amount may be much greater. Globally, it is estimated that 1.3 billion tonnes of MSW were generated in 2010 and that value is projected to increase to 2.5 billion tonnes per year by 2025 (Hoornweg and Bhada-Tat, 2012). The collection, processing, and disposal of MSW potentially leads to adverse environmental impacts, undesirable land uses, and reduced housing values. Increasing urbanization magnifies these impacts as population densifies and local disposal options (ie, landfills) become limited. Therefore, a focus on key opportunities, grand challenges, and potential solutions in our field is needed. The attendees of the 8th Intercontinental Landfill Research Symposium held in Crystal River, Florida US, October 2014 gathered to consider the grand challenges in th