Our faculty Q&A series wraps up with an update from Professor Xinning Zhang, an environmental microbiologist jointly appointed in the Department of Geosciences and the High Meadows Environmental Institute. This month, the ComPOSTer interviewed Dr. Zhang to learn more about how her lab is extending its research in microbial metabolism and biogeochemcical cycling on the Princeton campus, and how it relates to environmental justice.
What are the main questions that your research group is asking about the composting process and how is the S.C.R.A.P. lab involved?
The Zhang lab is broadly interested in understanding the role of microbes in decomposition and greenhouse gas cycling within man-made and natural environments. As the environmental and human health harms of using industrial fertilizers to promote plant growth have become clear, many communities, including the University and the township, are exploring compost as a nutrient rich amendment to soils in place of industrial fertilizers.
Working with the S.C.R.A.P. lab, members of the Zhang group (Gabrielle D’Arcangelo ’21, Galen Cadley ’21, Dr. Jared Wilmoth) have been studying the microbial decomposition of food and garden waste into compost and greenhouse gases like carbon dioxide and methane with the aim of optimizing Princeton University’s aerobic digester for producing nutrient rich compost with low net greenhouse gas emissions. Specifically, we would like to determine (a) who the main microbial actors are in the compositing process, (b) how these microbes work together to make healthy compost, and (c) how microbes and their activities respond to changes in the composition of incoming food waste flows and environmental characteristics like aeration levels and temperature.
What have been the preliminary findings to-date and the next steps in the research?
While there is insufficient sample consistency to make any firm conclusions, preliminary findings of the microbial community analysis have identified Lactobacillus and Acetobacter to be the most dominant bacterial groups (indicating a rapid uptake of simple sugars), followed by Clostridium and Chitonophaga (complex carbon degradation), and less than 1% of methane-producing organisms, the most dominant being the oxygen-intolerant hydrogen gas consumer, Methanobacterium.
An accumulation of the latter category or “methanogens” was found during a power outage and when on-loading/off-loading of material was halted. These results indicate that to avoid increased methane emissions, compost materials should not be allowed to sit for long durations (> a couple days) in the composter, particularly in the back end of the unit where oxygen-free conditions favoring microbial methane production easily develop.
Future work will aim at evaluating whether increases in aeration frequency and/or changes in food waste/bulking agent composition will further reduce composter methane levels. However it is important to note that even optimally working municipal waste composts can contain anaerobic pockets allowing the presence of about 1% methane-producing bacterial species, so these results are consistent with those found in other composting operations.
Why is this research important and how does it relate to environmental justice?
The application of industrial fertilizers leads to numerous environmental problems, most notably the eutrophication of water supplies with detrimental effects on water quality, fisheries health, and greenhouse gas emissions. Unfortunately, these environmental harms are disproportionately borne by people of color in lower income neighborhoods. We hope that our work with the S.C.R.A.P. lab on the science behind composting will aid in weaning our food and landscaping system off industrial fertilizers to promote environmental health and justice.
Thank you for your loyal following during this unusual year of hardship and sorrow due to a global pandemic and acts of national racial injustice. Usually the last ComPOSTer of the year serves as an ode to the past year, but I think we can all agree that we rather leave 2020 behind. Still, with the New Year only several hours away, the ComPOSTer takes a moment to look back on the (brief) composting highlights of 2020, but more importantly, what is to come in the New Year. We are optimistic about 2021!
2020 Year in Review
January – March : Started off the year strong, just where we left off after our first full calendar year of operations. We converted 14 tons of food scraps into nutrient-rich compost before COVID-19 forced our facility to shutdown early in Mid-March.
April: Debuted a new video highlighting the behind the scenes processes and the people involved in the journey from food scrap to compost
Launched a faculty Q&A blog series led by Wesley Wiggins ’21
Began site planning for SCRAPPY’s new location along Washington Rd. south of Lake Carnegie
Other 2020 Highlights:
The S.C.R.A.P Lab was featured in…
A combined 10 presentations, webinars and tours
Campus as Lab projects:
Faculty-sponsored research projects: 3 active
Junior papers/senior theses: 2 completed
Student course projects: 1 completed
WHAT’S IN STORE IN 2021
Re-construction of our composting facility at our new home will begin early next year with operations expected to resume in Spring 2021. We will continue to engage our students as operational assistants, albeit under new social distancing and other covid-related guidelines. Otherwise we plan to pick-up where we started on our operational and research efforts, including:
Expanded compostables collection in the food gallery of Frist Campus Center
Integration of research efforts with operational testing of different feedstocks and recipes
Testing of new food scraps collection and drop-off systems to expand reach across campus
Before the Thanksgiving break, I attended the New Jersey Composting Council’s annual Organics Waste Summit on November 19th. Included in the topics of the virtual event were legal updates around the state of organics in New Jersey. Read on for highlights:
First, some background:
To achieve NJ’s goal of reducing statewide emissions 80% by 2050 (from 2006 levels) , emissions from the waste sector must be reduced by 15%
Waste management was the largest source of non-energy GHG emissions in both 2006 and 2018.
In 2018, GHG emissions from waste management was over 5 million metric tons CO2e as shown below:
Updates on Recent Organics Recycling-Related Laws & Regulations
Aimed to directly or indirectly advance progress toward the “80×50” goal:
New Jersey Protecting Against Climate Threats (NJ PACT) – Signed January 2020: Directs the Department of Environmental Protection (DEP) to make sweeping regulatory reforms to reduce emissions and adapt to climate change.
Commercial Organics Recycling Mandate– Signed April 2020; Regulations Pending; Stakeholder Meetings Anticipated Early/Mid 2021; Mandate Effective October 2021: Establishments (e.g. hospitals, prisons, schools, restaurants, supermarkets) in the state that generate 52 or more tons of food waste annually must arrange for separate recycling if an authorized facility is located within 25 road miles.
Exemptions to Solid Waste Regulations for Small-Scale Food Waste Recycling Activities – NJDEP Stakeholder Meeting November 2020; Proposal Anticipated Early 2021: Aimed to make regulations easier to comply with for those looking to start micro/community-scale composting operations
Environmental Justice Legislation – Signed September 2020; Stakeholder Meeting October 2020 (with additional meetings anticipated); Proposal Anticipated Early/Mid 2021: Aimed to prevent new environmentally damaging projects (e.g. landfills) from siting themselves in “burdened communities,” Learn more, including how to participate on the NJDEP EJ website
Cannabis Legislation – pending after NJ voters approved a ballot question to legalize recreational marijuana in November 2020: Given that waste processing of cannabis residue needs to happen in-state, regulations and processes must be outlined to make sure the residue is diluted and sterilized as is most commonly required by governments in other states where cannabis is legalized. If the residue is combined with organic material, the resulting feedstock can be safely composted by effectively reducing levels of THC in discarded marijuana.
Professor Daniel Rubenstein is the Class of 1877 Professor of Zoology in the Department of Ecology and Evolutionary Biology. Last month, I interviewed him about the intersections between food, agriculture, and the environment and how these topics related to environmental justice.
Interview edited for length and clarity
Q: Why are you interested in food, agriculture, and the environment?
A: I’m a behavior ecologist and what that means is you look at how the environment shapes animal behavior. So you’re looking at how changes in environmental factors, ecology, climate, etc. affect different species and in different environmental contexts. I’m interested in unraveling those patterns and I use a lot of modeling and comparative analysis to try to find general rules.
The species that I have studied most extensively are the equid, or the horses, zebras, and the wild asses. They’re all very closely related evolutionarily because they’re all the same genus. There are very few species left on the planet (only seven) and are not particularly numerically abundant anymore anywhere but they’re widely distributed.
Now, when they cover the planet, everyone who is a farmer who has livestock cattle, sheep, and goats believes that every grass blade in the environment belongs in the belly of their livestock and when they see horses, zebras, or wild asses eating the vegetation, they are very unhappy. And they want them gone and so they persecute them and cause the extinction of these equids. Since I study them and people consider them vermin, I got involved in farming. I needed to talk with the pastoral people and the commercial ranchers who didn’t like the animals that I studied. In order to find out why they persecuted them, I started doing experiments to demonstrate that in fact there’s not so much competition between them. It’s actually mutualism because the equids can eat the stems in the straw that the cattle find difficult to eat and therefore they open up the grasslands, take away the negative foods, stimulate the growth of the good, highly nutritious foods as long as there’s moisture in the soil and therefore benefit the cattle. And so the “vermin”, all of a sudden now are facilitating the growth of the cattle and the cattle — by feeding with their tongue — are stripping away the larvae that parasitize the guts of the equids and so as a consequence, there’s a joint mutualism using different currencies.
And so this experience made me interested in farming and I teach a course on agriculture, human diets, and the environment, precisely to talk about these issues and other issues like where did farming come from? Why did it supplant hunter-gathering (which was a perfectly good lifestyle)? How do you deal with the fact that you have no nitrogen in your soils or water? What are the resulting impacts on biodiversity? I set up the course so that the students would need to play with and analyze farming data to really sink their teeth into what evidence exists that explains how different types of farming have different impacts on the landscape, lead to different productivities, profits, and also to different distributions. Who can afford organic foods? If you’re poor, you can’t. And so now you have a social equity issue as well playing into it.
Q: How does the S.C.R.A.P. Lab relate to your course?
We received a grant from the university to examine different farming practices on several farms around Princeton. In the summer, we put out sensors in the field to measure metrics like evapotranspiration which is a measure of plant metabolism via water intake. If the water is going up through the plants it means the plants are photosynthesizing so via evapotranspiration you know how hard the plants are working effectively in terms of productivity. The students in the class pick different projects so they can compare commercial industrialized farming with organic farming, biodynamic farming, or precision agriculture which puts the artificial fertilizer in places where plants appear are needed rather than blanketing the landscape.
On Princeton University-owned farmland, we’re also interested in top-down pressures of herbivores eating the maize or soybean since the farmers leasing the land predicted that 30% of their crops were disappearing due to deer. So we sent out experiments to test whether that in fact was true by fencing off some of the lands with an electric fence at the same time that we are assessing the bottom-up factors (e.g. soil fertility). And that’s where the composter comes in. We can apply artificial fertilizer, which is what the farmers currently do, or we can have the soil additions be the compost. Each of these has different effects on the outgassing of CO2 as well as energy inputs. It turned out that the main cause of the loss of food was the herbivores or the deer but the nutrients do matter. We will be examining the effects further along with cover crops as well.
Q: Why is it important that we study the intersections between these three fields at Princeton University?
A: I think it’s important for us to study it on campus because we all bring slightly different perspectives to the notion of how plant productivity in general operates. One of the things about food is that students love food. It becomes a touchstone, a magnet that brings people into understanding – well, what am I eating? Is it healthy? What impact is my diet having? Everyone has strong beliefs about this. Some say “I’m a meat-eater because humans evolved to be meat-eaters”. Others say “I’m going to stay as an omnivore”. And others say that the footprint is too great, therefore, I’m going to become vegetarian, in fact, I’m going to become vegan. And so people come in with these really strong beliefs. It turns out there’s no perfect way to eat. That each one of these diets has issues and difficulties in one way or the other. When you do a life cycle analysis with all of the inputs, it turns out that what you think is the best type of farming often has hidden costs that you don’t appreciate. So there’s a lot of issues and my course brings out these issues to force people to rethink their beliefs.
Others who are biogeochemists and genomicists can really look at biology or chemistry and bring in the understanding of different breeds, different genetics, and the relationship between the genetics of the plants vs the insects and pests. So when you can start to look at genomics, you can start thinking about ways in which you can build better plants that get into GMOs (Genetically Modified Organisms). Crop engineering has very low impacts on the environment, both in terms of maintaining biodiversity and in managing water and gas production, but brings up issues questioning if GMOs are healthy for you and others, so there are unintended consequences. And the more we can bring knowledge to dealing with these trade-offs and preconceived notions, we start to make better decision-makers by sharing the knowledge with students and colleagues.
Even if we can’t agree on the right answer, the more information we can give students, the more skills we can give them to think through these wicked problems which are not easy to solve. That’s why the introductory, environmental nexus course was created which was based on the four pillars of Climate, Food, Water, and Biodiversity. We had to make sure in the Environmental Studies program that there were upper-level courses to build upon the themes that were being introduced in the foundational courses. And so that’s how my course arose, and then there are other courses such as history and literature courses that deal with farming, diets, and self-worth. We’re trying to think about putting together a food certificate program that would bring these together going forward.
Q: How is the work that you are doing related to environmental justice?
A: The justice implications are very real. Organic produce is much more expensive. If I go to the supermarket, I can get an ear of sweet corn for 30 or 50 cents depending on whether it’s on sale. If I go to an organic farm or a farmers market, that same ear of corn is going to cost me 75 cents or even $1, and that’s much more expensive. If you’re limited on money and you want to eat natural foods you’re going to go buy food at the grocery store and not at the organic farm. And there may be pesticides on that food. Are you washing it carefully enough? If not, then you’re ingesting chemicals that will impact your health. The organic farmer would have grown it without chemicals or a different set of chemicals that are deemed to be safer for you than the ones they use in industrial agriculture. So right away, the limits in your income and the ability to get out to a community-sponsored agriculture location are very, very different.
When I conduct different livestock rearing experiments in Kenya’s 55,000-acre, Mpala Conservancy, we open them to the pastoral herds in the community and hire the children as the herders. They’ll live at Mpala, earn some cash, and in doing this new type of herding they are seeing the difference in the growth and health of their cattle. I can publish a paper on it and do a community presentation, but the telegraph from child to father is much faster and much more effective. By participating, you take ownership of the experience and you can spread it much faster because you become an ambassador.
At Princeton, we hope to create a farm and invite kids from Trenton and Ewing, who may not have really healthy diets and engage them in actually growing and tasting vegetables. In doing so, they may experience something novel, and probably compel them to switch their diets. But most importantly, we will give them the crops to take back and sell within their communities. And that’s our belief that if we bring kids from urban centers and bring them into farming, not that they’re going to be farmers in the future, but they will start to appreciate and become aware that diet is something they can choose if they have access.
Professor Satish C. Myneni is a Professor in the Geosciences Department and a part of the Molecular Environmental Geochemistry Group. I had the pleasure of being a student in his class GEO363/CHM331- Environmental Chemistry: Chemistry of the Natural Systems which discussed geochemistry in abundant detail. Earlier this week, I conducted an interview related to his work on the geochemistry of compost and how the S.C.R.A.P. Lab is incorporated into his research.
Interview edited for length and clarity.
Q: What are the main questions that your research group is asking about compost and how is the S.C.R.A.P. Lab involved?
A: We are trying to understand the chemical variations that happen during compost formations In other words, as raw materials convert to compost, we are studying how the organic molecule chemistry changes and how the bioavailability of metals like iron, manganese, coppers, zinc, and other key elements change. We also want to make these materials used for specific applications. We were looking into the basic leaf litter and wood chips as feedstocks, and then we thought that it would be really interesting to look into and compare them with how food compost from the S.C.R.A.P. Lab behaves. For example, the leaf compost we get is not very rich in nitrogen whereas the food compost has more nitrogen. Can we mix these things to enhance the rate and improve the quality of composting for specific nutrients? Maybe the one with more nitrogen can be applied to lawns and the one with low nitrogen and high phosphorus can be applied to trees so that you can use leaf and food compost, mix them in different ratios and even add fertilizer to improve the rate of conversion on the compost to make them available for different applications
The S.C.R.A.P. Lab is providing food waste that we need for our study. However, it is not pure food waste because it is mixed with a lot of wood which has a big impact on the product. So that is something we have to work out but it is a very good source in getting partly altered food waste from the S.C.R.A.P. Lab.
Q: What are the main research methods your lab is using to answer these questions?
A: We have both field and lab components. In the field, we have different piles: a pure leaf litter pile, leaf litter plus food compost, and leaf litter plus compost plus fertilizer. The fertilizer that we add is coming from commonly-used lawn fertilizers which is mostly urea or nitrogen-based fertilizer. We are adding that to enhance the rate of composting and we do these three different treatments in three different ways. In the last treatment where we add the fertilizers, we add the fertilizers at different ratios (in increasing rates) and also at different times, and we also look at the composting material we get and the leachate material that is produced. These samples from the field form all the different compost piles and we get many samples from these at different time points in the field.
Once we are in the lab then we look at the different organic carbon and metal concentrations and the type of organic carbon that is in both solids and liquids (leachate material). And we are also looking into the bioavailable matter that can be extracted which is going to change with the composting time and the amount of fertilizer we are adding. We use luminescence spectroscopy to look at the types of concentrations of metals and the type of organic carbon that is there. In addition, we use the mass spectrometer and Nuclear magnetic resonance (NMR) spectroscopy in chemistry to get an idea of organic compounds.
Q: What are the main findings so far?
A: Kiley Coates ‘20, who did all of the initial work for her Senior thesis, myself, and some of my graduate students set up the piles and started the experiment in the early part of the year, right before the pandemic. The experiment was going nicely and the temperature in the piles started rising which is what you would expect. And then the pandemic happened and, unfortunately, we could not obtain more samples, so we had to restart the whole project.
Q: Why is this research important?
A: In Princeton (and in other places too) most people believe that fallen leaves are a problem and they just leave them on the street so that the municipality can collect them at different times. This is not only a major hazard for people biking or walking around the streets, but at the beginning of the spring, many people go and buy compost from somewhere else for their lands and gardens. However, they don’t realize that they can compost all of these leaves and use them in their own gardens. We wanted to come up with an alternative method where you are able to convert that big pile of leaves in your backyard into a smaller pile very rapidly with a tenth or a twentieth of the fertilizer that people usually apply. When you do that the compost takes the nitrogen and converts the more labile pool of nitrogen to an organically bound nitrogen form that is much more stable and once it is there in the organic matrix, you can actually apply this ground-up leaf compost to your lawn and slowly release nitrogen. That way, there is no big burden of nitrogen in the surface runoff waters which reduces eutrophication issues while keeping your lawns nice and green.
You can also manage your food waste materials. When you mix them with leaf litter you can get rid of the smell which is one of the things that people complain about compost. The chemicals that give that bad smell are absorbed by the leaf litter, so you can eliminate the bad odor and get all the key nutrients that you need. Overall, I think our research can contribute much more to the reduction of man-made fertilizers, and in turn, nitrogen and phosphorus losses from our lawns.
Continuing our review of Campus as Lab efforts, this post will provide an update on a project examining the environmental and economic implications of transitioning campus agricultural land from conventional to sustainable farming practices.
The project, led by Professor Daniel Rubenstein and assisted by me, involves engaging undergraduate students in measuring the relative importance of different soil amendments (including S.C.R.A.P Lab compost!) and weed control methods on crop productivity, soil health, and profit. Additionally, our team is analyzing the impact of low-cost fencing in reducing crop damage from deer overgrazing.
The ultimate goal of the project will be to develop a set of recommendations on how the University can farm in a more environmentally responsible and cost-effective way as the current industrial model of growing a rotation of corn and soybeans using fossil-fuel based inputs is carbon intensive, degrades soils, and pollutes waterways. Alternative and more sustainable practices that we are testing include diversifying the crop rotation, using natural soil amendments like compost, and ensuring ground cover over the winter with a cover crop in order to increase the soil’s ability to supply nutrients to crops without relying on excess use of chemical inputs.
Below is a photo essay describing the project and progress to-date:
In a few weeks, the soybeans will be harvested using a yield counter to obtain accurate data on the productivity of each plot. We will conduct statistical analyses to determine the relative effectiveness of fencing, soil amendment, and weed control method on yield. In the spring, we will take soil samples and run the same analyses for initial impacts on soil fertility compared to baseline levels collected earlier this year. We hypothesize that the sections receiving compost and planted with winter rye will have a more favorable soil pH, a higher percentage of organic matter, and optimum levels of nutrients versus the sections that did not receive the compost or rye treatments.
Professor Zhiyong (Jason) Ren is a Professor in the Civil and Environmental Engineering Department and is the Acting & Associate Director for Research at the Andlinger Center for Energy and the Environment. I had the pleasure of being his student in the Fall of 2019 in his class Resource Recovery for a Circular Economy. He recently started a project with Professor Anu Ramaswami on developing new methods and technologies to manage food waste in our society. In this interview, I ask him what this project is and how it relates to the circular economy, the S.C.R.A.P. Lab and environmental justice.
Q: How does the work that you are doing relate to the circular economy?
A: My research is very much related to it. When you talk about the circular economy you talk about the 3 R’s: recycle, reuse, and reduce. I am more on the reuse side because we are trying to improve the values of the waste and convert it into a value-added product. Not to mention that in this project we try to actually make better value-added products out of traditionally low-price products. This has been a challenge in waste valorization. If you actually can make profits using technology made of waste material that makes economic sense then that makes the technology more applicable in the real world.
Q: Can you describe the work you are during with Professor Ramaswami?
A: Professor Ramaswami and I along with other professors in other universities have been issued an INFEWS (Innovations at the Nexus of Food, Energy, and Water Systems) award from the USDA. My part of the work is looking into the technological advancements of treating food waste generated from different places and developing technologies to convert food waste to make better products. Especially if there is any possibility to produce biogas which is a cheap energy source. We’re also looking at the possibility of biochar which can enhance the anaerobic treatment process to produce energy, water, and fertilizer from food waste and hopefully then go back and actually put these resources back into community gardens. So it is a closed loop utilization of food. That’s my side of the project and we’ll work with Professor Ramaswami’s group analyzing the benefits and challenges of different technologies by using life cycle assessments and economic analysis tools to understand the system.
Q: Why do we want to develop new methods of managing our food waste?
A: Because it’s a problem, that’s for one. Food waste certainly occupies a lot of landfills, and we should not have a lot of food waste anyways because we do not want to waste a lot of food. Secondly, if we have to generate food waste we have to give it a better use. You don’t want to just throw it away and leave it rotting somewhere like a landfill which causes different issues. It would be better utilized for beneficial use which is basically the principle of a circular economy.
Q: How does the S.C.R.A.P. Lab fit into your project?
A: The campus composter and facility is a very important demonstration tool to campus as an educational tool and also is a good approach to convert campus food waste into something valuable. It is certainly a good example of waste valorization. On the research side, this approach compliments what we do because the technology developed in my lab is not at the scale of commercial application yet. The S.C.R.A.P. Lab serves as a benchmark to which alternative waste valorization technologies like producing protein out of food waste may be compared against. Other things can actually be in collaboration with the compost facility. It is a very important facility for our community.
Q: How would our current system for handling food waste contribute to environmental injustice? And how does your project seek environmental justice?
A: Currently a lot of food waste goes to landfill so you see how unpleasant those places are and certainly everyone has a notion of “Not in my Backyard” (NIMBY), don’t build a landfill in my backyard. I would assume most of these landfills would be closer to land and neighborhoods that are lower income and are disproportionately disadvantaged communities. So you would help to reduce those types of construction and reduce the impact on some of these communities. And from the economic side you could develop technologies to make waste a valued product that creates a lot of job opportunities and businesses within the waste management industry. As a result, waste companies can use these technologies which will create circular economy jobs that pay better and generate revenue products itself which will be economically beneficial as well.
Peter Jaffé is the William L. Knapp Professor of Civil Engineering and Professor in the Civil and Environmental Engineering department. Earlier this week, I conducted an interview with him regarding a recent research project on removing a pollutant called PFAS or Per- and poly-fluoroalkyl substances, a topic of great concern among composters. In the summary of the interview below, I ask Professor Jaffé about these pollutants and the bacteria that can remove them.
Q: What are PFAS and why is it important to develop methods to remove them?
A: It stands for per- and poly-fluorinated substances. There are about 4000 different fluorinated compounds that the chemical industry has manufactured. They are interesting because the carbon-fluorine bond is the strongest covalent bond in organic chemistry, which gives them a lot of stability, and as such the compounds have been used to create water and heat resistant products. Two main compounds are perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). PFOS was developed by 3M which makes Scotchgard a water repellent spray and is also used as firefighting foam. PFOA was developed by DuPont to make Teflon which is a long carbon-fluorine polymer, commonly used in non-stick cookware. These molecules are a big challenge because they were built to be stable and they have no easy analog in nature so organisms haven’t evolved to degrade them so now there are health effects that we associate with them. They have developmental effects and are possibly carcinogenic, and lead to kidney diseases. They have been used quite aggressively since post-WWII and we haven’t really tracked them very much. It was only in the last decade or so that we became concerned about them.
Q:What other types of products can you expect to find PFAS in?
A: They are in all kinds of consumer products, because when they stick to something they become water repellent. Pizza boxes have PFAS so that they don’t get too wobbly too quickly, so do cardboard food plates. Any rugs that are stain resistant, some of your clothing, airplane parts…you name it. It is pretty much everywhere.
Q: How did you discover that Acidomicrobium bacterium A6 was able to remove PFAS?
A: We first noticed that there is a process for oxidizing ammonium to nitrite in anaerobic sediments under iron reducing conditions. After we first published this finding, other researchers noticed the same including a Japanese researcher who found something similar in a reactor. They called that process Feammox which is an analog to anammox, another anaerobic ammonium oxidation process that we were studying. A microbiologist that we were working with managed to identify the organism that is responsible for this oxidation, Acidomicrobacterium A6. She managed to then grow it in a pure culture and do genomic sequencing.
Looking at the sequencing, we noticed that it had a series of interesting genes, some oxygenation related, and those seem to be linked with the process of ammonium oxidation. Later we noticed that it had some sequences for dehalogenase enzymes. We said, “Ah, let’s try and see if we can do something with PFAS” and lo and behold we tested it and it could defluorinate them, at least most of those we have tested. There are some highly branched ones that we have difficulties with but almost everything else we can defluorinate, which is pretty stunning because so far there has been no other organism that has been shown to defluorinate the perfluorinated ones. There are some organisms that can take a single fluorine out when you have some carbon-hydrogen bonds and some carbon-fluorine bonds, but when you have no hydrogen bonds and it is all fluorine bonds so far this is the first one that has been identified.
Q: What are the limitations of using A6 to remove PFAS and how are you planning to overcome those limitations?
A: From a technological point of view, it’s an anaerobic autotrophic organism so it grows very slowly. The doubling time is somewhere between 10 to 14 days as opposed to E. coli which could be half-a-day or fewer. Anytime you have to deal with a bacterium that grows slowly that becomes hard. Another problem is that when we want to grow it in a reactor it uses ferric iron and the stoichiometry is 6 irons per ammonium assuming 100% efficiency (and it’s not 100% efficient) so the amount of iron in minerals that you have to add is large. Plus a goop of magnetite ferrihydrite will build-up in the reactor and you cannot keep running it. So the challenge is how can we keep growing this organism without iron? We have shown that it can be grown in microbial electrolysis cells, but the challenge is how do we go from these little vials to a continuous flow reactor. We are struggling with that right now.
Q: Are there any implications related to composting or potential testing opportunities with the S.C.R.A.P. Lab?
A: Since there are PFOA precursors in pizza boxes and paper plates, if they are composted, then you’ll have PFAS in the compost, and then you will certainly not want to use the compost as a soil amendment because plants will take up the PFAS. It is something that the university should look at, but the unfortunate thing is that these analyses aren’t cheap. If you send the sample to a commercial lab, one analysis is about $450 so you want to think carefully before you spend too much money.
Q: And how does your project seek environmental justice?
A: Not directly but there are of course usually lower-income neighborhoods in locations close to industrial facilities where firefighting foam has been used so I would say that you have PFAS proportionately higher in lower-income neighborhoods. The highest PFAS are typically around military installations because they use a lot of firefighting foam in the hangars where they put planes in. I am not sure if this is still done today but in the past, these facilities would perform tests where they fill the whole hangar with foam in case a plane catches fire or something and the foam runs out and spills into the groundwater. So yes it is likely that concentrations of PFAS are higher in groundwater close to facilities so in that sense coming up with a methodology to degrade them is an indirect way to address environmental injustice.
Professor Jaffé ended the interview by stating, “I’m excited about the work. We’re excited about this organism that could oxidize ammonium, but we’re excited to have one that can target the most complicated contaminants. I have 4 new Ph.D. students coming this year and all of them want to work on different aspects so we’ll have quite strong activity in the next couple of years.”
Princeton’s fall semester officially begins today. Over the course of this semester, the ComPOSTer will provide updates related to the relocation of the S.C.R.A.P. Lab composting facility, and feature a Q&A series with Princeton faculty who are conducting research at the S.C.R.A.P. Lab or on other topics related to composting. But before we head into the new semester, this post will wrap up the unofficial end of summer with highlights from the past month. Read below to learn about event composting and an alum profile featuring former assistant, Ishy Anthapur ’20.
Waste Less Wednesday Zoom Social Series: Composting at Events
Earlier this month, my colleague, Lisa Nicolaison, and I co-hosted a session on Johns Hopkins University’s Waste Less Wednesday Summer 2020 Zoom Social series. Check out the video recording below to hear about Princeton University’s experience hosting low waste events through the collection and composting of food and compostable serviceware.
Alum Profile: Ishy Anthapur ’20
Ishy reflects on her time working at the S.C.R.A.P. Lab and discusses her post-graduation plans. Congrats Ishy!
I worked at the S.C.R.A.P. Lab for the summer of 2019 while I was also doing research on campus for my senior thesis in the EEB department. I learned a LOT about Princeton’s sustainability plan and all the strides forward we’ve made (the S.C.R.A.P. lab being a huge part of that)! I also realized that the campus could be doing a lot more to deal with the amount of food waste in general.
My current plans are to pursue a P55 Fellowship in Boston at the Community Day Charter Public School. The S.C.R.A.P. lab affirmed my belief that community-based projects and services are so important to making an impact in terms of environmentalism and sustainability. I’m looking forward to trying to live as green as possible as I start my new job and my new life as an alum!