Research Interests
Promoting volatile fatty acid production in anaerobic digestion of food waste
Anaerobic digestion (AD) is a biological process that breaks down complex biodegradable organics in the absence of oxygen. AD process produces value-added products volatile fatty acids (VFAs), hydrogen gas, and methane gas (CH4), making it an important technology for capturing the energy and resources embedded in organic wastes. CH4 is the final product in conventional digesters. However, difficulties in obtaining air permits and growing interest in recovering more valuable chemicals, such as VFAs (e.g., $1900/ton butyric acid compared to $160/ton CH4), are driving research into alternatives to CH4. VFAs are precursors of CH4 in AD, therefore, arresting CH4 production is needed to promote VFA accumulation. My overarching goal was to develop chemical-free methods shaping the microbial communities towards suppressing methanogens and favoring hydrolytic and fermentative bacteria.
Investigation of key phosphorus (P) biotransformation pathways in anaerobic digestion using metagenomics
P mines are non-renewable and overexploited due to anthropologic activities, with 80% being used as fertilizers. Nearly 50% of the P from mines flows to waste streams. When not managed properly, the P in waste enters waterbodies, causing eutrophication. AD offers a platform to recover P along with C from these wastes. Yet, very little exploration has been done on organic P transformation pathways in AD. Therefore, a map for P transformation in AD systems is needed to facilitate P recovery in practice. To address this knowledge gap, my current study focuses on determining the transformation and fate of P speciation in AD. I will apply metagenomics tools to look in depth at the P- transformation related functions of microorganisms present in AD.
Publications
Haflich, H*, Ding, H.*, Call D.F, Coronell, O., Impact of electrodialysis physical and operating parameters on volatile fatty acid production during sequential batch anaerobic digestion of food waste. In preparation.
Ding, H. and Call, D.F., Intermittent heat shocks increase generation of longer chain volatile fatty acids during anaerobic digestion. Submitted.
Ding, H., Barlaz, M.A., de los Reyes III, F.L. and Call, D.F., 2022. Influence of inoculum type on volatile fatty acid and methane production in short-term anaerobic food waste digestion tests. ACS Sustainable Chemistry & Engineering.
Ding, H., H., 2019. Studies on the Growth of Anaerobic Ammonium Oxidizing Bacteria and the Start-Up of Moving Bed Biofilm Reactors (Dissertation, The University of Arizona).
Zhang, R., Yin, X., Ding, H., Wang, L., Zhou, Q. 2019. Analysis for effects of lanthanum (III) on the aboveground modules and respiration of soybean populations. Ecotoxicology and Environmental Safety, 167: 196-203.
Jiao, L., Ding, H., Wang, L., Zhou, Q. Huang, X. 2017. Bisphenol A effects on the chlorophyll contents in soybean at different growth stages. Environmental Pollution, 223: 426-434.
Recent Awards
EREF Scholarship, Environmental Research & Education Foundation (2021-current)
Second Place Poster Award, 2023 NC One Water Annual Conference (2023)
Student Poster Award, 2023 AEESP Research & Education Conference (2023)
First Place Poster Award, EWC Graduate Research Symposium, NC State University (2023)
People’s Choice Poster Award, Sustainable Phosphorus Summit (2022)
Waste Management Research and Study Scholarship, Air & Waste Management Association (2020)
Skills to Highlight
During my PhD, I have developed a set of skills that I am proud of. I do not mean that I am very good at them, or better than other researchers in the field. I mean to say that I am proud because of the time and the efforts I put in learning these skills.
Bioinformatics
Because I work with anaerobic digestion, I must work with complex microbial communities. The bioinformatics tools that I am familiar with include 16S rDNA analysis, and some metagenomics for DNA data obtained from illumina or Nanopore sequencing platforms. I use DADA2 for illumina 16S rDNA data processing, and R for the subsequent analysis. For Nanopore 16S data, I pieced together a pipeline (Unix) using the individual programs written by others. Right now, I am working hard on writing the pipeline for metagenomics. The programs for metagenomics data processing and analyses are available, but my pipeline aims to have clear explanation for each program choice, and to process batches of samples. The pipelines and codes I used or put together are/will be publicly available, both on my Github and this website.
Programming
I never programmed or learnt programming before grad school. And I always tried to dodge it. But working with bioinformatics, it was unavoidable to learn how to code. I started learning coding in the second year of my PhD. And now I am pretty comfortable with R. Once I started working with Nanopore sequencing, I started learning to use Bash commands to process big batches of data. Recently, I got my hand on a teeny bit of HTML.😊
Laboratory Operations
You could find more lab skills I have in my CV. Here, I want to mention that I think I am a very careful planner when doing lab. I am rather independent in designing experiments/protocols. I like to plan experiments very carefully beforehand and keep good records of my protocols. I also like my lab space clean.😎
