The ComPOSTer: Interview with Professor Z. Jason Ren

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.

Professor Zhiyong (Jason) Ren; Source:

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.

The ComPOSTer: Introducing Wesley Wiggins and an Algae-based Class Project

Hello everyone! My name is Wesley Wiggins and I am the newest writer for the ComPOSTer. I am a Princeton University undergraduate in the Class of 2021 and I am concentrating in the Department of Geosciences while obtaining a certificate in Environmental Studies. I am a member of the Princeton University EcoReps and was the former co-president of the Princeton University Geosciences Society or PUGS. Additionally, I have been an Operational Assistant at the S.C.R.A.P. Lab since Fall 2018 so I’ve spent plenty of time with SCRAPPY and working with food waste and composting.

Wesley Wiggins ’21 in Cape Town, South Africa
Photo Credits: Linh Nguyen

In the Fall 2019 semester, I worked on a project which incorporated the composter for my class ENE321: Resource Recovery for a Circular Economy taught by Civil and Environmental Engineering Professor Z. Jason Ren. This class discussed the topic of a circular economy which is the idea that resources should be reused and repurposed instead of how our linear economy simply puts items into waste. Our final project for this course was to create a business idea and pitch for a company that incorporates elements of the circular economy, and when I first heard of this idea my mind immediately turned to compost. 

Composting takes food scraps and uses it to create a soil additive that enriches the earth which can assist in growing new food and/or keeping the environment healthy. My team also wanted to incorporate a new element and produce something from compost. Through our research, we learned that the process of composting emits biogenic CO2 and we wanted to repurpose that gas and produce something new. Our minds turned to the process of photosynthesis in which water and carbon dioxide contribute to building organic matter so we wanted to find a product that we could grow easily and then sell to consumers. This is when we came across the algae species, Arthrospira maxima and Arthrospira platensis more commonly known as Spirulina.

Spirulina (Arthrospira platensis and Arthrospira maxima) contains 55-70% protein by dry weight, as well as high amino acid content and nutrients. It grows best in environments with high CO2 concentrations, a high pH, and high temperatures.

Spirulina are a globally cultivated algae species for food production because of their high protein content and nutritional value. We decided that the nutritious algae would be an excellent food product to sell as our business product and the only thing left to decide was how to grow the spirulina. We decided that the best way to grow them and incorporate the compost would be to use a photobioreactor which is a closed system that would allow us to control the inputs and outputs of the spirulina growth mixture. We could also take the CO2 from an industrial composter like SCRAPPY and feed it into our photobioreactor to cultivate the spirulina.

A photobioreactor is a device that cultivates photosynthetic organisms in a closed system. The benefits of using this device is the ability to control both the inputs and outputs of the system with a decreased risk of contamination.

After settling on an idea, my team had to settle on a company name and company roles. The members of my team were myself as the Chief Technological Officer, Jivahn Moradian ‘20 as the Chief Financial Officer, and Gabby D’Arcangelo ‘21 as the Chief Executive Officer. When deciding on a name we wanted something that represented both the algae and the use of carbon dioxide from the composter. So the name we settled on was AlgaeHG or AlGHG. The GHG in the title is short for Greenhouse gases which we are using to create our product in the form of CO2.

Though the company was created for a class project, the three of us had quite a fun time brainstorming the science, engineering, finances, and algae puns for our little class project. And we were thankful to Gina and the S.C.R.A.P. Lab for letting Gabby and Jivahn visit the Lab during my shift, and for all of the other assistance, we were able to receive. 

Gabby D’Arcangelo ‘21, Wesley Wiggins ’21, and Jivahn Moradian ‘20 (from left to right) presenting the AlgaeHG business pitch and presentation in ENE321: Resource Recovery for a Circular Economy.
Photo Credits: Professor Z. Jason Ren