UCT-led project creates pipeline for sustainable food waste management system

To bolster sustainable practices on campus and ensure everyone remains eco-conscious, the Centre for Bioprocess Engineering Research (CeBER) in the University of Cape Town’s (UCT) Faculty of Engineering & the Built Environment has devised a one-of-a-kind project that breaks down waste: to use it as an energy source for cooking or to produce fit-for-purpose water that can later be used to irrigate on-campus vegetable gardens.

Wrapping your head around the Waste-Energy-Food-Water Nexus project’s scientific nitty gritties might take a bit of time, especially for a non-scientific mind. So, UCT News sat down with project lead, Dr Thanos Kotsiopoulos, to help us simplify the initiative.

The project forms part of UCT’s sustainable campus initiative – a R10 million five-year long campus-wide project created to support the environmental sustainability ambitions of UCT’s Vision 2030. The initiative includes leading research, feasibility studies and proof-of-concept living labs on campus.

Niémah Davids (ND): Tell us about the Waste-Energy-Food-Water Nexus project. 

Dr Thanos Kotsiopoulos (TK): The project aims to expand the anaerobic digestion (AD) process – a four-stage biological process that uses anaerobic bacteria to breakdown waste – into a multi-product system that incorporates a range of useful stages, including using biogas (a renewable fuel that’s produced when organic matter like food or animal waste is broken down by microorganisms in the absence of oxygen) as an energy source for cooking or alternative applications.

“During this project, the carbon dioxide produced during the AD process is partially removed by an algae scrubber.”

During this project, the carbon dioxide produced during the AD process is partially removed by an algae scrubber (a water filtering device), and we intend to harvest the algal biomass for further processing to produce biofuels (liquid fuels produced from renewable energy sources, including plants and algae), as well as algal-derived bioproducts such as natural pigments.

The nutrient-rich effluent stream, created through the AD process, is then challenged through an aeroponic system (also referred to as a vertical farm – the practice of growing plants in an air or mist environment without any substrate) to produce fit-for-purpose water. Solids generated through AD can also be used as fertiliser. Since these vertical farms use constructed arrangements to support plant development, these structures have the potential to contribute to UCT’s interior and exterior landscaping design while also functioning as prospective low-cost climate control arrays that offset building cooling requirements and electricity costs.

ND: Why was there a need to start this project?

TK: The project aims to address certain environmental challenges we face. These include increasing food waste volumes, the costs associated with disposing this waste, as well as the significant carbon and water footprints that emanate from landfill disposal. So, the purpose of this project is to use circular design thinking to produce renewable energy and bio-based products using food waste, and to develop and implement a campus-wide, integrated sustainable food waste management system to help facilitate a resource-efficient campus.

All this is important because we currently face significant sustainability challenges like climate change, waste management and resource depletion. This project addresses these issues by promoting a closed loop system where resources are efficiently used, where minimal waste is generated, and renewable energy is produced or offset. By using organic waste as a feedstock to produce biogas, the project demonstrates how we can decrease fossil fuel resilience and conserve water. This approach advocates for utilising available resources and reduces those environmental impacts associated with traditional practices.

ND: What are some of your main objectives?

TK: We have three main objectives: to fast-track sustainability of a traditional anaerobic digestion (multiple processes by which micro-organisms break down biodegradable material in the absence of oxygen) food waste system; to use products on campus to save costs and support small, medium and macro enterprises; to serve as a living laboratory that educates various communities on sustainable on-campus practices and to promote collaborative partnerships across various faculties and departments.

ND: What positive results has this work yielded thus far?

TK: Thus far we have been able to validate this integrated system at lab scale, and successfully scale the project. We’ve been able to generate biogas with approximately 80% methane (a gas found in small quantities in the atmosphere) – and this far exceeded our expectations. We also managed to identify an algal strain that is showing good promise with scrubbing carbon dioxide from the methane-rich biogas.

“We’ve been able to generate biogas with approximately 80% methane – and this far exceeded our expectations.”

In addition, a sub-project devised by a group of fourth-year students involved developing a heat transfer model to simulate the energy balance across the green wall system. This model demonstrated that vertical green walls can significantly reduce energy usage to maintain a stable internal environment. Cornerstone to this project’s success would be widespread adoption of the technology and to achieve collaborative change in the way that we view waste and its potential as a resource. This all requires more education to ensure that we abide by UCT’s recycling initiatives.

ND: What are some of the notable highlights to date?

TK: Definitely the potential of aeroponic systems and how to integrate this process into the food waste management system. The added benefit of these vertical gardens is already in line with UCT’s aesthetics, which makes it easier to incorporate.

ND: How will you measure the success of this project?

TK: We’ll need to observe whether the project can be integrated effectively across campus. Yes, it may seem complicated, but it’s simple to implement and can easily be operated by anyone, even those with limited knowledge of the engineering behind it.