A Systematic Carbon and Energy Balance of the Penn State Eco-Machine™ and the Implementation of a Vertical Farming System to Increase Duckweed Production
Open Access
- Author:
- Belles, Eric
- Area of Honors:
- Civil Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Rachel Alice Brennan, Thesis Supervisor
John Michael Regan, Thesis Honors Advisor - Keywords:
- Eco-Machine
Duckweed
carbon
energy - Abstract:
- Due to the changing climate, the demand for environmentally friendly methods that maintain societal standards grows in importance. The Penn State Eco-Machine™ is an example of an alternative method to conventional wastewater treatment that decreases environmental impacts. A variety of microorganisms, macroinvertebrates, algae, and plants contribute to the treatment of wastewater and the storage of carbon and nutrients in the Eco-Machine™ with theoretically little energy input. However, an in-depth analysis of the system’s net carbon and energy yields has not been systematically performed to evaluate its true environmental footprint relative to conventional methods. In this study, carbon and energy balances were performed on each step of the Eco-Machine™ system. Carbon storage from biosynthesis and carbon release from respiration were determined using laboratory measurements and theoretical calculations. It was determined that the biological carbon uptake is higher than the wastewater-derived carbon influx, resulting in a net-carbon accumulation in the system. Similarly, the energy consumption of each mechanical component, and the theoretical energy production by renewable resources, were calculated. It was determined that the solar array was able to provide enough energy to meet electrical components required for operation of the Eco-Machine™, with heating requirements met by supplemental propane. By analyzing the resulting data sets, several opportunities to improve the overall sustainability of the system arose, such as sealing leaks in the greenhouse structure, increasing the air compressor efficiency, and maximizing the yield of plant biomass that can be used for the production of beneficial byproducts like fertilizer, fodder, and biofuels. In particular, the production of duckweed, a floating aquatic plant with a high growth rate, was noted as underutilized. Although the Penn State Eco-Machine™ was not originally designed to maximize duckweed yield, a pilot-scale vertical farming system was constructed and monitored for several months as part of this study to determine if significant improvements to the system’s carbon and energy balance could be achieved. With current lighting technology, the energy required to power the vertical farming system was found to be higher than the resulting energy that could be produced from duckweed-derived biofuels (ex., ethanol and methane); however, the protein-rich duckweed can be utilized in sustainable agriculture to increase the favorable impact the Eco-Machine™ has on the local bioeconomy. The addition of a larger scale vertical farming system could provide a greater increase in duckweed yield from the Eco-Machine™. Particularly in geographic regions which do not require heating, Eco-Machines™ are a promising alternative wastewater treatment method that can provide beneficial byproducts to support sustainable agriculture.