Team:MichiganState/Product Design
Product Design
Overview
The decomposition of organic materials deep within landfills is a problem that has not gone unnoticed. The large amount of methane dissipating into the atmosphere is contributing to the greenhouse gas crisis, and landfills have started to implement Landfill Gas (LFG) Projects where “ LFG can be captured, converted, and used as a renewable energy resource” (2019.) Extraction pipes and welling directs the LFG from the deep portions of the landfill to a system where the gas can be treated, then methane can be used to power generators to send electricity along a grid. Any excess methane that is not used to power generators is flared, due to the fact that you are unable to store energy in the form of electricity. Therefore, at times of high methane production not all emissions can be utilized by the generators and converted to electricity.
The practical application of this synthetic biology project aims to convert the excess methane to a 2,3 Butanediol that can be readily stored and later used as a precursor to biofuel. Due to the fact that the methane would be treated for the generator that pure methane could be used by our theoretical bioreactor. The bacteria would have to work without the presence of oxygen because of the reactive qualities of methane and oxygen. It is known that many smaller and older landfills across the United States do not have LFG Projects. Future advancements would involve implementing our biological system at these landfills in a quicker and less expensive than that of the current large scale LFG Projects.
Project Specific
Methylomicrobium alcaliphilum has been genetically modified to convert methane to 2,3 Butanediol evidenced by the findings of a colleague of Michigan State Marina G. Kalyuzhnaya and other accredited contributors (DucNguyena, G.Kalyuzhnaya, Yeol Lee, & AbstractMethane, 2018.) In this study, the maximum theoretical yield of gaseous methane to liquid 2,3-butanediol is 0.809 g (2,3-BDO)/1 g CH4 . However, the experiment resulted in 0.0318 g (2,3-BDO)/1 g CH4, which is a 3.93% yield (DucNguyena, G.Kalyuzhnaya, Yeol Lee, & AbstractMethane, 2018.) In this study, concentrations of 10 g/L of 2,3-butanediol did not inhibit growth of Methylomicrobium alcaliphilum, while concentrations of 20-40 g/L proved to be toxic. Further research would be put forth to combat this issue. In an additional study using the engineered strain Klebsiella pneumoniae to produce 2,3-butanediol, 92.2% of the theoretical maximum was produced (2019.) If Methylomicrobium alcaliphilum were to produce yields of 90% of the theoretical yield, this would result in 0.7281 g (2,3-BDO)/1 g CH4.
This yield is still unlikely to be economically and practically worth the time. Therefore, the strain needs further optimization to be used in the landfill setting. Due to this disconnect, the focus was largely on testing the bacteria on different plastics relating to the theoretical bioreactor in order to evaluate growth and stability. The theoretical bioreactor would be composed of filter in which a biofilm of 20Z bacteria would reside, methane would feed from the piping system to the top and converted by the bacteria on the filter and the resulting biofuel precursor would be drained to the bottom.
The biological approach of decreasing landfill methane emissions was done in the hopes to convert any methane currently dissipating into the environment into a sustainable alternative. Further work is required to bridge the gap between what the strain does in lab and the practical large scale application.
References
Basic Information about Landfill Gas. (2019, July 30). Retrieved from https://www.epa.gov/lmop/basic-information-about-landfill-gas
DucNguyena, A., G.Kalyuzhnayac, M., YeolLeea, E., & AbstractMethane. (2018, April 16). Systematic metabolic engineering of Methylomicrobium alcaliphilum 20Z for 2,3-butanediol production from methane. Retrieved from https://www.sciencedirect.com/science/article/pii/S1096717618301101.