Origin

The parents of one of our team members worked at a coal-fired power plant, and he grew up watching his parents live under smoke-billowing chimneys. He told us about his shock when he witnessed the amount of exhaust gases emitted from the coal-fired power plants and his concerns about the impact of the working environment on his parents and other staff. Inspired by his story, we decided to systematically study the series of problems caused by the exhaust gases emitted by coal-fired power plants. In the end, we found that the exhaust emissions from coal-fired power plants not only affect the mental health of the people involved, but more seriously, it exacerbates the environmental crisis caused by the greenhouse effect, which is closely related to everyone. What's even more alarming is that the greenhouse effect doesn't manifest suddenly but gradually infiltrates into everyone's lives, leading us to frequently overlook this grave issue.

Background

Through investigation, we found that the aggravation of the greenhouse effect of thermal power plants is primarily attributed to their substantial carbon dioxide emissions. Greenhouse gases such as carbon dioxide in the atmosphere can absorb long-wave radiation from space and the Earth's surface. This absorption results in an increase in the temperature of the lower atmosphere and the Earth's surface, leading to global warming. As of now, China hosts over 3,000 thermal power plants, and the carbon emissions from thermal power generation in China for the year 2022 amounted to 4.85 billion tons, representing almost half of the country's total CO₂ emissions for that year. According to the latest data, the energy supply mode led by thermal power plants contributes 42.7% of the total CO₂ emissions resulting from fossil fuel combustion, which has significantly intensified the greenhouse effect.

Due to the extensive release of greenhouse gases through the combustion of fossil fuels, the concentration of carbon dioxide on Earth has reached levels not seen in nearly 2 million years, resulting in a 1.1°C increase in global temperatures. Over the past decade, the Earth has experienced higher temperatures than at any point in the past 125,000 years.

Global warming, caused by excessive greenhouse gas emissions, is merely the initial stage of the crisis, while the subsequent series of natural disasters it triggers are the true challenges that humanity must confront. As temperatures continue to rise, about half of the world's population will face severe water scarcity for at least one month each year; 950 million people living in the world's drylands will face a range of problems including water stress, heat stroke and desertification^[1]. At the same time, global warming will bring large-scale glacier melting, causing irreversible sea level rise. Currently, the sea level has been rising faster than ever in last 3,000 years. As a result, nearly 50 percent of coastal wetlands have disappeared in the past 100 years. Each year, extreme flooding and storms caused by rising temperatures have forced more than 20 million people to leave their homes. In addition, rising temperatures will reduce global food production and increase the spread of vector-borne diseases such as malaria, West Nile virus and Lyme disease, further endangering human safety and health^[2]

As mentioned above, one of the primary drivers of the severe greenhouse effect is the extensive burning of fossil fuels. To address this issue at its core, we decided to go back to the root cause and explore the reasons behind the large burning of fossil fuels. Eventually, we have found that the low energy efficiency of fossil fuels led to an increase in their use, further creating a vicious circle that intensified the greenhouse effect. For instance, the temperature of unemitted exhaust gases from a thermal power plant typically falls within the range of 80-100°C. However, the heat contained in these gases is often not directly utilized, leading to a reduction in energy efficiency. Therefore, we decided to employ synthetic biology to tackle the climate crisis by addressing the apparent status quo of large greenhouse gas emissions and improving the low energy efficiency of thermal power plants, targeting both the symptoms and the root cause of this problem.

Cyanobacteria and Shewanella

In order to address the issue of greenhouse gas emissions, our team collected information on various carbon-sequestering microorganisms and pathways. After thorough research, we ultimately selected the strain Synechocystis sp. PCC 6803 as our helper to capture carbon dioxide. At the same time, in order to enhance the energy output of thermal power plants, we decided to use the emerging microbial fuel cells (MFC) in recent years, with the aim of further harnessing the fixed CO₂ through microorganisms. MFC is a very good direction, in which the commonly used strain of Shewanella oneidensis MR-1 can use lactic acid for electricity production which can be fed into thermal power plants to reduce the use of fossil fuels. By modifying Synechocystis sp. PCC 6803 , it can convert fixed carbon dioxide into lactic acid as a carbon source for S.oneidensis MR-1. As for S.oneidensis MR-1, we have also employed synthetic biology methods to improve its electricity production capacity and contribute more to CO₂ emission reduction.

Hardware

We tried to build a fermentation plant for our co-culture system to facilitate testing in the laboratory and prepare for future implementation in thermal power plants. In the process of design and research, we found that the current synthetic biology-related projects often encounter the problem that the fermentation results are inconsistent with the simple shake flask culture in the scale-up process before putting into actual production, and there is a lack of a miniature fermentation device to estimate the production effect of the project. Therefore, we have built a micro-modular fermentation equipment system, which can simulate the results of pilot trials and even production in the laboratory. The fermentation equipment system is constructed by multiple modules, and through the replacement of different parts in the module, the cultivation of different strains and different conditions can be realized. A set of fermentation system thus is built according to our co-culture system.

References