Team:UESTC-China/project introduction

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INTRODUCTION

Energy crisis

With the continuous development and utilization of energy (Fig.1), the earth's energy storage is crisis. Energy consumption of coal, oil and other non-renewable energy sources has not yet found a perfect substitute. A large number of energy consumption has seriously threatened the sustainable development of today's society [1]. When we keep looking for clean energy, a large amount of energy was wasted because of our improper operations. So we have to reuse the often neglected wastes of our lives and turn them into the energy we consume.

Fig. 1 World primary energy consumption, 1992 to 2007 [1]. mtoe: Million tones oil equivalent
Straw is an ideal renewable energy resource

Straw is an agricultural byproduct of cereal plants. It makes up about half of the yield of cereal crops such as corn, barley, rice and wheat. Take corn as an example, according to FAO statistics, global corn production in 2016 was approximately 1060 million tons (Fig.2) [2]. Every kilogram of harvested grain produces 1.2 kg of corn stalks, giving an estimate global corn straw production is 1272 million tons in 2016.

Fig. 2 Corn stalk production around the world, 2000 to 2016 [2].

How to use the large amount of corn stalks produced every year is a serious problem. However, emissions of methane and nitrous oxide from the on-site combustion of corn residues demonstrates that we don’t make use of these treasure. Much of straw are left or burnt in the field. This leads to the release of methane and airborne carbon particulate matter, which can have adverse effects on human health and climate change caused by regional atmospheric phenomena. Biogas production and returned to field is not the best choice. Straw is a biofuel substitute to coal and the use of straw as a carbon-neutral energy source is increasing rapidly, especially for biobutanol. Therefore, in order to improve the utilization rate of straw resources, we decide to use it to produce clean energy.
Biobutanol and hydrogen are ideal clean energy

More long-term application of straw to produce clean energy, the most mature technology at present is the production of ethanol [3][4]. But there are still many problems in the application process of ethanol gasoline. For example, ethanol can easily lead to liquid phase delamination and thus affect the use, and the engine can easily accumulate carbon [5] and cause engine damage.

Biobutanol and hydrogen belong to the new liquid and gas fuel respectively, which are important research field of new clean energy. The carbon chain of butanol is longer and the calorific value and boiling point are higher than that of ethanol. Moreover, the calorific value of butanol is very close to that of gasoline, higher than that of methanol and ethanol. So butanol has better fuel economy [6]. And the use of butanol gasoline is not like ethanol gasoline it will not cause engine damage [7][8]. Pure hydrogen fuel is carbon-free and has zero-emission. So if the engine is converted to hydrogen fuel, it will greatly expand the range of engine premixed combustion, improve fuel economy and reduce nitrogen oxide emissions [6].

In our project, the renewable straws were biodegraded into glucose and further converted into clean energy biobutanol and hydrogen through the improved super E. coli (Fig 3).

Fig. 3 Conversion of straw into biobutanol and hydrogen
References

[1]https://www.bp.com/content/dam/bp/en/corporate/pdf/energy-economics/statistical-review/bp-stats-review-2018-full-report.pdf

[2]http://www.fao.org/faostat/en/#data/QC

[3] Yu J, Shi K, Wang S, Xu Z, Zhai R, Wen Z & Jin M. 2018. Analysis of crop straw distribution in China and research progress on converting crop straw into fuel ethanol. Biotechnology & Business, 4: 33-40.

[4] Alvira P, Tomás-Pejó E, Ballesteros M & Negro MJ. 2010. Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: A review. Bioresource Technology, 101:4851-4861.

[5] Han X，Qin J, Pei Y，Wang L & Zhou J. 2016. Formation of GDI injector deposit from different fuels. Journal of Combustion Science and Technology, 22: 236-240.

[6] Peng S，Zhang J，Ma Y，Zhao H & Huo W. 2015. Numerical simulation of combustion of butanol mixed hydrogen. Science & Technology Vision, 5:184-185, 194.

[7] Zang J, Zhu R, Zhang D, Sun Y & Lin M. 2016. Experimental research on performance of engine fueled with ethanol/gasoline and butanol/gasoline blend. Journal of Heilongjiang Institute of Technology, 30:8-11.

[8] Trindade WRDS & Santos RGD. 2017. Review on the characteristics of butanol, its production and use as fuel in internal combustion engines. Renewable and Sustainable Energy Reviews, 69: 642-651.