'Constructed wetlands as biofuel production systems' on nature climate change

Updated:15/02/12 11:37:10 AM CST

On January 22, Professor Chang Jie’s research group at College of Life Sciences, Zhejiang University, had their research paper “Constructed Wetlands as Biofuel Production Systems” published online on Nature Climate Change, one of the publications of Nature Publishing Group publishing high-quality original and cutting-edge research on the science of climate change.

According to the experiments and data of their research, originally built as an alternative to traditional sewage treatment plant, constructed wetland sewage treatment system can produce bio-energy in addition to treating domestic wastewater, achieving a win-win situation of environmental pollution control and bio-energy production.

Currently most of the existing bio-energy production systems mainly rely on food crops, such as corn, soybean, sugar cane, and plant biomass such as straw, perennial herbs or algae on waste land. The reliance on food crops may lead to food and land crisis or water pollution, while that on plant biomass means minimal production with extra nitrogen fertilizer use. In recent years, scientists have been trying to develop bio-energy production systems which can reduce both greenhouse gas emissions and nitrogen fertilizer use.

After a decade of experimental observation and data collection, the research team headed by Professor Chang Jie and Ge Ying concluded that optimizing the structure of constructed wetlands can promote the efficiency of sewage treatment and plant biomass with a potential of 1836 GJ ha-1 yr-1. Theoretically the use of total waste nitrogen produced in China will make it 1.6×108 GJ yr-1, equivalent to 6.7% of national gasoline consumption. At the same time, the greenhouse gas emissions are significantly reduced. The findings of the research show a great potential of promoting the approach worldwide to tackle climate change and energy crisis.

Abstract:

Clean biofuel production is an effective way to mitigate global climate change and energy crisis. Progress has been made in reducing greenhouse-gas (GHG) emissions and nitrogen fertilizer consumption through biofuel production. Here we advocate an alternative approach that efficiently produces cellulosic biofuel and greatly reduces GHG emissions using waste nitrogen through wastewater treatment with constructed wetlands in China. Our combined experimental and literature data demonstrate that the net life-cycle energy output of constructed wetlands is higher than that of corn, soybean, switchgrass, low-input high-diversity grassland and algae systems. Energy output from existing constructed wetlands is ~237% of the input for biofuel production and can be enhanced through optimizing the nitrogen supply, hydrologic flow patterns and plant species selection. Assuming that all waste nitrogen in China could be used by constructed wetlands, biofuel production can account for 6.7% of national gasoline consumption. We also find that constructed wetlands have a greater GHG reduction than the existing biofuel production systems in a full life-cycle analysis. This alternative approach is worth pursuing because of its great potential for straightforward operation, its economic competitiveness and many ecological benefits.

Source:zju.edu.cn