| Being as a renewable energy, biofuel has attracted worldwide attention. Clean biofuel
production is an effective way to mitigate global climate change and energy crisis.
Biofuel may offer a promising alternative to fossil fuels, but serious concerns arise
about the adverse greenhouse gas consequences from using nitrogen fertilizers.
Waste-nitrogen recycling is an attractive idea. Here we advocate a win-win approach
to biofuel production which takes advantage of excessive nitrogen in domestic
wastewater treated via constructed wetland (CW) in China. This study will carry on
environmental effect analysis of CW as a biomass generation system through field
surveys and controllable simulated experiments. This study intends to evaluate net
energy balance, net greenhouse effect potential and ecosystem service of CW as
biomass generation system, and make comparation with traditional wastewater
treatment plant and other biofuel production systems. This study can provide a
innovation mode in order to solve the dilemma between energy crops competed crops on
production land and excessive nitrogen fertilizer of our traditional energy plant
production.
Data both from our experimental CWs in China and other researches on comparable
CWs worldwide showed that the biomass energy yield of CWs can reach 182.3 GJ
ha−1 yr−1, which was two to eight times higher than current biofuel-production
systems. Energy output from CW was ∼137% greater than energy input for biofuel
production. If CWs are designed with specific goal of biofuel production, biofuel
production can be greatly enhanced through the optimization of N supply, hydraulic
structures, and species selection in CWs. Assuming that 2.0 Tg (1 Tg = 1012 g) waste
nitrogen contained in domestic wastewater is treated by CWs, biofuel production
can account for 1.2% of national gasoline consumption in China. The proportion
would increase to 6.7% if extra nitrogen (9.5 Tg) from industrial wastewater and
agricultural runoff was included. This approach is also suitable for use in other
countries, and can help promote sustainable development for energy and environment. |