Second generation bioenergy

Rapeseed and Sorghum/Photo taken in Quemoy, Taiwan

"A new generation of biofuels could meet almost half of Britain’s renewable transport needs, but without them the UK will miss its 2020 target, a new Government-commissioned report warns." [1]

What's 'a new generation of biofuels' about?

We've heard  news about first-generation bioenergy - bioethanol, produced mainly from food-based crops, like sugarcane and corn. And the food v.s. fuel competition has driven concerns in terms of food security. Whether subsided bioenergy has influence on food price and caused political unrest around developing countries is debatable [2]. 

While second-generation bioenergy, might be less controversial, converted from inedible part of plants- leaves, stalks, stems etc. and can avoid turning food into fuel. There are several processing platforms for producing different biofuels, among these routes, lignocellulosic biomass for ethanol has some promising perspectives [3].  There are four types of lignocellulosic biomass, including  agricultural residues, dedicated energy crops, wood residues, and municipal paper waste [4]. S. Yuan et al.[3] used net energy balance (NEB) as an indicator to examine whether a biofuels platform is environmentally and economically sustainable. A high positive NEB means higher energy output than input for biomass production and processing. For instance, ethanol from some popular lignocellulosic feedstocks in Europe, Switchgrass, and Miscanthus can yield 150-500 GJ/ha/yr and 250-550 GJ/ha/yr respectively. Compared with some first-generation biofuels platforms, NEB of maize and sugarcane is 10-80 GJ/ha/yr and 55-80 GJ/ha/yr respectively. They also proposed that if the hurdle of efficient convention into ethanol from lignocellulosic biomass can be overcome, then a NEB of  up to 600 GJ/ha/yr will be a plausible expectation [3]. In addition to higher energy gain and lower production costs,  poplar and switchgrass have a negative carbon balance, which means more carbon dioxide is fixed by the plants than emitted from production and usage of bioenergy [3]. If more carbon is sequenced by biomass crops, then bioenergy can be a feasible solution and mitigation to global warming.      

References

1.Greenwise

2.Bioenergy: Fuelling the food crisis?

3.S. Yuan et al., Plants to power: bioenergy to fuel the future, 2008, Trends in Plant Science.

4.Wikipedia: Lignocellulosic biomass