Second Generation Biofuels: An Unproven Future Technology with
By Helena Paul and Almuth Ernsting
What are second generation biofuels?
In this paper, we refer to second generation biofuels as meaning biomass-to-liquid technologies,
namely cellulosic ethanol and Fischer-Tropsch gasification, which are intended to use
lignocellulosic biomass. Those technologies are not yet commercially available. Some companies
refer to certain agrofuel technologies which use existing feedstocks like palm oil or rapeseed oil
as ‘second generation’ (for example Neste Oil’s NExBTL diesel, which uses high-pressure
hydrogenation of fatty acids).
Can second generation biofuels play a role in mitigating climate change?
Any technology which can help to mitigate climate change must
a) Have the potential to become commercially available on a large scale within the next 5-8
years: Unless we begin to reduce global emissions and introduce technologies and policy
measures which can help us shift to a low-carbon society within that period, a mass extinction
event may become unavoidable. [see: “Global temperature change”, James Hansen et al, PNAS,
September 2006] ; AND
b) Be proven to have the potential for large-scale emissions reductions, once life-cycle emissions
of all greenhouse gases have been considered, not just at the micro-level, but at the global level.
If a technology, directly or indirectly, destroys ecosystems which play an essential role in the
Earth’s carbon cycle, then it risks accelerating, not mitigating global warming.
As we show below, there is evidence that second generation biofuels satisfy neither of these
When will second-generation biofuels become commercially available?
The only commercial cellulosic ethanol refinery is run by Iogen Corporation in Ottawa. It uses
more energy than it produces, and, in terms of energy use and output, performs considerably
worse than first-generation corn ethanol. The different processes needed to refine cellulosic
ethanol, including pre-treatment and distillation, are extremely energy-intensive.
The United States Department of Environment are funding research into cellulosic ethanol, and
they have identified significant ‘biological barriers’ which need to be overcome if cellulosic ethanol
is to become a viable option. [Fuel Ethanol Production, DEO, Genomics:GTL,
Enzymes can break
down cellulose, but they cannot do so efficiently and they can only produce a very dilute mixture
which is then distilled into ethanol. Making cellulosic ethanol viable is not a matter of scaling up
existing technology and gradually improving efficiency gains: Firstly, scientists will have to better
understand plant physiology and the mechanisms which prevent cellulose from being broken
down by fungi and microbes. This will require some major scientific breakthroughs. Secondly,
scientists will have to either find or, more likely, genetically engineer microbes or fungi which can