Sustainable biofuels possible

Energy Matters0

While I deplore the use of foodstuffs for the production of biofuels, I feel that I should reiterate yet again that other choices are possible without resorting to that or destroying the environment. Many people are starting to become aware (at last) that woody biomass is a viable source of liquid fuels, but they usually think in terms of inefficient old processes like acid or enzymic hydrolysis followed by fermentation. In fact, there are other processes to convert such biomass to transport fuels, such as biogas, thermal pyrolysis, gasification followed by catalytic conversion to methanol, dimethyl ether or even hydrocarbon fuels.

I recently came across an NREL paper describing a process using gasification followed by catalytic conversion to mixed alcohols, mainly ethanol. It is called Thermochemical Ethanol via Indirect Gasification and Mixed Alcohol Synthesis of Lignocellulosic Biomass and it can be downloaded from .


Combined, all process, market, and financial targets in the design represent what must be achieved to obtain the reported $1.01 per gallon, showing that ethanol from a thermochemical conversion process has the possibility of being produced in a manner that is ‘cost competitive with corn-ethanol’ by 2012.

This still raises the question of whether we should be producing relatively expensive fuels from biomass while the fuel efficiency of most cars is still very poor and the planning of our cities still condemns most people to commuting long distances by car and delivering our goods by road freight. It also raises the question of whether there are more efficient fuel/vehicle combinations than ethanol/petrol blends in conventional ICE vehicles, and what we will do as the supply of petrol declines.

We are now on the cusp of Peak Oil, and even with marginal sources of oil such as polar oil, deepwater oil, tar sands, heavy oil, gas condensate and coal liquids, we are very close to the point where total supplies must start to decline. Once that decline starts, annual supplies will fall at 3-4% a year, so we will need to adjust our demand to the available supply. That suggests that with the current concept of 10% ethanol in petrol, we will need to get production up well beyond the Biofuels Target of 350 ML (which is only 1% of demand) as quickly as possible to reach 3,500 ML. But what then? Most conventional cars cannot take more than 10% ethanol, so we would have to start using flexible fuel vehicles, such as the ones that Holden is exporting to Brazil, which can run on a variety of blends up to 85% ethanol.

As the percentage of ethanol increases, the fuel will get more expensive, and other alternatives will need to be considered. While considering other fuel/vehicle combinations to reduce the overall cost of motoring, we should also be looking at radical alternatives that could make a real difference. Hybrid and fuel cell cars come to mind, but the latter will not run on petrol. It is often suggested that they will have to run on hydrogen, but that is not true either because they can run on any hydrogen carrier that can be catalysed to hydrogen at a low temperature (which excludes petrol) using an onboard catalyst unit or reformer, such as natural gas (CNG) and alcohol fuels.

Whatever we do, we will need to use transport fuels more efficiently and stop using petroleum based fuels. That transition needs to start now. Coal liquids are not a genuine alternative because they involve the production of large amounts of greenhouse gases and lock us into the continued use of petroleum fuels. Biofuels may play a part in that transition, but we should avoid the mistakes of other countries and ensure that the net energy production made out of biomass is positive. This will mean a very different approach to the Biofuels Taskforce, and the realisation that low-level ethanol/petrol blends do not represent a long-term solution. While we are developing the biomass conversion processes and building up supplies of biomass (such as mixed species long-rotation plantations on salt-affected land that is unsuitable for agriculture), we could be producing transitional supplies of the hydrogen carriers mentioned above using our abundant supplies of natural gas that we just cannot wait to export overseas as LNG. At the same time, we could be converting our chemical, plastic and fertilizer industries to gas feedstocks as well so that we are less dependent on oil. Eventually, they too could run on biomass.

The need to develop viable alternatives to petroleum fuels is now urgent, but we should be aware of all the traps.
Chris Mardon. 

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