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 The ‘green’ credentials of biofuels are under the spotlight having been blamed in recent months for exacerbating rising food prices around the world. As research studies draw attention to potential problems with biofuels, national and state governments are rethinking their policies, and beginning to consider standards that could govern the production and use of biofuels. Is it possible to minimise the potential impact of biofuel production on the environment?

Researchers from the University of Washington and The Nature Conservancy in Seattle are looking at just this issue. By analysing the life cycle of biofuels, they are trying to identify the potential impact of biofuel feedstocks to help guide policymakers in the environmentally sound choice of biofuel.

Energy Efficiency News talked to Martha J. Groom of the University of Washington about the pros and cons of biofuels and the principles that could be used to determine a better policy for their use in the future.

What legislation currently covers biofuels?

There are many varied requirements, although most proscribe targets for biofuel use, not standards for growing the fuels. But this is changing.

In the US, we are still at the drawing board, but the Boxer Bill (US Advanced Clean Fuels Act ) is certainly a step in the right direction.
The UK Government is seriously investigating how and when to use biofuels, and published a very good review of biofuels, which includes principles for sustainably producing such fuels.

 What should policymakers do when considering biofuels?

They should ask a suite of questions about the biofuel sources they are considering. Are these biofuels displacing land uses that would have high costs to biodiversity (i.e. is new land being cleared?), or might they displace local farmers and food supply? Do the biofuels require high inputs to produce, and can they be produced sustainably? What are the GHG emissions over the entire life cycle of production, including from soils as they are cultivated, as the fuel is burned, and as other fuels are burned to grow/manufacture/transport/ the feedstock.

It would require an immense amount of land to grow biofuels sufficient to replace petroleum-based fuels. Thus, a part of any solution to curbing GHG emissions and our negative impacts on the earth will be energy conservation. We simply need to reduce energy use substantively below our current levels.

The EU is similarly debating adding standards, and is making progress as well. I expect most advances toward standards to be seen in the UK and EU, and in local markets in the US.

What are the ‘best’ and ‘worst’ biofuels?

Corn-based ethanol is the clear worst choice. It has higher impacts than virtually all other choices, largely because of the industrial farming methods used to grow the feedstock and the relatively low return gained from this feedstock. Unfortunately, the US has thrown its policies and subsidies behind this choice almost wholesale – we need to slow and reverse this course. New studies also show that corn-based ethanol may have as great or greater GHG emissions than traditional fuels, so it is not helping us fight global climate change.

The best choices are mostly in the future. Algae is exceedingly promising, but a long way away due to the number of technical and biological challenges to be overcome. However, it deserves special attention because it has the potential to produce fuel on a large scale with a very small ecological footprint.
Cellulosic biomass used to create biodiesel is also fairly promising, although we need to pay attention to the methods to grow the trees used (e.g. poplar) in ways that are maximally friendly to the environment. This could be particularly promising where it involves restoration of more degraded lands.

Some interesting work has also been done to investigate alternative grasses that may be able to grow without the massive inputs required by corn, e.g. switchgrass or native prairie grasses. However, these still need to be fully tested to ensure they do not cause other problems.

To the extent that we can recycle wood waste or crop wastes, or used cooking oil, such substrates generally are good choices.

(See attached table.)

What makes algae a particularly attractive biofuel feedstock?

We need relatively efficient fuels, as more efficient fuels generally require less land area to grow. This is largely why algae is so attractive a possible biofuel – the conversion efficiency in algae is potentially much higher than any other biofuel, allowing a small area of algae to produce as much fuel as much, much larger areas planted in other types of oil crops, and ethanol crops.

The growth rates of algae species are also remarkably high, so per unit area and time you get the generation of a great deal more biomass, from which you can extract oils that can be converted to biodiesel. No perennial or even annual crop can grow anywhere near as rapidly as algae.

How can the efficiency of energy extraction from biofuels be improved?

Cellulose is hard to break down, and there is a lot of research going into how to do it more efficiently. This would allow more energy to be accessed from cellulosic fuels, e.g. woody plants. These are the fuels that would allow more carbon sequestration as they are grown, and if they can be harvested without killing trees, more of a carbon neutral outcome.

For algae, the barriers are more in cultivating the algae without shift among algal communities.

What we can expect from biofuels in the future - how much reliance should we put on them as part of moving to a lower carbon economy?
When we get to the point that we can grow algae as a feedstock for biofuels, I think we have a lot of potential. We can use algae to scrub CO₂ emissions from factories and power plants, and gain some biofuels in the process. We could provide transportation fuels on a compact scale. However, it is a while before this is likely to be possible. 

Current research is looking at how to make cellulosic biomass from waste wood products or other wastes, as well as from fast growing trees, profitable. This will probably come to pass much sooner.

Instead, I think we should mostly rely on energy conservation – to vastly reduce our consumption.
 

For further information:
Martha J. Groom, Elizabeth M. Gray, and Patricia A. Townsend, Biofuels and biodiversity: principles for creating better policies for biofuel production. Conservation Biology (2008), 22 (3), 602-609
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1523-1739.2007.00879.x?cookieSet=1&journalCode=cbi