Issues Magazine

The Case for Second-Generation Biofuels

By Glenn Tong

Biofuels have been pegged as the great hope for sustainable and “green” fuel. Policy-makers set targets for the replacement of fuel sold in petrol stations with biofuels. Recently, however, biofuels have received an onslaught of negative media publicity.

Criticism of biofuels centres around the competition between crops produced for first-generation biofuels and food. The United Nations (UN) Food and Agriculture Organisation commented that first-generation biofuels have had “a significant impact on world crop prices”. The report also called for government policies to be “urgently reviewed in order to preserve the goal of world food security, protect poor farmers, promote broad-based rural development and ensure environmental sustainability”.

Similarly, the UN special rapporteur on the right to food, Jean Ziegler, has been quoted as saying that biofuels are a “crime against humanity”. Ziegler has also commented that “the sudden, ill-conceived rush to convert food – such as maize, wheat, sugar and palm oil – into fuels is a recipe for disaster”.

The European Commission was an early adopter of biofuels, penning the 1998 Fuel Quality Directive, which required that 10% of fuel sold in petrol stations should be derived from biofuels by 2020. In 2008 several members of the European Union called for a review of this directive, wanting to enforce stricter environmental and sustainability standards on biofuel procurement and use within the European Union.

These comments have received a high level of publicity, tarnishing all types of biofuels. Yet there is a clear distinction between first- and second-generation biofuels.

First-generation biofuels are made by extracting starch or sugar from feedstocks to produce ethanol. This can include materials such as maize, wheat or sugar cane. The term also covers the extraction of oil from oilseed crops such as canola to produce biodiesel.

By contrast, second-generation biofuels can be produced from plant structural material (known as lignocellulose) or waste biomass. This means that waste products such as forestry waste, or parts of crops that are usually not utilised, can be used to produce fuel. Fuel extracted from these products is known as cellulosic ethanol.

In spite of Ziegler’s highly publicised words, his report to the UN General Assembly strongly supports second-generation biofuels, saying that “instead of using food crops, biofuels should be made from non-food plants and agricultural wastes, reducing competition for food, land and water”. Ziegler went on to encourage technological advances that could allow the conversion of agricultural wastes into fuel.

Improved Varieties

Some of this research is currently taking place in Australia. For example, Farmacule Bioindustries Pty Ltd and the Queensland University of Technology are developing sugar­cane varieties that can potentially be used to produce ethanol from bagasse (sugarcane pulp) while maintaining the plant’s ability to produce commercial sugar products. This is being achieved by modifying the plant to include cellulases (enzymes that operate after harvest to convert cellulose in the plant into fermentable sugars).

The Molecular Plant Breeding Cooperative Research Centre (MPBCRC) is working to develop improved cereal crops and pasture species. Technologies currently being developed by the MPBCRC could have important applications in the production of second-generation biofuels.

A significant problem in producing biofuels is that a consistent level of cellulose will need to be present in any plant that will be processed for biofuels. Large improvements are needed in biomass and seed yield, digestibility and stress tolerance to extreme climatic events such as drought. Due to the types of improvement that are needed and the speed at which it will need to happen, the technology to achieve this will most likely need to involve genetic modification (GM). This also means that substantial amounts of time, effort and money will be needed to gain regulatory approvals and market acceptance.

MPBCRC and its partners are developing the following GM traits for biofuels.

High Digestibility

Lignin is part of the structural material of a plant, and is located in the cell walls. One particular type of lignin has been linked to indigestibility, and its production can selectively be “turned down”. The technology to do this has been tested in perennial ryegrass and shown to be highly effective. Applying this to a crop such as wheat could mean that the underutilised part of the plant, wheat straw, could be made highly digestible and thus easier to ferment in a cellulosic ethanol plant.

Drought Tolerance and High Energy

The biosynthesis of fructans can be “turned up”, which could improve drought tolerance and increase the water-soluble carbohydrate levels in the plant. Combining this with low lignin traits could result in an easily digestible and high-energy product that could be used as a cellulosic ethanol feedstock for biofuel production.

Cheaper and More Efficient Cellulose Hydrolysis

One of the most costly steps in the production of cellulosic ethanol is adding cellulases, which are enzymes that act to break down cellulose. Cellulase expression within the plant itself may provide a cost-effective solution.

Biomass Conversion Technologies Pty Ltd (BCT), one of MPBCRC’s commercial partners, is focusing on developing technologies that would allow cellulases to be expressed within wheat straw. This will require advances to ensure that adequate levels of cellulases are expressed at the required times. Advances will also be needed to develop inducible promoters that tell the plant when and where to express the cellulases.

Much of this research is still at the laboratory stage, with many of the technologies at least 10 years from market. A number of non-technological problems need to be addressed before biofuels derived from wheat straw become viable alternatives to fossil fuels.

Economic Viability

Production of biofuels needs to be able to compete economically with currently available fuels. Current methods of producing biofuels are only competitive when oil reaches very high prices of at least $70–80 per barrel. To increase the economic viability some problems must be overcome.

  • Input costs for feedstock need to be minimised. Effects of climate, such as drought and frost, currently have a large impact on price fluctuations. However, the technological advances detailed above can significantly mitigate these effects.
  • Transportation costs need to be significantly reduced.

A number of approaches could be taken to address the above challenges. One approach that could be viable in countries like Australia, where there are dense wheat-growing regions, is the strategic location of ethanol plants near biofuel crops to reduce transport distances. Another approach could be partial processing of the feedstock on farm (e.g. performing the cellulase digestion on farm and transporting a crude cellulose digest rather than straw). The in planta cellulase technology being developed by BCT could be particularly helpful in this strategy.

Consistency and Quality of Supply

For biofuels to be economically viable, a consistent supply needs to be developed. Grain growers are usually at risk from extreme weather conditions such as drought and frost. Research into GM crops indicates that traits may be able to be developed that could increase drought, frost and salt tolerance and disease resistance.

MPBCRC is conducting Australia’s first field trials for drought-tolerant GM wheat in Victoria. These trials have shown some exciting results to date, with a number of promising candidate genes being tested. However, these products will take at least a decade to reach the market.

Support of Sustainable Agriculture Practices

It should be recognised that converting all agricultural by-products into ethanol could jeopardise sustainable and environmentally sound farming practices. For example, no-till farm practices (avoiding ploughing or turning the soil while leaving some residual crop after harvest) has been estimated to reduce greenhouse gas emissions by up to 80%. This practice also maintains soil quality, reduces erosion and conserves water by improving absorption.

Second-generation biofuels can co-exist with these types of sustainable agricultural practices. For example, at present yield levels of wheat straw residue, sufficient levels can be maintained to continue their positive environmental impact. In the near future, improvements in biomass yield are expected, which will further aid the practices.

Emerging Potential

None of these issues is insurmountable – second-generation biofuels have significant potential. WorldBioPlant.com has estimated that in 2007 there were 954 biofuel plants across 56 countries, with an estimated cumulative output capacity of over 163 billion litres. A 2005 report by the US Department of Agriculture and Department of Energy estimated that the USA could produce more than 1 billion tonnes per year of biomass for cellulosic conversion from crop residues, forest by-products and other underused resources. This amount of biomass could replace up to 30% of US petroleum use by 2030.

Economic benefits are potentially enormous. The Rural Industries Research and Development Corporation (RIRDC) in Australia has issued a statement that “biofuel production has the potential to give farmers new options to diversify their income streams, to offer new employment opportunities, to reduce greenhouse gas emissions and to provide greater fuel security for Australia”. A case study produced by RIRDC for the production of Sarina ethanol from sugar estimated that $7.7 million was added to household incomes in the region.

Similarly, a report by Washington State University’s energy program found that the production of second-generation biofuels in eastern Washington could produce an extra 400 jobs, with an economic advantage of $19.6 million.

Environmental benefits also exist. Most importantly, depending on the feedstock and processing method, a significant reduction in carbon dioxide emissions can be achieved compared with conventional fuels. When evaluating over a product lifecycle, second-generation biofuels could also have reduced energy inputs.

Challenges exist before the production of second-generation biofuels can compete with petroleum-based fuels. As well as the technological and logistical advances needed, a change in the public perception of biofuels as “crimes against humanity” is required.

Second-generation biofuels have the potential to provide a sustainable source of fuel, alleviating the global fuel crisis without negatively impacting on food supplies.