New biofuel crop potential
From the September 2006 edition of Agriculture Today.
With fuel from non-renewable sources becoming increasingly expensive, an option for farmers in the future may be to grow crops for renewable energy.
Some crops have an energy output to input ratio of six to one.
NSW Department of Primary Industries (DPI) private forestry and bioenergy specialist, Brendan George, said tree or woody crops suitable for the low rainfall wheatbelt might be suitable to produce biofuels.
Mr George said a national Cooperative Research Centre for Plant-Based Management of Dryland Salinity (CRC Salinity) project he leads is working closely with researchers in other states, who have identified crops that have the potential to economically produce a range of energy products.
"Experience in Western Australia shows that mallee, for example, could produce a range of products as diverse as ethanol, electricity, activated carbon, eucalyptus oil, charcoal, panel board products, paper and pulp, chemicals and manufactured animal feeds," he said.
"At the same time, alley farming of mallees has environmental benefits, including salinity control, biodiversity enhancement and shelter for stock."
NSW DPI’s partnership in CRC Salinity has enabled the opportunity to investigate the relevance of this research at a site established at Spring Ridge in the north east of the State.
WA CRC Salinity researcher John Bartle said the problem with using grains such as wheat, canola and corn for biofuel production was that the energy outputs were not much bigger than the energy inputs.
"These annual crops must expend the full establishment cost to achieve each harvest, and they are dependent on large inputs of chemicals and fertilisers containing high levels of energy," Mr Bartle said.
"While the cost of initially establishing a mallee crop is relatively high in terms of energy inputs, ongoing energy costs are small because the crop regenerates by coppice after regular harvest on a three to four year cycle, and this can be sustained indefinitely.
"With a planting layout designed to intercept surplus agricultural water, yields are high and management inputs are low."
When energy used in production and conversion to a useable fuel were included, Mr Bartle said the ratio of energy outputs to inputs was less than two for annual crops and about six for mallee.
On the production side, to achieve commercial yields, woody crops could only be grown on a small proportion of a farm, because of the extra water they would have to capture in addition to rain falling on the planted area.
These systems are yet to be fully exploited in NSW.
In the WA wheatbelt, the woody crop area would usually be less than 10 per cent of any farm or catchment and be dispersed in the form of narrow belts on the contour. Mr Bartle said farmers would need to continue conventional agriculture in the between-belt areas.
"In this alley farming layout, the woody crop and the conventional agriculture would be complementary," he said.
"This improves the woody crop yield but also contributes to salinity control.
"The woody crop could also capture nutrients that leach below the rooting depth of annual crops."
According to Mr Bartle, careful species selection could offer multiple product potential.
"This could include higher value products such as wood chips for wood products, eucalyptus oil from the leaves, or carbon sinks," he said.
"These high value uses could reduce the effective cost of the bioenergy production."
Ethanol from cereals and biodiesel from canola have the important advantage of being available to immediately introduce new transport fuels into the market and develop familiarity among consumers during the transition towards more efficient biofuels.
"However, ethanol from woody crops is likely to become more competitive in the medium term as the technology to produce ethanol from woody feedstocks improves and becomes more widely available," Mr Bartle said.
"Bioenergy researchers estimate that current woody biomass conversion technology could deliver ethanol at 82 cents a litre, but this is being rapidly improved."
Contact Brendan George, (02) 6763 1238.
Matthew Crosbie is NSW Communications Co-ordinator for the CRC for Plant-based Management of Dryland Salinity.
