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In the last five years, bioenergy has attracted global attention as a sustainable energy source that may help with rising energy costs, and address environmental concerns related to greenhouse gas emissions. It may also generate new income and employment to farmers and regional communities around the world, writes Winthrop Professor Kadambot Siddique , Chair in Agriculture and Director UWA Institute of Agriculture.

Bioenergy is energy generated through biofuels - of biological and renewable origin, such as fuelwood, charcoal, livestock manure, biogas, biohydrogen, bioalcochol, microbial biomass, agricultural waste and byproducts, energy crops and others.

First generation biofuel production may increase greenhouse gas emissions as a result of burning forests to clear land for feedstock crop cultivation such as new oil palm and sugarcane plantations, heavy use of fertilisers and pesticides as well as direct effects on reduced food availability and associated price effects. Burning food crops such as corn, wheat, soybean, canola and sunflower to produce biofuels creates major ethical concerns.

Water scarcity, especially in the developing world, is cause for concern for agricultural productivity, health and sanitation. Between one to 2000 litres of water are required to produce one litre of either ethanol or biodiesel. In addition, escalating fossil fuel prices and peak oil debate pose other threats. Increasing demand for biofuels is leading to the diversion of food and feed. The OECD estimates that 38 per cent of US corn crops and 50 per cent of Brazilian sugar production are used for ethanol production, and almost all of Europe's oilseed harvest will be needed to meet its 2009 target for biodiesel. This may result in reduced food availability and shift food and feed production to less productive and marginal lands, reducing yields. For example, the corn required to fill just one standard urban vehicle tank with bioethanol could feed one person in Africa for a year.

The environmental benefits of using conventional crops such as corn, soy bean, canola and mustard for biofuel production are less clear. Cultivation of oil palm, sugarcane and soybean may add to global warming if grown on newly cleared rainforest land or drained peat bogs. The cultivation and processing of these crops takes considerable amounts of energy, resulting in additional greenhouse gas emissions that cancel out any benefits.

Second generation biofuels made from plant material grown on non-agricultural land, plant or organic wastes such as straw, wood chips and microalgae, and contents of landfill are potentially attractive. These materials do not require cultivation or compete with food production, and also have low carbon footprints. Abandoned land, previously used for agriculture or pasture, which has not been converted to forest or urban areas has the greatest potential for yielding biomass energy that reduces net GHG emissions and avoids competition with food production. On a global scale, potential above-ground plant growth on these abandoned lands has an energy content representing about five per cent of world primary energy consumption in 2007.

At present, Australia's biofuels industry has the capacity to produce around 140 ML of ethanol and 320 ML of biodiesel annually. A number of recent reviews concluded that industry growth continues to be constrained by: limited availability and high potential feedstock costs, inefficient processing technology, low consumer confidence and uncertain government policies. Diversion of existing grain crops and agricultural lands to produce biofuel feedstock will compete with food and feed supply. In Australia greater research and development attention should focus on non-food biomass, such as eucalypts, native grasses, microalgae and plant species such as Pongamia. The main benefits of such plants are that they can be grown on marginal lands and areas where current food production systems are not established. Emphasis should be placed on farm forestry and areas in northern Australia where water is less limited when compared to the traditional grainbelt. Increased resources should be allocated to research and development into cellulose-based biofuels.

The global potential for biomass energy production is large in absolute terms, but it is not enough to replace more than a few percent of current fossil fuel usage. Thus biofuel may be a small part of the answer to global energy scarcity and mitigation strategies to climate change. Priority should be given to energy conversation strategies together with the development of other renewable energy sources such as geothermal, solar, wind and tidal.