Bioenergy is energy derived from organic matter (biomass) to generate electricity and heat, or to produce liquid fuels for transport. It is a renewable energy.
What is bioenergy?
Bioenergy is the chemical energy contained in organic matter (biomass) which can be converted into energy forms that we can use directly, such as electricity, heat and liquid fuel. Biomass is any organic matter of recently living plant or animal origin. Unlike coal, the organic matter is not fossilised. Biomass comes in many forms, such as:
- forestry products e.g. logs, tree prunings, sawmill residue
- agricultural products e.g. sugarcane waste (bagasse), crop stubble, straw, manure, poultry litter, oilseeds, nut shells
Bioenergy is a unique form of solar energy which is both renewable and carbon neutral. It is considered renewable because its source—biomass—is replenishable (Bioenergy myths and facts [PDF, 1.4 MB], published by the Clean Energy Council).Of the massive amount of solar energy that falls on the Earth’s surface, about 0.02% is captured by plants through photosynthesis and stored as energy in the plant. When we convert biomass to energy (through processes such as combustion, gasification, pyrolysis, anaerobic digestion or fermentation), the carbon dioxide released from the biomass circulates through the biosphere and, through photosynthesis, is reabsorbed in equivalent stores of new biomass.
How do we convert biomass to energy that we can use?
Bioenergy plants can range from small domestic heating systems to multi-megawatt industrial plants requiring hundreds of thousands of tonnes of biomass fuel each year. A variety of technologies exists to release and use the energy contained in biomass. They range from combustion technologies that are well proven and widely used around the world for generating electricity generation, to emerging technologies that convert biomass into liquid fuels for road, sea and air transport. We can convert biomass to energy through processes such as:
- combustion (burning the biomass)
- gasification (converting biomass to gaseous fuel)
- pyrolysis (decomposing biomass at high temperatures in the absence of air)
- anaerobic digestion (using microorganisms to decompose biomass, producing gas comprising mostly methane and carbon dioxide)
What is bioenergy used for?
About 10% of the planet’s energy requirements are currently met from biomass, mainly for cooking and heating in developing countries, but also increasingly for fuelling a growing number of large-scale, modern biomass energy plants in industrialised countries. In Australia, the two most used forms of bioenergy are burning wood for heat and using sugar cane waste (bagasse) to create steam which is then used to power the sugar mill:
- Australia burns around 4,000,000 tonnes of firewood every year.
- Our sugar industry has used bagasse to meet its electricity and heat requirements for more than 100 years.
Bioenergy has the potential to benefit Australia economically by:
- reducing CO2 emissions (if it is substituted for fossil fuels)
- securing energy supplies
- stimulating regional employment and development, especially through new rural industries.
In some situations, bioenergy may compete for biomass and land which would otherwise be used for food production. In Australia, the price of biomass for use as food, fibre and transport fuel is higher than for use as bioenergy (converted to power or heat). The industry view is that this situation will not change in the period to 2020 (see Section 4.2 of the Australian Bioenergy Roadmap [PDF, 4.5 MB], developed by the industry and published by the Clean Energy Council in 2008). Bioenergy myths and facts [PDF, 1.4 MB], published by the Clean Energy Council, explains how:
- Bioenergy is not a driver of clearing native forests.
- The rising cost of food in Australia is caused by a whole range of issues, not energy crops.
- The right choice of energy crops can have a positive effect on water retention. Certain eucalyptus species, for example, have very good water-use efficiency when you consider the amount of water needed per ton of biomass produced.