Wood Waste Energy

Discussion

Woodwaste - wood residue from timber production - can be burned to generate electricity, eg as a subsitute for coal.

Woodwaste includes branches and stumps left over when a log is extracted from a tree, and sawdust and shavings after the log is sawn into timber.

However, much wood waste comes from the logging of native, old-growth forests, leading to loss of biodiversity.

Further such energy production is considered as both renewable and greenhouse netural, because the wood can be regrown in plantation forests, sequestering carbon as it grows.

Old-growth forests take a long time to renew, especially when large areas are logged. Plantation forests, even incorporating habitats to foster biodiversity, are no subsitute for old-growth forests in terms of biodiversity maintenance.

Emitting a quantity of carbon into the atmosphere and then drawing it back down afterwards should not be considered greenhouse neutral; it results in a pulse of carbon dixoide being added to the atmosphere for a considerable period.

Meanwhile, adding energy extraction to the value of old-growth forest logging, will only add to the pressure to log old-growth forests.

Readings

Converting Tree Waste into Electicity

CSIRO, 5 January 1998

Wood residues currently left in the forest to decay or produced in sawmills have considerable potential as a renewable energy source. Using them for energy or fuel production might reduce greenhouse gas emissions in Australia by up to 10 percent.

In sawmills 65 percent of the log ends up as sawdust, shavings or slabs, another 40 percent of the tree is left in the forest as the crown or stump. Currently these are either burnt or left to rot so the energy embodied in these residues is wasted. Using them for energy consumption is ‘greenhouse neutral’.

A CSIRO survey, presented at a recent Biomass Taskforce Symposium, shows that energy from wood residues is even cheaper than using coal.

Biomass Beckoning

Australian Energy News, Issue 7, March 1998

Wood waste is available in large quantities and could produce electricity for less than the cost of coal fired electricity. Wood residues could be delivered to industrial boilers for $0.25c/MJcompared with black and brown coal at between $0.27-$0.29c/MJ.

Macquarie Generation Biomass Co-Firing

Australian Greenhouse Office

Australia produces about 50 million tonnes of biomass residue annually. Much of it is either burned in the field and factory sites, stockpiled or placed in landfill.

The natural breakdown of biomass releases previously stored carbon as part of the carbon cycle. When placed in a landfill the biomass can decay anaerobically and produce methane. Methane is a potent greenhouse gas estimated to be 21 times more damaging than carbon dioxide (CO2). By co-firing with fuel diverted from landfill the greenhouse benefits are even more significant.

Under accounting measures adopted by international agencies researching climate change, the use of sustainably harvested biomass for electricity generation is granted a 'zero' greenhouse gas status.

Macquarie Generation conducted a biomass cofiring trial at their Liddell Power Station, integrating untreated timber industry by-products such as sawdust and wood shavings into the coal fuel stream. The trial enabled Macquarie Generation to sell almost 3,000 megawatt hours of greenhouse emission ‘credits’ to Great Southern Energy and Energy Australia. These two energy retailers are required to meet greenhouse reduction targets as part of their NSW retail licenses.

Burning Wood for Electricity

ABC, 21 August 1999

Burning Trees for electricity: is renewable energy as green as we think? As biomass energy takes off around the world a battle is brewing over burning native forests.

Forests in the Furnace

Nature Conservation Council of NSW, 12 June 2000

There is no benefit in switching to biomass energy if crop production destroys native ecosystems, reduces biodiversity, pollutes wetlands and waterways with fertiliser and chemical run-off, and exacerbates salinity problems.

Electricity generators in NSW have begun substituting coal with sawdust and woodchips from nativeforests. While the burning of timber releases carbon in the same way as coal, burning wood allegedly enables the industry to reduce their greenhouse emissions. This is because the carbon accounting methodology only counts the emissions from coal, and not from wood.

Carbon stored in forests is far more than just that found in the trees. Up to 80% of the carbon stored in an old forest is in the soil. Logging operations seriously disturbs the delicate balance of forests and releases this stored carbon.

Biomass - Burning Forests For Power

The Wildnerness Society, 31 August 2001

Electricity producers are proposing to substitute coal with native forest wood products as a way of "reducing greenhouse gas emissions". While the burning of timber releases carbon in the same way as coal, the electricity industry claims that biomass is regarded as greenhouse neutral because new trees are grown to replace those which are logged.

The energy industry and the government describe what is being burnt simply as 'forest waste'. However [this could include]: old trees, not suitable for sawlogs; silvicultural thinnings (trees removed to promote the growth of sawlogs); sawdust, bark, heads and butts (these are uneconomical to woodchip and would be unlikely to be used as biomass); whole trees currently used for woodchips.

Between 60% and 90% of what is logged from our native forests is already declared waste and turned into woodchips. The removal of this material deprives forests of vital nutrients to the soil and endangers native species' habitats.

Wilderness Society Forest Campaign - Background Information


13 April 2005