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Published: 26 September 2011

Clay locks up more carbon, improves soil health

An Australian environmental research team has developed a low-cost novel solution for reducing carbon in the atmosphere while improving soil fertility, using natural materials.

Adding compost-containing clay materials to soil can help lock up carbon as well as increase fertility.
Credit: Lou Gold/Flickr/visionshare

According to Professor Nanthi Bolan from The University of South Australia, adding compost-containing clay materials to soil can help lock up carbon, while also increasing fertility.

‘Traditional ways to lower carbon emission while increasing soil fertility include spreading organic wastes, such as composts and manures, on agricultural land – but research has shown that these degrade quickly,’ he says. ‘This results in the release of carbon dioxide.’

Prof. Bolan says that another popular method in recent times involves converting organic wastes to biochar through pyrolysis, which turns carbon into a form that cannot easily escape back into the atmosphere.

‘However, biochar production, especially in large amounts, takes a lot of energy. Burning it can also release other greenhouse gases, such as carbon monoxide and methane, into the air. At the same time it will also destroy precious plant nutrients such as nitrogen.

‘Our challenge was to come up with a method that will allow us to tie carbon added through manures and composts to the soil while keeping their fertiliser value.

‘So we tried co-composting manures and composts with compounds such as iron oxide, aluminium oxide and allophane clay, and spreading this mixture on agricultural soils.

‘These compounds are easily obtained from nature, especially allophane clay, which can be found in locations that contain volcanic ash.’

The researchers found the compost enriched with clay not only locked up more carbon, it also contained more nutrients to fertilise the crops.

Prof. Bolan says that although the compost has a shorter life than biochar in soil, avoiding pyrolysis of manure and compost to produce biochar can save their fertiliser value and prevent the emission of other greenhouse gases.

‘The long-term carbon storage function of biochars contradicts their fertiliser value, which requires that certain biochar materials be biodegradable. Our method, by co-composting of the organic material with clay materials, has proven to effectively stabilise soil, and can add to the long-term soil carbon pool.

‘Adding these materials to compost means that farmers only need to buy these “value added” composts and spread it on their soil.

‘Our next step is to find practical ways to produce large quantities of this material, and identify the ideal quantities for binding carbon and retaining fertility.’

Source: CRC for Contamination Assessment and Remediation of the Environment

Published: 26 September 2011

Renewable energy sector to benefit from wind-speed research

Craig Macaulay

While some recent international studies have shown a decrease in wind speeds in several parts of the globe, including Australia, more recent results from CSIRO show that Australia’s average wind speed is actually increasing.

The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
Credit: Gregory Heath

CSIRO scientists have analysed wind speed observations to understand the causes of variations in near-ground-level wind and explore long-term wind speed trends.

Accurate estimates of long-term trends provide a useful indicator for circulation changes in the atmosphere and are invaluable for the planning and financing of sectors such as wind energy, which need to map risk management under a changing climate.

‘We have a good picture of wind energy availability across Australia from previous CSIRO wind mapping and, with the growth of wind farms, there is an emerging need to understand how climate change can affect the wind resource,’ says Dr Alberto Troccoli, lead author of a recent paper published in Journal of Climate. 1

‘Wind power production is expected to increase greatly over the coming years and the associated electricity system will be subject to variations of several hundred megawatts – depending on wind availability.

‘The ability to quantify with accuracy these long-term variations is essential to the sector from an economic point of view.’

Dr Troccoli said that, averaged across Australia over 1989–2006, wind speeds measured at a height of 10 metres had increased by 0.69 per cent per annum, compared to a decline of 0.36 per cent per annum for wind speeds measured at 2m height.

‘The potential for increasing the efficiency of energy operations by using quality weather and climate information is therefore apparent and one of the first steps is the standardisation of wind recording stations.

‘Wind observations, like other meteorological variables, are sensitive to the conditions in which they are observed – for example, where the instrumentation sits relative to topographical features, vegetation and urban developments.’

The team found that the wind speed trends over Australia are sensitive to the height of the station, with winds measured at 10m displaying an opposite and positive trend to those reported by a previous study, which analysed only winds measured at 2m.

Light winds measured at 10m, a height that represents better the free atmospheric flow, tend to increase more rapidly than the average, whereas strong winds increase less rapidly than the average winds. Light and strong wind measured at a height of 2m tend to vary in line with the average winds.

‘Our work shows a number of challenges with the consistency of the observations during their period of operation and between sites across Australia,’ adds Dr Troccoli.

‘The quality of future wind observational datasets will depend on having consistency between sites, particularly with respect to measurement procedure, maintenance of instrumentation, and detailed records of the site history.’

He said the work has implications for a variety of sectors beyond wind energy including building construction, coastal erosion, and evaporation rates.

The conjunction of energy and meteorology is the central theme of the International Conference Energy & Meteorology on the Gold Coast in November.

Read Dr Troccoli’s thoughts on What’s the energy forecast? Bringing meteorology and generation together in the online forum, The Conversation.

1 A. Troccoli, K. Muller, P. Coppin, R. Davy, C. Russell and A. Hirsch (2011) Long-term wind speed trends over Australia. Journal of Climate, doi: 10.1175/2011JCLI4198.1

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