BCIA Research Investment Manager
|Agricultural opportunities for brown coal|
|By David McManus, Research Investment Manager, BCIA|
|Australian soils are among the least fertile in the world, and in order to maximise productivity, Australian agriculture is heavily dependent on the use of imported chemical fertilisers. Victoria’s brown coal deposits represent a huge carbon resource, with significant potential for local manufacture of agricultural products derived from brown coal. David McManus overviews BCIA’s research activities in this area.|
|While the use of chemical fertilisers is undoubtedly beneficial, it comes at a cost. Repeated applications of chemical fertilisers can alter the soil composition, increasing salinity and reducing organic carbon content. Whereas soil carbon levels of over 10% were recorded in Australia in the 1840s, levels are now often less than 1%. Soil structures have collapsed to the extent that much more horsepower is needed to cultivate them, and plant roots can no longer proliferate readily through them.|
The majority of organic matter present in healthy soils is in the form of humic substances, formed by the breakdown of lignified plant tissue. Essentially the same humic substances are found in peat, compost and brown coal. While the majority of Australian soils are deficient in humic substances, Victoria has a huge supply of preserved organic matter in its brown coal deposits. Using brown coal as a soil supplement is potentially a simple way to rebuild soil carbon and thus rejuvenate degraded soils and improve agricultural productivity.
Sporadic research has been conducted on the agricultural potential of Victorian brown coal over many years, although the results were often inconclusive and not followed up. It is well established that brown coal has high water holding capacity and cation exchange capacity, both of which improve soil properties. Alkaline treatment of brown coal liberates a high proportion of humic substances, which are reputed to have plant growth-promoting properties.
In order to better understand the implications of using brown coal and humic substances as agricultural inputs, BCIA has supported research efforts at Monash University, led by Associate Professor Tony Patti. This has included funding for a three-year research project as well as PhD scholarship funding for Ms Karen Little, Mrs Azita Kargosha and Mr Biplob Saha.
|These research efforts have led to a number of interesting and useful observations, including the following.|
- Humic substances stimulate the proliferation of bacteria associated with nitrogen cycling in the soil.
- Beneficial plant growth-promoting bacteria were found to survive for up to 3 months when inoculated into brown coal.
- Humic substances are not rapidly decomposed by soil microbes and may be stable in the soil for many years (although this is yet to be confirmed).
- Brown coal can make phosphate fertilisers more bioavailable by complexing with calcium ions (which form insoluble precipitates with phosphate).
|Figure 1: Rice in glasshouse trial after 30 days. |
(Copyright © 2015 by Monash University)
- Brown coal can improve the performance of urea by binding to ammonium ions, leading to reduced losses through leaching and nitrous oxide (a potent greenhouse gas) emissions and improved soil N retention.
|Through the course of this research it has become apparent that the effectiveness of brown coal and humic substances on plant growth is dependent on complex interactions between the soil, plants and microbial species. The research to date has led to the development of sophisticated tools to help understand these interactions, but more research is necessary.|
Even so, it is clear that there is commercial potential for the research already completed. This potential is beginning to be explored with the assistance of two local companies, Torreco and Feeco Australia. Torreco uses a torrefaction process to heat the brown coal briefly in an oxygen-deficient atmosphere, which makes the coal very dry and brittle, and thus easier to grind and granulate. Feeco Australia has expertise in granulation technology, and has produced experimental batches of granules containing blends of brown coal/humic substances and chemical fertilisers.
The granules that have been produced are hard and dense, and are suitable for direct injection into the soil using conventional agricultural equipment. These products have the potential to significantly improve fertiliser use efficiency and are suitable for use in low emissions no-till farming practices. To develop these products further, the manufacturing process needs to be scaled up, so that enough product can be made for testing in large-scale field trials.
|As reported in the June 2015 issue of Perspectives, Australian Carbon Fertilisers has been testing a similar product in field trials, observing yield increases of 27% in pasture and 38% in wheat. Increased plant yields require increased photosynthesis, which extracts more CO₂ from the atmosphere.|
The use of brown coal blended with conventional fertilisers thus offers a number of environmental benefits.
- Reduced input of chemical fertilisers, through increased fertiliser use efficiency.
- Reduced greenhouse gas emissions from chemical fertiliser manufacture.
- Reduced leaching of fertilisers, preventing pollution of waterways.
|Figure 2: Benalla pasture trial showing biomass effects. (Copyright © 2015 by Australian Carbon Fertilisers Ltd.)|
- Reduced volatilisation of urea, with less production of NO₂, a potent greenhouse gas.
- Increased soil carbon levels, both directly through addition of coal to the soil and indirectly through increased root growth.
|Improved soil stability and structure, with better water retention and less tendency to blow away as dust.Given that over 60% of Australia’s rural landscape, i.e. more than 500 million hectares, has been affected by soil degradation, there is a huge potential market for agricultural products based on Victorian brown coal. The equipment needed to manufacture such products is relatively inexpensive, so this is one of the most prospective new manufacturing opportunities for the Latrobe Valley.|
The costs involved for field trial validation are high. Chemical fertilisers such as urea and superphosphate, which are now universally used, were validated through government funded research and not by fertiliser companies. No single company would have funded this research, since the results would have been quickly utilised by the competition.
Exactly the same situation applies today with brown coal- based fertilisers. Further independetly-funded research is required to demonstrate efficacy and reproducibility in large-scale field trials. This will unlock the market for these products and open the door to a range of new manufacturing opportunities in the Latrobe Valley.