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Hemp: The multi-use crop that might be the answer to climate change

By David Leigh - posted Wednesday, 13 July 2011

The recent and spurious debates over carbon tax have filled the airwaves with opposing and venomous soliloquy. In what is the biggest reform to the Australian economy in many years, arguments from the Liberals appear to be focused, not on a cleaner, greener and therefore safer future, but rather a business as usual scenario. Labor is pressing the point that whatever the cost impacts, low-income households will be compensated.

The argument pressed by the Greens and in particular, Christine Milne, is that the tax and the massive  $10 billion about to be invested in renewables will promote change in the way energy is produced and drive Australia towards a cleaner and cheaper future. The formation a Clean Energy Commission by the Multi Party Commission for Climate Change (MPCCC) is a good way of administering that process.

Issues such as whether or not petrol and diesel should or should not be included in the assessment appear relevant enough until the fuel concerned becomes a renewable resource and therefore carbon tax exempt.


The transport (liquid) fuel question is a good one and one, which will obviously resurface at some point in the future and is why it should be discussed now. Transport makes up a proportion of everything we purchase and consume. If we are to be honest and tackle climate change, we must approach the problem from all sides. Burning fossil fuels and deforestation are the two main causes of warming and of acidification of our air, land and water. The Earth’s finite resources are challenged right now and it must be said that the Gillard approach of “enough talking, it’s time for action” is commendable and should be applauded.        

Non-fossil fuels are being made now from many renewable sources. Plant-based ethanol and bio-diesel have been around for a while. Extracts from plants such as corn, sugar cane and even poppy seeds are being made into fuels. The recycling of spent fish and chip oil into a diesel substitute has also had some success. One cultivar that is repeatedly overlooked is hemp. This is likely because of the stigma attached to the plant from its historic drug use. The very corporations responsible for the change our poor, overburdened planet has had to suffer have manufactured this reputation at a far greater rate than any drug product.

Hemp is one of the oldest plants to be cultivated by man. It has many uses and its earliest exploitation was for fibre. Hemp and flax were plants used by lake dwellers between 4300 and 800 BC and were also grown around the lakes as a staple food source. The seeds and the leaves can be eaten and the seed meal contains around 25 per cent protein, they are also high in natural antioxidants and Omega oils. It is those same oils that have the ability to defeat the argument for carbon tax on transport fuels before it even arises.

One acre or 0.4 hectares of commercial hemp will produce around 500 gallons or 1892.7 litres of bio-diesel from the seeds. That is more than enough to keep the average commercial utility going for around a year and a family car going for a year and a half.

The stems and leaves of the plant can also be converted to bio-ethanol via the process or pyrolysis, the same method used to make bio-char, a soil fertiliser. Pyrolysis (enclosed burning without oxygen) will also produce electricity as a by-product.

Hemp is also a great soil improver, converting poor, low yield land into good food producing loam. It does this by dropping leaves onto the soil and by the release of nitrogen from the root nodes after harvest. As a rotational crop, hemp can be used instead of fertiliser (another carbon saver) and because of its low water use will save money and energy and therefore more carbon.


Scientists have already discovered that soil carbon take-up can reverse human-made climate change impacts. We know that 25 per cent of greenhouse gas emissions are as a result of farming activities and that by improving soil carbon by just 1 per cent it is possible to reverse that, making agriculture carbon neutral: “Every tonne of carbon lost from soil adds 3.67 tonnes of carbon dioxide (CO2) gas to the atmosphere. Conversely, every one tonne increase in soil organic carbon represents 3.67 tonnes of CO2 sequestered from the atmosphere and removed from the greenhouse equation”.  

Growing hemp instead of clear-felling forests or plantations is a much better way of fulfilling the need for fibre. As an example, one-hectare of hemp will produce as much quality paper as 4.1 hectares of trees and can be grown in 90 days (a business cycle) rather than twenty five years. The harvesting and processing is far less energy intensive and does not require harsh chemical use.

This multi-use crop can help Australia, not only in the conversion to a green energy economy but also sustainable farming and forest industries and should be one of the tools used by the newly-formed Sustainable Energy Commission proposed by the MPCCC.

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About the Author

David Leigh is a film maker and novellist who currently lives in Tasmania.

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