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New South Wales researchers experiment with cannabis “mop-crop”

Posted on April 28, 2004

[TV Program Transcript]

KERRY O’BRIEN: With water restrictions in force for many of our major cities, there’s plenty of incentive to make better use of one of our most precious natural resources.

One promising scheme now under trial is the use of what’s called a mop crop — a plant so greedy for water and nutrition it can be used to soak up effluent that would otherwise be dumped into our waterways.

Genevieve Hussey reports on the unlikely plant that’s now being touted as the answer to one of Australia’s biggest environmental problems.

GENEVIEVE HUSSEY: For decades, the far north coast of NSW has been home to Australia’s counter-culture.

The lush fertile valleys around Nimbin have been renowned for communes and cannabis.

Near Bangalo, a short drive from Nimbin, Keith Bolton is checking his own cannabis crop.

He has thousands of 2 metre high plants, all perfectly legal.

According to Keith Bolton, you could smoke the entire crop and all you’d get would be a headache.


In other words, if you smoke it you don’t get stoned.

We grow the hemp a lot more densely.

We grow 200 seeds per square metre because we want to maximise stems rather than, say, the leaf material.

GENEVIEVE HUSSEY: Keith Bolton is a researcher with Southern Cross University, growing industrial cannabis or hemp.

He calls it a ‘mop crop’, greedy for nutrients and water.

This trial plot is watered with effluent from the local sewerage plant, which would otherwise have been discharged in the waterways.

In just 100 days, it’s soaked up 10 million litres of treated sewage.

KEITH BOLTON: This project is about turning waste water into resource water.

Currently, most effluent produced in Australia is dumped as a waste into the rivers and oceans.

GENEVIEVE HUSSEY: Every year, Australia dumps 1,500 gigalitres of effluent from sewerage plants into our waterways and the ocean.

That’s the equivalent of 750,000 Olympic swimming pools of sewage.

Despite a rising standard of processing, the effluent can cause serious environmental problems.


You run the risk of algal blooms, and you may have the problem of degradation of seagrass in the environment from the high levels of, say, nitrogen and phosphorus that might be going out to sea or into the waterways.

GENEVIEVE HUSSEY: Dr John Radcliffe has just completed a major study for the Australian Academy of Technological Sciences looking at how we’re recycling water.

He says drought over the past few years has placed an extra strain on Australia’s water supply and encouraged councils to re-use their effluent. 10 per cent of sewage is now being recycled.

Within 10 years, Canberra, Melbourne and Perth plan to double that figure.

DR JOHN RADCLIFFE: A lot of the water we are using in our cities, although it’s drinking water quality, doesn’t need to be used for what it’s being used for — for watering gardens or flushing toilets.

And we can restructure our water so that we use recycled water for that sort of thing.

PHIL KING, BYRON SHIRE COUNCIL: Water is a fairly scarce resource.

Unless we start using it wisely and using it more than once, our water shortages are going to become more of a problem in the future.

GENEVIEVE HUSSEY: Byron Shire Council says it’s already looking for innovative solutions to its waste water problems.

The council is working with Keith Bolton, planting a mop crop of 500,000 paperbark trees to rehabilitate land near its sewage treatment plant.

PHIL KING: First of all we wanted to clean up all the waterways.

And secondly to actually use the effluent that comes out of our systems, treated water that comes out of systems, as resource and not considered a waste.

GENEVIEVE HUSSEY: Mop crops are not only helping solve an environmental problem — in the case of hemp, researchers hope they could turn it into a moneymaker.

Industrial hemp is worth $200 a tonne.

In the lab, they’re working out just how much fibre can be harvested from Keith Bolton’s hemp.

KEITH BOLTON: On our last crop we yielded 18 tonnes of dry matter per hectare in a 100 day-cycle, which is very rapid growth.

And that’s exactly what we’re looking for when we do mop crops.

PHIL WARNER: ECOFIBRE INDUSTRIES: Hemp is one of those commodities — there’s fibre and there’s cellulose in it, and you use fibre in almost every daily application you can think of, from plastics to furnishing to flooring to insulation.

It’s everywhere.

GENEVIEVE HUSSEY: Keith Bolton is already experimenting with other mop crops, including a fibre plant called kenaf and bamboo.

For him, a controversial crop of cannabis has served its purpose.

KEITH BOLTON: Of course, well, who wants to come and talk about sewage?

Not a whole lot of people.

So I guess hemp, we knew, would attract a certain amount of attention to a very important issue about dealing with this waste water.

Related articles:

Man, that’s good sewage — but hemp trial has dope dealers in a spin
Saturday, March 6, 2004

Hemp saves sea from sewage dumps
Thursday, February 12, 2004

Copyright © 2004, Australian Broadcasting Corporation. All rights reserved.

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