Dishing the dirt: Australia’s move to store carbon in soil is a problem for tackling climate change


Robert Edwin White, University of Melbourne and Brian Davidson, University of Melbourne

To slow climate change, humanity has two main options: reduce greenhouse gas emissions directly or find ways to remove them from the atmosphere. On the latter, storing carbon in soil – or carbon farming – is often touted as a promising way to offset emissions from other sources such as energy generation, industry and transport.

The Morrison government’s Technology Investment Roadmap, now open for public comment, identifies soil carbon as a potential way to reduce emissions from agriculture and to offset other emissions.

In particular, it points to so-called “biochar” – plant material transformed into carbon-rich charcoal then applied to soil.

But the government’s plan contains misconceptions about both biochar, and the general effectiveness of soil carbon as an emissions reduction strategy.

Emissions rising from a coal plant.
Soil carbon storage is touted as a way to offset emissions from industry and elsewhere.

What is biochar?

Through photosynthesis, plants turn carbon dioxide (CO₂) into organic material known as biomass. When that biomass decomposes in soil, CO₂ is produced and mostly ends up in the atmosphere.

This is a natural process. But if we can intervene by using technology to keep carbon in the soil rather than in the atmosphere, in theory that will help mitigate climate change. That’s where biochar comes in.

Making biochar involves heating waste organic materials in a reduced-oxygen environment to create a charcoal-like product – a process called “pyrolysis”. The carbon from the biomass is stored in the charcoal, which is very stable and does not decompose for decades.

Plant materials are the predominant material or “feedstock” used to make biochar, but livestock manure can also be used. The biochar is applied to the soil, purportedly to boost soil fertility and productivity. This has been tested on grassland, cropping soils and in vineyards.

A handful of biochar.
Biochar is produced by burning organic material in a low oxygen environment.

But there’s a catch

So far, so good. But there are a few downsides to consider.

First, the pyrolysis process produces combustible gases and uses energy – to the extent that when all energy inputs and outputs are considered in a life cycle analysis, the net energy balance can be negative. In other words, the process can create more greenhouse gas emissions than it saves. The balance depends on many factors including the type and condition of the feedstock and the rate and temperature of pyrolysis.

Second, while biochar may improve the soil carbon status at a new site, the sites from which the carbon residues are removed, such as farmers’ fields or harvested forests, will be depleted of soil carbon and associated nutrients. Hence there may be no overall gain in soil fertility.

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Third, the government roadmap claims increasing soil carbon can reduce emissions from livestock farming while increasing productivity. Theoretically, increased soil carbon should lead to better pasture growth. But the most efficient way for farmers to take advantage of the growth, and increase productivity, is to keep more livestock per hectare.

Livestock such as cows and sheep produce methane – a much more potent greenhouse gas than carbon dioxide. Our analysis suggests the methane produced by the extra stock would exceed the offsetting effect of storing more soil carbon. This would lead to a net increase, not decrease, in greenhouse gas

Beef cattle grazing in a field
Farmers would have to increase stock numbers to benefit from pasture growth.
Dan Peled/AAP

A policy failure

The government plan refers to the potential to build on the success of the Emissions Reduction Fund. Among other measures, the fund pays landholders to increase the amount of carbon stored in soil through carbon credits issued through the Carbon Farming Initiative.

However since 2014, the Emissions Reduction Fund has not significantly reduced Australia’s greenhouse gas emissions – and agriculture’s contribution has been smaller still.

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So far, the agriculture sector has been contracted to provide about 9.5% of the overall abatement, or about 18.3 million tonnes. To date, it’s supplied only 1.54 million tonnes – 8.4% of the sector’s commitment.

The initiative has largely failed because several factors have made it uneconomic for farmers to take part. They include:

  • overly complex regulations
  • requirements for expensive soil sampling and analysis
  • the low value of carbon credits (averaging $12 per tonne of CO₂-equivalent since the scheme began).
A farmer inspecting crops.
For many farmers, taking part in the Emissions Reduction Fund is uneconomic.

A misguided strategy

We believe the government is misguided in considering soil carbon as an emissions reduction technology.

Certainly, increasing soil carbon at one location can boost soil fertility and potentially productivity, but these are largely private landholder benefits – paid for by taxpayers in the form of carbon credits.

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If emissions reduction is seen as a public benefit, then the payment to farmers becomes a subsidy. But it’s highly questionable whether the public benefit (in the form of reduced emissions) is worth the cost. The government has not yet done this analysis.

To be effective, future emissions technology in Australia should focus on improving energy efficiency in industry, the residential sector and transport, where big gains are to be made.The Conversation

Robert Edwin White, Professor Emeritus, University of Melbourne and Brian Davidson, Senior Lecturer, Department of Agriculture and Food Systems, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

We composted ‘biodegradable’ balloons. Here’s what we found after 16 weeks

‘Biodegradable’ balloons after 16 weeks in freshwater.
Jesse Benjamin, Author provided

Morgan Gilmour, University of Tasmania and Jennifer Lavers, University of Tasmania

After 16 weeks in an industrial compost heap, we unearthed blue and white balloons and found them totally unscathed. The knots we spent hours painstakingly tying by hand more than four months ago were still attached, and sparkly blue balloons still glinted in the sun.

These balloons originally came from packages that advertised them as “100% biodegradable”, with the manufacturers assuring they were made of “100% natural latex rubber”. The implication is that these balloons would have no trouble breaking down in the environment.

Read more:
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This appeals to eco-conscious consumers, but really just fuels corporate greenwashing — unsubstantiated claims of environmentally friendly and safe products.

Holding perfectly intact balloons in our hands after four months in industrial compost, we had cause to question these claims, and ran experiments.

What’s the problem?

This problem is two-fold. First, balloons are additional plastic waste in the environment. They are lightweight and can travel on air currents far from the point of release. For example, one 2005 study found a balloon travelled more than 200 kilometres.

alt text
Not much changed after 14 weeks.
Morgan Gilmour, Author provided

When they pop, they float back to the earth’s surface and land in, for example, the ocean or the desert, and wash up on beaches where animals can eat them, from sea turtles and seabirds to desert tortoises.

The stretchiness of balloons means they can get stuck in animals’ digestive tracts, which will cause choking, blockage, decreased nutrient absorption and effectively starve the animal.

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Second, what most consumers don’t realise, is that to shape milky natural rubber latex sap into the product we know as a balloon, many additional chemicals need to be added to the latex.

These chemicals include antioxidants and anti-fogging (to counteract that cloudy look balloons can get), plasticisers (to make it more flexible), preservatives (to enable the balloon to sit in warehouses and store shelves for months), flame retardants, fragrance and, of course, dyes and pigments.

Even more chemicals have to be used to make the additives “stick” to the latex and to stick to each other, enabling them to work in tandem to create a product we expect to use for about 24 hours. So, the balloons can’t be “100% natural rubber latex”.

A little girl on a park bench lets go of a pink balloon
Balloons can travel vast distances in the sky before they pop and are eaten by animals.
Unsplash, CC BY

And yet, despite substantial evidence of harm and the presence of these chemicals, balloon littering persists. Balloon releases are common, with only some regional regulations in place, such as in New South Wales and the Sunshine Coast.

Lying for decades

While some factions of the balloon industry denounce balloon releases, these claims are only recent.

For decades, the industry relied on one industry-funded study from 1989 which claimed that after six short weeks, balloons degraded “at about the same rate as oak tree leaves” and there was no way balloons were a threat to wildlife.

That study was not peer-reviewed, its methods are unclear and not repeatable, and the results are based on only six balloons.

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Because balloons are frequently reported to be at sea, ingested by wild animals and washed up on beaches, it’s clear they’re not breaking down in only six weeks. Anecdotal studies have tested this to varying degrees, confirming balloons don’t break down.

Only one peer-reviewed scientific study has quantified balloon degradation, and that also occurred in 1989 — the same year as the industry study. They tested elasticity for up to one year, which means the balloons were intact for that whole time.

Person with a rake buries blue latex balloons in the compost
We tested the claims of the balloon industry.
Dahlia Foo, Author provided

We wanted to know: has anything changed since 1989? And why aren’t there more studies testing balloon degradation, given the passion behind the balloon issue?

So, we set out to quantify exactly how long latex balloons would take to break down. And we asked if balloons degraded differently in different parts of the environment.

Our experiment tested their claims

Industrial composting standards require that the material completely disintegrates after 12 weeks and that the product is not distinguishable from the surrounding soil.

We designed an experiment: after exposing balloons to six hours of sunlight (to simulate typical use, for example, at an outdoor party), we put blue and white balloons in industrial compost, and in saltwater and freshwater tanks.

We allowed for aeration to simulate natural conditions, but otherwise, we left the balloons alone. Every two weeks, we randomly removed 40 balloons from each treatment. We photographed them to document degradation. Then we tested them.

The author prepares to sample latex balloons in front of water tanks
The author sampling latex balloons.
Jesse Benjamin, Author provided

Were the balloons still stretchy? We tested this in the University of Tasmania engineering lab to determine tensile (resistence) strength. We found that in water tanks, the balloons became less stretchy, losing around 75% of their tensile strength. But if they had been composted, balloons retained their stretchiness.

Were the balloons still composed of the same things they started with? We tested this by taking spectral measurements of the balloons’ surface. The balloons showed signs they were exposed to ultra violet light in the water tanks, but not in the compost. This means their chemical composition changed in water, but only slightly.

Finally, and most importantly, did the balloons lose mass?

After 16 weeks, the balloons were still recognisably balloons, though they behaved a little differently in compost, water and saltwater. Some balloons lost 1–2% mass, and some balloons in freshwater gained mass, likely due to osmotic absorption of water.

Four dirty, deflated white balloons in a row on a black background.
These are white latex balloons 16 weeks after we composted them.
Jesse Benjamin, Author provided

What can we do?

It’s clear latex balloons don’t meaningfully degrade in 16 weeks and will continue to pose a threat to wildlife. So what can we do as consumers? We offer these tips:

  • do not release balloons outdoors
  • do not use helium-filled balloons outdoors (this prevents accidental release, and saves helium), which is a critically limited resource
  • if you use balloons, deflate and bin them after use
  • consider balloon alternatives, like bubbles
  • make educated purchases with federal Green Guidelines in mind.

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The Conversation

Morgan Gilmour, Adjunct Researcher in Marine Science, University of Tasmania and Jennifer Lavers, Lecturer in Marine Science, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.