Introduction
As we face the challenges of climate change and the need for decarbonisation, we must explore innovative solutions that can help us achieve our goals. Agriculture and mining are two industries that can combine to play a crucial role in carbon sequestration.
Enhanced rock weathering (ERW) is a process that involves taking quarry by-products and spreading them onto farmland to absorb carbon dioxide from the atmosphere. This process has been shown to be a highly effective carbon capture method that permanently sequesters carbon.
Moreover, the application of ERW has proven to be highly beneficial to soil health, improving crop yields and enhancing soil fertility. With the right implementation strategies, this approach can deliver long-lasting benefits to the environment as well as supporting sustainable agriculture and forestry.
The scale of the opportunity for ERW in Australia is significant, with our vast areas of land and abundant sources of basalt. Mining and quarrying companies are well-positioned to provide the necessary resources and skills to establish this industry, thereby opening up new opportunities for carbon removal.
However, it is not without its challenges. The university studies and bench tests validating the science need to be converted into field trials. This presents many technical problems. Soil science is a complex and irregular domain. Understanding that domain will be a key determinant in the overall success of enhanced rock weathering as a methodology for carbon removal.
In this discussion, we will explore the concept of ERW, the challenges associated with the developing field of measurement, reporting, and verification (MRV), and the opportunities that science can contribute to ERW leadership. We will also discuss the commercialisation pathway for enhanced rock weathering.
We believe that by combining the opportunities of mining and agriculture, it will form part of the climate change solution.
There are 63mHa of improved pasture in Australia, approximately one-third of which is used for cropping. The map below shows soil enhancer by application rate across Australia. This land asset provides a significant opportunity for Australia to be at the forefront of enhanced rock weathering.
While the link between soil health and productivity has always been paramount for farming, the measurement and management of soil carbon levels has revolutionised in recent years.
Some of this has been led by organics and the regenerative agriculture movements as well as developing agronomy research and the availability of new information and practices from around the world
Increasing soil carbon is widely regarded as beneficial to soil function and fertility and has been associated with increased agricultural productivity. With soil being considered a major world carbon sink (as well as a source of carbon emissions), increasing the amount of carbon in agricultural and rangeland soils is seen as one way of decreasing atmospheric carbon dioxide (CO2) concentrations and mitigating climate change.
Mining and quarrying, on the other hand, have traditionally been associated with negative environmental impacts, such as habitat destruction, water pollution, and greenhouse gas emissions. Enhanced rock weathering is a way in which mining and quarrying themselves can form part of the net-zero solution. Already we are seeing the push by the leading mining houses to decarbonise and we believe in the right resources that enhanced rock weathering can form part of their insetting and offsetting decarbonisation roadmaps.
Enhanced rock weathering is a process that involves the application of crushed silicate rocks to soil. The increased surface area of the crushed rock, spread over large areas of arable land leads to an increased rate of weathering. As the rock weathers, it reacts with the dilute carbonic acid in the water and precipitates out the calcium and magnesium as a bicarbonate.
The basalt rock also contains a variety of other mineralogy which becomes available as it breaks down such as copper, iron, zinc, and potassium, which enriches the soil and improves its water retention capacity. This process reduces the acidity of the soil, lifting the soil pH thereby improving crop productivity.
Much has already been discussed about the benefits from the mineralisation of carbon as a form of storage. The fact that this methodology removes carbon on a geological timescale, doesn’t put restrictions on land usage and has value for the agricultural sector makes it a very strong methodology for broad adoption within Australia.
Taking a step back, if we’re going to scale the carbon sequestration to the levels required to meet our warming targets, utilisation of Australia’s agricultural resource needs to be unlocked.
We know agriculture has the potential to sequester large amounts of carbon in the soil and there are two levers available through ERW to unlock this resource:
1) Increasing cation exchange and nutrient availability; and
2) Restoring pH balance to ideal growing conditions.
Basalt has been demonstrated to shift the soil pH. Current trials that demonstrate this is the type of data that we need to replicate and define in Australia to ensure ERW’s uptake here.
Basalt is readily abundant in Australia - both in quarries as part of the resource, and as mining overburden. Through this, mining and quarrying operations can provide a source of crushed silicate rocks. Currently, we are focused on operating mines and off taking the by-product. As mining equipment technology providers develop carbon neutral machines, we expect to be able to access the additional sources of basalt.
Finally there is an opportunity to integrate carbon removal methodologies like enhanced rock weathering on other land like mining rehabilitation sites, which can help accelerate the restoration of these areas to functioning ecosystems.
Case Studies of Successful ERW projects
There are several examples of successful ERW projects or applications of basalt in agricultural practices.
Specifically, basalt crusher dust from the Andes is used extensively in South American agriculture to improve soil health. Papers by Manning & Theodore (2018); Burbano et al (2022); and Swoboda et al (2022) all explore the various interactions and effectiveness of basalt in agricultural systems.
In Australia, we need to replicate this work. To do so, we are developing projects in a wide variety of environmental conditions and farming systems.
Challenges and Potential Solutions for Implementing Enhanced Rock Weathering in Australia
It’s not all plain sailing. There are several challenges to scaling enhanced rock weathering in Australia.
The ACCU market provides confidence and credibility to the development of projects; however the homogenisation of prices means that carbon projects aren’t rewarded for their quality. Consequently, we are selling into the voluntary market in Europe as well as dealing directly with CDR customers who have their own expertise inhouse.
Within the market, we are also beginning to see the recognition of projects’ ability to occur in parallel with other environmentally and/or socially beneficial programmes – sometimes referred to as stacking. At the moment these are generally between carbon credits and biodiversity credits. Stacking is not currently possible for carbon credits but as the measurement systems improve, we believe there is an opportunity for ‘stacking’ these projects thereby opening more land – especially as different methodologies target carbon in different forms.
Another challenge, also revolves around sequestration rate. As is well known, the weathering rate is entirely dependent on the mineralogy of the rock. Consequently the market is only accepting the amount of carbon weathered in the first 20 years. This is not a deal breaker but does further reduce the total available resource size for the basalt.
Probably the biggest challenge for ERW is the measurement, reporting and verification of CDR. Currently we use a mesocosm set-up that measures the inputs and outflows in the representative soils, but it is slow, expensive, and imprecise. New technology is on the horizon however more work needs to be undertaken before it can form part of the MRV solution.
Australian agriculture and mining are two industries that can play a crucial role in carbon sequestration and achieving net zero emissions. By implementing practices such as enhanced rock weathering, these industries can sequester large amounts of carbon and reduce greenhouse gas emissions.
Furthermore, by collaborating and sharing resources, these industries can achieve economic benefits, enhance biodiversity, and restore degraded ecosystems. As we continue to face the challenges of climate change, ERW offers an innovative solution that can help us achieve our goals and create a more sustainable future.
Comments