Concrete which has partly been made using spent coffee grounds has been used in the construction of a footpath that is being built as part of Victoria’s $90 billion plus Big Build program.

As part of the Pakenham Roads Upgrade project in Melbourne’s outer eastern suburbs, concrete which has partly been mixed with biochar that has been made from spent coffee grounds has been laid on a footpath along the busy McGregor Road.

Using an innovation developed by Royal Melbourne Institute of Technology (RMIT), the project saw environment and social science engineering company Earth Systems convert five tonnes of spent coffee grounds into two tonnes of useable biochar.

The biochar was then used as part of 30 meters of cubed concrete that was laid along the footpath.

This replaced a portion of the river sand that is currently being used on the project.

All up, the equivalent of around 140,000 tonnes of biochar was used.

The latest initiative comes as the construction industry worldwide is aiming to adopt circular economy initiatives as part of efforts to reduce carbon emissions and to minimise the volume of construction waste that ends up in landfill.

Potential in respect of spent coffee grounds is significant.

Worldwide, around 10 billion kilograms of spent ground coffee is generated annually. If used in concrete, this could replace up to 90 billion kilograms of sand.

In Australia alone, around 75 million kilograms of ground coffee waste is generated each year.

Whilst most of this currently goes to landfill, this could potentially replace up to 655 million kilograms of sand in concrete. (As spent coffee is a denser material compared with sand, one kilogram of spent coffee could replace up to 9 kilograms of sand.)

All up, the volume of organic waste which currently goes into landfill (including the spent coffee grounds) contributes around 3 percent to Australia’s greenhouse gas emissions.

The waste from spent coffee grounds cannot be added directly to concrete as it would decompose over time and weaken the material.

However, RMIT has developed a technique to make the concrete 30 percent stronger by turning the waste coffee grounds into biochar. This uses a low energy process without oxygen at 305 degrees Celsius.

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The footpath and upgrade of McGregor Road is being delivered as part of the Pakenham Roads Upgrade package.

This involves upgrades to several major roads in the outer south-eastern Melbourne suburb of Pakenham, which are being undertaken to relieve bottlenecks, improve traffic flow and improve safety.

It is part of Victoria’s Big Build Program, in which the state last year said it was investing around $90 billion to deliver more than 165 road and rail projects.

The coffee concrete is one of several circular economy initiatives being deployed on the Pakenham project.

Other initiatives include reusing the in-fill soil and material for the Princes Freeway embankments and using foam bitumen and rubber tyre road barriers.

The project was the second on which coffee concrete has been trialled.

Earlier this year, RMIT teamed up with Macedon Ranges Shire Council to conduct a  world-first trial of coffee concrete in a footpath in Gisborne, Victoria.

The Institute is now engaging with a commercialisation partner as well as construction and agriculture firms who could potentially benefit from using biochar products.

The coffee concrete trial was undertaken with the support of project owner Major Road Projects Victoria (MRPV) and construction contractor Bild Group.

The ground coffee used for the research was provided by the indigenous-owned coffee supplier Talwali Coffee Roasters.

MRPV Program Director Brendan Pauwels said coffee concrete had the potential to cut costs and remove vast amounts of waste material from landfill.

“These numbers are remarkable in terms of ecological benefit, and we’re excited to see the Pakenham Roads Upgrade be the first Victorian Big Build project to use the coffee concrete,” he said.

Bild Group CEO Stephen Hill said his company was the first to employ the technology on a major infrastructure project.

He says deployment of the technology made good business sense from a triple-bottom-live viewpoint.

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