Coffee Biochar Concrete Carbon Sequestration

Coffee biochar concrete sequesters carbon and makes a stronger building material.
Reading Time: 3 minutes

Coffee biochar concrete sequesters carbon and makes a stronger building material. Image: Unsplash

Reading Time: 3 minutes

Coffee biochar concrete sequesters carbon and makes a stronger building material.

Coffee is one of the most popular drinks worldwide; on average, 400 billion cups of coffee are consumed each year. As a result, approximately 18 million tonnes of coffee grounds are produced annually. Coffee grounds can be used for a variety of purposes. It can be used to fertilize your garden or added to compost. Coffee grounds can neutralize odors, can be used to exfoliate your skin, tenderize meats, and many other uses.  

Despite all of these amazing uses for coffee grounds, the reality is that most of the coffee grounds produced actually end up in landfills; about 75% in fact. Rotting coffee grounds generate methane, a powerful greenhouse gas contributing to warming. Rotting coffee grounds also emit carbon dioxide, nitrous oxide, and ammonia. While there have been programs from coffee shops that will donate their coffee grounds to customers to use in their gardens (Starbucks has been part of the Grounds for Your Garden program since 1995), but most coffee shops are not implementing these initiatives.  

Researchers from the Royal Melbourne Institute of Technology University in Australia have found a way to use coffee grounds on a larger scale and to eliminate the risk of them ending up in landfills. And that is to use coffee biochar concrete in the construction industry.  

The researchers have developed concrete that is almost 30 percent stronger than traditional concrete by mixing in coffee-derived biochar. The coffee biochar was created using a low-energy process called pyrolysis. The organic waste is heated to 350 degrees Celsius without oxygen to avoid the risk of generating carbon dioxide. Under pyrolysis, organic molecules vibrate and break down into smaller components, creating biochar. This is a similar process that is used to roast unused beans to enhance their taste, except without the use of oxygen.  

In coffee biochar concrete, about 15 percent of the sand they would use to make concrete is replaced with the coffee biochar, thus creating new concrete. The coffee biochar is finer than sand, and its porous qualities help to bind to organic material. Reducing the total use of sand in concrete will minimize the construction industry’s environmental footprint. It is said that over 50 billion metric tons of natural sand are used annually in construction. Sand mining significantly stresses ecosystems, including riverbeds and riverbanks, coffee biochar concrete can relieve some of that pressure on the environment.  

The cement industry is the third largest source of industrial air pollution, including sulfur dioxide, nitrogen oxides, and carbon monoxide. Moreover, cement currently accounts for around 8% of global carbon dioxide emissions. Turning coffee- biochar into concrete will reduce the construction industry’s reliance on continuous mining of natural resources, making the industry more sustainable.  

When introduced into concrete mixtures, the coffee biochar concrete was found to act as a microscopic carbon repository within the concrete matrix. The alkaline conditions within hardened concrete enable biochar to mineralize and firmly bind carbon dioxide into its structure over time. Concrete containing even a small percentage of spent coffee biochar was shown to sequester meaningful quantities of CO2 from the curing process and surrounding environment.

Utilizing waste coffee grounds to synthesize biochar for carbon sequestration could offer a sustainable way to offset concrete’s sizable carbon footprint while giving new purpose to spent grounds. With further research, coffee biochar concrete could provide a feasible carbon capture pathway for the construction industry.

The researchers estimate that if all the waste grounds produced in Australia annually could be converted into coffee biochar, it would amount to roughly 22,500 tonnes. Compare that to the 28 million tonnes of sand that are required to produce over 72 million tonnes of cement concrete in Australia. Just think: Australia has over 13 thousand coffee shops, whereas the United States has over 38 thousand coffee shops. If this project expands outside of Australia, coffee biochar concrete could significantly impact the environment and waste.  

The research on coffee biochar concrete is still in the early stages; there is still a lot of testing to be done, but it shows that there are innovative and unique ways to reduce and repurpose organic landfill waste. Once the researchers can account for things like durability, the researchers will collaborate with local councils on future infrastructure projects, including the construction of walkways and pavements. Just think, we are one step closer to adding sustainability into the construction industry and one step closer to walking on coffee biochar concrete!

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