Coffee biochar makes for lower-carbon, stronger concrete

Around the world, people produce over six million tons of coffee grounds, according to the International Coffee Organization. While some of those grounds make their way to compost, most end up in landfills. Researchers in Australia have been finding ways to use coffee grounds to make concrete. And now, an in-depth analysis shows that concrete made with the organic waste is not only 30% stronger, it also reduces carbon dioxide emissions by 26%.

Others have used coffee grounds to make biofuels, biodegradable plastic and to soak up toxic pollutants. Infusing concrete with coffee grounds impacts sustainability in multiple ways. First, just like any other organic matter, decaying coffee grounds in landfills produce the greenhouse gas methane. So keeping the waste out of landfills benefits the climate.

Meanwhile, manufacturers make concrete today by mixing cement with sand. Mining that sand bears its own carbon and ecological footprint. The new results, published in the International Journal of Construction Management, quantify these sustainability impacts. Materials scientists at RMIT University in Australia two years ago found a way to add coffee grounds to concrete without affecting its strength.

They heated the grounds at 350°C in the absence of oxygen to make biochar. They then replaced 15% of the sand in concrete with the coffee biochar. This increased the concrete’s strength by 30%.

.IRPP_ruby , .IRPP_ruby .postImageUrl , .IRPP_ruby .centered-text-area {height: auto;position: relative;}.IRPP_ruby , .IRPP_ruby:hover , .IRPP_ruby:visited , .IRPP_ruby:active {border:0!important;}.IRPP_ruby .clearfix:after {content: "";display: table;clear: both;}.IRPP_ruby {display: block;transition: background-color 250ms;webkit-transition: background-color 250ms;width: 100%;opacity: 1;transition: opacity 250ms;webkit-transition: opacity 250ms;background-color: #eaeaea;}.IRPP_ruby:active , .IRPP_ruby:hover {opacity: 1;transition: opacity 250ms;webkit-transition: opacity 250ms;background-color: inherit;}.IRPP_ruby .postImageUrl {background-position: center;background-size: cover;float: left;margin: 0;padding: 0;width: 31.59%;position: absolute;top: 0;bottom: 0;}.IRPP_ruby .centered-text-area {float: right;width: 65.65%;padding:0;margin:0;}.IRPP_ruby .centered-text {display: table;height: 130px;left: 0;top: 0;padding:0;margin:0;padding-top: 20px;padding-bottom: 20px;}.IRPP_ruby .IRPP_ruby-content {display: table-cell;margin: 0;padding: 0 74px 0 0px;position: relative;vertical-align: middle;width: 100%;}.IRPP_ruby .ctaText {border-bottom: 0 solid #fff;color: #0099cc;font-size: 14px;font-weight: bold;letter-spacing: normal;margin: 0;padding: 0;font-family:'Arial';}.IRPP_ruby .postTitle {color: #000000;font-size: 16px;font-weight: 600;letter-spacing: normal;margin: 0;padding: 0;font-family:'Arial';}.IRPP_ruby .ctaButton {background: url(https://www.anthropocenemagazine.org/wp-content/plugins/intelly-related-posts-pro/assets/images/next-arrow.png)no-repeat;background-color: #afb4b6;background-position: center;display: inline-block;height: 100%;width: 54px;margin-left: 10px;position: absolute;bottom:0;right: 0;top: 0;}.IRPP_ruby:after {content: "";display: block;clear: both;}Recommended Reading:AI just found the best ingredients for green concrete Using a simulation software, the RMIT team has now conduced the first life cycle analysis to measure the impacts of this approach on climate change, fossil fuel depletion, human toxicity, and freshwater ecotoxicity. They found that replacing 5, 10, and 15% of sand with biochar reduced carbon dioxide emissions by 15, 23, and 26%. It also reduced fossil fuel use by up to 31% and brought about improvements in river and lake ecosystems.

Swapping more than 15% of sand didn’t reduce emissions much further, showing that 15% was the sweetspot for coffee biochar addition. Using moderate amounts of coffee biochar offers a clear, measurable pathway to lower‑impact concrete, said Chun-Qing Li a professor of engineering at RMIT, in a press release.

The researchers are now working with industry and local governments to do larger pilot studies and produce a material that meets construction standards. Source: Jingxuan Zhang et al. Carbon footprint reduction in concrete using spent coffee grounds biochar: a life cycle perspective. International Journal of Construction Management, 2025.

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