In the quest for sustainable construction materials, a team of researchers from the Instituto de Ciencia y Tecnología del Carbono (INCAR) in Oviedo, Spain, has uncovered promising potential in an unlikely source: organic waste. Led by Álvaro Amado-Fierro, the team has been exploring the use of hydrochar, a carbon-rich product derived from hydrothermal treatment of organic waste, as a partial substitute for cement in mortars. Their findings, published in Case Studies in Construction Materials, could pave the way for more eco-friendly and cost-effective building materials, with significant implications for the energy sector.
The construction industry is a major consumer of energy and producer of carbon emissions. Cement production alone accounts for about 8% of global CO2 emissions, according to the International Energy Agency. This is where hydrochar comes in. By using organic waste as a raw material, hydrochar production can help divert waste from landfills and reduce the demand for virgin materials. Moreover, the hydrothermal process used to create hydrochar requires less energy than traditional cement production methods.
Amado-Fierro and his team have been investigating the properties of hydrochar derived from stabilized organic waste. “We found that hydrochar has distinct physicochemical properties compared to wood-based biochar, which has been more widely studied,” Amado-Fierro explains. “This makes it an interesting candidate for use in construction materials.”
The researchers created mortar samples with 2.5% of the cement replaced by hydrochar or biochar. They then monitored the hydration process over 28 days. What they found was intriguing: while the control samples and those with biochar showed early formation of portlandite, a key component of cement hydration, the hydrochar-containing samples showed delayed hydration. This delay, confirmed by advanced statistical techniques, resulted in a compressive strength of around 16 MPa, about 70% lower than that of the control after 28 days of curing.
However, this lower strength doesn’t necessarily mean hydrochar is a non-starter for the construction industry. “The reduced compressive strength limits its use to non-structural applications, such as masonry and low-load pavements,” Amado-Fierro notes. “But there are several alternative approaches we’re exploring to overcome these limitations.”
One such approach could involve combining hydrochar with other supplementary cementitious materials, like fly ash or silica fume, to enhance its strength and durability. Another could be to optimize the hydrothermal treatment process to tailor the properties of the hydrochar to better suit its intended use.
The potential commercial impacts of this research are substantial. If hydrochar can be successfully integrated into construction materials, it could open up new markets for waste management companies and create opportunities for energy providers to offer hydrothermal treatment services. Moreover, it could help construction companies meet increasingly stringent environmental regulations and reduce their carbon footprints.
The energy sector, in particular, stands to benefit. As the world transitions to renewable energy, the demand for sustainable and low-carbon construction materials is only set to grow. Hydrochar, with its potential to reduce waste and lower energy consumption, could play a key role in this transition.
The research by Amado-Fierro and his team is a significant step forward in this field. By shedding light on the unique properties of hydrochar and the challenges it presents, they’ve opened up new avenues for exploration. As they continue to refine their approach and overcome the limitations of hydrochar, the future of sustainable construction looks increasingly bright. The findings were published in Case Studies in Construction Materials, a journal that focuses on the practical application of construction materials research.