# Harbin team turns rice husks into biochar that adsorbs 6.01 mmol/g CO₂ at 0 °C in lab tests

- Published: 2026-11-05 08:40 UTC
- Section: Machines & Making › Materials science
- Tags: rice husk biochar, CO₂ adsorption at ambient pressure, adsorption-compressed CO₂ energy storage, hierarchical porous carbon, nitrogen-doped biochar, micropores 0.7 nm, CO₂ regeneration cycles, molecular dynamics and DFT, The Innovation Energy
- URL: https://realtech.media/news/rt-1d8e821d35efe7ba3ae0a46f_harbin_team_turns/

**Laboratory-stage biochar from rice husks adsorbed 6.01 mmol of CO₂ per gram at 0 °C and kept 92.05% of its capacity after 20 cycles, a candidate for adsorption-compressed CO₂ energy storage.**

![Harbin team turns rice husks into biochar that adsorbs 6.01 mmol/g CO₂ at 0 °C in lab tests](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/f8831e1897867e86.jpg)
*Minh Ha-Duong, Wikimedia Commons, CC BY-SA 4.0*

Researchers at Harbin Institute of Technology have made a porous biochar from rice husks that adsorbs CO₂ at ambient pressure and releases it over repeated cycles, according to a study in The Innovation Energy (2026, vol. 3, issue 1, article 100131) [1]. The material, named UHTCK, adsorbed 6.01 mmol of CO₂ per gram at 0 °C and retained 92.05% of its capacity after 20 adsorption-desorption cycles, the authors report [1].

The work addresses adsorption-compressed CO₂ energy storage, one option for smoothing the intermittency of wind and solar power. Conventional compressed-gas storage depends on high-pressure equipment, which is costly and safety-sensitive. The adsorption variant instead uses materials that bind CO₂ at ambient pressure and release it on demand, so the adsorbent must hold a lot of gas, take it up quickly and give it back easily [1].

## Pore structure and synthesis

The biochar was produced in two steps: hydrothermal treatment of rice husks, an agricultural waste, followed by chemical activation with potassium hydroxide [1]. The result is a hierarchical pore system. Narrowly distributed micropores centered at about 0.7 nm serve as storage volume, and a developed network of mesopores works as transport channels. Nitrogen-containing functional groups are deliberately introduced onto the pore surfaces [1].

Diffusion modeling showed that the connected pores speed up gas transport during uptake and release [1]. Nitrogen-doped mesopores were found to optimize diffusion kinetics [1].

## Mechanism from simulations

The team combined adsorption measurements with molecular dynamics simulations and density functional theory calculations to relate pore structure to adsorption-desorption equilibrium [1]. The simulations showed CO₂ confined as a monolayer in micropores and accumulating near the walls of mesopores [1].

Functional groups at the pore edges raise surface polarity. Nitrogen and oxygen groups form weak, electrostatic, hydrogen-bond-like interactions with CO₂: strong enough to hold the molecules, weak enough to let them leave quickly [1]. According to the authors, high microporosity provides the storage capacity, while nitrogen-functionalized surfaces and mesopores balance adsorption and heat, which meets the requirements of adsorption-compressed CO₂ storage at ambient conditions [1].

The study remains a laboratory materials investigation. Capacity was measured at 0 °C, and real storage systems will impose their own temperature and pressure schedules. The authors present the combination of ordered multiscale pores and controlled surface chemistry as a set of design principles for CO₂ capture materials that operate without high-pressure hardware [1].

## Sources

1. [The Innovation Energy](https://doi.org/10.59717/j.xinn-energy.2026.100131)
2. [EurekAlert](https://www.eurekalert.org/news-releases/1150406)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-1d8e821d35efe7ba3ae0a46f_harbin_team_turns/