90,000 Tons CO₂e annually by 2040. This is the reduction potential of increased miscanthus use in construction in Denmark. This is the ambition of the new project, PROMISE, which includes Aarhus University, Roskilde University, and DTU in collaboration with StrawTech, Saint-Gobain Denmark A/S, and crop farmer Ole Møller Helbæk from Thise. GUDP has granted approximately 8.5 million DKK to PROMISE to expand the applications of miscanthus and transform it into a high-value crop.

Miscanthus is highly effective at capturing and storing CO₂ from the atmosphere. Once established, it requires minimal maintenance for more than 20 years while remaining on the land. Additionally, miscanthus provides excellent shelter for wildlife and insects.

Despite its many desirable properties, the crop has only seen limited adoption in Denmark. The primary reason for this is that miscanthus has not yet played a significant role in feed or food production. As a result, it has remained a low-value crop, making it less attractive for farmers to cultivate.

Combining Green Biorefining and Pyrolysis

PROMISE will divide the miscanthus harvest into an autumn harvest and a spring harvest. Project leader Aidan Mark Smith, Associate Professor at Aarhus University, explains:

"In the autumn, when the carbon content of miscanthus peaks, we harvest the green leaves. From these leaves, we extract protein that can be used as feed for monogastric animals. This expands the use of miscanthus from being solely an energy crop to also becoming a feed crop."

The protein extraction will take place through green biorefining. This process leaves behind a protein paste suitable for feed, along with a fiber fraction.

The fiber fraction is not suitable as feed, which is why the project is exploring the potential to produce biochar from this fraction.

The reason for harvesting only the leaves in autumn while leaving the stems in the field over winter is that the stems dry naturally in late winter, reducing their mineral content.

When the dried stems are harvested in the spring, the biomass undergoes pyrolysis to create biochar, binding carbon into stable carbon molecules that remain intact on a geological timescale.

"The second aspect we are investigating in the project is how we can use biochar from miscanthus in building materials. Buildings typically last at least 50 years, but if biochar can be incorporated into construction materials that are not burned at the end of their lifespan, it would be a highly effective way to store carbon," explains Aidan Mark Smith. He continues:

"Fundamentally, we are taking a crop that grows exceptionally well in Denmark, absorbs significant amounts of CO₂ from the atmosphere, converts it into feed and building materials, and allows the agricultural and construction sectors to share in reducing their climate footprint with this method."

The construction materials in which biochar is expected to be used are based on geopolymer technology, which repurposes mineral wool waste as a substitute for cement.

The project aims to reduce CO₂ emissions by 90,000 tons CO₂e annually by 2040 through the cultivation of 5,000 hectares of miscanthus—achieved partly through land-use changes and bio-based energy production and partly by storing carbon in biochar.

Additionally, the perennial growth of miscanthus—with its deep, permanent root system and low nitrogen requirements—is expected to reduce nitrogen leaching by more than 200 tons per year.

*PROMISE received a project grant approval in GUDP’s second application round in 2023 and is expected to be completed by the end of 2027.

About the project

Project Title: PROMISE - Products of Miscanthus - Multipurpose production and use of miscanthus for food, materials, and negative emissions

Approved Grant: 8,408,856 DKK

Project Duration: April 2024 – December 2027

Project Participants: Aarhus University, Roskilde University, DTU, Saint-Gobain Denmark A/S, StrawTech, Ole Møller Helbæk

Project Leader: Aidan Mark Smith, Associate Professor at Aarhus University

Read more on StrawTech project website