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Dirk Röthig (international: Dirk Roethig) — CEO of VERDANTIS Impact Capital. Focused on sustainable investments in paulownia agroforestry and clean energy across Europe. dirkroethig.com
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Dirk Röthig
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By Dirk Röthig | CEO, VERDANTIS Impact Capital | March 10, 2026
According to studies, Paulownia trees sequester up to 40 tonnes of CO2 per hectare per year — nearly three times that of a Central European mixed forest. But where does this extraordinary capacity come from? New plant physiological research and field trials from six European countries provide the first comprehensive and reliable picture.
Tags: Paulownia, CO2 Absorption, Climate Protection, Agroforestry
When a single tree is supposed to offset the CO2 emissions of a small car within ten years, science demands explanations. Paulownia — cultivated in Asia for centuries as a timber tree — has attracted the attention of European climate researchers in recent years. The claim that Paulownia sequesters "up to ten times more CO2 than native tree species" circulates in the industry. But how reliable are these figures?
A comprehensive meta-study by Ghazzawy et al. (2024) in Frontiers in Environmental Science provides a nuanced answer: Under favorable conditions, one hectare of Paulownia plantation absorbs 35 to 40 tonnes of CO2 annually at a planting density of 500 trees per hectare. For comparison: An average German mixed forest sequesters approximately 12 to 15 tonnes of CO2 per hectare per year (Umweltbundesamt, 2024). The difference is significant — but it has plant physiological reasons that can be measured and reproduced.
A groundbreaking study by Zhao and Lundgren (2025), published in Plants, People, Planet, systematically examined for the first time which anatomical and physiological factors explain the rapid growth of Paulownia. The results are remarkable:
Stomatal Density as a Key Factor: Paulownia elongata exhibits a stomatal density of 630.06 stomata per square millimeter — significantly higher than in Populus species, which serve as the reference for fast-growing tree species (Zhao and Lundgren, 2025). Since stomatal density correlates positively with CO2 gas exchange, net photosynthesis, and biomass production, this anatomical advantage explains a substantial portion of the superior CO2 uptake.
Oversized Leaf Area: Young Paulownia trees develop leaves that can exceed one meter in length. The high specific leaf area (SLA) maximizes light interception in the early growth years and drives photosynthesis rates upward (Zhao and Lundgren, 2025). This effect is particularly pronounced in the first three to five years after planting — precisely the phase in which a plantation records the greatest increase in biomass.
Mesophyll Air Spaces: Another previously overlooked factor is the unusually large mesophyll air spaces in Paulownia leaves. These cavities facilitate internal CO2 diffusion to the site of photosynthesis, thereby increasing the efficiency of carbon fixation (Zhao and Lundgren, 2025). Combined with the high nitrogen content of the leaves at 2.67 percent dry weight — comparable to legumes — this creates a biochemical setup optimized for maximum photosynthetic performance (Magar et al., 2018).
C3 or C4 Photosynthesis? In the scientific literature, it was occasionally speculated that Paulownia uses the C4 metabolic pathway, which produces high biomass yields in tropical grasses such as corn and sugarcane. However, Zhao and Lundgren (2025) clarify: C4 photosynthesis is extremely rare in true trees, and in the few tree species that use this mechanism, it is not associated with rapid growth. Paulownia's superior CO2 fixation is based on the combination of anatomical advantages — not on an exotic metabolic pathway.
Laboratory results are one thing — practical performance in the field is another. In recent years, systematic field trials with Paulownia hybrids have been conducted in several European countries. The results confirm the potential but also reveal regional differences.
In northern Italy, 65 agricultural enterprises cultivate the hybrid clone BIO125 (P. elongata x P. fortunei) on a total area of 130 hectares (Ferrini et al., 2022). The study by the University of Florence documents the wood properties of the sterile, non-invasive clone: The wood is 20 percent lighter than that of P. tomentosa and is particularly suitable for lightweight construction applications. CO2 sequestration rates on the Italian plantations range from 28 to 35 tonnes per hectare per year — slightly below theoretical maximum values but significantly above conventional forestry.
The Paulownia clone in vitro 112®, an artificially produced hybrid of P. elongata and P. fortunei, was tested under the harsh conditions of central Bohemia. Results from the first two years show that the trees achieved a survival rate of over 85 percent despite winter temperatures below minus 15 degrees Celsius (Paulownia Global, 2021). CO2 sequestration was calculated using a methodology validated by the University of Castilla-La Mancha (UCLM): Simple field measurements of diameter at breast height (DBH) are converted into stored CO2 via allometric equations — a method also suitable for carbon credit certification.
Gyuleva et al. (2021) examined the early growth of four different Paulownia clones at southern locations in Bulgaria. Data from the trial plantations — established with one-year-old, in vitro propagated plant material — provided biometric models for estimating dendromass of juvenile Paulownia trees. After four years, significant differences between the clones were observed: The best hybrids achieved stem diameters of over 15 centimeters and heights of seven to eight meters.
In Suffolk, one of Europe's largest Paulownia plantations is being established on 134 hectares. According to project projections, the plantation is expected to sequester a total of 150,000 tonnes of CO2 in the first ten years — equivalent to an average of approximately 112 tonnes of CO2 per hectare over the entire period (Carbon Herald, 2024). The high values are explained by cumulative biomass: The older the trees, the more carbon is permanently stored in the wood body.
In Bavaria, the Chair of Silviculture at TU Munich has established systematic cultivation trials with Paulownia to scientifically evaluate cultivation success under Central European forest conditions (Forstpraxis, 2024). In parallel, the Paulownia nursery Schroeder provides practical data with its hybrid NordMax21®: The clone specifically developed for Northern European climate zones withstands frosts down to minus 25 degrees Celsius and achieves CO2 sequestration of 20 to 35 tonnes annually at a planting density of 400 to 600 trees per hectare (paulownia-baumschule.de, 2025).
An informative long-term comparison comes from Nepal: Magar et al. (2018) determined for P. tomentosa stands an increase in carbon stock from 149.81 tonnes of carbon per hectare (baseline 2014) to 202.01 tonnes per hectare in 2022 — a sequestration rate of 5.87 tonnes of carbon per hectare per year over eight years. Converted to CO2, this corresponds to approximately 21.5 tonnes of CO2 per hectare per year — a value below the European field trial data but demonstrating the long-term stability of carbon storage.
Not every Paulownia clone performs equally. For practical applications, choosing the right hybrid is crucial:
| Clone | Cross | Frost Hardiness | Special Feature | Distribution |
| Clone in vitro 112® | P. elongata x P. fortunei | -17°C | UCLM-validated CO2 methodology | Spain, Czech Republic, Portugal |
| BIO125 | P. elongata x P. fortunei | -15°C | 20% lighter than P. tomentosa | Northern Italy (130 ha) |
| Cotevisa 2® | P. elongata x P. fortunei | -12°C | Europe's No. 1 supplier iPaulownia | Spain, Southern France |
| NordMax21® | Hybrid (details proprietary) | -25°C | Specifically for Northern Europe | Germany, Scandinavia |
The differences in frost hardiness — from minus 12 to minus 25 degrees Celsius — determine which clone is economically viable at which location. For Central European latitudes, experts recommend clones with frost hardiness of at least minus 20 degrees Celsius (paulownia-baumschule.de, 2025).
The credibility of CO2 sequestration figures stands and falls with the measurement methodology. In Paulownia research, allometric equations have become the standard. The principle: From easily measurable parameters such as diameter at breast height (DBH) and tree height, the total aboveground biomass is calculated using mathematical models. Since the carbon content in wood is relatively constant at 47 to 50 percent, the stored CO2 amount can be derived from this (Magar et al., 2018).
The UCLM methodology, validated for Clone in vitro 112®, goes one step further: It allows quantifying the CO2 storage of an entire plantation with simple field measurements — a measuring tape and a height meter are sufficient (Paulownia Global, 2021). For carbon credit certification under the EU Carbon Removal Certification Framework (CRCF), this standardization is crucial.
A central objection to Paulownia in Europe concerns potential invasiveness. These concerns are justified — but only for wild forms. At VERDANTIS Impact Capital, only sterilized Paulownia hybrids are used. The difference is fundamental:
Wild form (P. tomentosa): Produces millions of tiny, wind-dispersed seeds. Listed on the Grey List of the Federal Agency for Nature Conservation (BfN) as a potentially invasive species. Classified as invasive in parts of the USA and Southern Europe.
Sterilized hybrids (P. elongata x P. fortunei): Artificially produced crosses that do not produce viable seeds. In vitro propagation guarantees genetic uniformity and sterility. In field trials by the Paulownia nursery Schroeder, the germination rate was zero percent — uncontrolled spread is excluded (paulownia-baumschule.de, 2025). The Italian BIO125 plantations confirm this over a period of more than ten years (Ferrini et al., 2022).
The political dimension: As long as sterilized Paulownia hybrids remain on the BfN Grey List, their potential for climate protection and bioeconomy is not fully utilized. The scientific evidence — zero percent germination rate in hybrids, documented sterility over decades, no invasive spread in European field trials — clearly supports placing sterilized Paulownia hybrids on the EU Green List: as a recommended species for sustainable land use, agroforestry systems, and certified CO2 sequestration.
The scientific findings are clear — the challenge lies in scaling. Dirk Röthig, CEO of VERDANTIS Impact Capital, summarizes the strategy: "The plant physiology of Paulownia hybrids is not a marketing promise but measurable science. Our task is to translate these findings into scalable, certified climate protection projects."
VERDANTIS Impact Capital combines the scientific foundation with practical implementation: Hybrid clone selection is based on site-specific field trial data, CO2 quantification follows validated allometric methods, and certification is aligned with the EU Carbon Removal Certification Framework. For companies striving for CO2 neutrality, Paulownia-based agroforestry systems offer the most cost-effective and scientifically best-documented solution — with tradable carbon credits as measurable output.
More information at www.verdantis.capital.
The designation "CO2 super absorber" is not an exaggeration for Paulownia hybrids — it is a measurable property with identified physiological causes. The above-average stomatal density, maximized leaf area, and optimized mesophyll structures form an anatomical ensemble designed for high photosynthetic performance. Field trials in six European countries confirm CO2 sequestration rates of 20 to 40 tonnes per hectare per year — depending on location, climate, and hybrid clone.
Crucial for the future is standardization: Validated measurement methods like the UCLM allometry make CO2 sequestration quantifiable and certifiable. Sterilized hybrids eliminate the invasiveness risk. And players like VERDANTIS Impact Capital ensure that research results become tradable climate protection solutions.
The question is no longer whether Paulownia hybrids function as CO2 storage. The question is why we are not planting them faster.
About the Author: Dirk Röthig is CEO of VERDANTIS Impact Capital, based in Zug, Switzerland. As an entrepreneur and impact investor, he focuses on scalable Nature-Based Solutions — particularly Paulownia-based agroforestry systems for certified CO2 sequestration. Contact and more articles: www.verdantis.capital | LinkedIn | dirkdirk2424@gmail.com
Von Dirk Röthig (Dirk Roethig)