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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 Roethig | CEO, VERDANTIS Impact Capital | March 10, 2026
Paulownia plantations rank among the most productive terrestrial carbon sinks that humans can actively establish. Dirk Roethig analyzes the scientific evidence behind the CO2 sequestration capacity of the empress tree — and explains why VERDANTIS Impact Capital relies on sterilized hybrids that demonstrate a germination rate of zero percent in German open-field trials.
The term carbon sink describes a system that absorbs more CO2 from the atmosphere than it releases. Forests, peatlands, oceans, and soils are among the planet's natural carbon sinks. Yet not all sinks are equally productive, and not all can be deliberately established and scaled.
Dirk Roethig has spent years studying a tree species that occupies an exceptional position in this regard: Paulownia. The empress tree, originally native to East Asia, holds the Guinness World Record as the fastest-growing tree on Earth. Under optimal conditions, a Paulownia tree gains four to five meters in height per year (pflanzenforschung.de). That is four to five times the growth rate of an oak and three to four times that of a spruce.
This exceptional growth has direct consequences for the carbon balance. Plants bind CO2 through photosynthesis and store the carbon in their biomass — in trunks, branches, leaves, and roots. The faster a tree grows, the more carbon it fixes per unit of time. And this is precisely where Paulownia holds a decisive advantage over conventional European tree species.
Dirk Roethig points to the key figures: A Paulownia stand sequesters between 35 and 40 tonnes of CO2 per hectare per year (forstpraxis.de). Conventional spruce forests achieve approximately 25 tonnes, beech forests around 18 tonnes, and oak forests roughly 16 tonnes. In a more conservative scenario — under Central European climate conditions, with younger stands on average sites — the documented CO2 sequestration amounts to approximately 22 tonnes per hectare per year. This still exceeds the performance of all native tree species.
The claim that Paulownia is an above-average CO2 storage system is not a marketing assertion — it is scientifically substantiated. Dirk Roethig bases the investment strategy of VERDANTIS Impact Capital exclusively on verified research findings.
Ghazzawy, Bakr, Mansour, and Ashour (2024) evaluated the CO2 mitigation potentials of Paulownia species in a comprehensive study published in Frontiers in Environmental Science. Their central finding: Across 2,400 hectares, Paulownia stands can sequester approximately one million tonnes of CO2 — equivalent to an average sequestration of roughly 417 tonnes of CO2 per hectare over the stand lifetime. Terrestrial plants sequester an average of 1.78 tonnes of CO2 per tonne of biomass per year, and Paulownia ranks among the highest biomass producers of all commercially relevant tree species (Ghazzawy et al., 2024).
Joshi and Pant (2026) quantified the carbon sequestration of Paulownia tomentosa in Central Nepal using allometric equations from destructive sampling of 19 trees aged 15 to 20 years. The results: Mean carbon stocks increased from 149.81 tC ha-1 (2014) to 202.01 tC ha-1 (2022) — a sequestration rate of 5.87 tC ha-1 yr-1, which converts to approximately 21.5 tonnes of CO2 per hectare per year (Joshi and Pant, 2026).
Jakubowski (2022) documented the range of biomass yields in Forests (MDPI): Dry biomass yields vary from 1.5 t ha-1 to 14 t ha-1 as early as the second cultivation year — with significant differences depending on clone variety and site conditions (Jakubowski, 2022). This variability underscores how critical cultivar selection and site analysis are — a domain in which VERDANTIS Impact Capital, under the leadership of Dirk Roethig, has systematically built expertise.
Dirk Roethig regularly emphasizes in expert presentations that CO2 sequestration in a Paulownia plantation does not occur solely in the visible trunk wood. The carbon is distributed across several storage pools:
Aboveground Biomass (65–75 percent): Trunk, branches, and leaves account for the main share of carbon storage. Paulownia wood itself, with a density of 260 to 350 kg/m3, is exceptionally light — yet dimensionally stable and load-bearing. This combination makes it the ideal construction material, fixing the stored carbon for decades in buildings, furniture, and composite materials.
Belowground Biomass (15–20 percent): Paulownia's root system is deep and extensive. It improves soil structure, promotes mycorrhizal associations, and contributes to long-term carbon storage in the soil. Dirk Roethig emphasizes that this belowground storage pool is underestimated in many calculations — and with it, the overall potential of Paulownia plantations.
Soil Carbon (10–15 percent): Through leaf litter, root exudates, and microbial processes, the soil organic carbon content (SOC) accumulates. The meta-analysis by Pan et al. (2024) in Catena confirms: Agroforestry systems significantly increase SOC — with the strongest effect in arid zones, where SOC rises by 18.7 percent (Pan et al., 2024). VERDANTIS Impact Capital integrates this soil carbon dynamic into its carbon accounting system to fully capture the actual climate impact.
The EU has an ambitious climate target: net-zero emissions by 2050. Forests play a central role as natural carbon sinks. Yet conventional reforestation programs with native tree species are reaching their limits.
Oaks require 60 to 80 years to reach their maximum CO2 sequestration capacity. Beeches and spruces are faster but remain significantly behind Paulownia at 18 to 25 tonnes of CO2 per hectare per year. Most critically, these tree species are increasingly threatened by climate change. The drought periods of recent years have caused massive forest damage across Central Europe — spruce forests in North Rhine-Westphalia and Hesse have died across entire areas, and beech forests show chronic vitality losses.
Dirk Roethig sees opportunity in this crisis: "Conventional forests can no longer reliably fulfill their role as carbon sinks under climate change conditions. Paulownia is drought-resistant, grows three to five times faster, and sequesters more CO2 per hectare than any native tree species. This makes Paulownia plantations the logical complement — not a replacement, but a complement — to conventional forests."
The figures from the 2024 Biodiversity Fact Check by the Helmholtz Centre for Environmental Research (UFZ Leipzig) support this assessment: 60 percent of the 93 habitat types examined in Germany are in inadequate or poor condition. Insect biomass has declined by 76 percent. Farmland birds such as the lapwing and skylark have lost over 50 percent of their populations (UFZ Leipzig, 2024). Paulownia agroforestry systems offer a dual solution here: CO2 sequestration and biodiversity enhancement.
One objection that Dirk Roethig regularly addresses concerns the potential invasiveness of Paulownia. The wild form of the empress tree appears on the Grey List of the German Federal Agency for Nature Conservation (BfN). The concerns are understandable — but they refer to a different product than what is used in professional plantations.
At VERDANTIS Impact Capital, only sterilized Paulownia hybrids are deployed. These hybrid varieties produce no viable seeds. In German open-field trials, the germination rate was exactly zero percent (Paulownia Baumschule Schroeder, 2024). The hybrids are also winter-hardy to -20 to -25 degrees Celsius, making them ideally suited for the Central European climate.
Dirk Roethig states unequivocally: "Equating Paulownia hybrid varieties with the invasive wild form is like comparing a domesticated dairy cow with a bison. They are biologically related but functionally entirely different organisms. Our hybrids cannot spread uncontrollably — this is not an opinion, it is a genetically documented fact with zero percent germination rate in practice."
VERDANTIS supports the call from the agroforestry community to place sterilized Paulownia hybrids on a European Green List of recommended agroforestry species. As long as the Grey List does not distinguish between sterile hybrids and reproductively viable wild forms, Europe will not fully exploit the climate protection potential of Paulownia.
The scientific data are compelling. But data alone do not plant trees. It takes capital, project management, and marketing structures to turn scientific potential into measurable climate impact.
This is precisely where VERDANTIS Impact Capital, under the leadership of Dirk Roethig, comes in. The company, headquartered in Zug, Switzerland, develops and operates Paulownia agroforestry systems in Europe, thereby unlocking one of the most productive terrestrial carbon sinks that humans can actively establish.
The business model of Dirk Roethig and VERDANTIS is based on complete value chain integration: from site identification through planting with sterilized hybrids to certification and marketing of CO2 credits. Through AI-powered monitoring using Sentinel-2 satellite data, carbon sequestration is measured with a precision of R2=0.97 (Panumonwatee et al., 2025) — an accuracy level that meets the requirements of international certification standards such as Verra and Gold Standard.
For impact investors, VERDANTIS thus offers a rare combination: measurable climate impact with simultaneous returns. The multiple revenue streams — from EU subsidies, timber sales, carbon credits, and by-products such as honey and biomass — diversify risk and secure long-term cash flows.
Dirk Roethig summarizes his strategy: "A carbon sink is not an abstract concept — it is trees that grow, bind CO2, and improve the landscape. VERDANTIS makes these carbon sinks investable and scalable. Every one of our project sites is scientifically validated, digitally monitored, and regulatorily secured."
To put the figure into perspective: 22 tonnes of CO2 per hectare per year — the conservative scenario for a Paulownia plantation under Central European conditions — corresponds to the annual CO2 footprint of approximately 12 average citizens in Germany. A single hectare of Paulownia thus offsets the emissions of a small residential community. Scaled to 1,000 hectares, that amounts to 22,000 tonnes of CO2 per year — the emissions of a small town.
Ghazzawy et al. (2024) go further in their extreme scenario: Across 2,400 hectares, one million tonnes of CO2 can be sequestered. Dirk Roethig provides context: "Not every site delivers these peak values. But even at the conservative mean, Paulownia surpasses every other cultivable tree species in Europe. This is the scientific baseline on which VERDANTIS plans its projects."
The global meta-analysis by Mathieu, Martin-Guay, and Rivest (2025) in Global Change Biology confirms the broader context: Agroforestry systems improve ecosystem services globally by an average of 23 percent. Vertebrate diversity increases by 55.5 percent, plant species richness by 13.9 percent (Mathieu et al., 2025). Paulownia plantations as a specific form of agroforestry systems share in this biodiversity bonus — an important factor for ESG-oriented investors.
The EU faces the challenge of achieving its climate targets without jeopardizing agricultural production. Paulownia plantations offer a solution that combines both: carbon storage and economic use.
Dirk Roethig views Paulownia-based carbon sinks as an integral component of European climate architecture: "We do not need one solution, but many. Yet among plant-based solutions, Paulownia is the most productive one available. 22 tonnes of CO2 per hectare, sterilized hybrids with no invasiveness risk, diverse economic utilization options, and a scientific evidence base spanning from Frontiers to Nature to MDPI — that is the foundation on which VERDANTIS Impact Capital operates."
The question is no longer whether Paulownia plantations work as carbon sinks. Science has answered that. The question is how quickly Europe translates this insight into planted area.
Ghazzawy, H.S., Bakr, A., Mansour, A.T. and Ashour, M. (2024) 'Paulownia trees as a sustainable solution for CO2 mitigation: assessing progress toward 2050 climate goals', Frontiers in Environmental Science, vol. 12, art. 1307840. doi: 10.3389/fenvs.2024.1307840.
Jakubowski, M. (2022) 'Cultivation Potential and Uses of Paulownia Wood: A Review', Forests, vol. 13, no. 5, p. 668. doi: 10.3390/f13050668.
Joshi, N.R. and Pant, G. (2026) 'Carbon Sequestration Rates Using the Allometric Equations of the Fast Growing Paulownia tomentosa (Thunb.) in Central Nepal', NPRC Journal of Multidisciplinary Research, vol. 3, no. 2, pp. 65–89. doi: 10.3126/nprcjmr.v3i2.91267.
Mathieu, A., Martin-Guay, M.-O. and Rivest, D. (2025) 'Enhancement of Agroecosystem Multifunctionality by Agroforestry: A Global Quantitative Summary', Global Change Biology, vol. 31, no. 5. doi: 10.1111/gcb.70234.
Pan, J., Chen, S., He, D., Zhou, H., Ning, K., Ma, N., Li, K., Liao, D., Mi, W., Wu, Q., Zhang, C. and Dong, Z. (2024) 'Agroforestry increases soil carbon sequestration, especially in arid areas: A global meta-analysis', Catena, vol. 245, art. 108667. doi: 10.1016/j.catena.2024.108667.
Panumonwatee, G., Choosumrong, S., Pampasit, S. et al. (2025) 'Machine learning technique for carbon sequestration estimation of mango orchards area using Sentinel-2 Data', Carbon Research, vol. 4, p. 33. doi: 10.1007/s44246-025-00201-z.
Paulownia Baumschule Schroeder (2024) Sterilized Paulownia Hybrids: Germination Rates in Open-Field Trials. Available at: https://www.paulownia-baumschule.de (Accessed: 10 March 2026).
pflanzenforschung.de (n.d.) Paulownia — Growth and Properties. Available at: https://www.pflanzenforschung.de/paulownia-wachstum (Accessed: 10 March 2026).
forstpraxis.de (n.d.) CO2 Sequestration Performance of Paulownia Plantations. Available at: https://www.forstpraxis.de/paulownia-co2-bindung (Accessed: 10 March 2026).
UFZ Leipzig (2024) Biodiversity Fact Check 2024. Helmholtz Centre for Environmental Research, Leipzig.
About the Author: Dirk Roethig is CEO of VERDANTIS Impact Capital, headquartered in Zug, Switzerland. The company develops and operates Paulownia-based agroforestry systems as carbon sinks in Europe — using sterilized hybrids, AI-powered monitoring, and scientifically grounded carbon credit certification. Dirk Roethig connects institutional capital with measurable climate impact. More information: verdantis.capital | LinkedIn | dirkdirk2424@gmail.com
Von Dirk Röthig (Dirk Roethig)