On 16–17 October 2025, the partners of S2B – Solar to Butanol – met in Stockholm, Sweden, to celebrate the project’s first year of activities.
Hosted by SciLifeLab at KTH, the consortium meeting combined scientific discussions with a lab visit, allowing partners to see where part of the S2B experiments are conducted.
Turning sunlight and CO2 into butanol: where we stand after one year
S2B aims to develop the next generation of photosynthetic microbes entrapped in nanomaterials that efficiently produce butanol, shifting conventional microbial suspensions to an artificial leaf architecture.
In the first year, the consortium made progress on three main fronts:
- Engineering photosynthetic microbes with the aim to channel more carbon and energy toward butanol.
- Developing advanced materials and reactor concepts to host the cells, capture sunlight and atmospheric CO2 to generate more butanol.
- Assessing the sustainability and feasibility of the overall concept from environmental, economic, and social perspectives.
Progress in engineering the microbial production system
The first year has focused on better understanding the photosynthetic machinery and tuning the cyanobacterial host that will drive S2B’s solar-to-butanol conversion.
Partners have:
- Designed and tested new metabolic engineering strategies to redirect carbon flux toward butanol.
- Explored how to increase photosynthetic performance and robustness under relevant operating conditions.
- Developed modelling approaches to describe butanol production and to help guide future strain improvement and process design.
Together, these efforts provide a scientific basis for building more efficient photosynthetic cell factories in the coming years of the project.
Building the solid-state platform: materials and reactor concepts
In parallel, S2B is advancing the materials and engineering side of the concept.
Over the past year, the consortium has:
- Developed and tested functional nanomaterials for cell immobilisation.
- Explored strategies for CO₂ capture and delivery at the cell level.
- Started integrating these elements into prototype reactor concepts, supported by multiphysics models that connect the processes inside the material with reactor design and operation.
These developments are essential steps toward future lab-scale prototypes that will demonstrate a more efficient solar butanol production.
Evaluating sustainability and feasibility from the start
Sustainability is a central pillar of S2B. Rather than being assessed only at the end, environmental, economic and socio-economic aspects are included from the beginning. Meaning that primary data is still largely missing, this, data is complemented from project targets and literature.
During the first year, partners have:
- Conducted preliminary Life Cycle Assessment (LCA) to identify environmental hotspots and improvement options.
- Performed preliminary Techno-Economic Assessment (TEA) to explore cost drivers and economic viability at different scales.
- Started developing a Social Life Cycle Assessment (S-LCA) to better understand potential social impacts and acceptance aspects.
These early evaluations support design choices across the value chain and will be refined as more data from ongoing experiments and prototypes becomes available.
What’s next?
As S2B enters its second year, the consortium will continue to:
- Refine engineered strains and biological models,
- Integrate materials and cells into improved solid-state prototypes,
- Test these systems under operating conditions,
- And update sustainability assessments based on new experimental data.
Updates on the following milestones, as well as videos and stories from the teams, will be shared on the project website and social media.
