A ring of glass and algae

700m² of algae absorbs more CO₂ than the building emits

−1,310 t

building net CO₂ over 20 years

700 m²

algae wall entire facade

grid electricity 100% solar

65,500

trees equivalent per year

Design section · plan · algae facade

section (top) + plan (bottom) · algae facade covers the entire south side

Carbon Ledger building only · 20 years

building materials + transport +60 t

occupant respiration (4 people × 20 years) +30 t

total emissions +90 t

algae wall (700m²) · uptake 20 years −1,400 t

building net −1,310 t CO₂

≡ 65,500 trees · one year of CO₂ absorption

Total Budget: $28,000,000

Hempcrete + bamboo + strawboard$10,000,000 Algae wall system (700m²)$5,000,000 Solar PV (30kW)$3,000,000 Ground-source heat pump (200m)$3,000,000 Glass curtain wall$6,000,000 Electric construction fleet (rental)$2,000,000 Forest restoration (20ha) · extra$4,000,000

Forest restoration is a separate project — not included in building carbon math

🌲 20 hectares of forest were planted around the building. This is not included in the carbon math — the building already achieves net‑negative on its own. The forest absorbs an additional 50 tonnes of CO₂ per year (1,000 tonnes over 20 years), but it's a separate restoration project. +50 t/yr

Grand Challenges climate project connections

How We Make Things

hempcrete + bamboo + strawboard — agricultural waste, no trees cut.

How We Plug In

30kW solar PV + Spanish grid (56% renewable) as backup — no battery.

How We Heat / Cool

1m hempcrete walls + 200m ground‑source heat pump — passive temperature control.

How We Get Around

EV charging + e‑bike storage — solar‑powered mobility.

Location why Andalusia, Spain

Andalusia, Spain · 3,000+ sun‑hours / year

solar 2× Norway hempcrete local supply chain grid 56% renewable + rising climate mild winter, manageable summer