Regenerative water technology

Clean water from
biogas wastewater

SAFIA is a regenerative biofilter that turns the liquid digestate of biogas plants into reusable water and microalgae biofertiliser. It is built on three decades of ESA life-support research.

Talk to the team How it works
  • Inspired by ESA MELiSSA
  • Business to business
  • Built for a global market
Illustration of a biogas plant with digester, separator and storage tanks surrounded by trees

Water is too valuable to be treated as waste. Our vision is a world where every biogas plant returns clean water to the land, and the nutrients go back into the soil.

2–3 billionpeople face water shortages for at least one month a year [1]
80%of the world's sustainable biogas potential lies in emerging and developing economies [2]
Founders on several continentsA team as international as the problem it solves

The problem

A growing sector with an unsolved problem

Biogas plants are multiplying across Europe and the world, and every plant produces digestate. Most of what goes into a digester comes back out as a wet, nutrient-heavy stream that operators have to manage within strict legal limits.

1,975biomethane plants operating in Europe (Q2 2026) [3]
€36Bof private investment committed to European biomethane [3]
25 Mtof digestate dry matter produced in Europe in 2024 [4]
35 bcmEU biomethane target for 2030 (REPowerEU), so far more digestate is on the way [15]
  1. Biomass
  2. Digesterabout 10% leaves as biogas
  3. Digestatemost of the input mass
  4. Solid–liquid separator
  5. Liquid fractionwhere SAFIA works
    Solid fractioncomposting
Roughly 85–95% of what enters a biogas plant leaves as digestate, depending on the feedstock. Handling it lawfully is one of the industry's largest unresolved costs.

Today's options

Existing technologies move the problem elsewhere

1

Ammonia stripping

≈ €5–7 per m³ [5]

Recovers nitrogen, but phosphorus and salinity are left untouched. Profitability depends on a cheap source of heat.

2

Reverse osmosis

≈ €4–12 per m³ [6]

Produces clean permeate, but the contaminants are only concentrated into a brine, not eliminated. Membranes foul and need constant upkeep.

3

Direct land spreading

≈ €1–4 per m³ near the plant, rising steeply with distance [7]

Limited by available farmland and, in Nitrate Vulnerable Zones, by the 170 kg N/ha per year cap of the EU Nitrates Directive [8].

The SAFIA technology

One loop. Three reactors.

SAFIA treats the liquid fraction in a closed biological loop. Each reactor hosts a different community of microorganisms, and each one feeds the next. Gases are recycled inside the loop, and a digital twin keeps the whole system in balance.

Liquid fraction
CO₂recycled to the algae
  1. R1

    Heterotrophic

    Bacteria break down the organic load and release CO₂.

  2. R2

    Nitrifying

    Biofilms convert toxic ammonium into nitrate.

  3. R3

    Microalgae

    Microalgae take up nitrate, phosphate and CO₂, and release O₂.

O₂returned to R1 and R2
Biological digital twinA model of the living system predicts and steers each reactor in real time.
Clean waterTargeting about 95% water recovery for agricultural reuse
Microalgae biofertiliserNutrients recovered as a bio-based product

Space heritage

Born from ESA's MELiSSA programme

MELiSSA (Micro-Ecological Life Support System Alternative) is the European Space Agency's closed-loop life-support project, which started in 1989. More than 30 organisations from 10 countries have spent over three decades learning to recycle waste, water and air with chains of microorganisms, so that astronauts on long missions can live off a closed loop [9].

SAFIA brings that compartment logic down to Earth. It pairs bacterial and microalgae reactors in a regenerative loop, applied to one of the biggest liquid waste streams of the energy transition.

MELiSSA-derived technology already treats more than 1.8 million m³ of water a day worldwide, according to ESA [10].

The MELiSSA loop: crew waste is degraded by thermophilic anaerobic bacteria, then photoheterotrophic bacteria, then nitrifying bacteria, then microalgae and higher plants, which return oxygen, water and food to the crew. Closed loop Waste VFAs, minerals Ammonium Nitrate O₂, water, food C5 Crew C1 Thermophilic anaerobic bacteria C2 Photoheterotrophic bacteria C3 Nitrifying bacteria C4 Microalgae & higher plants
The MELiSSA loop, simplified. The circled compartments, nitrifying bacteria and microalgae, are the stages SAFIA brings to Earth. Adapted from ESA MELiSSA.

Business model

Business to business, for biogas producers

We work with biogas and biomethane plant operators who need to manage their wastewater. SAFIA turns that cost into two recoverable resources.

Reclaimed water

Process water fit for agricultural reuse, at a time when Europe is setting quality rules for water reuse (Regulation (EU) 2020/741) [11].

Microalgae biomass

A bio-based fertilising product for a European biofertiliser market forecast to triple, from about USD 0.7B in 2024 to USD 2.1B by 2033 [12], under the EU Fertilising Products Regulation [13].

Policy tailwinds

  • REPowerEU: 35 bcm of biomethane by 2030, about four times the 8.2 bcm installed today [3][15].
  • RENURE (Directive (EU) 2026/288): lets processed, manure-derived nitrogen be applied above the 170 kg N/ha cap. Nutrient recovery is becoming an asset [14].
  • Global demand: the IEA estimates sustainable biogas potential at nearly 1,000 bcm-equivalent a year, about a quarter of today's world gas demand [2].

Roadmap

From lab loop to TRL 6 in three years

  1. Year1

    Hardware & biological setup

    Core technical architecture, reactor start-up, and training of the biological digital twin.

  2. Year2

    Integration & stress testing

    Full system assembly and rigorous testing for stability and reliability.

  3. Year3

    TRL 6 validation & commercial prep

    Validation in a relevant operational environment and preparation for market entry.

State of the art

Where SAFIA sits in the research

Microalgae grown on digestate, nitrifying pretreatment and digital twins have each been shown to work separately. SAFIA's contribution is to combine them in one regenerative, controlled loop.

Energies · 2024

Nutrient recovery from digestate: a review

Stripping and struvite are mature; microalgae-based recovery is the emerging route.

Zielińska & Bułkowska Bioresource Technology · 2025

Long-term outdoor microalgae treatment of digestate

Long-term outdoor operation, with treatment savings of about €3.4 per m³ of digestate.

Rossi, Mantovani, Marazzi, Mezzanotte, Ficara Chem. Eng. Journal Advances · 2024

Ammonium pretreatment enables algae on digestate

Cutting ammonium by 95% made pilot photobioreactor cultivation possible. Ammonium control is the key step, and it is what SAFIA's R2 does.

Leca et al. Algal Research · 2024

Digital twins for algal cultivation

A framework for using digital twins to monitor and control algae systems, including wastewater cases.

Sheik et al. Membranes · 2025

Membranes for liquid digestate

Fouling and cost still limit full-scale membrane treatment of digestate.

Zielińska & Bułkowska ESA · MELiSSA

MELiSSA technology transfer

How ESA's closed-loop life-support research already reaches water treatment on Earth.

European Space Agency

Ecosystem

Partners

The MELiSSA partner for applications on Earth

SEMiLLA IPStar is a partner in the MELiSSA consortium. It looks after commercial applications of MELiSSA technology on Earth, working with the partners who developed each technology to turn it into products, pilots and companies in water, nutrients, food and circularity assessment.

  • GreenCoLabAlgae biotechnology collaborative laboratory
  • INESC TECSystems, computing and control research
  • A4F Algae for FutureIndustrial-scale microalgae production
  • LEPABE, University of PortoProcess engineering, environment and biotechnology

Get in touch

Let's talk water

Investors, biogas operators, research partners and journalists are all welcome. Tell us who you are and we'll get back to you.

  • Investors: the opportunity, roadmap and team
  • Biogas operators: pilots and site assessments
  • Partners: research, engineering and funding programmes
I am reaching out as

Sources
  1. UNESCO, UN World Water Development Report 2023.
  2. IEA, Outlook for Biogas and Biomethane.
  3. EBA / GIE, European Biomethane Map 2026 update.
  4. European Biogas Association, Digestate in Europe: state of play 2026.
  5. Bolzonella et al. (2018), nutrient recovery from digestate at full scale.
  6. Zielińska & Bułkowska (2025), Membranes.
  7. Consorzio Italiano Biogas (2024), optimised digestate distribution.
  8. Council Directive 91/676/EEC, Nitrates Directive.
  9. ESA, MELiSSA: how it began.
  10. ESA, MELiSSA technology transfer.
  11. European Commission, Water Reuse Regulation (EU) 2020/741.
  12. IMARC Group, Europe Biofertilizer Market.
  13. Regulation (EU) 2019/1009, Fertilising Products Regulation.
  14. European Commission (2026), RENURE measures.
  15. European Commission, Biomethane and REPowerEU.