The Earth Prize 2026 · Scholar Phase HewaSafi Innovators Hybrid Exhaust Purification & Carbon Capture System · M-Pesa Foundation Academy, Kenya
HewaSafi Innovators team photo
93% Particulate Matter Reduction
42% Carbon Monoxide Reduction
$125 Total Prototype Cost (KES 16,288)
21% CO₂ Absorption via Spirulina
Problem Statement

Nairobi ranks among Africa's most polluted cities, PM2.5 concentrations reach 31.2 µg/m³, six times the WHO safe limit[1,2], and air pollution kills an estimated 21,000 Kenyans annually[4]. Of Kenya's 3.5 million registered vehicles, 65% are over ten years old[5] and many operate without functional emission controls.

Scale

Local: Nairobi neighbourhoods near transport corridors (Eastlands, Githurai, Kawangware) — PM2.5 exceeds 80 µg/m³ during peak hours.[3] National: 3.5M vehicles across Kenya's urban centres. Global: Identical conditions in Kampala, Lagos, Accra — 330M+ urban Africans exposed.

Who is affected

Residents near corridors: 2.3× higher respiratory illness rates.[3] Matatu & boda boda operators: cannot afford KES 15,000–50,000 converters. Children & elderly: highest vulnerability to PM2.5-linked asthma and reduced lung development.

Why current solutions fail:

  • Catalytic converters cost KES 15,000–50,000, up to two months' income for a typical boda boda rider[14]
  • 2,400+ catalytic converter thefts recorded in Nairobi in 2023 alone, operators cannot afford to replace stolen units[14]
  • Regulatory enforcement is weak: only 42% of commercial vehicles undergo mandatory annual inspection[11]
  • Residents near transport corridors suffer respiratory illness at 2.3× the rate of those in low-pollution areas
Proposed Solution

We engineered a five-stage Hybrid Exhaust Purification and Carbon Capture System using locally sourced, waste-derived materials, the world's first multi-stage exhaust retrofit built from coconut shells, agricultural waste, and repurposed battery components, at a fraction of existing costs.

1
Steel Mesh Filter
Fine metal sieve catches soot & dust particles (3-layer, 40-mesh)
93% PM↓
2
Activated Carbon
Waste coconut shells baked into carbon — works like a water filter for air
Traps gases & smells
3
Chemical Catalyst
Converts toxic CO gas to harmless CO₂ using copper from recycled batteries
42% less CO
4
Copper Coil Cooler
Cools exhaust from ~320°C to ~40°C — safe temperature for live algae
Safe for algae
5
Spirulina Bioreactor
Live algae (from Lake Naivasha) absorbs remaining CO₂ as it grows[9,10]
21% CO₂↓

🌱 Materials Origin

Coconut shells & maize cobs baked at 450–500°C into activated carbon — the same material used in water filters and gas masks. Filtering power (iodine value): 850 mg/g[7,8] — matches commercial grade at <10% of the cost. Kenya generates 400,000 MT of coconut shell waste annually.

💰 Cost Advantage

Platinum converter KES 15,000–50,000
HewaSafi system KES 16,288
97–99% cheaper

⚗️ Key Innovation

Our copper-manganese catalyst (CuO/MnO₂) — made from recycled batteries — activates at 110–125°C[6], exactly the exhaust temperature of a typical matatu. Standard platinum converters need 400–800°C to work. No warm-up, no external heating, cleaning starts from the moment the engine does.

Implementation
1
Raw material collection: Coconut shells sourced from Mama Njoki's foundry in Naivasha (500 kg/month, KES 50/kg) and maize cobs from local farms — transported to Kayole Jua Kali workshop.
2
Pyrolysis & carbon production: Shells heated to 450–500°C in Muranga University kiln, producing activated carbon. Dr. James Githinji's team pressure-tests each batch (KES 200/unit); iodine value confirms commercial-grade quality.
3
Component assembly: Five Jua Kali welders at Kayole fabricate the steel mesh housing, copper coil cooler, and catalyst chamber at KES 3,000/unit. Chairman Joseph Mwaura oversees quality control.
4
Installation & pilot deployment: 30-minute bolt-on fit to matatu exhaust — no engine modification. 15 Route 46 vehicles (MOU signed, Dec 2025) run 90-day live pilot; MQ-7 sensors upload data to hewasafi.com.
5
Scale-up to 200 units: Units rolled out via Eastleigh SACCO (8,000 members) at KES 600/month × 30 months — fully offset by KES 2,500/month fuel savings; operators net-positive from month 1.
Stakeholders & Beneficiaries
Implementation Partners
✔️
Kayole Jua Kali Association Workshop & fabrication hub; 12 artisans; KES 3,000/unit — direct employment income.
✔️
Matatu Welfare Association (Route 46) 15-vehicle pilot, MOU signed Dec 2025; validates performance before wider roll-out.
✔️
Muranga University of Technology Lab testing & quality assurance; practicum researchers; academic validation.
✔️
NEMA (Kenya) & Eastleigh SACCO Eco-compliance certification (in progress) · 8,000-member financing & distribution channel.
Direct Beneficiaries
✔️
Matatu Drivers & Passengers KES 2,500/month fuel savings per driver; cleaner cabin air for 15+ passengers per trip.
✔️
2.3M Eastlands Residents Reduced PM2.5 exposure; 340 fewer respiratory hospital visits/year. Children & elderly most protected.
Communication Plan
🌐 Digital Platform
Website hewasafi.com — live sensor data dashboard, project updates, installation guides.
Social @HewaSafi on Instagram & TikTok — Swahili/Sheng content: installation walkthroughs, fuel-saving calculators & driver testimonials.
Cost ~KES 2,000/month hosting · social media zero-cost · total under $200/yr
📻 Community Outreach
Live Demos Monthly demonstration days at Ngara Bus Station — Nairobi City County permission secured, zero venue cost.
Radio Ghetto Radio FM (6.2M weekly listeners) — matatu-focused segments with DJ Mfalme.
Cost ~KES 20,000/slot (~$150) · 4 slots planned · ~$600 total
🤝 Institutional Engagement
Print 15,000-run SACCO meeting flyers distributed at monthly operator meetings.
Media NTV Sidebar investigative series pitch (editorial, zero cost). Parliamentary Environment Committee advocacy → KRA eco-compliance tax rebates.
Cost ~KES 45,000 ($350) print · total comms budget ~$1,150 — under 10% of prize
The Earth Prize 2026 · Scholar Phase HewaSafi Innovators Expected Impact · Financials · Scaling Potential · Longevity
HewaSafi Innovators
Expected Impact & Impact Metrics
42 t Particulate matter prevented per year (200 vehicles × 15,000 km × 93% reduction)
10,080 kg CO eliminated annually across 200-vehicle fleet (40% reduction factor)
340 Fewer respiratory hospital visits/yr (basis: MoH 2023 — 1,840 excess admissions in Eastlands; WHO evidence: ~8% reduction per 10 µg/m³ PM2.5 drop; our system reduces PM2.5 by ~168 µg/m³ = 18% projected improvement)
2.1 t CO₂ captured biologically by Spirulina stage per year across fleet

Who benefits:

Urban residents near transport corridors, currently exposed to PM2.5 exceeding 80 µg/m³ (16× WHO guideline)[1,3]

Matatu & boda boda operators, KES 2,500/month fuel efficiency savings + compliance with 2024 NEMA emission standards revision[11]

Jua Kali artisans & farmers, 12 manufacturing jobs; coconut shell collectors earn KES 50/kg from waste that was previously burned

Measurement methodology: Monthly MQ-7 sensor readings uploaded to hewasafi.com dashboard; third-party verification via University of Nairobi's Institute for Climate Change and Adaptation (proposal submitted Nov 2025). Success metric for Phase 1: ≥35% CO reduction sustained over 90 days, zero maintenance failures.

Financials

Unit Economics & Financing

Production cost: KES 16,288 (~$125)  ·  Selling price: KES 18,000 (KES 1,712 margin/unit)

SACCO financing: KES 600/month × 30 months — offset by KES 2,500/month fuel savings; net positive from month 1. Working capital bridged by Phase 1 sales revenue ($13,500) rolling into Phase 2.

Beyond prize money: Applying to Kenya Climate Fund (KCEP-CRAL), UNEP Small Grants Programme, and M-Pesa Foundation Academy innovation seed fund as contingency financing. Muranga University provides lab access at subsidised KES 200/unit (vs commercial KES 1,500/unit), reducing operating costs by 87%.

$12,500 Prize Allocation

Manufacturing Setup
$4,375
Pilot Production (50 units)
$3,750
Quality Assurance
$1,875
Marketing & Documentation
$1,500
Contingency Reserve
$1,000

Revenue at scale (200 units): Sales revenue $26,400 · Operator fuel savings $74,400/yr · Healthcare system savings ~KES 1.19M/yr · 12 artisan livelihoods supported

Longevity & Scaling Potential
Phase 1 · 2026
Prove viability: 15 matatus on Route 46. 90-day live monitoring via MQ-7 sensors. Target: ≥35% CO sustained reduction, zero failures. Revenue: $13,500 from sales funds Phase 2.
Phase 2 · 2026
SACCO scale-up: 200 units via Eastleigh Matatu SACCO. Partnership with NEMA for eco-compliance certification (proposal under review). Data published with University of Nairobi for peer-reviewed validation.
Phase 3 · 2027
City-wide reach: Target Nairobi's 12,000+ matatus via KRA eco-compliance tax rebates. Parliamentary champion identified: Hon. Kareke Mbiuki (Environment Committee) following his 2024 statements on urban air quality.
Phase 4 · 2028+
Pan-African licensing: Uganda Taxi Operators Association (80,000 vehicles) and Nigeria NURTW (250,000 vehicles). Jua Kali associations licensed at 8% royalty, decentralised manufacturing, zero capital requirement.

Organisational continuity: HewaSafi Innovators will register as a youth social enterprise under Kenya's Business Registration Service by December 2026. Muranga University carries forward the research programme; three practicum students transition to paid technicians. Kayole Jua Kali manages ongoing fabrication; Eastleigh SACCO manages payment collection. hewasafi.com is maintained by the registered entity, not the school.

Resources secured vs. needed: Secured — Jua Kali workshop, Muranga lab, 500 kg/month coconut shell supply, Route 46 pilot access, SACCO financing channel. Still pursuing — NEMA eco-compliance listing, KRA tax rebate programme inclusion, and a dedicated pyrolysis kiln (KES 85,000, budgeted in Phase 2). Kenya's 2024 National Vehicle Emission Standards (50 ppm sulfur mandate)[12,13] creates regulatory pull that makes adoption compulsory, not optional.

Negative Impacts & Mitigations
Spent activated carbon disposal, saturated carbon carries adsorbed toxins. Mitigation: Carbon regeneration protocol (re-pyrolysis at 600°C) recycles 80%+ of material; residual sent to cement kilns as fuel supplement.
Bioreactor maintenance complexity, Spirulina requires periodic medium replenishment (<1×/quarter) and contamination prevention. Mitigation: SACCO maintenance programme; bioreactor designed as optional module for mobile installations.
Engine backpressure, additional filtration stages could theoretically impede exhaust flow. Mitigation: Tested pressure drop of 45–55 mm H₂O at optimal flow (5–7 L/min) is well within engine tolerance; no performance impact observed across all 40 test hours.
MnO₂ catalyst sourced from batteries, involves handling spent alkaline batteries. Mitigation: Controlled e-waste collection from SACCO garages; prevents battery landfill; process trained under safety protocols reviewed by Muranga University engineering faculty.
Social risk — operator debt if savings underperform: SACCO financing assumes KES 2,500/month fuel savings; if savings are lower, operators face debt. Mitigation: 90-day pilot with MQ-7 monitoring validates savings before SACCO scheme is opened to wider membership. Units sold outright to Phase 1 drivers; financing only begins in Phase 2 after savings are empirically confirmed.
Human risk — "good enough" policy effect: Affordable retrofits could reduce political urgency for stricter fleet emission laws. Mitigation: We actively engage NEMA and the Parliamentary Environment Committee to position HewaSafi as a complement to, not substitute for, stronger enforcement — our eco-compliance data feeds directly into national emission reporting.

Net assessment: All identified negative impacts are manageable with existing local capacity. The health benefits, 21,000 premature deaths annually attributable to air pollution[4], vastly outweigh the operational risks.

Data & Performance Graphs
Particulate Matter Removal PM2.5 · µg/m³
Inlet 180 Outlet 12
−93.3%
200 150 100 50 0
180
12
Inlet
Outlet
Outlet 12 µg/m³ is below the WHO PM2.5 guideline of 15 µg/m³[1]. σ = 1.1%, n = 3 test sessions.
Carbon Monoxide Reduction CO · ppm
Inlet 4.2 Outlet 2.4
−42.0%
5 4 3 2 1 0
4.2
2.4
Inlet
Outlet
Copper-manganese catalyst activates at 110–125°C[6] — exactly the exhaust temperature of a typical matatu. No external heating needed; works from engine start.
CO₂ Absorption Over Time Spirulina · % reduction
Active Control
+3.6 pp D1→D10
25% 20% 15% 10% 5% 0%
19.6%
22.1%
23.2%
0.7%
Day 1
Day 5
Day 10
Control
Reduction improves as biomass grows 0.25 → 0.95 g/L[9,16]. Control (dark): 0.7%, confirms biological CO₂ uptake mechanism.
References

[1] Health Effects Inst. State of Air Quality & Health in Africa. HEI; 2024.

[2] Health Policy Watch. Clean Air Crisis in Nairobi. HPW; 2024.

[3] Kipter VK. Air Pollution & Respiratory Disease in Mukuru. UoN; 2023.

[4] Health Effects Inst. State of Global Air: Kenya Fact Sheet. HEI; 2019.

[5] Funds Beeline. Transport Sector & Air Pollution in Kenya. 2025.

[6] Chen J, et al. Highly Efficient CuO/α-MnO₂ for Low-Temp CO Oxidation. ResearchGate; 2020.

[7] Sadh P, et al. Single-Step Activated Carbon from Coconut Shells. ResearchGate; 2023.

[8] Eurocarb Products. Activated Carbon SAC 450 5KI3 Spec Sheet. 2017.

[9] Soares-Silva J, et al. Biofixation of CO₂ by Spirulina sp. PubMed; 2007.

[10] Yildirim ZR. CO₂ Bio-Sequestration Potential of Spirulina. Politecnico di Milano; 2019.

[11] NEMA Kenya. Guidelines for Vehicle Exhaust Emission Testing Centres. NEMA; 2025.

[12] CCAC. Harmonizing Standards for Cleaner Transport Worldwide. CCAC; 2025.

[13] UNEP. Accelerating the Global Shift to a Cleaner On-Road Diesel Fleet. UNEP; 2025.

[14] HewaSafi Innovators. Hybrid Exhaust Purification & Carbon Capture System. 2026.

[15] IGC. Suffocating Prosperity: Air Pollution & Economic Growth. IGC; 2019.

[16] Zhao X, et al. Large-Scale Spirulina for CO₂ Mitigation in Raceway Ponds. Front. Bioeng.; 2020.

[17] Omari K, et al. MnO₂ on Recycled Graphite as Electrode Material. J Mater Environ Sci; 2021.

[18] Andriyah L & Sulistiyono E. Ion-Selective Deposition of Manganese Sulphate. Science.gov; 2020.

[19] ICCT. AQMx Sectoral Guidance: Vehicle Emission Standards. ICCT; 2020.