Project Bio-Soil: July-December 2025
Turning maize stems and agricultural waste into biochar using pyrolysis (high-heat, low-oxygen burning). Mix biochar with compost and goat dung. Apply to demonstration farms and track soil improvements.
What Biochar Does
Biochar is stable, porous carbon that stays in soil for centuries. It:
- Retains nutrients and water in sandy or degraded soil
- Improves soil structure (better root penetration, aeration)
- Enhances microbial activity
- Sequesters carbon (removes it from atmosphere)
- Mimics Terra Preta (ancient Amazonian fertile soil)
The Situation in Nakivale
- Degraded soil from years of monoculture farming
- Climate variability: unpredictable rain, prolonged droughts
- Limited agricultural productivity
- Reliance on chemical fertilizers (expensive, damages soil long-term)
- Maize stems usually left to rot or burned (releases CO2)
How We Make Biochar
1. Biomass Collection
Surveyed Kabazana A&B, Misiera, and Kigali village for maize stem sources. Collected from 31 farms using tricycles for transport.
Challenges: Termite damage, unexpected rainfall affecting quality, 2025 drought reduced available biomass (farmers harvested less due to heat stress).
Solution: Early sourcing immediately after harvest, improved storage to keep dry, diversified biomass sources (added other plant materials and goat dung).
2. Pyrolysis in Kon-Tiki Kilns
Earth Kon-Tiki kilns used initially (Rwanda training model). Then fabricated 2 metallic Kon-Tiki kilns locally.
Kiln specs: Locally welded by Nakivale artisans. Cost: 350,000 Ugx → 500,000 Ugx (price increased due to material costs). Permanent installation at Kabazana A site.
Production schedule: Evening sessions (cooler, safer while awaiting full PPE delivery). June-August output: 61 sacks biochar.
3. Mixing and Application
November 2025: Mixed biochar with 1,900 kg goat dung and vermicompost.
Applied to:
- 9 maize farms (planted)
- 128 banana seedlings
- 23 fruit trees (jackfruit, bull's heart)
- 5 farmer test plots for individual evaluation
Results: 6 Months
Production:
- 6,100 kg total biochar produced
- 4,600 kg applied to farms
- 1,500 kg in storage for 2026 expansion
Soil Improvements Observed:
- Better water retention during dry spells
- Faster maize germination (more uniform)
- Banana seedlings didn't wilt under strong sun (common problem solved)
- Up to 20% higher establishment rate vs. untreated plots (despite drought)
Farmer Behavior Change:
- Shift from "maize stems = waste to burn" → "maize stems = resource for biochar"
- Over 5 farmers directly engaged in surveys, interviews, training
- Awareness raised: neighbors asking about "black gold"
What Farmers Say
"I always left my maize stems to rot in the field, thinking it would help the soil. The team explained that this can harbour diseases and release carbon. I was sceptical about biochar, but after applying the mixture to my spinach and eggplant plot, I noticed the soil stayed moist for longer during a dry spell. The plants also looked greener and healthier compared to my other garden."
"Using the biochar mix was a new experience. I have applied it around my young banana seedlings and cassava. It is too early to see significant yield increases, but the seedlings have not wilted under the strong sun, which is a common problem. This gives me hope for a better harvest."
"I received the mixture and used it when planting my maize. The germination was faster and more uniform than in the past. I am now telling my neighbours about this 'black gold' and why we should not just burn our farm waste."
Challenges and How We Adapted
Technical Delays:
Prolonged price negotiations with welders, power outages slowing kiln fabrication.
Response: Renegotiated costs, adjusted timeline, worked with multiple welders.
Resource Limitations:
Insufficient PPE, transport breakdowns, inconsistent maize stem availability due to financial delays.
Response: Prioritized essential safety equipment purchase, rescheduled transport during drier periods.
Environmental Factors:
Heavy rainfall disrupting production and biomass drying, extreme heat reducing daytime productivity, 2025 drought limiting biomass supply.
Response: Evening work sessions, early collection after harvest, diversified biomass sources.
Key Lessons
- Community engagement is fundamental: Direct interaction and farmer testimonials build trust better than technical explanations alone.
- Local fabrication creates ownership: Community welders building kilns supports local economy, ensures easy maintenance.
- Proactive logistics matter: Planning for transport, storage, weather disruptions keeps activities running.
- Safety first: Fieldwork with fire requires strict PPE protocols to protect team.
2026 Plans
Scale Up Production:
- Use both kilns for continuous production
- Target: 40 tons biochar
- 1,500 kg reserve ready for early planting season
Expand Application:
- More farms across settlement
- Wider crop range
- Possibly expand to host communities
Formal Monitoring:
- Collect soil health data
- Track crop yields systematically
- Final results from 5 test farmers (January 2026)
Community Model:
- Train 100 champion farmers as biochar producers or biomass collectors
- Peer-to-peer learning and broader adoption
Partnerships:
Strengthen relationships with organizations specializing in agricultural tools and renewable energy to boost production capacity.
Demonstration Sites
- Kabazana A (primary site with kilns)
- Kabazana B
- Kigali village