Blue carbon: mangrove conservation and carbon markets in West Africa

Executive summary

Mangrove forests in West Africa are being lost to the communities who depend on them for cooking fuel and artisanal production. This study measures the real-world climate impact of three livelihood interventions—improved cookstoves, fish smoking ovens, and solar salt installations—in Sierra Leone and Guinea. The finding: total carbon savings are nearly three times higher than standard projections suggest, and the tool making the biggest difference is one that conventional carbon markets often overlook.

Three tools, one forest: what carbon markets miss

Mangrove forests store extraordinary amounts of carbon and protect coastlines, but in Sierra Leone and Guinea, the communities living alongside them depend on mangrove wood to cook food, smoke fish, and boil salt. That dependence is the main driver of localised deforestation. West Africa Blue (“Blue”) is tackling it through three practical interventions:

1. Improved cookstoves
2. Improved fish smoking ovens
3. Solar salt installations.

Blue is pursuing carbon certification under the Verra Verified Carbon Standard. But like most standard approaches, its internal model relies on assumed displacement ratios rather than observed behaviour, and it cannot disaggregate how much each intervention individually contributes to total carbon savings. As carbon markets face growing scrutiny over credibility, Blue needed a more rigorous, evidence-based answer: which activity delivers the most measurable climate impact, and at what cost?

Data and method

• Mitigation outcome assessment (MOA) framework, grounded in consequential carbon accounting: rather than comparing emissions to a fixed baseline, the MOA traces the full causal chain of each intervention and quantifies every significant change in emissions, including rebound effects and the minor footprint of manufacturing the technology itself.
• Field data collected May–June 2025: a direct performance comparison of an improved fish smoking oven against a traditional banda; a cookstove usage survey across 67 communities in the Sherbro River Estuary project area (Sierra Leone); and wood consumption measurements for traditional salt boiling in Guinea.
• Primary field data combined with kitchen performance tests, household surveys, biomass and soil carbon stock measurements, GIS-derived deforestation data, and Blue’s internal financial records.
• 30-year projection horizon (2024–2054) using logistic growth functions to model technology adoption; 2024 cookstove usage rate of 44.5% derived from field survey.
• Parallel discounted cash flow (DCF) analysis calculating the net present cost for Blue as project developer and for participating communities, combined into a marginal abatement cost (MAC) curve expressing cost per verified carbon unit for each intervention.
• Spatial correlation analysis testing whether village-level cookstove adoption rates correspond to observed deforestation outcomes in 2024.

Findings

• Real-world savings are nearly three times higher than projected. The MOA calculates total lifetime emission reductions of approximately 15.9 MtCO₂e across both projects—compared to Blue’s internal estimates of 5.7 MtCO₂e. The gap arises because the MOA uses observed fuelwood consumption and actual usage rates, rather than modelled assumptions. Blue’s model is deliberately conservative to avoid over-crediting; the MOA reveals how much more mitigation is actually happening in the field.
• Fish smoking ovens are the standout intervention by a wide margin. In Sierra Leone they avoid 8.4 MtCO₂e over 30 years—over half of total reductions across both countries. The reason is scale: a traditional fish smoking banda consumes around 7,084 kg of mangrove wood per household per year; an improved fish smoking oven uses just 420 kg. That is a 94% reduction. No other intervention comes close in absolute terms.
• Cookstove performance is held back by behaviour, not technology. Despite strong efficiency ratios, cookstoves in Sierra Leone underperform their theoretical potential because many households continue using traditional three-stone fires alongside their improved stove—a practice known as “stacking.” With an adjusted usage rate of 44.5%, just under half of deployed stoves are meaningfully displacing old cooking methods. This is a well-known challenge that standard crediting methodologies tend to smooth over; the MOA captures it directly.
• All interventions are financially viable. Every intervention in every scenario produces a negative marginal abatement cost, meaning projected carbon revenues exceed implementation costs over the project lifetime. For Blue, total net present costs range from −USD 1.7 million (Guinea cookstoves) to −USD 19.1 million (Sierra Leone improved fish smoking ovens). Communities also benefit directly through reduced wood purchasing costs.
• Smaller interventions are the most cost-effective per unit of abatement. Despite improved fish smoking ovens generating the most total carbon savings, Guinea cookstoves and solar salt installations rank as the most cost-effective per verified carbon unit, because their lower implementation costs produce very low marginal abatement costs. This creates a genuine strategic trade-off: improved fish smoking ovens maximise total climate impact and carbon revenue; Guinea interventions maximise cost-efficiency and community benefit per unit.
• Cookstove adoption leaves a weak but consistent signal in forest data. A spatial correlation of −0.33 was found between adjusted cookstove usage rates and 2024 deforestation rates across village clusters—meaning higher adoption corresponded to lower forest loss. This is directionally consistent with expectations, though not statistically conclusive at this sample size. It provides early empirical support for the conservation effectiveness metric Blue uses in its credit methodology.

Bottom line: all three interventions work, but improved fish smoking ovens are by far the best

All three interventions work. They deliver real, verifiable emission reductions grounded in observed behaviour, and they do so at a net financial benefit for both Blue and local communities. But they do not work equally. Improved fish smoking ovens should be the priority for scaling: no other activity comes close in absolute mitigation or carbon revenue potential. Guinea cookstoves and solar salt installations should follow as highly cost-effective additions that strengthen community co-benefits. Cookstoves in Sierra Leone require targeted investment in user engagement to close the gap between theoretical and realised performance. Across all interventions, the MOA framework reveals substantially more climate impact than conservative ex-ante models—because it captures what actually happens when these technologies reach real households.

Implications for decision-makers

For Blue and project developers

• Prioritise improved fish smoking ovens for large-scale carbon credit generation. Invest in user retention and stacking-reduction programmes for cookstoves to close the performance gap. The MOA framework piloted here is directly replicable as new project areas come online and should become standard practice.
• Carbon credit revenue, not implementation cost, drives financial outcomes. The most important levers are the discount rate and the timing of credit issuance—not procurement efficiencies. Securing favourable financing terms and managing the pre-verification cash flow period should be the financial priority.

For carbon market buyers and certifiers

• Field-grounded accounting that uses observed adoption rates and actual fuelwood measurements produces more credible emission reduction claims than modelled displacement assumptions. Procurement standards should reward this level of empirical rigour rather than defaulting to standardised default factors that are increasingly under scrutiny.

For policymakers and Article 6 negotiators

• Livelihood-based blue carbon interventions can deliver both high-integrity mitigation and direct economic benefit for coastal communities. Frameworks that combine carbon accounting with community co-benefit evidence—fuel savings, health outcomes, time savings—would strengthen the social licence of these projects and address additionality concerns in voluntary markets.

For financiers and impact investors

• Financial viability is robust across all interventions and scenarios. The key risks are not unit costs but discount rate and the timing of credit issuance. Concessional or blended capital structures that reduce the effective financing cost and smooth cash flows during the pre-verification period could materially enhance project returns and accelerate deployment.

Authors

Max Meyer

Max is a recent gradate from the MSc Climate Change Finance and Investment at the University of Edinburgh Business School. He now works for West Africa Blue, a blue carbon project developer, to support community-based mangrove conservation and restoration.