School ultrafiltration delivered by LifeStraw; Virridy is the carbon developer. This worksheet counts only Virridy's outlays, and says so everywhere.
The partner funds the filters; the carbon layer finances replacement cycles and turns delivery into credits. That makes this a different model from the Amazi Meza Rwanda worksheet: no full-delivery-cost figure exists here, so no GiveWell-comparable $/DALY is claimed. The honest headlines are climate cost-effectiveness and carbon financing per student-year.
Program: LifeStraw Max gravity ultrafiltration (no power, ~100,000 L per unit) in Kenyan schools; target 4,500 schools and 2M+ students over 20 years. Gold Standard SDWS V2.0 yield basis, 0.049 credits per person-year, CORSIA channel with 42,000 credits contracted for 2026–2029. A real risk is stated up front: credits are currently held unsold pending CORSIA labeling, and scenario S2 prices that risk.
| Series | 2025 | 2026 | 2027 | 2028 | 2029 | 2030 | 2031 | 2032 | 2033 | Total |
|---|---|---|---|---|---|---|---|---|---|---|
| Net credits (tCO₂e) | 0 | 11,449 | 5,817 | 12,562 | 15,613 | 18,664 | 21,715 | 21,715 | 21,715 | 129,250 |
| Implied students served | 0 | 233,653 | 118,714 | 256,367 | 318,633 | 380,898 | 443,163 | 443,163 | 443,163 | 2,637,755 student-yrs |
| Buy price to partner ($/cr) | 9.20 | 9.20 | 9.30 | 9.50 | 9.60 | 9.70 | 9.80 | 9.90 | 9.90 | — |
| Initial purchases ($) | 210,000 | 808,000 | 242,000 | 0 | 0 | 0 | 0 | 0 | 0 | 1,260,000 |
| Ongoing credit purchases ($) | 0 | 0 | 0 | 119,339 | 149,885 | 181,041 | 212,807 | 214,978 | 214,978 | 1,093,029 |
| Virridy carbon outlays ($) | 210,000 | 808,000 | 242,000 | 119,339 | 149,885 | 181,041 | 212,807 | 214,978 | 214,978 | 2,353,029 |
Credits and prices are proforma inputs; the implied-students row is a formula (credits ÷ 0.049 yield) and is flagged: the 2026 credit figure includes an issuance backlog, so that year's implied students overstate actual reach. Initial purchases are the guaranteed first batch plus early replacement-cycle financing; ongoing purchases are credits × the contracted buy price from 2028.
| TOTAL VIRRIDY OUTLAYS, 2025–2033 | $2,353,029 | Formula initial purchases + ongoing credit purchases |
| Implied student-years served | 2,637,755 | Formula total credits ÷ 0.049 |
| Carbon financing per student-year | $0.892 | Formula outlays ÷ student-years |
Every figure on this page divides by this one cost, and the build fails programmatically if any figure uses a different denominator. What this cost is NOT: it is not the cost of delivering safe water to these schools. Filters, distribution, and program operations are funded by the partner and do not appear in the proforma. A full-delivery-cost $/DALY would require the partner's capex data and is deliberately not computed.
| Input | Value | Provenance | Basis |
|---|---|---|---|
| Diarrheal incidence, school-age | 0.60 episodes/child-yr | Judgment · flagged | Cloned from the Rwanda model; Kenya-specific GBD lookup pending. Tested 0.30–1.20 in S3–S4. |
| Diarrhea reduction, point-of-use filtration | 34% | Evidence-anchored | Wolf et al. 2022 (Lancet), filtration risk ratio 0.66. |
| School share of daily drinking water | 30% | Judgment · flagged | No time-use survey; same assumption as the Rwanda model. |
| Delivery effectiveness (safe at the point) | 90% | Sensor-measured | Portfolio monitoring record: 90.3% of samples safe under monitored delivery (n=1,685). |
| YLD per episode | 0.002215 DALY | Formula | 0.188 disability weight × 4.3 days ÷ 365 |
| Step | Value | Computation |
|---|---|---|
| Episodes averted, 2025–2033 | 145,288 | 2,637,755 student-yrs × 0.60 × 0.34 × 0.30 × 0.90 |
| DALYs averted (raw) | 322 | episodes × 0.002215. Years lived with disability only; mortality excluded (conservative). |
| $ / DALY, carbon-financing basis | $7,312 not GiveWell-comparable | $2,353,029 ÷ 322. Dollars through the carbon layer per DALY in the system, NOT DALYs purchased by Virridy: the partner delivers the health impact. |
| Evidence adjustment (section E) | × 0.432 | 322 → 139 DALYs adjusted |
| $ / DALY adjusted, financing basis | $16,927 | $2,353,029 ÷ 139 |
| xCash, three frameworks | 0.094× / 0.041× / 0.147× | GiveWell default / egalitarian / wellbeing weights; moral-uncertainty weighted 0.097×. Stable, and immaterial: the basis label, not the framework, drives interpretation. |
| Factor | Score | Basis |
|---|---|---|
| Internal validity | 0.80 | Meta-analytic anchor, judgment links in the chain. |
| External validity | 0.75 | Household point-of-use trials transferred to Kenyan school delivery: a cross-country, cross-setting transfer. |
| Publication bias | 0.80 | Systematic review without an independent funnel-plot confirmation here. |
| Implementation quality | 0.90 | Operational program, credits issued and held; CORSIA labeling still pending. |
| Composite | 0.432 | Formula product of the four, reported alongside raw, never silently multiplied in. |
| Residual baseline-practice factor | 0.80 | Judgment · flagged The yield is already reconstructed to SDWS V2.0 (0.049, like Rwanda); this prices residual baseline risk pending a measured school baseline survey. |
| Delivery effectiveness | 0.90 | Sensor-measured The same cell the health chain uses. One usage number, two consumers. |
| Credit integrity ratio | 0.72 | Formula 0.80 × 0.90 × 1.00 leakage |
| $ / tonne, credited basis | $18.21 | $2,353,029 ÷ 129,250 t · 10.2× below the $185 social cost of carbon |
| $ / tonne, integrity-adjusted | $25.29 | $2,353,029 ÷ (129,250 × 0.72) · 7.3× below the SCC |
| CORSIA labeling status | PENDING | Credits are held unsold until labeled. This is the model's load-bearing commercial assumption, priced in S2. |
| Scenario | Varied input | DALYs | $ / DALY fin. basis | $ / tonne | vs SCC | Reading |
|---|---|---|---|---|---|---|
| Base case | — | 322 | $7,312 | $18.21 | 10.2× | as above |
| S1 · contracted-only volumes | 42,000 cr | 105 | $13,825 | $34.42 | 5.4× | downside book: $1.45M outlays; financing $1.69/student-yr; still well under the SCC |
| S2 · CORSIA labeling never lands | sell voluntary $10/t | 322 | $7,312 | $18.21 | 10.2× | proceeds $1.29M against $2.35M outlays: net −$1.06M. The commercial reversal condition, stated plainly. |
| S3 · incidence low | 0.30 | 161 | $14,626 | $18.21 | 10.2× | — |
| S4 · incidence high | 1.20 | 644 | $3,656 | $18.21 | 10.2× | — |
| S5 · buy price $9.90 flat | $9.90 | 322 | $7,361 | $18.33 | 10.1× | outlays $2.37M: the model is insensitive to the buy-price path |
Recomputed, not asserted: the climate metric stays 5.4–10.2× below the social cost of carbon in every scenario, including the contracted-only downside. The fragile finding is commercial, not climatic: without the CORSIA label, the carbon layer runs a roughly $1.1M net loss at voluntary floor prices.
| Dimension | Rating | Assessment |
|---|---|---|
| Effect-size quality | The chain is cloned from the Rwanda model with zero Kenya-specific inputs: incidence, school water share, and severity mix are all pending. Preliminary is the ceiling until the Kenya burden lookup and any program evaluation data are traced. | |
| Counterfactual robustness | Another carbon developer could plausibly serve the partner; the counterfactual for Virridy's outlays is partner-funded replacement cycles at a slower cadence, not modeled in v1. The health-side counterfactual is not Virridy's to claim. | |
| Moral-weight transparency | All frameworks reported; ranking stable. The labeled cost basis, not the framework, is what drives interpretation. | |
| Attribution | The central caveat of the whole model: Virridy finances replacement cycles; the partner delivers and capitalizes the health impact. The $/DALY figure is dollars-through-the-carbon-layer per DALY in the system. Quoting it without that label is a misuse of the model. | |
| Excluded factors | Full delivery cost is unknown to this model (partner-borne). CORSIA labeling risk is real and priced in S2. The 2026 implied-students figure overstates that year because the credit figure includes an issuance backlog. | |
| Ranking stability | The climate metric is robust in every scenario (5.4–10.2× below the SCC, 7.3× integrity-adjusted). The commercially fragile finding is S2: CORSIA labeling is the reversal condition. |