Climate-Smart Design

Every solution is designed to keep working through floods, drought and heat, and to cut emissions along the sanitation chain.

Climate-smart by design

Climate damages sanitation. Floods wash pit and septic tank contents into homes and water sources, droughts leave flush toilets dry, heavy rain collapses unlined pits, and emptying trucks cannot reach flooded neighbourhoods.

Sanitation drives climate change. Excreta decomposing without oxygen in pits, tanks and drains releases methane. In Kampala, a whole-city study found sanitation produces about 189 kilotonnes of CO₂ equivalent a year, more than half of the city's emissions.

Source: Johnson et al. (2022), Communications Earth & Environment 3, 80.

Diagram: poorly managed sanitation releases greenhouse gases that raise temperatures; droughts, floods and storms then destroy infrastructure, displace people and contaminate water — How sanitation and climate change feed each other. Adapted from GWP and UNICEF.

Adaptation: keep working through floods, drought and heat

Avoid exposure: raised slabs and sealed, lined pits that floodwater cannot enter.
Withstand it: precast linings that do not collapse in heavy rain.
Need little water or power: dry and low-flush options, gravity-fed treatment.
Recover fast: standard parts artisans can replace in days.

Mitigation: cut emissions along the sanitation chain

Safely managed, not just built: sludge emptied, treated and reused.
Capture methane: biogas that replaces firewood and charcoal.
Compost instead of dumping: avoids methane, replaces synthetic fertiliser.
Low-energy treatment: wetlands and baffled reactors that run mostly by gravity, with little or no electricity.

The climate case for each solution

SolutionAdaptationMitigation

Market-Based WASH Products

Toilet-in-a-BoxLined pits that resist collapse; slab can be raised above flood level; dry or low-flush options for drought.Twin, emptyable pits make safely managed sanitation possible; produced locally, cutting transport.

Biosand filterSafe drinking water when floods contaminate sources; no power needed.Reduces the need to boil water with firewood or charcoal.

Pit emptyingEmptying before the rains prevents overflowing pits during floods.Regular emptying and treatment limit methane from full pits.

DEWATS

Constructed wetlandsTreated water reused in dry seasons; vegetation cools the neighbourhood; mostly gravity-fed, with little power to fail.Near-zero energy use; plants and soils store carbon.

Anaerobic baffled reactorsBuried and robust; no electricity or moving parts.No energy use; can be fitted to capture biogas.

Resource Recovery

Compost and co-compostOrganic matter helps soils hold water through drought.Avoids methane from dumped waste; replaces synthetic fertiliser; stores carbon in soil.

BiogasLocal, reliable cooking energy.Captures methane and replaces firewood and charcoal.

Climate services for programmes and cities

Following the GWP and UNICEF framework for climate-resilient WASH: understand the problem, identify options, deliver solutions, and monitor.

Climate risk assessment

Hazards, exposure, vulnerability and capacity along the sanitation service chain.

Climate-resilient design

Design features that avoid, withstand and recover from floods, drought and heat.

Emissions estimates

Direct and indirect greenhouse gas emissions of sanitation options, to choose low-carbon designs.

Climate finance support

The technical and climate rationale for climate-finance proposals and programme design.

Free resource

Climate-Smart Sanitation: A Practitioner's Guide from the Field

Our practical guide for donors, NGOs, water utilities and municipalities: climate hazard scorecards and emission estimates for eight sanitation, wastewater and resource recovery technologies, a tool for choosing the right option, and guidance on climate finance and monitoring.

Henock Belete Asfaw, H2E Enterprise. 2nd edition, 2026. PDF, 36 pages.

Download the guide (PDF)

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