The same tonnage of manure or crop residue is fed down two pathways at once. Left in an open pile, it decomposes anaerobically in pockets throughout the heap and most of the methane it produces bubbles straight out into the air — methane traps roughly 28× more heat than CO₂ over a 100-year horizon, so this "free" decomposition has an outsized climate cost per tonne.
Route the same waste into a sealed, oxygen-free digester instead and the biogas (methane + CO₂) has nowhere to go but the gas-storage dome. Piped out and burned in a generator, the captured methane becomes CO₂ — a much less potent gas — while the electricity it produces displaces power that would otherwise come from the fossil grid. That's the double benefit: avoided methane release, plus displaced fossil generation.
- Feed rate — tonnes of waste per simulated day entering both pathways simultaneously.
- Waste type — manure, crop residue and mixed feedstock have different biogas yields per tonne.
- Cumulative CO₂-eq — running total climate impact of each pathway; watch the digester's total grow far more slowly, and eventually fall behind the open pile's by a wide margin.
- Emissions avoided — the gap between the two cumulative totals: what the digester saves purely by existing instead of the open pile.