International audienceThe sun could be blocked by an asteroid impact, supervolcanic eruption, or nuclear winter caused by burning of cities during nuclear war. The primary problem in these scenarios is loss of food production. Previous work has shown that alternate foods not dependent on sunlight, such as bacteria grown on natural gas, calories extracted from killed leaves, and cellulose turned into sugar enzymatically, could feed everyone in these catastrophes and preparation for these foods would save lives highly cost-effectively. This study estimates the price of alternate foods during a catastrophe scenario with global trade and information sharing, but no migration, loans, aid or conflict. Without alternate foods, for a five year winter, only ~10% of the population would survive. The price of dry food would rise to ~100/kg,andtheexpenditureonthisfoodwouldbe 100 trillion over five years. If alternate food were $8/kg, the surviving global population increases to ~70%, saving >4 billion lives. The probability of a loss of civilization and its impact on many future generations would be much lower in this scenario and the total expenditure on food would be halved. Preparation for alternate foods would be a good investment even for wealthy people who would survive without alternate foods. A non-governmental mechanism of coordinating the investments of these rich people may be possible. Identifying companies whose interests align with alternate food preparations may save lives at a negative cost