Some trains may have composting toilet tanks, which use bacterial action to break down solid and liquid waste. Only the broken down clean liquid is released to the trackbed after sterilisation. The solid waste only has to be emptied every half year.

Modern passenger trains in 2026 utilize sealed vacuum or biological retention systems, meaning waste is no longer dumped directly onto the tracks. In a Vacuum System, high-pressure suction pulls waste into a large onboard storage tank, similar to an airplane toilet. This tank is then emptied at a service depot using specialized pumping equipment. In a Biological (Bio-digester) System, which is increasingly common in 2026 on networks like Indian Railways, waste is treated in an anaerobic tank where specific bacteria break down the solids into water and gas, leaving only a treated, odorless liquid that is safe for the environment. These systems have eliminated the "dirty track" issues of the past and allow toilets to remain functional even when the train is stopped at a station. High-speed services typically have sensors that notify maintenance crews when a tank is nearing its 500-liter capacity to ensure uninterrupted service.