Recology announced on Tuesday that San Francisco residents and businesses have composted more than 620,000 tons of waste through the city’s green-cart recycling program since the program began in 1996. Recology handles recycling and composting for San Francisco.

Participation in San Francisco’s composting and recycling programs became mandatory this fall.

According to Recology, the city’s composting since 1996 has prevented the creation of 137,000 tons of methane gas and put 18,400 metric tons of carbon dioxide back into the soil (an effect equal to taking 3,600 cars off the road). “We should never throw peelings, leftovers, coffee grounds, or anything else we can compost in the trash,” said Mike Sangiacomo, CEO of Recology, in a press release. “Instead place all materials that can be composted in a green collection cart; that is a direct and highly effective way to help protect the environment.”