L.A. Compost volunteers Yoichi Nagano and Esko Robinson work at the group’s regional hub in Griffith Park. Another round of “aggressive Googling” led Leong to a group called L.A. Compost and the start of a life-changing conversion that began — naturally enough — with broccoli stems, coffee grounds and banana peels. Composting became bigger than itself: a gateway to friendships, …