By Karl Palmquist, Chair, Sierra Club New York City Group
New York City’s food system accounts for about twenty percent of the city’s greenhouse gas emissions, third after buildings and transportation. One major source of food-related emissions is from food waste, when leftover food scraps are sent to landfills and produce significant amounts of methane, as well as carbon dioxide. One way to reduce emissions from this sector, particularly those emissions associated with food waste, is through composting. The process of composting organic waste—a category that includes both food scraps and yard waste – strongly reduces methane emissions.
As of April 1, 2025, organics waste must be source-separated—a term indicating that prior to refuse collection, organics waste needs to be isolated in separate containers from other refuse (e.g., similar to how recyclable materials must be separated from regular trash) so that it does not end up in landfills. The materials separated into brown bins ultimately go to municipal composting facilities or to anaerobic digesters. The former are locations that contain large compost “piles” where organic waste is added and turned regularly to promote the breakdown of organic waste and transformation into compost. In anaerobic digesters—a process that is separate and distinct from what occurs in compost piles—anaerobic bacteria breakdown organics waste in air-tight chambers that have low oxygen levels.
During anaerobic digestion, biogas can be collected and utilized. However, to make the process more efficient, organic waste is mixed with sewage sludge (i.e., human and household waste) in the anaerobic digesters. By combining these waste streams, harmful pollutants (such as PFAS) from sewage sludge are introduced into food waste. The Atlantic Chapter wrote a briefing paper about this topic, and the harmful impacts on New York’s farmland, two years ago.
Despite the ecological value provided by New York City’s evolving organics collection and processing system, it still represents a highly centralized process that lacks significant community engagement. Programs like the city’s Master Composter Course give residents a chance to understand how composting works and its benefits. Furthermore, new, proposed legislation seeks to decentralize organics processing by requiring that certain amounts of organics waste be processed as compost in each borough. These two initiatives, as well as the long-standing efforts that occur at community gardens and other sites around the city, offer a glimpse into a more hopeful and sustainable future, one that prioritizes and centers grassroots initiatives such as community composting. The real benefits here are that when organic waste is turned into compost locally (e.g., near where it is collected). This requires fewer vehicle miles travelled for large trucks and offers communities the benefits of creating healthy soils from their own food scraps.