Food waste is approximately 14% of the household waste we discard. Food waste is of concern to environmental agencies and municipalities because in landfills, food waste is a primary cause of methane gas emissions, a very potent greenhouse gas, and the methanogens that food waste supports in landfills also cause the mobilization of other pollutants in landfills, resulting in an increase in both air pollutants and leachate.
In waste combustors, food waste is a cause of nitrogen oxide emissions, which is also a greenhouse gas, as well as a cause of smog and respiratory illness. Moreover, since food waste can contain as much as 70% water, it is not a high Btu fuel, and therefore is not well-suited for combustion. The best disposal option for food waste is neither landfilling nor incineration. Ideally, food waste should be composted. If you have a compost bin where you live, you can incorporate food waste into your home compost -- if not, consider setting up a home compost system. Home composting avoids transportation of organic wastes, saving fuel and other resources associated with transporting waste. There are many resources describing the options for home composting -- these range from backyard bins to vermicompost (worm bins), and can be tailored to fit your needs. In some communities (such as San Francisco), food waste is collected in curbside recycling programs, usually along with yard waste. Typically, in a municipal composting system, you can compost a wider variety of wastes (including animal products and food-soiled paper) than you might be able to accommodate in home composting. Check with your local waste management authority to find options for the disposal of food and yard wastes in your community.
If you don't have access to composting, you can dispose of most food waste in under-sink food waste disposers, also known as garbage disposals. Many municipal wastewater treatment facilities have anaerobic digesters that extract energy in the form of biogas from solids in the waste water, and most can produce soil amendments such as fertilizer from processed solids. Some wastewater treatment systems benefit from the addition of food solids because that can make the process of converting waste into energy more efficient, but too much or the wrong types of food waste can overwhelm the system. This is one of the reasons it makes sense to use in-sink disposers as a complement to municipal and backyard composting programs.
Moreover, in-sink food disposal systems increase the amount of water used at home. Although this increase is only a small amount for any individual home, the added water from tens of thousands of homes switching to in-sink disposal units can be significant. Finally, cooking oils, fats, and greases should never be disposed of down the drain. Even if you use hot water, detergents, or garbage disposals, oils can congeal in pipes and potentially contribute to sewage backups.
To sum up, food scraps should not be sent to landfills or incinerators. Instead, the best option for disposing of food waste is composting, whether at home or in a municipal system. The next best option is typically an in-sink waste disposer -- but check to make sure your community isn't running low on water before using garbage disposals, and make sure only to put allowed wastes down the drain.