Thirteen percent – more than 30 million tons – of the municipal solid waste collected in 2007 was food waste. This comes from our homes and from restaurants, of course, and from food production facilities. Right now, around 3 of that 13 percent is diverted from landfills and used for other purposes – most often for composting.
These are among the many food facts I gleaned from an educational session called “Food Waste: Compost, Digest or Other Use?” at Waste Expo, a solid waste industry conference held this week in Las Vegas. Two things are clear: food that lands in landfills is food wasted, but just what to do with all those food scraps is a matter of a debate.
Broadly, food can be turned into one of two things: energy or compost. Sometimes it is turned into both. Last summer, Jen wrote a post about how food waste is turned into compost and energy by Northern California’s Jepson Organics . And just east of San Francisco, the East Bay Municipal Utility District – like many other waste water treatment plants around the country – use anaerobic digesters to convert the methane formed during the digestion process of food and biosolid waste (poop, basically) into renewable energy.
This brings us to an important question: is it better to turn food waste into compost or send it down your drain disposal (if you have one) to a digester at waste water treatment plants? While there wasn’t an all-out food fight over this topic at the Waste Expo event, the session moderator (and waste reduction consultant) Steve Sherman did a good job of trying to start one (all in the name of friendly debate, of course).
Core to the debate is how we think about food waste. Panelist Kendall Christensen argued that food waste is liquid waste and should be sent through sewers to water treatment facilities that convert it into energy (and fertilizer, as a by product). Of course, Christensen is also a consultant for food waste disposal vendor Insinkerator, so I had a hard time viewing him as impartial. Still, he has a compelling argument: food is largely comprised of water and sending food through existing sewage systems uses less energy than trucking food waste (which is very heavy) to far-flung composting facilities (and most composting facilities are, in fact, far from urban centers). A number of waste water treatment plants, such as the Milwaukee Metropolitan Sewage District, are encouraging residents to install and use disposals, because they want to collect more feed stock for their digesters.
But this seems like a solution only in places with sewage networks fit to handle an influx of food waste. Food – specifically, fats and oils from food waste – can also cause sewage overflow problems and this is of major concern in coastal areas in California, where overflows send sewage into the ocean on a somewhat regular basis along the Southern California coast. And in fact, many water districts actively discourage their customers to use waste food disposals at home. Christensen admitted that there are some areas where sending food scraps through sewage networks might not be advisable, but he also argued that some municipalities discourage the use of disposals based on misinformation.
Peter Klaich, vice president of sustainability and waste reduction for International Environmental Management (part of waste management firm Oakleaf) talked about the different types of permitting required to collect food waste and the hurdles and areas of opportunity his firm sees in the business.
One area that represents both a hurdle and an opportunity are the food courts inside malls, he explained. These collections of restaurants generate an enormous amount of food waste and disposing through regular waste management (landfill) is a huge expense because the waste is so heavy. So Oakleaf has been working with food courts to collect the waste and bring it to composting facilities. This saves the businesses money and generates revenue for Oakleaf. However, the collection is labor intensive, because the restaurant workers or Oakleaf folks need to schlep the stuff to a central area.
Klaich asserts that some food service companies stand to realize savings “in the six digits” by diverting food waste for composting, and notes that farmers can also save by using compost to fertilize fields instead of chemical fertilizers, which often end up polluting groundwater.
Composting food waste and using in wastewater digesters are both better options than putting it in a landfill, where it takes up space and generates methane than in many cases is not captured for energy use. Perhaps the answer is to compost it in places where favorable weather makes this possible year-round and where composting can take place close to the farmers and companies that will benefit from the end product. And perhaps food should be handled as a liquid waste in places where the sewage network is prepared to handle it and where wastewater treatment plants want more food waste for their digesters.
If you have experience in deriving value from food waste, or just have an opinion on this food debate, chime in by leaving a comment.