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Leftovers--Into the Trash or Kitchen Disposal? Nitty-gritty

By Georgia Griffin

When disposing of food waste, I often compost. But some food wastes are not supposed to go in the compost pile. Is it more environmentally sound to scrape your plate into the trash or send it down the kitchen disposal? And on a related note, if I blow my nose into a tissue, is it better to throw it in the trash or the toilet (without any extra flushing)?

Asked by Lauren Woodard, PhD '09, Houston, Texas

Reduce and reuse leftovers

Leftover food opens the door to creativity. For example, no matter how hard my mom tries to scale back the amount of brown rice she makes for one dinner, we always end up with leftovers. The fear of one of us going hungry—and the wily expanding nature of rice—leaves us with heaps of cooked grain. The challenge: Disguise these bland brown granules in fresh dinner dishes, comforting desserts, and even breakfast goodies (a secret brown rice muffin) to break the monotony of a bagel and cream cheese.

My favorite creations with brown rice include vegetable fried rice, vanilla rice pudding, and rice quiche. Fried rice is a healthy and fast meal, not to mention a great way to use up aging veggies and eggs nearing their expiration date. I like to throw in pineapple, ginger, and fresh lime juice to spice it up. Rice also makes great stuffing for tomatoes and sweet peppers. But my favorite is rice pudding: it uses up a lot of leftover rice all at once, it is a great dessert, breakfast, and snack, and can be tailored to your individual taste. Adding cinnamon, nutmeg, and raisins makes rice pudding an energizing way to start your day. Slowly simmering with vanilla, cream, and sugar concocts a rich and satisfying dessert.

A friend of mine stopped eating gluten this summer. As a diehard gluten lover who could not afford the gluten-free pasta, beer, and other substitutes, he was forced to start experimenting. We discovered that leftover rice makes an excellent gluten-free bottom crust for quiche. I enjoyed it so much that I willingly make rice crusts even though I have no dietary restrictions. One cup of pre-cooked brown rice tossed with eggs, Swiss cheese, and curry powder also adds a unique crunch to your quiche.

And rice is just the beginning—the tip of the riceberg, so to speak.

Leftover meat and veggies can be recycled in soups and quesadillas; pasta and beans work well in salads; and sauces are great in casseroles. The options are infinite, so long as you’re wiling to think outside the box—and the Tupperware.


Compost what you really can’t use

Industrial composting: big is beautiful

I was baffled when my high school science class took a field trip to a local vegetable farm and I was told that compost smells good. The farmer held a handful of velvety dark and moist soil up to his nose and breathed in like he was inhaling heaven. To my amazement, he was right. Composting is the ultimate form of recycling of resources. Microorganisms such as bacteria and fungi feed on carbon-rich organic waste, nutrients, water, and oxygen to produce a high quality fertilizer. Farmers swear by compost—it improves soil structure, texture, aeration, water retention, and nutrient content. Thus, compost can reduce irrigation and fertilizer inputs and divert waste from landfills and wastewater treatment plants. Aerobic decomposition, with plenty of air, produces carbon dioxide instead of methane, a far more potent climate-changing emission that is produced by anaerobic, or airless, decomposition in landfills. Starting a compost pile in your back yard is not complicated—and especially if you have kids, can be a lot of fun.

Large-scale composting facilities can process all food waste—in addition to yard waste and sewage—and are the ideal alternative to landfills. They use a variety of techniques to optimize the temperature, moisture and oxygen conditions. The compost produced by industrial facilities is stable, free of pathogens and seeds, and has various beneficial uses for the land. The anaerobic digester in San Francisco distributes its finished compost product to farmers in the Central Valley to be used for biofuel crops and landscaping and in the worst-case scenario landfill cover, says Peter Drekmeier, the former Palo Alto mayor and composting advocate. This technology “mimics natural processes,” he says. “When we think of water, we don’t like to think of it as recycled,” Drekmeier observes. “We trust nature more than we trust ourselves.” But in nature everything gets recycled. In his book Cradle to Cradle: Remaking the Way We Make Things, William MacDonough put it this way: “In nature, waste is food, or to put it more accurately, there is no waste.”

Courtesy EPA
TRASH: Discards according to the Environmental Protection Agency

Food waste is the single largest component of municipal solid waste dumped in landfills, the U.S. Environmental Protection Agency (EPA) reports. Composting this organic waste—at home or industrially—would close the loop between our food consumption and production, produce renewable energy, reduce climate-altering gas emissions, and save space in existing landfills.

Environmental showdown: sewage treatment plants vs. landfills

There is no clean answer when it comes to wastewater treatment plants and landfills. When not properly designed and operated, both can cause major environmental damage. Decomposing organic matter in the anaerobic environment of both landfills and sewage facilities releases the potent greenhouse gas methane. Many sewage treatment facilities use the methane gas produced to supply heat for the waste digestion. However, only two percent of these plants use gas produced to make electricity, according to the Federal Energy Management Program—and many, including the Palo Alto water treatment facility, burn the biogas and biosolids produced. The Sierra Club reports that flaring gas ultimately has a lesser impact on the atmosphere than capturing and converting methane. This has led sewage incineration to be a common practice in the United States. In a study at the Hyperion (Los Angeles) sewage treatment plant, the value of biogas produced from anaerobic digestion of food waste appears to exceed the cost of processing the food waste and disposing of the residual biosolids. There is a fertile opportunity for more energy production in the future.

Methane is produced so quickly in landfills that it is difficult to capture with conventional technology. While most landfills nowadays attempt to capture the methane they produce, they may still let as much as 95 percent of it escape, according to Stanford Zero Waste Manager Julie Muir. The bottom line is we do not really know how effective recapture mechanisms are. Unlike anaerobic digesters, dumps were not designed to capture biogas. Landfills are the largest human-related source of methane in the United States, accounting for 34 percent of all methane emissions according to the EPA. Emissions from landfills are expected to decline as facilities continue to adopt new technologies in accordance with The Landfill Rule. From a climate perspective, sewage via kitchen disposals currently beats landfills.


The wastewater problem

There are other environmental consequences of dumping waste into our water system, however. In sewage treatment facilities, water is separated from biosolids and returned to local waterways. There is a small pond beside my hometown’s wastewater treatment facility that was heavily featured in high school dares. Luckily, I never had to jump in slimy algae-laden pond, but plants and animals in local waterways don’t have the option to stay away.


Excessive nutrients result in over-fertilization of waters and excessive growth of a few plant species. Once they die, they suck up all the oxygen, suffocating fish, shellfish and many other plants and animals. Environment Canada describes the many environmental and health impacts of poorly treated wastewater.

Landfills can pollute waterways as well, especially after rainfall and the runoff it can produce. Worse, organic matter gets mixed with hazardous materials in the landfill to create toxic leachate. Even modern landfills, which are lined multiple times and covered with soil to prevent seepage, often smell, attract vermin and are harmful to wildlife. Food waste that breaks down once it is buried in the ground can destabilize landfills, causing “garbage slides” and making pollution more likely. The United States has put a lot of effort into improving landfill sanitation and undergoing extensive efforts to pre-treat waste. Reducing the food waste entering landfills will bolster these efforts and have many environmental and potentially health benefits.

Ultimately both sewage treatment facilities and landfills are overflowing with problems. It is best to know your local facilities and regional environmental concerns to determine the safest way to dispose of your food waste. But in the end, producing waste comes with a price. As Julie Muir likes to say: “If you’re not for zero waste, then how much waste are you for?” Large-scale composting offers an economically sound, socially beneficial and environmentally friendly solution—without the waste.

GEORGIA GRIFFIN, '13, is an Earth Systems major.


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