Posts Tagged ‘alternate daily cover’

by: David Emmerson, LCCHS Science Teacher and Solana Center Master Composter

Kitchen waste, yard clippings, paper, coffee grounds, and other organic materials that are produced in the home are all considered “biodegradable”. This term has a positive connotation, especially to us environmentalists. It means that they can be broken down into their raw materials by a variety of living organisms such as microbes (helpful bacteria, protozoa and fungi), earthworms and many different arthropods. Many of our choices at stores are based on purchasing materials that will biodegrade or “rot”.  The theory is that the materials will then be reincorporated as plant nutrients and find their way back into the food chain in a healthy ecosystem.

Leslie turns a Biostack compost bin.

In the United States and in many other developed countries, we over-produce and generate a lot of waste. We have become a throw-away society, keeping our homes neat and tidy by either rinsing things down our drains or putting wastes in plastic bags out on the curb where it all goes out of sight, out of mind. The illusion is that we have solved our problems and shouldn’t worry because the waste will biodegrade on its own. We sometimes further the cause by putting “green” waste into special bins to be picked up separately to be kept out of landfills. However, most of us don’t realize is that almost all of the biodegradable material that we flush, rinse or throw out is going to end up breaking down in an anaerobic environment either as sewage sludge or in most cases in landfills. The separated green waste most often gets used as ADC, “Alternate Daily Cover” to top off the day’s trash which is then layered over the next day, so it gets buried anyhow. Locally, the cities of San Diego and Oceanside have composting facilities where green waste collected at the curb can be taken to be composted or mulched. But if you do not live in those cities or in an area where composting facilities are available, you do not necessarily keep it out of the landfill by separating it.

When organic material decomposes without oxygen, the microorganism can only partially break it down. One of the major end products of this type of decomposition is methane gas (CH4). Methane makes up a little over half of the gas that comes from landfills. Global methane emissions from landfills are estimated to be between 30 and 70 million tons each year. Most of this landfill methane currently comes from developed countries, where the levels of waste tend to be highest. The EPA indicates that methane is about 10% of the green house gases released in the US each year. But it is 72 times more effective (over a 25 year period) at contributing to global warming than the better known greenhouse gas, carbon dioxide (CO2). Landfills are the second largest source of human-related atmospheric methane, almost one fourth of the methane we release now comes from landfills. Landfills provide ideal conditions for methane production, with lots of organic material and anaerobic conditions. The huge amounts of waste that are buried in landfill sites means that methane is produced for years after the site is closed, due to the waste slowly decaying under the ground. Having the waste we produce at home shipped to landfills means further greenhouse gas produced from the fuel burned.

The Solana Center garden abounds from the compost ammended soil.

By properly composting kitchen waste and yard clippings you can ensure that the waste will not sit in a landfill producing methane. Instead, it will go to work at creating healthy soil and reducing amount of water runoff. Several very effective composting methods are available for domestic use, with vermi-composting (using worms) being particularly effective at quickly converting kitchen waste into good quality garden compost.

Even if you are not serious about gardening, you will improve the water retention of your soil and improve the health of the lawn, shrubs, trees or other landscaping if you turn your organic wastes into compost and put it back into the ground. Healthy soil is an important factor in protecting our water resources. Compost increases soil’s ability to retain water and decreases runoff. Runoff pollutes water by carrying soil, fertilizers and pesticides to nearby streams and sewer drains. Compost encourages healthy root systems, which also decrease runoff. Healthy root systems mean healthy plants and thus better growth and carbon sequestration. If we use compost, we can reduce or eliminate the use of synthetic fertilizers (which come from petroleum). Many people add fertilizer to flowers or lawns even if they are not gardening. Only a 5% increase in organic material quadruples soils capacity to hold water. Not too interested in back breaking work with a shovel to turn the compost into the soil? Don’t want to pay for a roto-tiller? Good news for you. It has been shown that simply top dressing soil with compost helps retain the mycorrhizal fungi nets that assist plant roots. It may actually be the most effective way to assist the plants you already have around your house.

Whether you are trying to grow award winning tomatoes or simply want to help the environment around your own home, composting is the thing for you. You will also contribute to the health of the general community in which you live and cut the amount of pollutants that go into the atmosphere from the wastes you’ve generated. Thanks in advance!

http://www.ars.usda.gov US Dept. of Agriculture website

http://www.ghgonline.org/index.htm a green house gas (GHG) website

http://www.epa.gov/ US Environmental Protection Agency website

http://www.globalchange.gov/ the US Govt. website for Fed. Research on Climate and Global Change


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In a step towards a more sustainable future, Chula Vista’s yard trimmings and green materials will no longer be sent to landfills for Alternate Daily Cover starting January of 2009. Instead, the waste will be used as soil amendments and mulch in San Diego County, cutting down landfill expansion by about 20,000 t1200lf-mulchingfilltrash1ons per year.

Alternate Daily Cover (ADC), as noted in an article by KPBS last month, is a major cause of environmental concern in Southern California. By using green waste as ADC to cover local landfills, San Diego cuts down on the rate of reuse and recycling of organic material in our agriculture. San Diego’s three major landfills were also observed to be releasing more than 50% more methane in to the air than otherwise predicted. Methane is one of the major contributors to global warming, having almost 21 times the effect on global warming compared to carbon dioxide.

In order to cut down on this impact, Allied Waste Services and Plant’s Choice, Inc. have started converting organic waste (such as yard trimmings and vegetable scraps) in to soil amendments for local agriculture. An expected 2,000 tons of waste will be diverted from the Otay landfill every month. The mulch and soil amendments produced will then be reused in the San Diego agricultural community, leading to a healthier and more cost-effective local crops. This program also helps San Diego get closer to achieving Zero Waste status.

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Ever wonder about what happens to all those food scraps, lawn clippings and other organic materials that you don’t compost at home and end up in the landfill? When a resident or business doesn’t compost or put their organics in the “green waste” bin, the organics are buried in the landfill and create methane, a greenhouse gas 21 times worst than carbon dioxide! In some areas, if you put your grass clippings in a “green waste” bin, then those  materials end up as alternate daily cover (ADC), which are ground and used to cover the landfill at night, which still creates methane! The state of California considers using organics as ADC to “count” as recycling.

David Streib/KPBS

Organics in the landfill decompose over time and create greenhouse gases. The California Air Board says 25 percent of those gases escape into the atmosphere. Photo Illustration: David Streib/KPBS

So, with this background, how much of an impact local landfills really have on global warming?  You might be surprised to find that San Diego’s trash is emitting up to twice the amount of methane then predicted.

Local landfills are notoriously bad for San Diego’s air quality.  In order to curb their effect on the planet, landfills must seek approval by the California Air Board (CAB) (www.arb.ca.gov) when it comes to gases released from our trash.  Recently, it has been discovered that the CAB has been drastically underestimating the amount of greenhouse gases being produced in San Diego.  When the Air Board was asked to figure out the actual amount of methane gas released from our landfills, they reported that two local landfills (Miramar and Otay) released 50% more methane than predicted, while the Sycamore landfill in Santee was almost double its predictions.

In an attempt to reduce the amount of methane they release, landfills then attempt to capture this methane as it escapes, so that they can burn it for energy production.  However, even the best capture systems can only get 75% of the methane our landfills produce; meaning that at least 25% of the greenhouse gases is entering the air.  By using a tarp or non-organic cover for the landfill at night instead of ADC, San Diego landfills could reduce their impact on global warming by almost 80%!

Actual is based on gas collection figures supplied by Allied Waste Industries in 2008. From KPBS article

* Miramar Landfill "Actual" is based on gas collection figures supplied by the City of San Diego for 2005. * Otay Landfill "Actual" is based on gas collection figures supplied by Allied Waste Industries in 2008 * Sycamore Landfill: "Actual" is based on gas collection figures supplied by Allied Waste Industries in 2008. From KPBS article

To learn more, check out this article on KPBS: http://www.kpbs.org/news/local;id=11305 and remember to compost at home to make a difference for our environment!

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