In the near future, I see modern landfills as a great way to bank or store less marketable resources for future use, lock away carbon, or add value to the carbon by turning it into energy. Today’s landfill have greatly reduced the potential for risk once associated with older landfills. Today’s landfills are built on a foundation of several feet of dense clay covered with a thick geotextile liner that is air- and watertight. This textile layer is covered with several feet of gravel or sand. As the waste is spread out at the end of each day, layers of dirt or other inert materials are used to cap it. All landfills produce leachate (liquid waste), which comes from the decomposition of waste within the landfill and water from the natural environment. This liquid must be dealt with. Modern landfills minimize fluid going in, such as rain, by covering areas that are not currently operational. All leachate that is drained out is sent to wastewater plants for treatment and purification. In high-tech and experimental landfills, the leachate is circulated in and out of the landfill to encourage faster decomposition of the organic waste. In the future, as resources buried in landfills find value, they will 10 Recycling Projects for the Evil Genius
be mined, and the land on which the landfill was located will be reclaimed. Landfill mining, reclamation, and excavation are happening on a small scale today in Japan and Europe, where land values are high.
Banking on Trash
When it comes to banking or storing carbon, modern landfills can do a great job. As things break down, decompose, or decay into their basic elements, the mass of those items is changed into gases and whatever. When this happens in the open air, where oxygen is present, the process of decay is more likely to produce such gases as carbon dioxide (CO2). The mulch we use in our flower beds and gardens is made from wood breaking down into CO2. Even the kitchen waste, grass clippings, and paper we use to make compost in an aerobic (oxygenated) pile produce CO2. With plastics, it’s the sun’s ultraviolet radiation that helps to speed up decomposition and again produce CO2. Many metals fall prey to oxidation, and oxidation is caused in part by water and the oxygen found in the air we breath that helps to create an electrochemical reaction that eats away at the metals. The process is even more aggressive if a salt or acid is put into play, making the electrochemical reaction even more aggressive.
Metals that are high in iron content oxidize (rust) very easily when unprotected, whereas metals such as aluminum, brass, copper, nickel, tin, and even gold hold up well in these conditions because they are less reactive to oxidation or even form their own protective coatings called oxides. In a covered landfill away from air (oxygen) and sunlight, metals and plastics can take up to hundreds of years to decompose. The plastics and metals in today’s landfills have little value because they are mixed with low-value trash that we actually had to pay someone to take and bury out of site and out of mind. To recycle those plastics and metals now would take a great amount of energy and money,
so unless their value skyrockets, don’t expect them to be mined out any time soon. In the short term, therefore, we know that there is a resource there that might be reused in the future. The things that decompose rather quickly in terms of the life span of a landfill are the organic compounds called biomass. Biomass is made of all kinds living or deceased organic material. As a waste source, biomass refers to plants and animals that are raised and harvested for our use and the waste produced from them in liquid or solid form. As biomass waste decomposes or decays into its most basic elements, the mass of the item is changed into gases and simpler, less complex molecular structures. Above-ground decomposition of biomass produces CO2gas via its interaction with oxygen and things that feed on it such as insects, some animals, fungi, plants, and aerobic microbes.
Aerobic Microbes
Aerobic microbial interaction with biomass involves the same process as when yeasts consume the starches and sugars found in biomass and in so doing produce CO2and ethanol (alcohol). In a compost pile, aerobic bacteria do their job by converting carbon to CO2, nitrogen to nitrates, and ammonia to ammonium, all of which help to make good rich soil.
Anaerobic Microbes
Anaerobic microbes are some of the oldest forms of life on earth and are responsible for the breakdown of organic material in the absence of oxygen. They produce a biogas as a waste product.
Anaerobic decomposition occurs naturally in swamps, water-logged soils such as in rice fields, deep bodies of water, and the digestive systems of termites, large animals, and even humans.
Anaerobic processes can be managed in an airtight environment such as a landfill or a covered lagoon used to store manure for waste treatment.
Chapter 2 I Recycling the Good, the Bad, and the Ugly 11
The anaerobic biogases (mostly methane) are calledlandfill gases(LFGs), and they are created by the anaerobic microbial feast that’s occurring on the decaying biomass waste buried within the landfill. The use of landfill gas for energy also has the added benefit of offsetting the use of fossil fuels such as coal and natural gas. Landfill gas emitted from decomposing garbage is a reliable and renewable fuel option that remains largely untapped at many landfills across the United States despite its many benefits. Generating energy from landfill gas creates a number of environmental benefits.
Landfill Gas to Energy Is Good for Many Reasons
I It helps to keep methane from escaping into the air. Methane is a potent heat-trapping gas that is much worse than the greenhouse gas CO2. Using it to produce electricity is a great way to further offset the use of nonrenewable resources such as coal, natural gas, and oil.
I There are many cost-effective options for reducing methane emissions while generating energy. Methane gas can be used to make another alcohol-based fuel called biomethanol, which is made synthetically from the methane gas that’s naturally occurring from methane-producing microbes that thrive in oxygen-free environments such as landfills and covered sewage lagoons.
I Projects help to reduce local air pollution.
I Projects create jobs, revenues, and cost savings.
I Landfill gas from 1,000 landfills could power nearly a million homes.
What a Gas
Municipal solid-waste landfills are the second largest human-generated source of methane emissions in the United States. Given that all landfills generate methane, it makes sense to use the gas for energy generation rather than flaring it off to convert it into CO2while wasting its heat energy or emitting it as a poisonous gas to the atmosphere. Methane is a very potent greenhouse gas that is over 21 times stronger than CO2. Methane also has a short atmospheric life and causes all kinds of undesirable chemical reactions as it breaks down. Turning methane emissions from landfills into energy is one of the best ways to achieve a near-term beneficial impact in mitigating energy cost and effects of methane emissions. When methane is used as a fuel and combusted, it’s converted to water and the much less potent carbon dioxide gas (which is 21 times less damaging to our air). If we use the methane from a landfill to make energy, those emissions are not considered to contribute to global climate change (they are carbon-neutral) because the carbon is being emitted from recently living biomass. Not all biomass can be considered a biofuel; coal, oil, and natural gas are fossilized biomass fuels. Their origin is from ancient biomass that has been locked away from our current carbon cycle for millions of years. The combustion of ancient biomass may disturb the current carbon balance in our atmosphere, and it’s a known fact that every action has an equal and opposite reaction. Today, our governments have banned the disposal of green waste, that is, grass clippings, leaves, limbs, and branches, in our landfills under the guise of saving landfill space. Recycling our green waste into compost and mulch produces the same amount of carbon dioxide emitted as a result of the natural decomposition of the organic waste materials outside the landfill environment. Thus, having that waste in our landfills again may help 12 Recycling Projects for the Evil Genius
us to make even more energy and cause no more harm than if we just allowed it to rot on the ground. This is just something to think about.
Benefits to the Local Economy
Landfills can generate revenue from the sale of the gas or energy they produce. Use of landfill gas also can create jobs associated with the design, construction, and operation of energy-recovery systems. Landfill gas projects involve all kinds of outside labor, and much of the money generated is spent locally for drilling, piping, construction, and personnel. The economic benefits from locally produced energy include employment, local sales, and tax revenue. An investment in locally produced energy helps manufacturers to use landfill gas as a direct replacement for more expensive fossil fuels such as natural gas. Some companies will save millions of dollars by investing in landfill gas energy.
How Landfill Gas Works
Landfill gas to energy involves collecting the combustible landfill gas. The gas, in turn, releases the heat energy that is stored in its chemical bonds through combustion. During combustion, the organic compounds in the landfill gas react chemically with oxygen and pressure to produce heat. This process releases the heat energy stored in the chemical bonds by breaking those bonds apart to form water vapor, carbon dioxide, and other less volatile compounds. When we ignite landfill gas in a reciprocating engine, gas turbine, or boiler to generate energy, we also reduce pollution associated with the use of the fossil fuels that normally would’ve been used to produce that same amount of energy.
Landfill gas is extracted from landfills using a series of wells and a blower or vacuum system.
This system moves the collected gas to a central point, where it can be processed and treated
depending on the ultimate use for the gas. From this point, the gas can be used to generate electricity or replace fossil fuels in industrial and manufacturing operations, or it can be upgraded to pipeline-quality natural gas.