Landfills A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...

are the primary method of waste disposal in many parts of the world, including United States and Canada. Bioreactor landfills are expected to reduce the amount of and costs associated with management of

leachate A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed. Leachate is a widely used term in the environmental sciences wh ...

, to increase the rate of production of

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...

(natural gas) for commercial purposes and reduce the amount of land required for land-fills.The Hinkley Center For Solid and Hazardous Waste Management, The Department of Environmental Engineering Sciences, University of Florida, The Civil and Environmental Engineering Department, University of Central Florida. (2008). Florida Bioreactor Landfill Demonstration Project: Executive Summary. Retrieved February 03, 2010, fro

/ref> Bioreactor landfills are monitored and manipulate oxygen and moisture levels to increase the rate of decomposition by microbial activity.

Traditional landfills and associated problems

Landfills are the oldest known method of waste disposal. Waste is buried in large dug out pits (unless naturally occurring locations are available) and covered. Bacteria and archaea decompose the waste over several decades producing several by-products of importance, including methane gas (natural gas), leachate, and

volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a t ...

(such as

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The under ...

(H₂S), N₂O₂, etc.). Methane gas, a strong

greenhouse gas A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxide (), methane ...

, can build up inside the landfill leading to an explosion unless released from the cell.Christensen, T. H. (1999). Landfilling of waste: Biogas Leachate are fluid metabolic products from decomposition and contain various types of toxins and dissolved metallic ions.Washington State Department of Ecology. (n.d.). Solid Waste Landfill Design Manual. Retrieved February 3, 2010, fro

If leachate escapes into the ground water it can cause health problems in both animals and plants.Kjeldsen, P. M. (2002). Present and Long-Term Composition of MSW Landfill Leachate: A Review. Critical Reviews in Environmental Science and Technology , 297-336. The volatile organic compounds (VOCs) are associated with causing

smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words '' smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odor. The word was then int ...

and

acid rain Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but ac ...

.Brosseau, J. H. (1994). Trace gas compound emissions from municipal landfill sanitary sites; Atmospheric-Environment. Atmospheric Environment, pp. 285-293. With the increasing amount of waste produced, appropriate places to safely store it have become difficult to find.

Working of a bioreactor landfill

There are three types of bioreactor:

aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cel ...

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

and a hybrid (using both aerobic and anaerobic method). All three mechanisms involve the reintroduction of collected leachate supplemented with water to maintain moisture levels in the landfill. The micro-organisms responsible for decomposition are thus stimulated to decompose at an increased rate with an attempt to minimise harmful emissions.Hinkley Center For Solid and Hazardous Waste Management. (2006). Bioreactor.org - General Info. Retrieved February 3, 2010, from Bioreactor.org

/ref> In

bioreactors air is pumped into the landfill using either Vertical direction, vertical or horizontal system of pipes. The aerobic environment decomposition is accelerated and amount of VOCs, toxicity of leachate and methane are minimised. In anaerobic bioreactors with leachate being circulated the landfill produces methane at a rate much faster and earlier than traditional landfills. The high concentration and quantity of methane allows it to be used more efficiently for commercial purposes while reducing the time that the landfill needs to be monitored for methane production. Hybrid bioreactors subject the upper portions of the landfill through aerobic-anaerobic cycles to increase decomposition rate while methane is produced by the lower portions of the landfill. Bioreactor landfills produce lower quantities of VOCs than traditional landfills, except H₂S. Bioreactor landfills produce higher quantities of H₂S. The exact biochemical pathway responsible for this increase is not well studied

Advantages of bioreactor landfills

Bioreactor landfills accelerate the process of decomposition. As decomposition progresses, the mass of biodegradable components in the landfill declines, creating more space for dumping garbage. Bioreactor landfills are expected to increase this rate of decomposition and save up to 30% of space needed for landfills. With increasing amounts of solid waste produced every year and scarcity of landfill spaces, bioreactor landfill can thus provide a significant way of maximising landfill space. This is not just cost effective, but since less land is needed for the landfills, this is also better for the environment. Furthermore, most landfills are monitored for at least 3 to 4 decades to ensure that no leachate or

landfill gases A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...

escape into the community surrounding the landfill site. In contrast, bioreactor landfill are expected to decompose to level that does not require monitoring in less than a decade. Hence, the landfill land can be used for other purposes such as reforestation or parks, depending on the location at an earlier date. In addition, re-using leachate to moisturise the landfill filters it. Thus, less time and energy is required to process the leachate, making the process more efficient.

Disadvantages of bioreactor landfills

Bioreactor landfills are a relatively new technology. For the newly developed bioreactor landfills initial monitoring costs are higher to ensure that everything important is discovered and properly controlled. This includes gases, odours and seepage of leachate into the ground surface. The increased moisture content of bioreactor landfill may reduce the structural stability of the landfill by increasing the pore water pressure within the waste mass. Since the target of bioreactor landfills is to maintain a high moisture content, gas collection systems can be affected by the increased moisture content of the waste.

Implementation of bioreactor landfills

Bioreactor landfills being a novel technology are still in the development phase and are being studied in the laboratory-scale. Pilot projects for bioreactor landfills are showing promise and more are being experimented with in different parts of the world. Despite the potential benefits of bioreactor landfills there are no standardised and approved designs with guidelines and operational procedures. Following is a list of bioreactor landfill projects which are being used to collect data for forming these needed guidelines and procedures:Kjeldsen, P. M. (2002). Present and Long-Term Composition of MSW Landfill Leachate: A Review. Critical Reviews in Environmental Science and Technology , pp. 297-336

United States

* California ** Yolo County * Florida ** Alachua County Southeast Landfill ** Highlands County ** New River Regional Landfill, Raiford ** Polk County Landfill, Winter Haven * Kentucky ** Outer Loop Landfill * Michigan ** Saint Clair County * Mississippi ** Plantation Oaks Bioreactor Demonstration Project, Sibley * Missouri ** Columbia * New Jersey ** ACUA's Haneman Environmental Park, Egg Harbor Township * North Carolina ** Buncombe County Landfill Project * Virginia ** Maplewood Landfill and King George County Landfills ** Virginia Landfill Project XL Demonstration Project

Canada

* Sainte-Sophie Bioreactor demonstration Project, Quebec

Australia

* New South Wales ** WoodLawn, Goulburn * Queensland ** Ti Tree Bioenergy, Ipswich

References

External links

Toward a Twenty-first Century Landfill
- Yolo County's Bioreactor Research Project web page.
Bioreactorlandfill.org
{{DEFAULTSORT:Bioreactor Landfill Landfill Biochemical engineering Bioreactors