Module 5-Composting
Core concepts
Compost:
Decomposed plant material that is high in nutrients.
Aerobic digestion: The process in which microorganisms
breakdown organic material in the presence of oxygen. This process is common in garden compost. Anaerobic digestion: The process in which microorganisms breakdown organic material in the absence of oxygen. This process is used to treat wastewater and landfill waste. In the landfill waste management system this process produces methane gas that can then be used a biogas as a replacement for fossil fuel.
Activated Sludge: a sewage treatment procedure in which the decomposition of the raw sewage is hastened by the addition to it of biologically active sewage sludge
The role of
microorganisms in human composting Watch a
compost (http://www.youtube.com/watch?v=RYssw7gvD_s&feature=relmfu)
Generally one thinks of worms when they think about composting, but they are not the only organisms found in compost. The key to the breakdown and recycling of plant material is microorganisms. Bacteria are the most numerous microorganisms found in a healthy compost environment. Actinobacteria are also very important in these systems. They have been shown to be extremely efficient at breaking down cellulose. In addition, fungi and yeasts are also found in these environments and also can breakdown the cellulose and lignin. General compost (http://www.youtube.com/watch?v=YZpCyMUFeAk)
Landfills can lack the correct conditions for the complex microbial community to thrive in. Decomposition can take a long time in land fills because it is designed to keep harmful or toxic chemicals out of the soil and water near the landfill. landfill (http://www.youtube.com/watch?v=VObNlRHgQZ8&feature=related) This is why garbage that goes to the dumb stays in the dump and does not decompose. There are new management practices that are attempting to correct this. Green Waste (http://www.youtube.com/watch?v=YY8BiVilLyw&feature=related)Wastewater treatment is another process that humans utilize the ability of microbes to breakdown organic material. Wastewater is the process of removing solid waste, chemicals, and household sewage. This is a complex process that includes physical, chemical, and biological processes (activated sludge) to remove the contaminants. The end product should be clean and contaminant free that can be released into a freshwater ecosystem.
What happens when you flush? (http://www.youtube.com/watch?v=jSWF09YOsDY&feature=related)
The role of
microorganisms in Leaf Cutter Ants composting
Leaf-cutter
ants use fresh leaf material to grow fungal gardens. Mature colonies (10-15 yr.
lifespan) can harvest ~400kg (dw) plant material per year. But the fungal
garden can’t use all of the nutrients that are found in the fresh material. Much
like humans, ants have dump piles that look very similar to open landfills. Atta
colombica is one of the only species of leaf-cutter ant that uses above-ground refuse
dumps. Though distribution is patchy, they can be locally abundant and generally
prefer lowland rainforests in Columbia, Costa Rica, and Panama. The dumps contain refuse
material composed of undigested plant material and spent fungal matter. Individual
colonies can produce ~200kg (dw) of refuse per year. Organic material
accumulates during 5-month dry season and then undergoes rapid decomposition during
rainy season. These dumps are considered to be “Nutrient Islands”.
Many studies show significant increase in fine-root mass of plants that are
growing near the dumps. Colonies have substantial impact on nutrient cycling
and redistribution of nutrients.
Tropical
forest soils are considered to be low in microbial diversity, soluble minerals,
organic matter, and pH. Nutrient cycling occurs rapidly in tropics and
organisms must quickly capture nutrients when they become available. This
environment is limited in phosphorus (P) and nitrogen (N). Limitation of P and
N is a common problem. Plants need lots of these nutrients to grow. In the
dumps of leaf cutter ants, microorganisms
efficiently breakdown the organic material and make the nutrients available to
the plants. The plants then become the base for complex food webs.
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